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engine here. The rest of us will carry on....


engines today. Singles are typically used in motorbikes, snowblowers, chainsaws etc. Vtwins are also found in motorbikes. The triple is almost unique to Triumph motorbikes
The V5 is something you'll find in some VWs. The V6 has the benefits of being
had no idea, did you?













A 2 stroke engine is different from a 4 stroke engine in two basic ways. First, the
combustion cycle is completed within a single piston stroke as oppose to two piston
strokes, and second, the lubricating oil for the engine is mixed in with the petrol or fuel.
In some cases, such as lawnmowers, you are expected to pre-mix the oil and petrol
yourself in a container, then pour it into the fuel tank. In other cases, such as small
motorbikes, the bike has a secondary oil tank that you fill with 2 stroke oil and then the
engine has a small pump which mixes the oil and petrol together for you.
The simplicity of a 2 stroke engine lies in the reed valve and the design of the piston
itself. The picture on the right shows a 4 stroke piston (left) and a 2 stroke piston (right).
The 2 stroke piston is generally taller than the 4 stroke version, and it has two slots cut
into one side of it. These slots, combined with the reed valve, are what make a 2 stroke
engine work the way it does. The following animation shows a 2 stroke combustion
cycle. As the piston (red) reaches the top of its stroke, the spark plug ignites the fuel-airoil mixture. The piston begins to retreat. As it does, the slots cut into the piston on the
right begin to align with the bypass port in the cylinder wall (the green oblong on the
right). The receding piston pressurises the crank case which forces the reed or flapper
valve (purple in this animation) to close, and at the same time forces the fuel-air-oil
mixture already in the crankcase out through the piston slots and into the bypass port.
This effectively routes the mixture up the side of the cylinder and squirts it into the
combustion chamber above the piston, forcing the exhaust gas to expel through the
green exhaust port on the left. Once the piston begins to advance again, it generates a
vacuum in the crank case. The reed or flapper valve is sucked open and a fresh charge

of fuel-air-oil mix is sucked into the crank case. When the piston reaches the top of its
travel, the spark plug ignites the mixture and the cycle begins again.

00:00 / 00:04

For the same cylinder capacity, 2 stroke engines are typically more powerful than 4
stroke versions. The downside is the pollutants in the exhaust; because oil is mixed with
the petrol, every 2 stroke engine expels burned oil with the exhaust. 2 stroke oils are
typically designed to burn cleaner than their 4 stroke counterparts, but nevertheless, the
2 stroke engine can be a smoky beast. If, like me, you grew up somewhere in Europe
where scooters were all the rage for teenagers, then the mere smell of 2 stroke exhaust
can bring back fond memories. The other disadvantage of 2 stroke engines is that they
are noisy compared to 4 stroke engines. Typically the noise is described as "buzzy".


4 stroke engines are typically much larger capacity than 2 stroke ones, and have a lot
more complexity to them. Rather than relying on the simple mechanical concept of reed
valves, 4 stroke engines typically have valves at the top of the combustion chamber.
The simplest type has one intake and one exhaust valve. More complex engines have
two of one and one of the other, or two of each. So when you see "16v" on the badge on
the back of a car, it means it's a 4-cylinder engine with 4 valves per cylinder - two intake
and two exhaust - thus 16 valves, or "16v". The valves are opened and closed by a
rotating camshaft at the top of the engine. The camshaft is driven by either gears










The following animation shows a 4 stroke combustion cycle. As the piston (red) retreats
on the first stroke, the intake valve (left green valve) is opened and the fuel-air mixture
is sucked into the combustion chamber. The valve closes as the piston bottoms out. As
the piston begins to advance, it compresses the fuel-air mix. As it reaches the top of its
stroke, the spark plug ignites the fuel-air mix and it burns. The expanding gasses force
the piston back down on its second stroke. At the bottom of this stroke, the exhaust
valve (right green valve) opens, and as the piston advances for a second time, it forces
the spent gasses out of the exhaust port. As the piston begins to retreat again, the cycle
starts over, sucking a fresh charge of fuel-air mix into the combustion chamber.

00:00 / 00:04

Because of the nature of 4 stroke engines, you won't often find a single-cylinder 4 stroke
engine. They do exist in some off-road motorbikes but they have such a thump-thumpthump motion to them that they require some large balancing shafts or counterweights
on the crank to try to make the ride smoother. They also take a little longer to start from

cold because you need to crank the single piston at least twice before a combustion
cycle can start. Any more than one piston and the engine gets a lot smoother, starts
better, and is nowhere near as thumpy. That's one of the advantages of V-6 and V-8
engines. Apart from the increased capacity, more cylinders typically means a smoother








Geek trivia: Mercedes-Benz needed to increase the performance of their diesel

passenger cars back in the 70's as their market share in the US was increasing. As
professionals with big V-8 luxury cars were trading them in for 2.4l diesels, the demand
for performance had to be addressed. Mercedes did not want to retool their 114/115
series chassis and there wasn't enough room in the engine bay for a six cylinder diesel.
There was, however, room for a straight-5. Benz engineers just hung another cylinder
on the back of the 4 cyl block and presto! The five cylinder engine was born. This
engine acquired a lot of status among the high line car owners. When Audi introduced
the C2 series cars (the 5000 in America, the 100 in Europe) in 1976, they offered a 5cylinder petrol engine too. It was basically a 1.8 litre 4-cylinder engine with an extra
cylinder. That took it up to 2.0 litres but the fifth piston made such an enormous
difference to the smoothness of the engine that it was often mistaken for a V6 or V8.
Why only 5 cylinders instead of going for a V6? Partly for the same rationale as
Mercedes (and it was a really tight fit) but primarily because Benz had made the
straight-5 configuration fashionable. A straight-5 was also more fuel-efficient than a V6.
It's also worth pointing out that nowadays, both Audi and VW have V5 engines with
three cylinders in one bank and two in the other. Same smoothness, better gas-mileage.
Thank you.


Mechanically, 4 stroke diesel engines work identically to four-stroke petrol engines in
terms of piston movement and crank rotation. (To be historically accurate, petrol
engines are mechanically similar to diesel engines - diesel engines came first) It's in the
combustion cycle where the differences come through. First, during the intake cycle, the

engine only sucks airinto the combustion chamber through the intake valve - not a
fuel/air mix. Second, there is no spark plug. Diesel engines work on self-ignition, or
detonation - the one thing you don'twant in a petrol engine (see the section on Octane
later). At the top of the compression stroke, the air is highly compressed (over 500psi),
and very hot (around 700 C - 1292F). The fuel is injected directly into that environment
and because of the heat and pressure, it spontaneously combusts (this system is known
as direct-injection). This gives the characteristic knocking sound that diesel engines
make, and is also why pre-igniting petrol engines are sometimes refered to as
Petrol engines typically run compression rations around 10:1, with lower end engines
down as low as 8:1 and sportier engines up near 12:1. Diesel engines on the other hand
typically run around 14:1 compression ratio and can go up as high as 25:1. Combined
with the higher energy content of diesel fuel (around 147,000 BTU per gallon versus
125,000 BTU for a gallon of petrol), this means that the typical diesel engine is also a lot
more efficient than your common or garden petrol engine, hence the much higher gasmileage


Because of the design of the diesel engine, the injector is the most critical part and has
been subjected to literally hundreds of variations in both design and position. It has to
be able to withstand massive pressures and temperatures, yet still deliver the fuel in a
fine mist. One other component that some diesel engines have is a glowplug. From
cold, some lower-tech engines can't retard the ignition enough, or get the air
temperature high enough on startup for the spontaneous combustion to happen. In
those engines, the glowplug is literally a hot wire in the top of the cylinder designed to
increase the temperature of the compressed air to the point where the fuel will combust.
These engines typically have a pictograph on the dashboard that looks like a lightbulb.
When starting the engine cold, you need to wait for that light to go out - basically you're
waiting for the glowplugs to get up to temperature. In really old diesel designs, this could
be as long as 10 seconds. Nowadays it's nearly instantaneous, or in the case of
advanced ECM systems, not needed at all.


Would you believe there is such a thing as a 2 stroke diesel engine? The two-stroke
cycle described above turns out to be highly beneficial for the diesel model, the major
difference being the inclusion of exhaust valves at the top of the cylinder. The burn cycle
works similarly too. At the top of the piston travel, the air is hot and compressed, just like
in a 4 stroke diesel. And like the 4 stroke, the injector sprays fuel in at that point and it
self-combusts. As the gasses expand, the piston is forced downwards and towards the
bottom of its stroke, the exhaust valves on the top of the cylinder open. Because the
gas is still expanding at this point, the combustion chamber empties itself through the
open valves. At the very bottom of the power stroke, the piston uncovers the air intake
and pressurised air fills the combustion chamber forcing the last remnants of the
exhaust gas out. As the piston begins its compression stroke, the exhaust valves close
and the air is compressed and voila - a two-stroke diesel engine. The other difference
between a 4 stroke and 2 stroke diesel engine is that the 2 stroke variety must have a
turbocharger or supercharger; you'll notice I mentioned the air intake fills the cylinder
with pressurised air.






As with 2 stroke petrol engines, every downward piston stroke is a power stroke,
meaning the 2 stroke engine has the potential to product twice as much power as its 4
stroke sibling. Typically you'll find 2 stroke diesels in maritime engines (like those on
needed for the same size of engine.


Old-school diesel engines used to sound like tractors when you started them on a cold
morning, and they used to spew particulates out of the exhaust to the point where the
back of the car went black. Newer generation diesels start much less noisily but for the
most part still have some issues with particulates in the exhaust. Toyota claim to have
solved this with their D-Cat and DPNR system. D-Cat stands for Diesel Clean Advanced
Technology and DPNR stands for Diesel Particulate NOx Reduction. The operating
principle is fairly sound. D-Cat is an advanced computer-controlled system for cleaning
diesel exhaust gasses which relies on the DPNR catalyser. This is a combination of

particle filters and normal gas-reduction catalysing metals that remove particulates,
sulphur dioxide (SO2) and nitrogen dioxide (NO2) from the exhaust gasses. A sensor
measures can tell when these filters are nearly full at which point a fifth diesel-injector
sprays a little fuel directly into the exhaust system. Combined with the exhaust gas
recirculation system, this results in all the collected pollutants being burned off, cleaning
the filter in the process. DPNR requires ultra-low sulfur diesel (ULSD) to work properly.
Shortly after this system was launched on the D-4D engined 2.0litre Toyota Avensis, the
complaints started to come in. Notably, Dutch car magazine AutoWeek (issue 42 / 2006)
exposed the problem when their DPNR-equipped Avensis started driving around with a
huge cloud of white smoke pouring out of the exhaust. They weren't the only ones to
have this problem. Hundreds of complaints were filed in Germany and other European
countries for the same thing. The problem was that the D-Cat/DPNR system needs to
'regenerate' as described above. The particulate and gas filters are cleaned via a
combustion mechanism in the exhaust, but this only happens at speeds below 160km/h
(99mph), and takes about 20 minutes each time. In Germany especially, where they still
have sections of unlimited-speed autobahns, people had been driving well over that
speed for miles on end, then stopping and turning the car off, only to repeat the cycle
twice a day during their commute. When this happens, the DPNR system never gets
time to regenerate normally and the particle filters become clogged and the DPNR
system forces a clean cycle to happen. This forced combustion results in white smoke
as there are too many pollutants trying to be burned off at the same time. And not just a
little white smoke. In the AutoWeek test, they thought their Avensis was on fire it was
trailing so much smoke. Toyota promised to sort this problem out with an improved









As of 2011 there wasn't much talk about this any more although there is still reference to
the problem in a Toyota TSB (White Smoke From Exhaust, DNPR Only)



It's worth mentioning the two sub-types of 4 stroke engine at this point. Because the
valves always open inwards, into the combustion chamber, they take up some space at
the top of the chamber. In an interference engine, the position of the piston at the top of
its stroke will occupy the same physical space that the open valves do whilst the piston
is at the bottom of its stroke. It's important to know if your engine is an interference
engine because if the timing belt breaks, at least one set of valves will stop in the open
position and the momentum of the engine will ram the piston in that cylinder up into the
valves requiring a very expensive engine repair or replacement. In a noninterferenceengine, the valves do not occupy any space that the piston could move into,
so if your timing belt snaps on one of these engines, in 99% of cases you won't suffer
any valve damage because the piston cannot physically touch the open valves. That is
the technical explanation of why its important to get your timing belt changed at the


The picture here shows the difference between the two types. On the left, circled in red
is where the open valve interferes with the position of the piston at the top of its travel.
On the right, a non-interference engine shows there is still a gap at the same point
(exaggerated for my picture).


When a piston in an engine reaches the top of its travel, that point is known as Top
Dead Centre or TDC. This is important to know because I don't think any engine
actually fires the spark plug with the pistons at TDC. More often than not, they fire
slightly before TDC. So how does your ignition system work, and what is ignition timing


Well generating the spark is the easy part. The electrical system in your car supplies
voltage to your coil and ignition unit. The engine will have a trigger for each cylinder, be
it a mechanical trigger (points), electronic module or crank trigger. Whatever it is, at that

point, the engine effectively sends a signal to the coil to discharge into the high voltage
system. That charge travels into the distributor cap and is routed to the relevant spark
plug where it is turned into a spark. The key to this, though, is the timing of the spark in
relation to the position of the piston in the cylinder. Hence ignition timing. Having the
spark ignite the fuel-air mixture too soon is basically the same as detonation and is bad
for all the mechanical components of your engine. Having the spark come along too late
will cause it to try to ignite the fuel-air mixture after the piston has already started to










Timing the spark nowadays is usually done with the engine management system. It
measures airflow, ambient temperature, takes input from knock sensors and literally
dozens of sensors all over the engine. It then has an ignition timing map built into its
time that it should fire the spark plug, based on the ignition timing map. At 3000rpm, in a
4 cylinder engine, it does this about 100 times a second. In older systems, the spark
timing was done using simple mechanical systems which had nowhere near the ability
to compensate for the all the variables involved in a running combustion engine.
Typically as an engine revs quicker, the ignition timing needs to advance because the
spark needs to get to the cylinder more quickly. Why? Well the fuel-air mix takes a finite
amount of time to combust. It won't burn any quicker or slower for any given engine
speed. So for higher speeds, the mixture needs to be ignited earlier in the cycle to
ensure that it begins to burn at the optimum timing point. In modern systems, this is all
taken account of in the ignition timing map. On older mechanical system, they used
mechanical or vacuum advance systems, so that the difference in the amount of
vacuum generated in the intake manifold, determined the advance/retard amount of the


Despite the speed that an engine turns, it is possible for mere mortals like you and me
to be able to check the ignition timing or an engine using (and you'd have never
guessed this) an ignition timing light. Timing lights are typically strobe lights. They work
by being connected to the battery directly and then having an induction coil clamped
around one of the spark plug leads - normally the first or last cylinder in the engine
depending on the manufacturer. When the engine fires the spark plug for that cylinder,
the inductive loop detects the current in the wire and flashes the strobe in the timing
light once. So if the engine is ticking over at 1100rpm, the strobe will flash 550 times a
minute (4 stroke engine, remember?). Fantastic. So you're now holding a portable rave
lighting rig but how does this help you see the timing of an engine? Well it's simple. You
must have seen strobe lights working somewhere - a rave, a stage show - they're used
to effectively freeze the position of something in time and space by illuminating it only at
a certain point and for a fraction of a second. Shooting a strobe at someone walking in a
dark room will result in you seeing them walk as if they were a flip-book animation on a
reel of film. This effect is what's used to visualise the timing of your engine. Somewhere
on the front of the engine there will be a notch near one of the timing belt pulleys and
stamped into the metal next to it will be timing marks in degrees. On the pulley itself
there will be a bump, recess or white-painted blob. When you point the timing light down
towards the timing belt pulley, remember it fires once for each firing of the cylinders?
Each time it fires, the white blob on the pulley should be at the same position in its
rotation - the strobe fires once for each ignition spark at which point the mark should be

in the same place, and the effect to you is that the whole pulley, timing mark and all, are
now standing still in the strobe light. The mark on the pulley will line up with one of the
degree marks stamped on the engine, so for example if the white dot always aligns with
the 10 mark, it means your engine is firing at 10 degrees before TDC. When you rev
the engine, the timing will change so the mark will move closer or further away from the










Note that in some engines, the two marks are simply painted or stamped, and there are
no degree markings. In this case, the marks align when the first piston is exactly at


After all that, it's worth pointing out that crank timing marks can be way off so it's worth
confirming that your TDC marker is actually TDC before pratting about with the timing.
It's not as bad now as it used to be, but in the bad old days, Rover V8's were particularly
bad for this, with some being as much as 12 off! So how you do confirm your TDC
really is TDC? Small cameras, a good set of feeler gauges, some cash and someone
who knows what they're doing.


The same timing marks exist stamped into the metal near, and on the pulley on the end
the cam. Essentially these marks are used to line up the cam to the correct position
when you're changing the timing belt. You have to make sure the engine is rotated to
TDC and that the cams are properly aligned too. If you don't, the cams will spin
permanently out-of-synch with the engine crank and the engine will run badly, if at all.

And engine without a spark plug is useless, unless it's a diesel engine in which case it
uses a glowplug instead. But we're talking about regular petrol engines here so the next
topic to get to grips with is the spark plug. It does exactly what it says on the tin - it's a
plug that generates a spark. Duh. So why spend time talking about it? Well with
apologies to George Orwell not all spark plugs are created equal. Some are more equal
than others. They'll all do the job but the more you pay, the better the plug. All spark
plugs share the same basic design and construction though.

The high voltage from your vehicle's high-tension electrical system is fed into the
terminal at the top of the spark plug. It travels down through the core of the plug
(normally via some noise-suppression components to prevent electrical noise) and
arrives at the centre electrode at the bottom where it jumps to the ground electrode
creating a spark. The crush washer is designed to be crushed by tightening the spark
plug down when it's screwed into the cylinder head, and as such, it helps keep the
screw threads under tension to stop the spark plug from shaking loose or backing out.
The insulator basically keeps the high-tension charge away from the cylinder head so
that the spark plug doesn't ground before it gets a chance to generate the spark.
The type of plug I've illustrated here is known as a projected nose type plug, because
the tip extends below the bottom of the spark plug itself. The other main type of spark
plug has the centre electrode recessed into the plug itself and merely grounds to the
collar at the bottom. The advantage of the projected nose type is that the spark is better
exposed to the fuel-air mixture.

Ground electrode (ground strap) types.There are plenty of different types of

grounding electrodes kicking around in spark plug designs nowadays, from 'Y' shaped
electrodes (like SplitFire plugs) to grooved electrodes like you'll find on Champion plugs
all the way up to triple-electrode plugs like the high-end Bosch items. They're all
designed to try to get a better spark, and to that end, you'll now find all sorts of exotic
materials turning up too. Titanium plugs, for example, have better electrical conductivity

than brass and steel plugs, and the theory is that they'll generate a stronger, more


Gapping a spark plug. Gapping a spark plug is the process of ensuring the gap
between the two electrodes is correct for the type of engine the plug is going to be used
in. Too large a gap and the spark will be weak. Too small and the spark might jump
across the gap too early. Generally speaking, the factory-set spark plug gap is just fine,
but if you're running an older engine, or a highly tuned engine, then you need to pay
attention to the gap. Feeler gauges are used to measure the gap, and a gapping tool is












Heat ranges. Something that is often overlooked in spark plugs is their heat rating or
heat range. The term "heat range" refers to the relative temperature of the tip of the
spark plug when its working. The hot and cold classifications often cause confusion
because a 'hot' spark plug is normally used in a 'cold' (low horsepower) engine and vice
versa. The term actually refers to the thermal characteristics of the plug itself,
specifically its ability to dissipate heat into the cooling system. A cold plug can get rid of
heat very quickly and should be used in engines that run hot and lean. A hot plug takes
longer to cool down and should be used in lower compression engines where heat
needs to be retained to prevent combustion byproduct buildup.
Thank you.


You keep seeing me talk about fuel-air mix or fuel-air charge on this page, but I thought
it wise to explain how this happens because it is pretty fundamental to the operation of



The fuel and air are mixed in one of two main ways. The old-school method is to use a
carburetor, whilst the new-tech approach is to use fuel injectors. The basic purpose is
the same though, and that is to mix the fuel and air together in proportions that keep the

engine running. Too little fuel and the engine runs 'lean' which makes it run hot. Too
much fuel and it runs 'rich' which conversely makes the engine run cooler. Running rich
can also result in fouled up spark plugs, flooded engines and stalling, not to mention
wasting fuel. Finding the right balance normally involves about 10 milligrams of petrol
for each combustion stroke.

Advantages : analogue and very predictable fuelling behaviour, simple and inexpensive




Disadvantages : carburetor icing in the venturi, imprecise fuel metering, float chambers
don't work well if they're not the right way up.


A carburetor is basically a shaped tube. The shape of the tube is designed to swirl the
incoming air and generate a vacuum in a section called the venturi pipe (or just the
venturi). In the side of the venturi is a fuel jet which is basically a tiny hole connected to
the float chamber via a pipe. It's normally made of brass and has a miniscule hole in the
end of it which determines the flow of fuel through it. In more complex carburetors, this
is an adjustable needle valve where a screw on the outside of the carburetor can screw
a needle in and out of the valve to give some tuning control over the fuel flow. The fuel
is pulled through the jet by the vacuum created in the venturi. At the bottom of the tube
is a throttle plate or throttle butterfly which is basically a flat circular plate that pivots
along its centreline. It is connected mechanically to the accelerator pedal or twist-grip
throttle via the throttle cable. The more you push on the accelerator or twist open the
throttle, the more the throttle butterfly opens. This allows more air in which creates more
vacuum, which draws more fuel through the fuel jet and gives a larger fuel-air charge to





When the throttle is closed, the throttle butterfly in the carburetor is also closed. This
means the engine is trying to suck fuel-air mix and generating a vacuum behind the
butterfly valve so the regular fuel jet won't work. To allow the engine to idle without
shutting off completely, a second fuel jet known as the idle valve is screwed into the
venturi downwind of the throttle butterfly. This allows just enough fuel to get into the
cylinders to keep the engine ticking over.


To make sure a carburetor has a good, constant supply of fuel to be sucked through the
fuel jets, it has a float chamber or float bowl. This is a reservoir of petrol that is
constantly topped up from the fuel tank. Petrol goes through an inline filter and a
strainer to make sure it's clean of contaminants and is then deposited into the float
chamber. A sealed plastic box is pivotted at one end and floats on top of the fuel.
Believe it or not, this is called the float. A simple lever connects to the float and controls
a valve on the fuel intake line. As the fuel drops in the float chamber, the float drops with
it which opens the valve and allows more fuel in. As the level goes up, the float goes up
and the valve is restricted. This means that the level in the float chamber is kept
constant no matter how much fuel the carburetor is demanding through the fuel jets.
The quicker the level tries to drop, the more the intake valve is opened and the more
petrol comes in to keep the fuel level up. This is why carburetors don't work too well
when they're tipped over - the float chamber leaks or empties out resulting in a fuel spill
- something you don't get with injectors. To combat this, another type of chamber is
used where carburetors can't be guaranteed to be upright (like in chainsaws). These
use diaphragm chambers instead. The principle is more or less the same though. The
chamber is full of fuel and has a rubber diaphragm across the top of it with the other
side exposed to ambient air pressure. As the fuel level drops in the chamber, the
outside air pressure forces the diaphragm down. Because it's connected to an intake
valve in the same way that the float is in a float chamber, as the diaphragm is sucked
inwards, it opens the intake valve and more fuel is let in to replenish the chamber.
Diaphragm chambers are normally spill-proof.


One of the problems with the spinning, compressing, vacuum-generating properties of

the venturi is that it cools the air in the process. Whilst this is good for the engine (colder
air is denser and burns better in a fuel-air mix), in humid environments, especially cool,
humid environments, it can result in carburetor icing. When this happens, water vapour
in the air freezes as it cools and sticks to the inside of the venturi. This can result in the
opening becoming restricted or cut off completely. When carbs ice up, engines stop. In
aircraft engines, there is a control in the cockpit called "carb heat" which either uses
electrical heating elements to heat up the venturi to prevent icing, or reroutes hot air
from around the exhausts back into the carburetor intakes. In cars, we don't have "carb
heat" but instead there's normally a heat shield over the exhaust manifold connected via
a pipe to a temperature-controlled valve at the air filter. When its cold, the valve is open
and the air filter draws warm air from over the exhaust manifold and feeds it into the
carburetor. As the temperature warms up, the valve closes and the carburetor gets
cooler air because the risk of icing has reduced. The symptoms of carb icing are pretty
easy to diagnose. First, your engine bogs down at high throttle then it loses power and
ultimately could stall completely. You'll stop on the side of the road and wait a couple of
minutes, then the engine will start and run normally. This is because with the engine off,
the heat from the engine starts to warm up the carbs and melts the ice so that when you
try to start it up again, everything is fine.


As car engines evolved, carburetors had to evolve to cope with the various demands.
It's not unusual to find five-circuit carburetors which have become so complex that
they're a nightmare to design, build and maintain. That flies in the face of one of the
carburetor's advantages, which used to be that they were simple. Why five circuits? The
main circuit is the one which provides day-to-day running capability. It's augmented by
accelerator and load (or enrichment) circuits which can vary the fuelling to accomodate
sudden acceleration or the need for more power (like driving uphill). The accelerator
circuit also adds a second butterfly valve in most cases which only opens at 70%
throttle or more. Then there's the choke circuit designed to provide extra fuel with the
throttles closed when the engine is cold, allowing it to start, and finally the idle circuit
which does the same thing but when the engine is warm, to keep it going. On top of all

of this, with the introduction of stricter emissions requirements came catalytic

converters, and these expensive boxes of rare metals just don't work well unless the
fuel-air ratio is very carefully controlled. And that's something carburetors just couldn't
keep up with. Small wonder then that this mechanical tomfoolery gave way to fuel

Advantages : precise and variable fuel metering, better fuel efficiency and better
Disadvantages : Fairly complex engineering that isn't very user-friendly. Binary on/off
functionality at low throttles, which is especially noticable on motorbikes where the
throttle becomes 'snatchy' and it becomes hard to ride smoothly at low speed.


Compared to carburettors, fuel injectors themselves are incredibly simple. They are
basically electro-mechanically operated needle valves. The image on the right shows a
cutaway of a representative fuel injector. When a current is passed through the injector
electromagnetic coil, the valve opens and the fuel pressure forces petrol through the
spray tip and out of the diffuser nozzle, atomising it as it does so. When current is
removed, the combination of a spring and fuel back-pressure causes the needle valve
to close. This gives an audible 'tick' noise when it happens, which is why even a quiet
fuel-injected engine has a soft but rapid tick-tick-tick-tick noise as the injectors fire. This
on-off cycle time is known as the pulse width and varying the pulse width determines
how much fuel can flow through the injectors. When you ask for more throttle either via
the accelerator pedal or twist-grip (on a motorbike) you're opening a butterfly valve
similar to the one in a carburettor. This lets more air into the intake system and the
position of the throttle is measured with a potentiometer. The engine control unit (ECU)

gets a reading from this potentiometer and "sees" that you've opened the throttle. In
response the ECU increases the injector pulse width to allow more fuel to be sprayed by
the injectors. Downwind of the throttle body is a mass airflow sensor. This is normally a
heated wire. The more air that flows past it, the quicker it disappates heat and the more
current it needs to remain warm. The ECU can continually measure this current to
determine if the fuel-air mix is correct and it can adjust the fuel flow through the injectors
accordingly. On top of this, the ECU also looks at data coming from the oxygen
(lambda) sensors in the exhaust. These tell the ECU how much oxygen is in the
exhaust so it can automatically adjust for rich- or lean-running.


When fuel-injection was first introduced, it was fairly simple and used a single injector in
the throttle body. Basically it was a carburettor-derivative but instead of having the
induction vacuum suck fuel into the venturi, an injector forced fuel into the airflow. This




or single-point


As engine design advanced, the single-point system was phased out and replaced
with multi-point or multi-port fuel-injection. In this design, there is one injector for each
cylinder, normally screwed into the intake manifold and aimed right at the intake valve.
Because fuel is only sprayed when the intake valve is open, this systems provides more
accurate fuel-metering and a quicker throttle response. Typically, multi-point injection
systems have one more injector for cold-starting which sprays extra fuel into the intake
manifold upstream of the regular injectors, to provide a richer fuel-air mix for cold
starting. A coolant temperature sensor feeds information back to the ECU to determine
when this extra injector should be used.

As you would expect though, technology marches on with no regard to home

mechanics, and the latest technology isdirect injection, also known as GDI (gasoline
direct injection). This is similar to multi-point injection only the injectors are moved into
the combustion chambers themselves rather than the intake manifold. This is nearly
identical to the direct injection system used in diesel engines. Essentially, the intake
valve only allows air into the combustion chamber and the fuel is sprayed in directly
through a high-pressure, heat-resistant injector. The fuel and air mix inside the
combustion chamber itself due to the positions of the intake valve, injector tip and top of
the piston crown. The piston crown in these engines is normally designed to create a
swirling vortex to help mix the fuel and air before combustion, as well as having a cavity
in it for ultra-lean-burn conditions (see picture to the left). The ECU controls the amount
of fuel injected based on the airflow into the engine and demand, and will operate a
direct injection engine in one of three modes: Full power mode is basically foot-to-thefloor driving. The fuel-air ratio is made richer and the injectors spray the fuel in during
the piston intake stroke. In stoichiometric mode the fuel-air ratio is leaned off a little. The
fuel is still sprayed in during the piston intake stroke but the burn is a lot cleaner and the
ECU chooses this mode when the load on the engine is slightly higher than normal, for
example during acceleration from a stop. Finally, when you're cruising with very little
engine load, for example when you're on wide-open motorway with no traffic (I know
that's hard to imagine when you live in England), the ECU will choose an ultra
leanmode. In this mode, the fuel is injected later on in the 4 stroke cycle - as the piston
is moving up its compression stroke. This forces the fuel-air charge right up next to the
tip of the spark plug for the best burn conditions and the combustion itself takes place
partly in the cylinder and partly in the shaped piston crown mentioned previously.

The ECU receives a wide number of sensor readings from all over the engine. Built into
the ECU is a fuelling and ignition map which is basically a gigantic table of numbers. It's
like a lookup table that the ECU uses to determine injector pulse width, spark timing
(and on some engines, the variable valve timing). So the ECU receives a set of values
from all its sensors, which it then looks up in the fuelling and ignition map. At the point
where all these numbers coincide, there is final number which the ECU then uses to set

the injector pulse width. These are the manufacturer's "blessed" fuelling routines, and
elsewhere on this page, there's a section dealing with chipping and remapping, whereby
aftermarket tuners can alter these mapping tables to make the engine behave


If you've got this far down the page, hopefully you understand that the valves are what
let the fuel-air mixture into the cylinder, and let the exhaust out. Seems simple enough,
but there are some interesting differences in the various types of valve mechanism.


Spring return valves are about the most commonly-used and most basic type of
valvetrain in engines today. Their operation is simplicity itself and there are only really
three variations of the same style. The basic premise here is that the spinning camshaft
operates the valves by pushing them open, and valve return springs force them closed.
The cam lobes either operate directly on the top of the valve itself, or in some cases, on
a rocker arm which pivots and pushes on the top of the valve. The three variations of
this type of valve-train are based on the combination of rocker arms (or not) and the




The most basic type has the camshaft at the top of the engine with the cam lobes








The second more complex type still has the camshaft at the top of the engine, but the
cam lobes operate rocker arms, which in turn pivot and operate on the tops of the
valves. With some of these designs, the rocker arm is pivoted in the middle (as shown
here) and with other designed, it's pivoted at one end and the cam lobe operates on it at
the midpoint. Think of a fat bloke bouncing in the middle of a diving board whilst the tip
of the board hits a swimmer on the head and you'll get the general idea.
The third type which you'll find in some motorcycle engines and many boxer engines are

pushrod-activated valves. The camshaft is actually directly geared off the crank at the
bottom of the engine and the cam lobes push on pushrods which run up the sides of the
engine. The top of the pushrod then pushes on a rocker arm, which finally pivots and
operates on the top of the valve. The image here shows the three derivatives in their
most basic form so you can see the differences between them. Note that the pushrod
type shows the camshaft in the wrong place simply for the purpose of getting it into the
image. In reality the camshaft in this system is right at the bottom of the engine near the
crank. The rocker arms shown here are also called fingers, or followers depending on
who you talk to.


Tappet valves aren't really a unique type of valve but a derivative of spring-return
valves. For the most part, the direct spring return valve described above wouldn't act
directly on the top of the valve itself, but rather on an oil-filled tappet. The tappet is
basically an upside-down bucket that covers the top of the valve stem and contains the
spring. It's normally filled with oil through a small hole when the engine is pressurised.
The purpose of tappets is two-fold. The oil in them helps quiet down the valvetrain
noise, and the top of the tappet gives a more uniform surface for the cam lobe to work
on. From a maintenance point of view, tappets are the items which wear and are a lot
easier to swap out than entire valve assemblies. The image on the left shows a simple
tappet valve assembly. I've rendered the tappet slightly transparent so you can see the
return spring inside.


Desmodromic valve systems are unique to Ducati motorbikes. From the Ducati
website: The word 'desmodromic' is derived from two Greek roots, desmos (controlled,
linked) and dromos (course, track). It refers to the exclusive valve control system used
in Ducati engines: both valve movements (opening and closing) are 'operated." Classy,
but what does it mean. Well in both the above systems, the closure mechanism on the
valve relies on mechanical springs or hydraulics. There's nothing to actually force the
valve to close. With the Ducati Desmodromic system, the camshaft has two lobes per
valve, and the only spring is there to take up the slack in the closing system. That's
right; Ducati valves are forced closed by the camshaft. The marketing people will tell
you it's one of the reasons Ducati motorbike engines have been able to rev much higher
than their Japanese counterparts. The idea is that with springs especially, once you get
to a certain speed, you're bound by the metallurgy of the spring - it can no longer
expand to full length in the time between cylinder strokes and so you get 'valve float'
where the valve never truly closes. With Desmodromic valves, that never happens
because a second closing rocker arm hooks under the top of the valve stem and jams it
upwards to force the valve closed. In fact, the stroke length, rods, and pistons all play
their part in valve timing and maximum engine speed - it's not just the springs and valve
float. This is why F1 cars use such a small stroke and pneumatic valves springs. In
truth, both systems, spring or Desmodromic only work well up to a limit. Newer
Japanese bikes have engines that can rev to the same limit as a Ducati just using


You can see the basic layout of a desmodromic valve on the right. As the cam spins, the
opening lobe hits the upper rocker arm which pivots and pushes the valve down and
open. As the cam continues to spin, the closing lobe hits the lower rocker arm which
pivots and hooks the valve back up, closing it. The red return spring is merely there to

hold the valve closed for the next cycle and doesn't provide any springing force to the
closing mechanism. This is a fairly simple layout for the purposes of illustration. The real
engines have Desmo-due and Desmo-quattro valve systems in them where pairs of
valves are opened and closed together via the same mechanism.


In the 80's, the buzzword was 16-valve. If you had a 16-valve engine you were
happening. You were the dogs bollocks, the cat's meouw. In Italy, your engine was a
quattrovalvole. So what the heck does all this mean? Well it's really, really simple.
"Traditional" 4-cylinder in-line engines have two valves per cylinder - one intake and one
exhaust. In a 16V engine, you have four per cylinder - two intake and two exhaust. (4
valves) x (4 cylinders) = 16 valves, or 16V. It follows that a 20V engine has 20 valves - 5
per cylinder. Normally three intake and two exhaust. Unless you've got a 5-cylinder Audi
or Volvo in which case you've still got 4 valves per cylinder. If you're in America, the
thing to have now is 32V - a 32 valve engine. Basically it's a V-8 with 4 valves per







And what do all these extra valves get you apart from a lot more damage if they ever go
wrong? A better breathing engine. More fuel-air mix in, quicker exhaust. When you get
further down the page (and if your wife / husband hasn't come and complained to you
about spending so damn long reading this stuff so late at night), you'll find some more
information on why this is A Good Thing.


An interesting topic which is useless without illustration, so instead of bogging this page
down even more, Variable Valve Timing has it's own page.


So you've got this far down the page and realised how ridiculously complicated
traditional 2 stroke and 4 stroke engines are. The pistons, connecting rods and crank
are all there to turn up-down motion into spinning motion. Then there's the complexity of
valves and valve trains, timing belts, tappets, springs, fuel delivery systems etc.etc.
There is a simpler way. Would you believe the rotary engine essentially has only three
moving parts? Conceived in 1957 by Dr. Felix Wankel, the rotary engine (also known as
the Wankel Engine or Wankel Motor) works on a very simple principle. The piston isn't a
piston at all, but a three-sided convex rotor. The rendering to the right shows a typical
example. When spun around a fixed pinion gear inside an epitrochoidal-shaped
chamber, the spinning of the rotor creates the suck-squeeze-bang-blow cycle simply by
the its position relative to the sides of the chamber. (If you ever used a Spirograph as a
kid, you'll have drawn trochoidal shapes without really knowing it). Basically, the
combination of the rotor and chamber shapes ensures that the three apexes of the rotor
are always in contact with the chamber walls whilst at the same time always creating
three different volumes. As the rotor spins, each volume gets larger and smaller in turn,
creating the compression and expansion volumes required for the engine to work. But
how does the spinning rotor connect to the output shaft? There's an eccentric wheel that
sits in a bearing inside the rotor. The spinning rotor transfers its motion to the eccentric
wheel and the centre of that wheel is connected to a crank on the output shaft.
A single Wankel rotor could therefore be considered to be the equivalent of three
pistons in a regular 4 stroke engine. The image below shows a single chamber of a
typical rotary engine. Most rotary engines use two chambers and thus two rotors. Hence
the three moving parts - the two rotors and the one output shaft. You can see there are
no valves required - the intake and exhaust ports are simple openings in the combustion
chamber that are covered and uncovered in the correct sequence by the spinning of the










The first is this - "If this is such a simple design, why doesn't everyone use it?"
Well yes, the design is simple. It's also smooth. Both rotors are continuously turning in
the same direction so you don't have the violent change of direction problem that a
normal engine has (up/down/up/down). As well as that, the design means that the
combustion cycle lasts through three quarters of each complete turn of the rotor, as
compared to one quarter of every second stroke of a 4 stroke engine. But all this clever
design does have some inherent problems. Rotary engines cost more to manufacture
because of the engineering tolerances required to make them work. The seals at the
rotor apexes have to be very finely manufactured to prevent premature wear. (The apex
seals are the equivalent of the piston rings in a normal engine). The low compression
ratio and relatively large combustion volumes mean that Wankel engines are also
typically less fuel efficient than normal engines, and a side-effect of that it is typically
more difficult to get these engines to pass emissions regulations. It's not impossible
though. Mazda saw the benefits of rotary engines back in 1961 and to-date have been
the only manufacturer willing to spend the time, money and resources required to get a
reliable, mass-producable design. Their current generation Renesis (Rotary Engine
Genesis) engine powers the Mazda RX-8. Mazda have a plentiful supply of information
on the history, design and implementation of their engines. Mazda rotary engines.
The second question is "Can I see an animation of this pinnacle of engineering
prowess?". The answer is yes because it won't make much sense otherwise. The
easiest way to understand how this all works it to keep your eye on just one of the
curved sides of the rotor as it spins and observe the size of the volume between it and
the chamber wall. As it passes in the intake port, the volume gets larger, generating a
vacuum which pulls air into the chamber. As it passes the top, fuel is injected. As it

approaches the left side of the chamber, the volume gets much smaller, creating the
compression. At that point, the spark plugs fire. The combustion process causes the
expansion of the gas which forces the rotor to continue its motion. Again thinking of just
one side of the rotor, you'll see the volume increase in size again (to accomodate the
combustion). Finally the leading rotor apex uncovers the exhaust port and as the
volume decreases again, the exhaust gasses are forced out. At this point, that one side
of the rotor is now ready to start its combustion cycle again. The bigger picture of
course is that while the side you were watching was going through its intake cycle, the
second side was going through its compression cycle and the third side was going
through its exhaust cycle. Hence why a single-rotor wankel engine is the equivalent of a
three-cylinder four-stroke engine. During that entire cycle you'll have noticed the
eccentric ring spinning in its bearing and in turn spinning the output crank.

00:00 / 00:04


It stands to reason that if you fill a metal engine with fuel and air hundreds of times a
second and make it explode, the whole thing is going to get pretty hot. To stop it all from
melting into a fused lump of steel and aluminium, all engines have some method of
keeping them cool.


You don't see this much on car engines at all now. The most famous cars it was used on
were rear-engined boxers like the original VW Beetle, Karmann Ghia, and Porsche
Roadsters. It is still used a lot on motorbike engines because it's a very simple method
of cooling. For air cooling to work, you need two things - fins (lots of them) and good
airflow. An air-cooled engine is normally easy to spot because of the fins built into the
outside of the cylinders. The idea is simple - the fins act as heat sinks, getting hot with
the engine but transferring the heat to the air as the air passes through and between
them. Air-cooled engines don't work particularly well in long, hot traffic jams though,
because obviously there's very little air passing over the fins. They are good in the
winter when the air is coldest, but that illustrates a weak spot in the whole design. Air

cooled engines can't regulate the overall temperature of the cylinder heads and engine,
so the temperature tends to swing up and down depending on engine load, air
temperature and forward speed. A famous problem with air-cooling is associated with Vtwin motorcycles. Because the rear cylinder is tucked in the frame behind the front
cylinder, its supply of cool, uninterrupted air is extremely limited and so in these
designs, the rear cylinder tends to run extremely hot compared to the front.
The image on the right is Ducati and shows the engine from the Monster 695
motorbike. It's a good example of modern air-cooled design and you can see the fins on
the engine are all angled towards the direction of travel so the air can flow through them

To some extent, all engines have oil-cooling. It's one of the functions of the engine oil to transfer heat away from the moving parts and back to the sump where fins on the
outside of the sump can help transfer that heat out into the air. But for some engines,
the oil system itself is designed to be a more efficient cooling system. BMW 'R'
motorbikes are known for this (their nickname is 'oilheads'). As the oil moves around the
engine, at some points it's directed through cooling passageways close to the cylinder
bores to pick up heat. From there it goes to an oil radiator placed out in the airflow to
disperse the heat into the air before returning into the core of the engine. Actually, in the
case of the 'R' motorbikes, they're air- and oil-cooled as they have the air-cooling fins on
the cylinders too. For a quick primer on how the radiator itself works, read on....

This is by far and away the most common method of cooling and engine down. With
water cooling, a coolant mixture is pumped around pipes and passageways inside the
engine separate to the oil, before passing out to a radiator. The radiator itself is made of
metal, and it forces the coolant to flow through long passageways each of which have
lots of metal fins attached to the outside giving a huge surface area. The coolant
transfers its heat into the metal of the radiator, which in turn transfers the heat into the
surround air through the fins - essentially just like the air-cooled engine fins. The coolant
itself is normally a mixture of distilled water and an antifreeze component. The water
needs to be distilled because if you just use tap water, all the minerals in it will deposit

on the inside of the cooling system and mess it up. The antifreeze is in the mix,
obviously to stop the liquid from freezing in cold weather. If it froze up, you'd have no
cooling at all and the engine would overheat and weld itself together in a matter of
minutes. The antifreeze mix normally also has other chemicals in it for corrosion
resistance too and when mixed correctly it raises the boiling point of water, so even in
the warmer months of the year, a cooling system always needs a water / antifreeze mix


The coolant system in a typical car is under pressure once the engine is running, as a
byproduct of the water pump and the expansion that water undergoes as it heats up.
Because of the coolant mixture, the water in the cooling system can get over 100C
without boiling which is why it's never a good idea to open the radiator cap immediately
after you've turned the engine off. If you do, a superheated mixture of steam and
coolant will spray out and you'll spend some quality time in a burns unit.

The complexities of water cooling. Water cooling is the most common method of
cooling and engine down, but it's also the most complicated. For example you don't
want the coolant flowing through the radiator as soon as you start the engine. If it did,
the engine would take a long time to come up to operating temperature which causes
issues with the emissions systems, the drivability of the engine and the comfort of the
passengers. In truly cold weather, most water cooling systems are so efficient that if the
coolant flowed through the radiator at startup, the engine would literally never get warm.
So this is where the thermostat comes in to play. The thermostat is a small device that
normally sits in the system in-line to the radiator. It is a spring-loaded valve actuated by
a bimetallic spring. In layman's terms, the hotter it gets, the wider open the valve is.
When you start the engine, the thermostat is cold and so it's closed. This redirects the

flow of coolant back into the engine and bypasses the radiator completely but because
the cabin heater radiator is on a separate circuit, the coolant is allowed to flow through
it. It has a much smaller surface area and its cooling effect is nowhere near as great.
This allows the engine to build up heat quite quickly. If you look at the first of the two
diagrams on the right, you can see the representation of the coolant flow in a cold
As the coolant heats up, the thermostat begins to open and the coolant is allowed to
pass out to the radiator where it dumps heat out into the air before returning to the
engine block. Once the engine is fully hot, the coolant is at operating temperature and
the thermostat is permanently open, redirecting almost all the coolant flow through the
radiator. If you look at the second of the two diagrams on the right, you can see the








It's the action of the thermostat that allows a water-cooled engine to better regulate the
heat in the engine block. Unlike an air-cooled engine, the thermostat can dynamically
alter the flow of coolant depending on engine load and air temperature to maintain an
even temperature.

The radiator fan. In the good old days, car radiators had belt-driven fans that spun
behind the radiator as fast as the engine was spinning. The fan is there to draw the
warm air away from the back of the radiator to help it to work efficiently. The only
problem with the old way of doing it was that the fan ran all the time the engine was
running, and stopped when the engine stopped. This meant that the radiator was having
air drawn through it at the same rate in freezing cold conditions as it was on a hot day,
and when you parked the car, the radiator basically cooked because it had no airflow
while it was cooling down. So nowadays, the radiator fan is electric and is activated by a
temperature sensor in the coolant. When the temperature gets above a certain level, the
fan comes on and because it's electric, this can happen even once you've stopped the

engine. This is why sometimes on a hot day, you can park up, turn off, and hear the
radiator fan still going. It's also the reason there are big stickers around it in the engine
bay because if you park and open the hood to go and start messing with something, the












The cabin heater. Most water-cooled car engines actually have a second, smaller
radiator that the coolant is allowed to flow through all the time for in-car heating. It's a
small heat-exchanger in the air vent system. When you select warm air with the heater
controls, you will either be allowing the coolant to flow through that radiator via an inline
valve in the cooling system (the old way of doing it) or moving a flap to allow the warm
air already coming off that radiator to mix in with the cold air from outside.
It's all these combinations and permutations of plumbing in a water-cooled engine that
make it so relatively complex.

No matter what type of cooling you choose for your car, it requires careful maintenance,
which the confident do-it-yourselfer can accomplish at home. You will be dealing with
some common hand tools and shop supplies, antifreeze, thermostat and gasket, caps
for the radiator and other stuff. Let's be honest - when it comes to buying parts, we try to
do it as quickly as possible. Fortunately, there are a lot of places online, where you can
get all this without headache. One of them is, They carry the finest









offer: Except the wide choice of

all needed parts for your Cooling system, you will be surprised with their attractive


If you live anywhere where it snows a lot, you'll have seen hundreds of motorists
stranded at the side of the road, hood up, with steam pouring out of their radiators on
the worst weather days - when it's snowing hard. It's counterintuitive at first - surely on
the coldest, snowiest day of the year, the last thing you'd need to worry about was
engine cooling? Well - sort of. If you're going on a long-distance drive - hours on end on
the motorway, you probably need to consider covering part of your radiator so it doesn't
get too much cold air - otherwise your engine will never quite get hot. That's rare
though. More common is the lazy motorist syndrome, where they'll come out to the car
park, clear the snow off the driver's side of the windscreen, get in and drive. Ten
minutes later, they're standing at the side of the road, freezing, in driving snow,
wondering why their engine blew up. Simple. They didn't clear the snow and ice away
from in front of the radiator grille on the front of their car. That large lump of snow and
ice blocks the airflow to the radiator so the engine just gets hotter and hotter until
eventually it overheats and blows the radiator or pressure relief valve. It's not helped by
the fact that on a good snow day, you'll be stuck in 5mph traffic anyway so there's not
even a chance the snow might dislodge itself. So don't be lazy - spend the extra 2
seconds to brush that stuff away from the front bumper before you get in.


The importance of overall engine design and cooling system design and efficiency is
very well illustrated by the fate that befell the original British Motor Corporation Mini
Minor. The following contribution is by Rodney Brown - a reader of this site.
In the Morris Mini, the water pump, fan and radiator block were mounted in the same
position as they were on the same 948cc engine which was concurrently being used in
the more conventional fore & aft engine layout of the Morris Minor 1000 saloon. Both
cars were designed by Alec Issegonis, and this was just post-war; England was
basically bust, so make do and mend was the order of the day. It took a genius like Alec
to make a fore & aft power train work transversely, by folding beneath itself to fit in a
very tight space. The Mini had to be kept small to keep development, production and



Because of all this, whilst the cooling fan and radiator were still where you would expect
to find them - at one end of the block, they now closely abutted the nearside front inner
wheel arch because the normally fore & aft engine was now turned 90 degrees so it
faced across the car. The arch inner flitch panel had suitable slots punched in it and a
close fitting cowl enclosed the fan blades on the inner face. Good radiator
cooling was possible as the engine was mounted on a sub frame which also carried the
suspension components, leaving only a small shock absorber to pass in front of (and
obstruct) the slots. The problem was that the Mini's front grille was large - as big an area
as the original radiator, but now with no radiator actually behind it - that was on the end
of the engine. Without something in the way, it offered little resistence to the flow of cold
air onto the engine, (now placed sideways) close behind the grille, with just enough
room to take off the distributor cap. (Early on before the cap was covered by a
protective boot and plug shrouds fitted, rain would drive through the grille onto the









The carburettor and inlet manifold shared the space between the engine and the
bulkhead with the exhaust manifold (which only just missed the bulkhead). Therefore

when the car was in motion, the whole of the side of the block facing the open grille was
bathed in a 30 - 60 mph icy blast whilst the opposite side was baked by
convection/radiation/conduction from an ill ventilated exhaust manifold. This is where
the problem lay. The side of the piston bores closest to the front of the car remained
relatively stable but on the side facing the rear bulkhead, where all the heat built up, it
caused the piston bores to expand. So circular piston bores were cold on one side and
hot on the other causing uneven distortion. The main effect of this was a poor fit of the
piston rings which increased oil consumption, and more disastrously, enabled blow-by
for unburnt fuel and combustion gasses which in turn pressurised the sump and
gearbox. Remember that space-saving folded design, where the gearbox was folded
under the engine? You've got it: the engine oil was also the gearbox oil. The
sump/gearbox was not vented initially, but like the engine block above it, was cooled by
an icy blast on one side and baked on the other! The consequences for the then-current
SAE30 single-weight oils were that the oil was essentially useless after 3,000 miles.
This rose to 6,000 miles with the advent of the multi grade oils, and it's interesting to
note that the development of these oils in England was prompted by the pressing need
to solve the problems posed by the Mini.


Petrol (or gasoline if you're American) is a distilled and refined oil product made up of
hydrogen and carbons - a hydrocarbon. A long-chain hydrocarbon to be exact (so don't
get it on your skin - its carcinogenic). It's designed to be relatively safe to handle, if
you're careful. ie. it doesn't spontaneously combust without extreme provocation. When
you have a petrol fire, it's not the petrol itself that is burning, it's the vapour, and this is
the key to fueling an engine. The carburettor or fuel injectors spray petrol into an air
stream. The tiny particles of petrol evaporate into a vapour extremely quickly, and
combined in a cloud with the air, it becomes extremely combustible. The smaller the
particles from the carburettor jet or fuel injector, the more efficiently the mixture burns.

00:00 / 01:18


Remember I said petrol doesn't spontaneously combust? Well it can if the conditions
are right, and the conditions are extreme heat and pressure - exactly the conditions you
find in the combustion chamber. When this happens, it's called detonation or preignition. Diesel engines rely on this process because they don't have a spark plug in the
traditional sense of the word. However in petrol engines, when this happens (also
known as dieseling), it's a Very Bad Thing. Engines are designed to have the fuel-air
mix burn at a fixed point in the cycle, not explode randomly. Whilst it might look like an
explosion, if you could film it on a super high-speed camera, you'd see the mixture
actually burns up very quickly rather than exploding. The video on the right is just that in-cylinder video of the 4 stroke combustion cycle. The intake valve is on the right, the
exhaust valve on the left. Detonation, dieseling or pre-ignition are all terms for what

happens when the fuel-air mix spontaneously explodes rather than burning. Normally
this happens when the mixture is all fouled up, and the engine is running hot. The
temperature and pressure build up too quickly in the combustion chamber and before
the piston can reach the top of its travel, the mixture explodes. This explosion tries to
counteract the advancing piston and puts an enormous amount of stress on the piston,
the cylinder walls and the connecting rod. From the outside of the engine, you'll hear it
as a knocking or pinging sound. The precise sound is very hard to describe because
every engine sounds slightly different when it happens. But the best way I can describe
it is a constant 'toc toc toc' type knocking sound.
Video credit: Original source unknown. Video also available on YouTube and Google Video.

The compression ratio of an engine is the measurement of the ratio between the
combined volume of a cylinder and a combustion chamber when the piston is at the
bottom of its stroke, and the same volume when the it's at the top of its stroke. The
its air-fuel mixture. Similarly, the higher the compression ratio, the greater the liklihood
of detonation.


So you know that a fuel-air mix, given the right conditions, can spontaneously combust.
In order to control this property, all petrols have chemicals mixed in with them to control
how quickly the fuel burns. This is known as the octane rating of the fuel. The higher the









Put on the geek-shades for a moment and I'll explain octane in more depth. If you don't
like being blinded by science, skip down a few paragraphs. For the rest of you, octane is
measured relative to a mixture of isooctane (2,2,4-trimethylpentane, an isomer of
octane) and n-heptane. An 87-octane gasoline has the same knock resistance as a
mixture of 87% isooctane and 13% n-heptane. The octane value of a fuel used to be
controlled by the amount of tetraethyl lead in it, but in the 70s and 80s when it became
apparent that lead was pretty harmful, lead-free petrol appeared and other substances
were introduced to control octane instead.



Just so you know, the octane number is actually an imprecise measure of the maximum
compression ratio at which a particular fuel can be burned in an engine without
detonation. There are actually two numbers - RON (Research octane number) and
MON (Motor Octane Number). The RON simulates fuel performance under low severity
engine operation. The MON simulates more severe operation that might be incurred at
high speed or high load and can be as much as 10 points lower than the RON. In
Europe, what you'll see on the petrol pumps is the RON. However, in America, what
you'll see on the petrol pump is usually the "mean" octane number - notified as (R+M)/2
- the average of both the RON and MON. This is why there is an apparent discrepancy
between the octane values of petrol in America versus the rest of the world. Euro95
unleaded in Europe is 95 octane but it's the equivalent of American (R+M)/2 89 octane.
In America, low altitude petrol stations typically sell three grades of petrol with octane
ratings of 87, 89 and 91. High altitude stations typically also sell three grades, but with
lower values - 85, 87 and 89.


There's a bunch of things that can affect how likely an engine is to have detonation
problems. The common ones are ambient air temperature, humidity, altitude, your
engine's ability to stay cool (ie. the cooling system) and spark timing. Fortunately,
nowadays the engine management system of modern cars can compensate for almost
all of these by advancing and retarding the ignition timing. This is where the computer

slightly adjusts the point in the ignition cycle at which the spark is generated at the spark
plug. With older engines that used mechanical points to send current to the spark plugs,
adjusting the timing was a manual affair that involved adjusting the distributor cap
Knock sensors. Most modern cars have knock sensors screwed into the engine at
multiple places. These actually detect the vibration or shock caused by detonation
(rather than trying to detect the sound) and can signal the engine management system
to change the ignition timing to reduce or eliminate the problem.


The higher the altitude above sea level, the lower the octane requirement. As a general
rule of thumb, for every 300m or 1000ft above sea level, the RON value can go down by
about 0.5. For example an 85 octane fuel in Denver will have about the same
characteristics as an 87 octane fuel on the coast in Los Angeles. As a practical example
of this, I currently live in Salt Lake City which is at around 4,200ft. We travel to Las
Vegas from time to time which is at around 2,000ft. Our Subaru has a minimum octane
requirement of 89 at sea level - so about 87 where we live. Last time we drove to
Vegas, the petrol station we stopped at had run out of 'premium' products so we had to
fill up with 85 octane. This, combined with the drop in altitude caused the 'check engine'
light to come on because we'd effectively taken the engine from 87 octane at altitude to
the equivalent of 83 octane at altitude - way below the minimum required by our car.
The graph here gives a rough idea of how the three main grades of petrol in America
perform with respect to octane at altitude.




















compression ratio for a carburettor engine without engine management. For modern
lowered by about 5 to 7 points.
Compression ratio




The exception to prove the rule. Nowadays, higher octane fuel might actually give you
more power but not because of the octane rating itself. Some petrol companies use a
denser blend for the higher octane products. Denser blends mean higher energy density



















Do these variations in energy density mean you'll get more power out of your engine
from premium blends? Yes, but not in a linear fashion - ie. if the premium product has
5% more energy density than the basic product, you won't get 5% more power out of
your engine, simply because of the inefficiencies of internal combustion and
thermodynamic considerations.


company very quickly and get a lot of publicity.


(explained above) that high octane = more power.

giving more power to bed for once and for all, in 2007 the UK TV showFifth Gear picked

for products that claim to increase your engine's power.
In England, octane boosters are typically also sold as "lead replacements" or "4 star
additive". A lot of European cars relied on the lead in 4-star petrol for the increased
octane. Lower octane unleaded fuels caused a lot of problems when they first
appeared, especially with cars that didn't have engine management systems. Knocking
and detonation became evident in a lot of cars and for some reason French and
German engines were more susceptible than most. Dumping a shot of octane booster in
the tank when filling up solved the problem by raising the RON a few points to make it
the equivalent of what old leaded petrol had been. Eventually, by the late 90s, most
English and European petrol stations introduced LRP - lead replacement petrol, and the
problem went away. Well. Sort of......
Picture credits: Halfords and Channel 5


Whilst LRP solved the problem of lower octane unleaded petrol, it introduced a new
problem. The lead in leaded petrol also had a secondary function and that was to
lubricate the valve seats - the top of the engine block where the valves "park" when not
being opened by the cams. With the advent of LRP, detonation went away but the
chemicals used to increase octane didn't have any lubricating function. Some older

engines started to suffer from increased wear to the valve seats, to the point where the
valves could no longer properly close and seal the intake and exhaust ports. There were
a couple of high profile cases before I left for America in 2001 but I've never been able
to find out the end result. If you have any information on what happened in these cases,
drop me a line and I'll include the info here.


In England during the 90s, supermarkets started a price war with the mainstream fuel
vendors by opening their own petrol stations and undercutting the Esso's and Shell's of
the world by as much as 5%. People flocked to these cheap outlets without doing any
proper research. There's an old saying that begins "if it's too good to be true....."In the
case of supermarket petrol, there was an obvious reason why it was cheaper - it was
the lower grade fuel that the mainstream outlets wouldn't take; product that had been
rejected in quality control, or had less additives and detergents than what you might get
from 'branded' fuel. A measurable percentage of engines started clogging up fuel lines,
running badly and failing emissions tests. It was also noticed that gas mileage dropped.
Eventually the supermarkets were forced to fall in line with the Big Boys, so much so








Skip forwards to 2005 and the first summer of high fuel prices in America. Lo and
behold, supermarkets started to sprout petrol stations and a lot of people were in the
same "cheap fuel" euphoria that the English were in 10 years previously. The American
market did it slightly differently though. Whereas in England, they started out with utterly
sub-standard petrol, in the US it is down to the additive and detergent blends (the same
system used in the UK now). All petrol vendors must have product that meets the EPA
minimum guidelines and typically, branded and unbranded trucks are filled from the
same supply at the refinery or distribution depot. The difference is that when a truck
from one of the majors fills up, they stop at the small company pump where that

company's additional detergent and additive pack is added after the main fill-up. This
blend of chemicals is the 'value-added' part of the premium brand offering that makes
their product meet and exceed the EPA guidelines. (The act of driving the fuel truck
mixes the additive pack into the petrol). I'm not entirely clear on the percentages here,
but I've spoken to tanker drivers who have claimed that it's as little has half a gallon of









There are other practices that vary between branded and unbranded petrol - for
example many branded suppliers have dedicated tankers for each product - tankers that
only ever carry petrol or only ever carry diesel. The unbranded suppliers have been
known to save money by using the same tankers for both fuels, with a cursory 'rinse'






This raises an interesting question then - are you better off to go branded, or to use the
cheapest stuff you can find and then every couple of months, get a bottle of Chevron
Techron additive (or whatever) and run that through your car?

As a substitute for genuinely cheaper fuel, a lot of supermarket chains now offer
cheaper fuel at a price. The catch is that you have to shop with them. Once you buy a
certain amount of stuff from their store, they'll knock off a percentage of the price of
petrol if you buy it from them. The fuel isn't the cheap and nasty sub-standard stuff of
yesteryear that they used to use - it's good, mainstream product. But they can hide the
price drop in the cost of the groceries and other items you buy in store. From your
perspective, you save 2 a tank when filling up. From the store's perspective, you just
spent 100 in shopping so giving you 2 back on your tank of gas is pocket change.
In America, some of the big-box chains, like CostCo and Sam's Club do the same thing.
Rather than go the "dodgy crappy petrol" route, they're offering discounted petrol for
shopping in their stores, discounting the petrol by a couple of cents per gallon as long
as you've bought more than $50 of products from them.



As all this information about petrol and gasoline is starting to run out of your ears, it's
worth bringing up the topic of fuel filters. Without fuel filters, none of this information on
petrol is worth anything. Why? In an ideal world, every time you fill your tank, the petrol
would come from brand new underground tanks, through brand new hoses and nozzles,
down a pristeen filler tube into a brand new gas tank. However, back in the real world,
that simply isn't the case. Tiny bits of metal flake off components. Things rust. Grit and
grime gets into the fuel through many different sources. For the most part, this sediment
settles at the bottom of the underground tanks in a petrol station, and at the bottom of
the petrol tank in your car. If you're unlucky enough to fill up just after the petrol station
has received a load of fuel from a tanker though, all that sediment will be nicely mixed
into the petrol, and you'll get a petrol-sediment mix in your petrol tank. Similarly, if you
insist on running your petrol tank down to the 'E' mark on the fuel gauge, you'll be
sucking up petrol-sediment mix from the bottom of your own tank. It's a good job then
that the men in lab coats decided to put in-line fuel filters in your car. These are










Carburettor engine fuel filters. These are the plastic in-line fuel filters. They look like a
little plastic container with a wavy yellow pad in them. They're typically designed to have
the fuel sucked through them via a mechanical crank-driven fuel pump up near the
carburettor. In some tuner vehicles you'll find this has been replaced with a tasty little
aluminium item, usually anodised in a nice colour, designed to make it nearly impossible



Fuel injection filters. These are the metal cannister-type fuel filters that are normally
buried under the car somewhere. They're designed to have the fuel pushed through
them by an electric high-pressure fuel pump, and so the pressure in the fuel line is
much higher. This is why they're made of metal. Internally, the filter material is normally
finer too.


Generally speaking, unless it's metal filings, then yes, most debris that you'd find in a
fuel system would burn during combustion but that's not the problem. The problem is
getting the fuel into the engine in the first place. Further back up this page you
(hopefully) learned about carburettors and fuel injectors. The one thing common to both
is the tiny hole at the end of the line where the fuel is finally atomised into the air. A good
sized grain of sand would be all it took to block that tiny hole and once that happens, it
doesn't matter how clever your engine is, it won't be getting any petrol. That is why you
have to filter fuel - to keep particulates from clogging areas of the fuel system vital to its
Most manufacturers will tell you that fuel filters are sealed-for-life, or life-time-of-the-car
items. Excuse my French but that's total bollocks. In normal operating conditions, in
'first-world' countries, you should change your fuel filter every 75,000 miles (120,000km)
or so. If you're into extreme motoring, like round-the-world touring, or working in 'thirdworld' countries, your fuel filter might need changing as much as every 5,000 miles.
That's not a slur on those countries, it's just a fact that the cleanliness of petrol station
holding and delivery systems isn't really a hot priority in those countries. Plus, if you're
involved in that sort of driving, chances are most of your petrol will come from a rusty
metal jerry can.


The job of an in-line fuel filter is to filter out sediment and particulates in the petrol that
might otherwise cause problems further down the line in the engine. If you think about it,
the average car probably has 40 to 50 litres of petrol go through the fuel filter every
week. It stands to reason then that eventually the filter is going to become clogged with

debris. Once your filter gets clogged, you start to get all sorts of followon problems. In
carburettor cars, you'll get sporadic and weak fuel supply which will lead to a stuttering
engine, or an engine that seems to have no power under acceleration. In a fuel injection
system where the fuel line pressures are much greater, a clogged filter can lead to a
burned out petrol pump or a blown fuel line connection on top of the fuel starvation
So just bear it in mind when you get to around 75,000 miles. If you're doing your own
servicing, change the filter. If you're using a dealer, insist it gets changed despite their
protests (and they will protest).


You might as well ask me to explain Unified Field Theory to you here. Locating the fuel
filter on any vehicle is a dark art known only to the robot that put your car together. The
filter can literally be anywhere in between the tank and the engine. For carburettor
engines it's most likely to be in the engine bay, probably with 50cm of where the fuel line
comes up from under the car, and clipped to some other tube or cable. For injection
filters, it's most likely to be attached to the chassis or a suspension component
underneath the car at the back axle, close to the fuel pump and petrol tank.


More often than not, there will be a mesh 'sock' on the pickup tube inside the petrol tank
itself. This is a much trickier filter to change as it's a sort of pre-filter to catch the really
large stuff. For the most part, these mesh filters don't block easily - anything sucked up
against them will normally wash off with the natural movement of the petrol in the tank.
Where it's possible to change the external filters yourself, doing the internal one is
probably a job best left to a decent mechanic.


Some carburettors have a last line of defence in the form of a metal gause filter just
inside the fuel intake. If you take the fuel line off a carburettor and peer inside, that's the
most likely place for this to be if there is one. It's worth knowing about this little joy
because if you go to all the trouble of changing your other in-line filter(s) and still have a
fuel starvation problem, it could be this last little bugger that's blocked. Now you know.

Thank you.


With the spiralling cost of fuel prices, people are looking at everything to get cheaper
fuel, and one of the silver bullets seems to be E85 Ethanol-blend gasoline. I say 'seems
to be'because once you do some research, which is what you're doing right here by
reading this, you'll learn it's not quite the magic solution everyone would have you

E85 is a blend of regular unleaded petrol with between 70% and 83% ethanol
depending on the geographic location and time of year. (If you must know, Google
for ASTM D 5798-99). Simply blending ethanol and petrol normally results in a product
with too low a vapour pressure, especially in the winter, which is why it is a process best








It's designed for so-called Flexible Fuel vehicles, and as such has been classified by the
US Department of Energy as an alternative fuel. The facts on E85 are a little hard to
come by, so I've tried to collect together and put as many as I can right here so that you,
dear reader, can try to cut to the chase. So what is a flexible fuel vehicle (FFV)? Well,
it's a vehicle with an engine and emissions system designed to be able to run on a
blend of unleaded petrol and ethanol up to a maximum of 85% ethanol. If E85 isn't
available, you can run them on just plain old petrol though. If you read all the hoopla
surrounding E85, you'll see this statement crop up time and time again: "It is a
renewable source of energy and reduces the crude oil imports needed to fuel America's

transportation system. Ethanol is a clean, environmentally friendly fuel.". Weeeeelllllll

yes. But more specifically, "sort of". It's true that it is partly based on a renewable source
of energy - ethanol is basically distilled corn oil (or wheat, barley, or potatoes. Brazil, the
world's largest ethanol producer, makes the fuel from sugarcane), and yes, it's a
cleaner and slightly more environmentally friendly fuel. There's a few 'buts' to go with all
this, and they're a big 'buts' - of Jennifer Lopez proportions. First, there isn't enough
farmland to grow enough corn to produce enough ethanol to meet gasoline demands,
and it wouldn't be a good use of it even if there was. Second, there's a huge hidden cost
in water - it takes 10 tons of water to process 1 ton of grain for ethanol [Ref: Plan B 2.0:
Rescuing a Planet Under Stress and a Civilization in Trouble by Lester R Brown. ISBN
0393328317]. Third, in 2007, in a report on the impact of biofuels, the Organization for
worse than the disease they seek to heal"."The current push to expand the use of
biofuels is creating unsustainable tensions that will disrupt markets without generating
significant environmental benefits," the OECD said. "When acidification, fertiliser use,
and mineral diesel," it added. And finally, in bold because it's the important part of this
paragraph. E85







What does this mean to you? Well it means you'll need a lot more of it for a start. Sure it
may be cheaper than regular petrol, but there's a reason - it's a terrible way to run a
vehicle. Even the governments own figures back that statement up. Check out one of
their lists of flexible-fueled vehicles for yourself. On average, putting E85 in a flexible
fuel vehicle will return a nauseating 25% worse gas mileage. E85 doesn't burn as
efficiently as regular petrol because it contains less energy per volume - 75,760btu per
gallon as oppose to 115,400btu per gallon for plain old petrol. This accounts for the 30%
increase in the amount of fuel required in the fuel-air mix during combustion, and the
corresponding drop in gas mileage. All this comes with an average drop of only 10% in
greenhouse gas emissions. If you go by historical precedent, and assume we all move
to FFV's, the income from regular petrol will drop so the oil companies will simply

increase the cost of E85. At that point, you're getting terrible gas mileage but paying
what you used to for just plain vanilla unleaded petrol. Remember - nothing is free. Of
course this doesn't need to be the case. E85's higher octane can allow the use of higher
compression, more efficient engines (if optimized for use on it). Look at the race car
teams - a lot of racing engines run on pure ethanol. And when engineered to take
advantage of it, high-compression, high-efficiency engines can reduce the gas-mileage
deficit to about 10% less than their petrol counterparts, which is much closer. But for
ethanol to be successful it must be priced below petrol so that the cents per mile cost is
favorable taking into account the drop in economy.


For a while now, Brazil (the country, not the Terry Gilliam film) has managed to be
largely independent of the world's fluctuating oil prices. By law, all Brazillian petrol must
be at least 25% ethanol - E25 - created from sugar-cane-fed biorefineries. By 2007,
almost all cars available in Brazil ought to be able to run on 100% ethanol. (It's worth
noting that Ethanol-only cars were sold in Brazil in significant numbers between 1980
and 1995). No longer dictated-to by Big Oil, the price of their E100 is relatively low and
thus it offsets the lower gas-mileage quite nicely. One argument put forth in America is
that using E85 will reduce the reliance on foreign imports - specifically oil. But you need
to look at the whole picture. E85 comes from corn, currently a crop used to feed people.
Assuming that America has enough spare capacity to farm corn for E85 for the current
demand, what happens when more people start using it? You can't increase farmland,
or drop production of corn for food, so the next alternative is importing it. At which point,
even using E85, you become dependent on foreign imports again. Brazil doesn't have
this problem because their system is in balance and so they supply themselves with
enough surplus to export their product. Most likely to America.



Something that isn't widely publicised is the difference in emissions between corn-based
ethanol, as used in America, and sugar-based ethanol, as used in Brazil. We're all told
that ethanol blend fuels produce cleaner exhaust and with sugar-based ethanol, that's
absolutely true. Even with corn-based ethanol, the gasses measured at an emissions
check are lower (about 25% less CO 2), which still looks good. But there is something an
ethanol E85 vehicle will produce through the exhaust that might surprise you. The
exhaust gas contains acetaldehyde (CH 3CHO) and lots of it, especially if the fuel source
or combustion process is contaminated with water (like cold-start condensation).
Acetaldehyde is a known carcinogen (source, source) and suspected neurotoxin
(source), and when exposed to its vapors, you or I would likely develop irritation of the
eyes, skin and the respiratory tract. In fact, Acetaldehyde is ranked as one of the most
hazardous compounds (worst 10%) to ecosystems and human health. It's obvious why
this isn't widely publicised, but then you might ask the question "why don't we see this in
the emissions test?". Simple. The emissions test doesn't look for it. You can't detect and






But wait - it gets better. The corn-based ethanol production process consumes more
fossil fuel energy than ethanol's actual calorific value. In other words, to produce a
gallon of ethanol to be used in E85, it takes more fossil fuel energy than you could
simply get by putting a gallon of refined non-blend petrol in your car. And as you know,






So does anyone care about this? In fact yes. The Australian government commissioned
a report on this topic - you can read it for yourself here: Ethanol health impacts. The
executive summary is this: ethanol does produce more of certain nasty emissions than
petrol, but less of others, and that if we break everything down into dollars (the only

figure the government understands) based on lost work due to illness (or death), there
isn't that much difference between the two except in one area - particulate emissions
(PM). PM are the nasty small pieces of carbon that can make it into your lungs, and as
with smoking can (and often does) lead to cancer after a long period of time, which can
then kill people. Ethanol combustion produces substantially less of this than petrol
combustion (at least at 10% concentrations, and presumably more so at higher
concentrations), so ends up being marginally healthier. However, it'd be healthier still to
switch over to CNG, or LPG, in combination with engine improvements to make sure
more of the fuel is properly combusted.
Thanks to Peter K Campbell for addition info on Ethanol and health.


Two words : rotting seals. And I'm not talking about dead sealife. E85 is pretty acidic,
and stuffing it in your regular petrol-engined car will do no end of damage to it. Apart
from the spark timing and the fuel-air ratio being totally different, E85 has a whopping
105 octane rating to deal with the pre-igntion problems of having 30% more fuel in the
fuel-air mix during combustion. The seals and gaskets in FFVs are designed to
withstand the acidic deposits that E85 generates during combustion. Generally
speaking, FFVs are manufactured to eliminate all bare aluminium, rubber and
magnesium parts - all items which E85 is known to rot, and all items which a normal
engine has by the bucketload. Another problem with E85 is that it's electrically
conductive. Regular petrol fuel pumps aren't really designed to work with a conductive
fuel, so using E85 with one could result in a fuel fire where the petrol is not only the fuel
for the fire, but the electrical path for the spark. FFV fuel lines aren't made of rubber, but






So you may get cheaper petrol but you'll get worse gas-mileage and a broken car, with
the possible bonus of a raging E85-fueled inferno to boot. However, there is a fly in the
ointment here, and it is E10. Because of petrol company practices (see below), most
fuel-injected engines designed and built since 1988 are already somewhat adapted to
using ethanol, just not in the percentage you find in E85.


It's not widely known but a lot of petrol companies now blend up to 10% ethanol into
their petrol products without really admitting to it, much less advertising the fact. If
you've noticed your car runs somewhat less than the advertised gas mileage, that's part
of the reason. Most of the gasoline in California is currently 5.7% ethanol (2% oxygen).
Ethanol is blended into petrol for a variety of reasons including

as an oxygenate to reduce CO and HC emissions

an octane booster

to provide volume in place of MTBE

There's nothing wrong or underhanded about this, it's just a cost effective means to
legitimate ends. So if the EPA tells you you should be getting 20mpg city and you're only
getting 18mpg, even driving with a feather right foot, it's not you, it's the petrol
companies. 10% ethanol blend will rob you of about 5% gas mileage, and EPA figures
assume a pure non-ethanol petrol. Apart from the emissions regulations, money is a
factor in ethanol blending - more product that is cheaper to produce but sold for the
same price. You can bet your bottom dollar (or euro) that the European refineries are
doing exactly the same thing.


In America at least, you can go to and lookup gas stations local to you that
do not blend ethanol with their gas. Interestingly, the Shell station closest to where I live
is a zero-ethanol station and it is consistently the cheapest branded petrol in my area.






If you know of similar sites for other countries, drop me a line and I'll add links to them.


15% ethanol blend is getting into corrosive territory, especially for vehicles not designed
with it in mind. In February 2011, the US House overwhelmingly voted to block the sale
of E15 fuel in America. Representatives voted 286 to 135 against the bill that would
have allowed the EPA to issue a waiver allowing petrol stations to sell E15. The
renewable fuels association criticised the decision but there was almost universal
support to block it from small enthusiast groups right up to SEMA (Specialty Equipment
Market Association). The argument for E15 fuel was that it would help reduce the US's
dependence on foreign oil. However, plenty of representatives understood the risks of
allowing fuel to go sale that would only safely work in some cars sold after 2007, as well
as the further drop in fuel efficiency that comes with a 50% higher ethanol content.
However in April 2012, the EPA disregarded all objections and pushed ahead to
approve the use of E15 blended petrol despite admitting that it will cause problems in
vehicles manufactured before 2001. (In reality, that restriction applies to any vehicle
built before 2007). This will be a problem for petrol stations as they will need to provide
both E10 and E15 fuel for their customers, meaning the installation and maintenance of
new underground tanks and above-ground blender pumps. That will be expensive and
there's a good chance that they'll either skip E15 altogether or simply stop selling E10





The EPA's move was for sure coupled to the ending of the 30-year tax subsidy on cornbased ethanol and the cessation of tariffs on ethanol imported from Brazil. The move
itself prompted many manufacturers to indicate that if you use E15 blend, it will void
your factory warranty. The battle continues.


So given the (obscured) facts about corn-based ethanol, why the big push in America to
go to E85? Simple. Money. The government is offering tax credits to the big car
manufacturers to produce FFVs, even if none of them ever run on E85. Similarly, tax
credits are now offered to the big oil companies to product E85 ethanol blend, even if
they don't actually sell it. And when they do sell it, it will make the more money because

you and I will need more of it to go the same distance. Finally, corn growers receive
federal subsidies for growing corn for ethanol production. Couple that with the 54 per
gallon tariff that is currently levied on Brazillian imports, and it shows how the cornbased ethanol has cornered the American market and is keeping the cheaper, cleaner,
sugar-cane ethanol at bay.


Picture credit: Volkswagen

Well that's the conundrum isn't it? The oil and car companies aren't going to give stuff
away free. So you have to choose. Do you want less cost at the point where you're
putting the petrol into your car, or less cost-of-ownership? It's like comparing financial
planning. If you get a flexible fuel vehicle, your immediate cost is much less - you could
be spending 30% less per fill-up. But the long-term costs become negligible because of
the bad gas mileage. On the other hand, if you take the long term investment point of
view, you should be looking at vehicles like the VW Polo Bluemotion. It's a threecylinder turbodiesel, which means at the point of filling it up, you'll actually be
spending more than a regular petrol vehicle. But it returns 70mpg (max), so you'll be
visiting the petrol station a lot less frequently. Don't understand the maths? Ok, lets lay it
I'm going to assume plain fuel costs here, so I'm not factoring in insurance, wear and
tear, initial cost of the vehicle etc. Ready? Okay, we're going to compare two vehicles.
Each drives 15,000 miles a year and each has a 16 gallon fuel tank. The owners of
these vehicles are Barbie and Ken, and to be suitably sexist, Barbie has a pink VW Polo
and Ken has a blue Ford Crown Victoria. They both fill up when the tank gets to 3
gallons left, so they drive 13 gallons at a time.















Ken stops and fills up every 156 miles.

15,000 miles = 225 gallons at 66.5mpg (split the values of 60mpg and 73mpg for city

















So whilst Ken pays much less each time he fills up, he's filling up nearly 6 times as
often, and at the end of the year, he's spent a whopping $1500 more in fuel costs on this
nice, 'clean, environmentally-friendly' E85 ethanol. Now I don't know about you, but it
seems to me that the pollution from 225 gallons of diesel is going to be a whole hell of a










Obviously this example is extreme, but it does use real-world facts and figures from
real-world vehicles you can buy right now. I did it to illustrate how being in posession of
the facts can help clear up the doublespeak and misinformation. So if you're considering
an E85-fuelled vehicle, you might want to do some more homework first, because it













For more information / propaganda, go to the official E85 fuel site.


In Europe, LPG has been an option for drivers for years. In Australia, it's been around
since the 60's. In England, it's still bubbling under and in America it's virtually unheard

of. So what is it? Well, put simply, it's petroleum or natural gas compressed to the point
where it becomes a liquid. The liquified gas is contained in a pressure vessel inside the
car somewhere - normally a tank in the boot (or trunk if you're American). There's a feed
line from there to the fuel injection system or carburettor and a solenoid switch
connected to a fuel-cutoff switch, both of which are controlled from a button or switch on
the dashboard. In one position, the LPG line is closed and the petrol line is open and
the car works just like every other car on the road. In the other position, the petrol line is
cut off and the LPG line is opened up. Liquid gas under pressure shoots up the line and
out of an injector nozzle either screwed into the side of the carburettor, or integrated into
the fuel injection system. As the gas expands out of the nozzle it cools down and
becomes a gas. The gas is highly combustible and when mixed with the air going into
the engine, creates a perfectly useable fuel-air mix for the engine to run on. Simple.
The gas itself is normally some derivative of butane or propane, or a combination of the
two. LPG is manufactured during the process or refining crude oil, and LNG is
manufactured during the refining process of extracting natural gas from the ground.
Once the gas is compressed, it becomes a liquid, and this is what is carried around in
the tank in the back of your car.


LPG is popular because for the most part, it's cheaper than petrol and it gives a pretty
good gas-mileage. There are three key issues that bother most people considering LPG
conversions. The first is the tank - it takes up a lot of space in your car. For some this
isn't an issue, but for others, they need the space and they don't like the idea of an ugly
pressure tank up on the roof of the car. The second issue is availability. On mainland
Europe this isn't a problem but in most of the rest of the world, you'd be more likely to
win the lottery than just stumble across an LPG filling station. The good news though is
that by flicking the switch on the dashboard, you can go back to regular petrol (as long
as you've got some in the tank) and keep filling up like that until you do come across
another LPG station. The third issue is cost. It costs a fair amount to get an LPG
conversion done. LPG is cheaper and in the long run you'll recover the costs and start
saving money, but that can take 50,000km or more. Another issue which some people
don't like is the idea of the pressurisation system. To fill up an LPG tank, you need to

hook on a pressurised hose to a special filler cap on the outside of the car. It's easy
enough to do, and it holds itself in place whilst you're refuelling, but for some, they just
don't like it. The tank itself will normally be fitted with an automatic fill limiter which looks
a lot like a toilet bowl float. When the tank is nearly full, the float operates a lever which
severely restricts the flow of gas into the tank. This causes enough backpressure for the
pump to realise that it's time to cut off the flow.

Hydrogen has been touted as the Next Big Thing in terms of eco-friendly fuels for our
cars but is it? Hydrogen can be used either in internal-combustion form similar to
burning petrol, or as a fuel source for a fuel cell that generates electricity for electric
drive motors. Currently both cases are a bit sketchy for mainstream transport. Future










The two main reasons are the cost of production and the problems with storing it once
Hydrogen does not exist as a source of energy without refining. It needs to be extracted
from something else in order to be used. This extraction process can be costly and dirty,
resulting in energy losses between 15% and 50% during extraction and compression. In
the case of using hydrocarbons as the source, the resulting hydrogen is more polluting
than petrol or diesel once burned. The more likely method of extracting hydrogen is
using water as the source and electrolysis as the method but that is both more
expensive and slower. Whilst it's true that for the most part the only exhaust from a
hydrogen vehicle is water, the problem is that the energy required and pollutants
released during the processes described above are no more appealling than the





To store refined hydrogen there are two options - compressed or liquified.

Compressed hydrogen occupies three times the volume of petrol for the same energy.
It's normally compressed to something like 12,000psi although doing so is technically
difficult and consumes a considerable amount of energy. Containing that pressure in a
tank is also difficult; a steel tank would weigh one hundred times the weight of the
hydrogen it contained which is impractical. A carbon fibre tank will do the trick but to

contain that pressure, the cost of the tank becomes prohibitive. It's also worth noting
that if a 12,000psi tank of hydrogen ruptured (for example in a collision) it would release











Liquified hydrogen, as with compressed hydrogen, also occupuies three times the
volume of petrol for the same energy. (Oddly, there's more hydrogen in a gallon of petrol
than in a gallon of liquid hydrogen). Unlike the compressed version, tanks to contain
liquid hydrogen are considerably lighter but must be extremely well insulated or actively
cooled. They're like a thermos flask inside another thermos flask so they're quite
delicate. Unfortunately because of its physical properties, hydrogen is one of the
hardest gasses to liquify, resulting in energy losses between 30% and 50% in the


On top of all that, hydrogen molecules are very small and can actually leak through the
walls of a steel tank. Kawasaki performed an experiment in Japan where they drove a
truck full of cooled hydrogen around and lost about 6% of the payload through leakage.
The hydrogen industry in general reckons that an average tank will lose 5% per day
through this process.

Because of all the above, the cost of the vehicles is currently prohibitive for all but the
developers. In 2010 all the development vehicles were over $1,000,000 a piece. There
were only 20 hydrogen fueled cars in America and even less in Europe and Asia. Arnold
Schwarzenegger's Hydrogen Hummer was a one-off $1,200,000 vehicle and wasn't






Assuming you could own a hydrogen vehicle, you then face the lack of infrastructure.
California's much-touted Hydrogen Highway is still a pipedream likely to be mired in

government debate forever because of the cost. Getting hydrogen to the filling stations
is also a problem. A typical petrol tanker can deliver 25 tons of petrol but only 400Kg of
hydrogen because of the tank requirements. So a hydrogen filling station would need 15
times the number of deliveries per day to keep it in business. Consider now the
commensurate cost in fuel consumed and pollution released to deliver all that hydrogen.
So to the consumer, the sticker shock would be extreme. All that expense in refining,










That's assuming you could reach the filling station in the first place. Remember
compressed hydrogen occupies three times the volume of petrol of the same energy, so
you'd need a tank three times the size of a petrol tank to get the same range. The
current demonstrator vehicles have hydrogen tanks that fill most of the trunk and a lot of
the rear passenger space, and can barely squeeze out 100 miles between fill ups. The
GM and Toyota hydrogen demonstrators are always trailered to their demonstrations
simply because they would never get there if they were actually driven. The highest
range to date from a hydrogen vehicle is BMW's hydrogen demonstrator that managed


The fuel cells for hydrogen-electric cars are another problem yet to be overcome. Whilst
they might increase the paltry range further, you need a lot of fuel cells to produce a
usable amount of electricity. Stack enough together and they have the equivalent weight
of the same number of batteries required to make a pure-electric vehicle but, with the
overhead of the pure cost of fuel cells. The fuel cells themselves are expensive to
produce and very fragile. They don't take well to bumps and jolts - the environment
they'd be exposed to in a vehicle - and they require relatively large amounts of relatively








Then there's that whole Hindenburg thing. Sure, the hydrogen didn't cause the fire, but it
fueled it. Imagine now crashing in a vehicle with fragile fuel cells, plumbing lines and
pressurised tanks full of hydrogen. The manufacturers are keen to point out that their
systems are super safe which is a fair comment but what about the 1 in 1000 crash that
will happen every now and then if the vehicles are delivered to the public? What about

the fact that hydrogen can't just be vented to the atmosphere because it's an explosion
Picture credit: BMW Press Kit


Let me start this section with the following statement: it takes more energy to get
hydrogen out of water than you can ever get back by burning hydrogen in an engine.
There's just no way around that energy can't be created or destroyed, but it can be
wasted, usually as heat. Getting hydrogen from electrolysis certainly does that, being
only 50-80% efficient at best. Those are the laws of thermodynamics and conservation
of energy, and no amount of clever marketing, lawsuits, doublespeak or clever words is









You might have come across ads on the web - maybe even ones that Google have fed
to this very page - claiming you can buy a kit to make your own car run on water. These
kits use high school physics to do it relying on simple electrolysis - the process of using
electric current to dissociate water molecules. The resulting gas is oxyhydrogen
(sometimes called Brown's Gas or HHO). It's what is used in some cutting torches. With
a little fuel-line plumbing and some basic handyman skills, you can fit such a device to
any engine, fill the extra tank with water, and be generating hydrogen in no time. The
gas is fed into the combustion chamber along with your normal fuel-air mix and
sometimes you'll see better gas mileage. However, you're using a lot of electricity from
the car's electrical system to generate the hydrogen, increasing the load on the
alternator, meaning more drag on the engine to turn the alternator, meaning a less


And that right there is the divisive argument that splits the car camp in half. Some
people are also so convinced that the internal combustion engine is so efficient that
nothing we can do that would increase power would make up for this reduction, and as
such refuse to even consider the possibilities. They find it difficult to get past the losses
introduced by the electrolysis of water into hydrogen as stated above. But what about
the improved efficiency in the combustion of the liquid fuel this hydrogen can cause?
Look back to the video at the top of this page. During combustion, the fuel burns rather

than explodes in the cylinder, which means that quite a bit of the energy is
released after the piston has already accelerated downwards, or even when it reaches
the bottom. As such, modern internal combustion engines are extremely inefficient at
converting liquid fuels to usable power. This is why the introduction of a gaseous fuel
with a much higher flame front (like hydrogen) can make a difference in fuel economy.
Hydrogen's flame front speed is so high it effectively doesexplode, so the addition of just
a few percent of it in the mix ensures that virtually all of the liquid fuel's energy is
actually turned into power - a short, sharp "bang" (relative to the speed of the regular
ignition) that pushes the piston down with great force, dramatically reducing emissions



So if this glorified high school experiment really works, why hasn't it been taken up by
the car manufacturers? Unfortunately you won't see this kind of radical improvement on
modern vehicles (at least without substantial additional modification) due to fuel
injection and the ECU. You can learn elsewhere on this page that the ECU has maps
set up to ensure the car works in a certain fashion. When you introduce extra oxygen
into the tailpipe (either with the hydrogen when produced by electrolysis, or because of
a more efficient combustion process) the computer thinks that you're running too lean
and hence increases the amount of fuel going into the vehicle - so you end up with more
power, but not necessarily a better fuel consumption. For HHO systems to work in
practice generally requires older carburettor engines and a serious modding of the
whole electrical system (and ECU on more modern vehicles) (see chipping and
remapping). In addition, an efficient hydrogen electrolysis system itself costs a few
hundred dollars to construct. Naturally that means there are plenty of dodgy operators
out there on the internet selling cheap systems that have little or no effect in your
vehicle in the real world. For a true hydrogen generator setup, you need deep pockets.
If you want to read more on this topic, there are papers available for purchase, most
notably the one by researchers at a Turkish university who showed that HHO generated
on-the-fly using a vehicle's own power source, improved efficiency of combustion in
4 carburettor vehicles (very important to note that point) by so much that overall fuel
usage dropped by up to 40%. That paper was published in the International Journal of

Hydrogen Energy in 2000 and is available here: Fuel economy improvement by on

board electrolytic hydrogen production.
Thanks to Peter K Campbell for pointing me in the right direction on this topic.


In August 2009, the first complaint against a company promoting a consumer-level HHO
system as being able to make your engine run further, cooler, and for less cost was filed
and upheld in England. Their ad was deemed to be misleading on 4 counts (and it
claimed that their system could turn your car into a petrol-hydrogen hybrid). The full text
of the adjudication should be searchable on the ASA website: Waterboost Hydrogen
Fuel System complaint.



No article on water powered cars would be complete without mentioning Stan Meyer or
any number of other people who claim to have made cars run on water alone. Stan
Meyer's idea was more unique than most - rather than generating hydrogen and storing
it to be burned later, he claimed his system was a water splitter that fractured water into
hydrogen and oxygen instantaneously to be burned. The water never got hot and he
claimed it wasn't pure electrolysis because he was using very low current. He spent a
lot of time selling the idea and getting patents for a system of electronics and oscillating
radio frequencies coupled to his separation chamber. It sounded too good to be true.
When he started telling the press that he'd been offered $1bn by the Arabs to sit on his
invention, and that he was getting 1700% more energy out than he was putting in, it
looked more and more like a scam. I believe Meyer was eventually convicted of fraud
for all this in 1996 and then died in mysterious circumstances in 1998. Conspiracy












The problem is that you have to remember other huge 'scientific breakthroughs' in this

area, like like Martin Fleischmann and Stanley Pons claiming to have solved cold fusion.
Something else that seemed to be too good to be true and in the end turned out to be
just that. I've got to stick to current scientific thinking on this for the time being, that
being the law of conservation of energy again. Until someone can publicly demonstrate
such a system that anyone can reproduce, and reproduce successfully and frequently,
Meyer's water fracture device will remain a mystery.




Gas-mileage is the quickest indicator of how efficient a car is in terms of fuel used for
distance driven. Engine size and power, driving conditions, weather (wind especially)
and vehicle weight all affect mpg. Measuring gas-mileage is really easy but it's
surprising how many people don't know how to do it. Basically, zero your trip counter
next time you fill up, then drive as normal. When you fill up again, let the petrol pump fill
to the auto-cutoff point and then make a note of the trip meter reading. Gas mileage is
the number of miles on your trip meter divided by the number of gallons the petrol pump
put into your tank. You'd be surprised the number of people who use the manufacturer
figure for the size of the tank in that calculation instead of the amount of petrol actually


In England and Europe, pumps deliver in litres, so in the UK it's miles-per-litre, although

most advertising still uses miles per gallon. It's worth noting that an English gallon is 1.2
US gallons. So when you see a car in England that advertises 40mpg, it's the equivalent





In the rest of Europe it's normally advertised as litres per 100 km. So for example,
28mpg (UK) is about 10litres/100km. Often this is short-handed to 1-in-10, meaning 1
litre used in 10km of driving.

The American EPA (Environmental Protection Agency) rates all cars sold in America
with gas-mileage figures, advertised as EPA-rated mpg figures on the new car sticker.
It's one of the things car manufacturers rely on to sell their vehicle, especially with
today's high fuel prices. Not many people understand this, so I'm here to take some of
that confusion away and tell you what the EPA figures really mean.

In the windows of every new car in an American showroom you'll see an EPA
information sticker, an older example of which is seen on the right (see below for the
latest revisions). There's a load of technical blurb on there to advertise the vehicle, but
on the older stickers there were two big numbers; the EPA-certified fuel information
figures. In this case 20mpg city and 28mpg highway. So you'd see these figures and
you get into your head a rough idea of how often you'd be filling up. The problem is that

were very rough


In the 1980s, the EPA conducted a study on their results vs. the real world, and
discovered most drivers got significantly lower mpg figures than the EPA predicted. As a
result, EPA estimates on the new car labels were dropped by 10% for city and 22% for
highway from their actual results. In 2006 they dropped another 8% from those figures










Even that isn't the end of the story though. What you really need to know is how the

EPA came up with their figures in the first place. Before you carry on, you might want to
put down any drinks or breakables because I know what your reaction will be at the end
of this. Ready?


Congress and car company lobbyists required the EPA to measure mpg figures using
the following simulated real world conditions in a lab. That's right - EPA testing happens
on a dyno in a lab, not on the open road.

Average highway speed : 49mph

Maximum highway speed : 60mph

Temperature : 75F

No rapid acceleration

No air conditioning

No passengers

No rough roads

No hills

No wind

No low tyre pressures

No ethanol in gas

The first problem is the last point : no ethanol in gas. In America, it's almost
impossible to buy zero-ethanol petrol - it's all E-10 (see E10 elsewhere) so you're
already going to be down 5% on the EPA figures even if you could meet all the other
requirements. And who drives like this? 49mph on the motorway? Maximum speed
60mph? Perhaps when the model-T Ford was the Big Thing, these were valid speeds,
but nowadays (and by 'nowadays' I mean 'in the last 6 decades') motorway speeds are
typically 70mph maxing out at 90mph (if you're in Europe anyway). What about the rest
of it - no hills, no passengers, no rough roads? Have the EPA actually driven a vehicle in




As a rough benchmark, driving at 65mph instead of 49mph will decrease mpg by 20%.
Driving at 75mph will take another 25% off that. In short, you could pay very little
attention to the EPA estimates because they were, for the most part, completely







They say a picture speaks a thousand words. I don't have a picture for you but I do have
a table. This is a quick reference for you to show all the various figures that went into
the EPA estimates, the advertising and what you should expect in the real world. It's
based on the Mercedes CLK320 sticker shown above. The blue row shows what you'd
see on the EPA sticker in the window of the car. The red shows the figure you'd see on
TV (eternal optimism) and the green row shows what you should expect when you
drove this car in the real world.

should expect












































Yes, apart from for one thing. Too many people tried to perpetuate the myth that the
EPA values were intended to suggest what a driver could expect to get in the real world.
As I've shown in mind-numbing detail above, this was simply not the case. Instead, they
were best used as a comparison between one vehicle and another, ie if one vehicle was
EPA-rated at 20mpg and another at 25mpg, then you could pretty safely conclude that
the latter gets 25% better mileage than the former, and nothing else. For a good read on
this subject see the Patrick Bedard column in the Feb 2006 issue of Car and Driver


Skip forward to 2008 and finally the EPA changed the way they measured mpg figures.
The big changes are:

The new tests start with the car at 20F. The old tests started at 75F. Why
the change? A cold vehicle uses more energy than a warm one. Cold
temperatures are especially hard on the batteries that power hybrids, so
hybrid mpg ratings dropped.

The new tests use a maximum highway speed of 80mph instead of 60mph. At
that speed more engine work is done to overcome drag than to actually keep
the vehicle moving at speed.

The new test includes hard acceleration. The old test used gentle
acceleration. This one also affects hybrids because hard acceleration relies
entirely on the regular petrol engine and uses none of the electric hybrid

The new test now assumes air conditioning is used 13% of the time. The old
test didn't use air conditioning at all. 13% is the mean average for all major
cities across all times of year for the US.

But even with these new standards, the EPA test still takes no account of hills or wind.
This has the effect of skewing the test in favour of larger vehicles like SUVs. If hills and
wind were included, the results would be radically different - larger, heavier vehicles use
more energy to travel into wind and up hills, ie. more fuel. The 2008 EPA estimates
would be far more useful if they included these factors. Because they don't the overall










For example. Assume a car gets 40mpg without the hills and wind test, and 38mpg with.
Now imagine an SUV doing the same tests gets 24mpg without the hills and wind, and
19mpg with. For the sake of comparison the car's 40mpg vs. the SUV's 24mpg doesn't
look as bad as the car's 38mpg vs. the SUV's 19mpg. But I digress.
So what's the outcome of this? Well first of all, the new figures are definitely much
closer to what you or I could get from a real car in the real world and this can only be
good news. Hybrids still suffer a hit of about 30% loss of mpg for highway and 20% for
city. Regular non-hybrids will drop about 12% for highway and 8% for city.
So it's a lot closer to the real world than it was, but is it close enough or should we still
just use the EPA figures as an arbitrary comparison of vehicle mpg as measured against

an arbitrary scale? Time will tell, but it could be argued that the major car manufacturers
and oil companies lobbied for this change to take the shine off hybrid vehicles - after all,
they're the ones that suffer the most with the new rating.



Time marches ever forwards and so do the EPA. In 2011 they introduced the latest
version of their informative window stickers. In addition to the baseline mpg, they now
contain further breakdowns of information such as the number of gallons per 100 miles,
bringing them in-line with the sort of figures Europeans are used to seeing - litres per
100km. There's also smog and greenhouse gas ratings, again very similar to the
European ratings for grams of CO 2 per km. On the right there is a 'savings' figure that
compares the sticker of the car you're looking at to an 'average' car. The details of the
'average' car are stated in the white text in the black box underneath: it gets 22mpg and
costs $12,600 in fuel over 5 years assuming 15,000 miles a year at $3.70/gallon for
petrol. This allows you, the consumer, to do some mental maths based on fluctuations









Finally there's a QR code that you can scan with a mobile device which will take you to
a site with more information about the vehicle in question, and an annual fuel cost
estimate. All in all, a nice revision to the label, designed to make it much more obvious
just how much of a petrol-hog that new SUV that you're eyeing up really is. The
information is far more clearly presented and there's a lot less ambiguity about
"between" figures.
New stickers for the latest generation of cars. In addition to the overhaul of the petrol
sticker, the EPA introduced a standardised sticker for E85, diesel, LPG (CNG), hybrid,
plugin hybrid, hydrogen and full electric vehicles at the same time. The full set of 2011

EPA stickers can be downloaded here as a PDF or you can see them on the EPA's fuel
economy website
If you're curious about what others are getting in the real world, there's three websites





the site mentioned above is the US government's own website where



and which










If you've read through all the history of the EPA above, it'll come as no surprise to learn
that car manufacturers were able to write software into their engine management
systems that could guess when the car was being tested in a lab. Volkswagen were the
first to be found out when it turned out some of their diesel engines emitted 30 times the
amount of NOx when driven on the road as they did when they were in lab conditions.
But it wasn't just VW. In the days and weeks following the VW revelation, companies
starting doing real-world tests both in the US and in Europe. Cars produced by Honda,
Mazda, Mitsubishi and Mercedes-Benz were found to emit more NOx than was
previously recorded, in official testing by a company called Emissions Analytics. They
test. Yet all the cars tested supposedly passed EUs official lab-based NEDC (New







On top of the Emissions Analytics tests, ADAC, the largest automobile club in Europe,
also tested cars on-road, and it too found that models produced by Renault, Nissan,





In November 2015, the EPA finally buckled and indicated that it would test all new cars
on actual roads instead of in lab conditions. The EPA have been doing these sorts of

roads tests for decades on trucks - they've just never done them on cars. They are not
the only ones changing the way they do emissions testing. European bodies are looking
at real-world testing too although their system isn't due to hit the roads (pun intended)


The sting in the tail of this story is the get-out clause though. The EPA say that the lab
tests will remain as the 'benchmark' and that road tests will only be carried out to try to
find defeat devices. So close and yet so far. What they need to do, of course, is get rid
of the lab tests completely and road-test all the vehicles.


American and European cars both report gas mileage and carbon emissions in their
advertising now. The same is likely true of most other countries. Calculating your own
carbon emissions from a given gas mileage figure isn't particularly complicated though.
When burned, 1 US Gallon of petrol produces 8.7kg of CO 2 and 1 UK Gallon of petrol
produces 10.4kg of CO2. European ratings are grams per km whilst US ratings are






















CO2 /


There can be some variation in this basic calculation, for example vehicles with
automatic stop-start engines (that stop when the car isn't moving, and auto-start when
you take your foot off the brake (automatic) or put a foot on the clutch (manual) can
have lower ratings because the engine isn't burning fuel when the car is stopped in
This explains why in many countries, the vehicle tax is levied on CO 2 emissions. The
more fuel-thirsty the car, the higher the emissions and thus the more tax you pay.


Here's a question for you : why do identical cars, made by the same manufacturer, get
less mpg in America than they do in Europe? I know a lot of you are reading this now

thinking"Aha - that's because an imperial gallon is larger than a US gallon". Yes, but
even adjusted for that, it's still true. Take for example the 2008 Honda Civic 1.8 i-VTEC
5-door manual. It's a good example of an average family saloon/sedan car. The trim
levels are identical, as are the engine and gearbox, and power and torque figures.
Oddly, the European cars weigh more for the same trim level. The following are all
converted to US gallons:











Peak power

Peak torque


Another example saloon / sedan car. The 2008 Volvo S40 2.4i. Again - same trim level,
engine and gearbox. Once again, the European car weighs more:











Peak power

Peak torque



Typically, the EU mpg test is now also done on a rolling road and takes less than 20
minutes (1180 seconds if you must know):

Urban (city) : cold engine, accelerations, steady speeds and decelerations.

The average speed is 12mph representative of city commute speeds (very
harsh on mpg) and the distance is 4.5 miles.

Extra-Urban (highway) : warm engine, accelerations, steady speeds (50% of

the test) and decelerations. Max speed is 75mph, average speed is 39mph,
distance is 4.3 miles.

So why the huge difference? You'd expect the figures to be within a couple of percent of
each other, but they're clearly not. In fact with the EU cars weighing more you'd expect
their figures to be worse. I've heard from engineers who work on economy testing for
the major car manufacturers and the same theme always comes out - driving the same
car with the same engine through the European (NEDC) and American (EPA Combo)

tests can often yield as much as 20mpg difference between the cycles. Most of the
difference comes from the cycle itself. The EPA cycle has much more violent
accelerations, more harsh braking and is very transient, hardly any of the cycle has
constant speed cruising. Some of the accelerations in the EPA cycle require near WOT
(wide open throttle) on an engine with 170Nm of torque. The EU cycle on the other
hand hand has extremely gentle accelerations and all the cruises are at a constant






There is also a different calibration between the US and EU engines and the US
engines have a higher loading of precious metals in the cat to soak up more emissions,
but these changes will not make a large MPG difference. There is a small amount of
enrichment and ignition retard on cold start but once the cat is up to temperature, which
happens quicker on the US cycle than EU, lambda 1.0 is always aimed for.
If you'd like to weigh in on this debate (ie, not Big Oil conspiracy), drop me a line. Other
suggestions so far:
Different Petrol Octane/Composition
Good idea but the calorific value of low-octane fuel is pretty much the same
as high-octane.
European and Japanese cars are designed for higher-octane fuels (higher
Might be true but most European vehicles run Euro95 petrol, which is the
equivalent of American (R+M)/2 89 octane. Plus, the engine specs are
identical - same compression ratio, same torque, same horsepower.
Different Oil Type/Viscosity used
Different 'Map' on the ECU for different emissions laws
Tyres - different rolling resistance?
For my money, the best one is the different engine map in the ECU for emission laws,
although emission laws are stricter in a lot of parts of Europe than they are in the US
which you'd think would make the mpg figures worse.


The Transatlantic Conundrum has generated more buzz on my email than Lindsay
Lohan getting out of a limo with no knickers on. Some of the ideas are quite sensible.
Some are way out in left field. Scott Brereton emailed me with one of the more


Like yourself I suspect that its related to engine maps, and I think it may be a quite






After doing some research it turns out that in the UK emissions standards measure
carbon monoxide(CO), hydrocarbons(HC) and lambda. Looking at the regulations for
the US, as far as I can tell CO, HC and nitrogen oxides(NOx) are measured. Due to
differing test methodologies, I can't make a direct comparison between the CO and HC











Since NOx is formed under lean combustion conditions, it might be the case that fuel
maps in the US are tuned richer than in the UK to minimise NOx production, this will
lead to higher CO and HC but if we suppose that the CO and HC standards required in
the US are more relaxed then those in the UK this would not be a problem. This richer
fuel map might go some way to explaining the differing fuel consumption figures seen
on either side of the Atlantic.
Reader Blaine writes: It's based in the US EPA's pre-occupation with NOx levels. Recall
that European smog police pay little attention to NOx, and concentrate on HC, CO, and
CO2. Also recall that NOx formation occurs at extremely high temps (2700+ degrees?).
US emissions systems use a catalyst to bring down NOx levels. The problem with this
catalyst is that it doesn't work at "low" temperatures - even those typically found in
exhaust systems. US emissions systems make this catalyst work by dumping raw fuel
(or running an exceedingly rich mixture) into the exhaust stream, to burn in this NOx
catalyst to keep it hot enough to perform the reduction reaction to eliminate/reduce NOx









Tuners in the US, on OBD-II vehicles, have figured out that eliminating this fuel
enrichment can result in a fairly substantial gain in fuel economy, especially when
combined with fuel-map and timing tweaks designed to increase fuel economy in other

It's the "good-fast-cheap" triangle: "good, fast, cheap; pick two". Automotive engines are
governed by a similar triangle: power, economy, emissions. European ECM's can pick
two; American ECM's can only pick one, by federal mandate - emissions (every other
consideration - power, fuel economy, driveability, etc - comes in as a distant second
place). By going to a more european style of ECM mapping, American tuners can work
some pretty amazing feats, and still maintaining emissions levels.
Thank you.


There are two values that are generally published for an engine which tell you how
strong the engine is, and they are torque and bhp - brake horsepower.
Torque is a measure of the twisting power of the engine. Torque is directly related to
acceleration; the more torque, the quicker you'll get up to speed. Horsepower is what
will keep you at speed once you've accelerated and is directly related to the torque
readings. So a high-torque, low-horsepower engine will accelerate well but be unable to
maintain a high speed. Similarly, a low-torque, high-horsepower engine will not have
much acceleration but will be able to go at a fair clout once it's going.


In England and the US, horsepower means Imperial horsepower. The technical
definition of this is "the power a horse exerts in moving 550 pounds of cargo a distance
of one foot in one second." This calculation can include just the horse and its own
weight. Horsepower can be defined many ways. One horsepower equals 746 watts, and
as such, proper SI units are normally used instead. The term horsepower is more a





The term brake horsepower came about because of an apparatus called a water brake
that can be used to measure horsepower. Today all manner of brakes are used from
hydraulic to electrical. They all perform the same function though, and that is to load up
the engine and measure the torque with strain gauges. BHP figures can be calculated

from the measured torque values to determine the power of the engine at any given
rotation. If bhp figures are published without any other data, you've got to assume
they're measured at the crank. The problem is that once you add on clutches, flywheels,
gears, driveshafts and all the other components between the engine and the wheels,
the actual power at the wheel is often noticably less. So sometimes you'll see bhp
figures noted as "at the wheel". This means the torque has been measured with the
wheel being turned through all the above connections to give a more accurate power
In the bad old days, bhp readings would be taken with the engine running in "optimum"
condition, ie. with no oil or water pumps attached, direct cold-air injection, super-cooled
coolant, no exhaust back pressure or catalytic converters and so on and so forth.
Fortunately today there are standards that have to be maintained. Most recently, in
2005 the SAE made some changes to the test procedures to eliminate some of the
'slop' in power measurements, and for car manufacturers to be able to make valid SAEcertified bhp claims, their tests must now be monitored by SAE representatives. The
results of this change were interesting if only because the bhp values for engines
changed without the engines themselves being modified. For example the Honda
Element engine remained exactly the same, but its bhp rating dropped from 170bhp to







It's worth pointing out that whilst the rest of the world used bhp or kW (kilowatts) to
publish power figures for engines, in America they typically used to use hp(SAE)
instead, meaning the rated power of the engine as installed in the vehicle, ie including
all the engine components, pumps, drivetrain etc. Having said that, even today, all
hp(SAE) or SAE-certified bhp figures are taken at the flywheel and thus still don't really
tell you how much power is getting to the wheels. The only way to know that is to put
your car on a dynomometer (a dyno) and get true at-the-wheel readings.


The formula to calculate bhp from a given torque reading is as follows:

Pi is obviously 3.14159, the torque value should be in pounds-feet and RPS is

revolutions per second - RPM/60. So do a little elementary maths and you can
massively simplify the formula down to this:

The formula to calculate regular horsepower from a given torque reading is as follows:

Pi is still 3.14159, but this time the torque value should be in newton-metres. Again,
simplified the formula becomes:


A little footnote here : assuming all other factors are the same - same octane of petrol,
same filters, same weight of vehicle etc., you lose about 3% of your engine's
horsepower for every 300m / 1000ft above sea level that you drive. Worth knowing next
time you go carving up the Stelvio Pass in Italy. At 9000ft, you're a full 27% down on
engine power compared to sea level.


Not satisfied with the power your lump is giving you? There are solutions, and of course
they depend almost entirely on how deep your pockets are. Almost any engine in any
car can be adjusted, tweaked, modified and tuned to give more power. The more money
you have to spend, the quicker your car will go.
Customizing your engine helps push your vehicle beyond its limits. You need only
reliable, premium quality performance parts to build a custom engine. If youre looking
for a trustworthy place to start shopping online, CARiD is that place. Dont wait another
moment and choose from the great variety of performance engine parts for cars &

trucks at Besides quality and reliable service, the parts are offered at fairly
competitive prices.


About the simplest and easiest modification to most modern engines is called chipping.
When it was first introducted, it involved removing the chip that contains the ignition
map from the engine management system, and replacing it with one with a modified
map. The new chip was designed for better torque, increased power, or just smoothing
out flat spots in the power or torque curve of the engine. Nowadays, chipping should be
more accurately referred to as Remapping. Gone are the days when you could just a
whip a chip out of the ECU. That's so 90's. Today, when you cough up your hard earned
cash at a tuner house, they'll plug a laptop in to your engine diagnostics port and upload
new software which changes all manner of things from turbo control, fuelling maps,
engine load and torque limiters all the way up to throttle-by-wire response (where
applicable). They write their own software after studying (read: reverse-engineering) the
car's ECU parameters using a rolling road and a laptop hooked to the diagnostics port.
From there they can re-write the engine management software to do what they want
rather than what the manufacturer wanted. Petrol cars respond well to remapping, but
for some reason, diesels respond much better, especially VW diesels. It's not
uncommon for a remapped VW ECU to generate 30% more power and torque after it's
been breathed on. Add a turbo to that and you can see even wilder gains. Realistically

though you ought to expect around a 5-7% increase in horsepower from a chip or
remapping operation.
Picture credit: Superchips

Getting your car remapped will take a couple of hours if you go to a reputable tuner
house. They'll pop your steed on a rolling road and hook it up to a dyno to get it right. In
some cases, you can get a remapping module which sits in-line with the factory-fitted
ECU, and then you can download or create your own mappings and upload them to the
unit yourself.Power Commander are one of the more notable manufacturers of this sort









But how can this work? More torque and horsepower without changing anything in the
engine? Well bear in mind that from the factory, most cars are sold to be more economy
and comfort biased than performance biased. Most engines have a lot of slack for
generating more power or torque, it's just a question of having the expertise to find it. A
lot of work does go into these chips and remapping programs which is why they can
cost upwards of $400 for a quality branded product. Whilst it might only be 5% by the
numbers, you likely will notice some of the other effects, like smoother acceleration due
to flat-spots in the torque curve being ironed out. Everyone I know who has chipped
their vehicles has enjoyed the modification, and relative to what you can do to a car, it's




Something to be aware of : chipping or remapping your car will likely void any warranty
you have on it because you're messing with the onboard computer which in turn is going
to adjust the running of the engine to be "different" from factory spec. And by "different",
the manufacturer normally means "no warranty". Having said that, some tuner houses
have perfected their software to the point where manufacturers own diagnostics
computers can't tell that an engine has been remapped. In that case it becomes a moral
issue for you - is it invalidating the warranty if they can't tell?


Some manufacturers do bolt-on upgrades to their vehicles. For example Dodge

introduced a bolt-on upgrade to their SRT-4 Neon in 2003. The kit comes with a
modified engine management computer (the whole thing, not just the chip) along with
high-flow fuel injectors. The nice thing about doing a factory upgrade is that you know
for 100% certain that the parts are going to fit, and are going to work together with each
other as well as your car. Since that original upgrade, Mopar have produced a veritable
treasure trove of bolt-on upgrades for Dodge vehicles, and with most of them you can
maintain some of the factory warranty. Factory upgrades are starting to include chips
too now, competing with the aftermarket chipping business. That was a move to counter
the warranty problems that some kits caused. Either way, factory bolt-ons are A Good
Thing. If you want improved performance but are nervous about third-party products,
getting something direct from Dodge, Ford, Toyota, Mazda etc. is a good way to go.

Picture credit: Dodge


Think of your engine as a breathing machine. It needs to breathe in fuel and air, and it
needs to breath out exhaust gasses. Anything that gets in the way of that process is

going to impede its ability to breathe. In reality of course, there are plenty of things in
the way from air filters and flow sensors in the intake system, to catalysers and bizarre
kinks and curves in the exhaust system. By eliminating or reducing these constrictions,
you can allow your engine to breathe more easily. Sort of like Nyquil or NightNurse for
an engine. By far the easiest and cheapest thing to start with is the air filter. From the
factory, air filters are designed to be a compromise of filtering the guck out whilst letting
the air through. Aftermarket manufacturers such as K&N and Jamex have been making
high-flow air filters for years. The design of the filters is slightly different and they allow
more air to pass through the filter whilst still stopping the majority of harmful particles.
Again, like all these things, the claims of increased power can be hugely exaggerated.
In truth, simply changing the air filter will probably add another 2 or 3hp to your engine.
More air going in more easily means the engine management system will adjust the
fuelling accordingly and you'll get a better fuel-air charge in the cylinder, resulting in a




Exaggerating the claims. As with most bolt-on performance parts, the box
will always be optimistic with their claims of power increase. A reader sent me a link to
this YouTube video testing a VW Golf Mk3, 1.8 litre engine with a stock OEM air filter
versus a conical high-flow filter. The filter manufacturer makes the claim that their
product will increase the power of your engine by 10%. In this particular test, the
horsepower went from 91.9hp with the OEM filter up to 93.6hp with the high-flow filter a difference of 1.7hp or 1.8%. This is basically an inconclusive result given the
measurement and fault tolerance of a rolling-road dyno which is normally in the 3%-5%
range. It's certainly not the 10% promised on the box and is closer the 2hp-3hp I would
expect from such a filter.

: High flow air filter test.


Moving on a step from simply changing the filter, you can then start looking at intake
upgrade kits, also known as cold air intake or induction kits (manufactured by
companies such as Injenand AEM). The basic idea with these is to make the passage
from the filter to the engine less convoluted. When air is forced to go around corners, it
causes turbulence which slows down the flow. By trying to make the intake pipes
smoother and straighter, the idea is to give the air more chance to get to the engine and
less chance of being screwed up in corners with turbulence. Cold-air kits normally
remove the factory airbox from the car and poke the air intake into one of the front
wings or right up front. The air in your engine bay is hot - really hot - and hot air is not
conducive to good combustion. By routing the intake to somewhere where it isn't going
to be sucking hot air from under the hood, you get cooler air going into your engine.
Because cooler air is denser, you can get a better fuel-air charge into the cylinder than
you can by simply changing the stock air filter. Cold-air intake kits can add another 3 or
4hp of raw power to the engine but more often than not, you'll notice an increase in
torque lower down the rev range too. The photo to the right was snaffled from a tuning
forum but it shows a nice example of a cold-air intake kit once fitted.
Picture credits: K&N, AEM


Cold air induction kits work pretty well but you need to do your homework first. A lot of
cars have throttle body heaters, whereby coolant from the engine is circulated around

the throttle body casing. The idea is to warm up the throttle body to prevent icing in cold
weather. The problem is that these systems are hard-wired and don't take account of
external air temperature, so even in the heat of summer, hot coolant is routed around
the throttle body. This is a problem for CAI kits because you've gone to all the trouble of
putting a nice kit in to suck cooler air into the engine, but at the final hurdle it runs
through a 75C throttle body which heats it up again, negating the whole point of the
CAI kit in the first place. The solution to this is a throttle body heater bypass, which
essentially involves pulling the coolant hoses off either side of the throttle body and
patching them together with a length of copper pipe and two hose clamps. When you do
this, the throttle body stays at ambient temperature and the CAI kit gets a chance to do
its job. The only downside to this is if you live in a cold, humid climate, you might suffer
from icing in the winter. But hey - if you do, reconnect the coolant hoses for the winter...


So you've eased the flow of air into the engine, what about the exhaust? Your typical
exhaust setup has kinks and bends in it to make it fit the engine compartment and under
the car. In some cases these can be smoothed and straightened out somewhat but
more often than not, the exhaust has to take the same route as stock. In this case, the
best option is for a larger exhaust. Larger diameter exhaust pipes can accommodate
more gas flowing through them and hence provide less constriction to the engine when
it is blowing out exhaust gasses. Typically a factory exhaust will have two constriction
points. There will likely be the catalyser at the front (where the exhaust is hottest and
makes the catalyser work best) and a muffler can at the back. High-flow cat-back
exhaust systems are so-called because the start at the output of the catalyser and

replace all the exhaust from there back. They will have larger diameter pipes and a
high-flow muffler at the end. Alternatively you can get header-back exhausts which
replace everything from the exhaust header to the back, typically removing the catalyser
in the process. These are sometimes affectionately referred to as catless or no-kitty
Adding a sports exhaust system like this can add another 4 to 5hp but you need to
make sure you get one which is made by a well respected manufacturer with a good
warranty. Because of the change in back-pressure, these exhausts can cause erratic
engine problems on some cars that rely on a certain amount of back-pressure to
operate properly. Note: back-pressure is the natural resistance to gas-flow in a normal
The picture here shows an example of a typical factory-fit exhaust on the left versus a
high-flow header-back exhaust on the right.


Picture credit: Pulstar

There's a little known method of squeezing some more efficiency out of your engine,
known as spark plug keying. The idea is simple - expose the spark to the incoming fuelair charge. If the grounding strap on the bottom of the spark plug faces the incoming
fuel-air charge, the spark is effectively 'shielded' from the mixture. The image on the left
shows a Schlieren photo of a spark emanating from a spark plug tip. You can see the
area behind the ground strap doesn't have as much exposure to the spark. Now I know
a spark is a spark, and any spark in a fuel-air environment is going to make it burn, but
if the spark is facing the intake valves, then there's nothing obstructing the mixture from

getting at it. In thousandths of a second, this does actually make a difference to your


The problem is that when you screw a spark plug into your cylinder head, you have no
idea which way the electrode gap is pointing. For best efficiency, it needs to be facing
the intake valves or ports as I mentioned above. The solution is pretty simple. Before
you install the spark plug, use a marker pen to put a mark on the insulator that aligns
with the electrode gap at the bottom of the plug. It's important to use a marker pen and
not a pencil because pencil lead is graphite, which conducts electricity. You don't want









Once the plug is marked, screw it into the cylinder

head remembering that you'll need a quarter turn to snug it up. If the mark on the
insulator is a quarter turn from facing the intake valves when the spark plug is fingertight, you'll know once it's snugged down that the gap will be facing the intake valves




If the mark isn't in the right place, don't go over tightening the spark plug to force it into
position! You can get keying kits which are basically replacement crush washers that
are slightly thicker or thinner than the standard one. They come in one-third, onequarter and one-half sizes, meaning that they can affect how far you can screw the
spark plug in by the matching amount. So if you finger-tighten the spark plug and the
mark on the insulator is facing totally the wrong way, once it's snugged down it will still
be a quarter turn away from the intake valves. By changing the crush washer to a
quarter-turn crush washer, you'll be able to get an extra quarter turn before the spark
plug is tight, which will solve your problem and the electrode gap will now be facing the
right way.


If you've changed your intake system and your exhaust system, there is one other place
full of nooks and crannies where intake charges and exhaust gasses can get
discombobulated, and that is the internal passageways in the cylinder head (shown in
red in the picture here). Most heads are cast from dies, a process where molten metal is
poured into a sand or ceramic die to create the required shapes. Small bits of swarf and
casting anomalies are normally dealt with where they are visible but it is possible that
the airways in the head still have some rough surfaces. Gas-flowing a cylinder head
involves taking it off the car and refining those airways with one of two methods. The
cheaper and more basic method involves manual polishing using different grades of
sanding and polishing tools. These are manually run around the passages, smoothing
off rough edges and polishing the airways to a chrome-like finish. The more expensive
method involves hooking the cylinder head up to a machine which pumps superheated
plasma through the airways, which literally melts a thin layer of them off based on the
actual flow of the plasma itself (which mimics airflow). Both methods achieve the same
results - teflon-smooth air passages for the intake charge and exhaust gasses. Getting
gas-flowed heads can add another 11 to 12hp to the engine, plus if you want to put a
large-bore exhaust on the car, then the gas flow method can widen the exhaust ports to
Rough or smooth? There's an ongoing debate about whether or not polished intakes
actually are the best thing for airflow. Some people go with the 'smooth is best' whilst
some reckon that a rough intake is better. Chroming or polishing the intakes gives a
smooth surface which impedes the airflow less, whilst the rough surface generates
turbulent surface 'bubbles' which move slowly, but allow the air on top to skip over them
quickly. The point of polished intakes isn't so much to give a smooth surface to the

actual intake as it is to make sure there are no kinks, metal seams or casting burrs that
will act as a restriction to the airflow.


You can squeeze even more power out of your lump if you change the cam or cams at
the top of the engine. Lightweight cams weigh less (duh!) and so impose less
mechanical drag on the internal parts of the engine. Less weight and less drag mean
less power lost to friction and driving the cams themselves. High-lift cams take a slightly
different approach. If you look at the 4 stroke diagram way back at the top of the page,
you'll see the lobes on the cams are what force the valves to open. The lobes on a
normal cam are egg-shaped. On a high-lift cam, they are more rounded-rectangular
shapes. The result is that as the lobe spins round, it begins to open the valve sooner,
keeps it open longer and then closes it later. The principal is simple : if the valve is open
longer, the engine can suck more fuel-air mix in before the combustion cycle. The
picture here shows an (exaggerated) example of high-lift cams. The camshaft on the
right shows a regular lobe shape and the one on the left shows how a high-lift lobe
might look. The difference is subtle but the one on the left would result in the valve
opening sooner, staying open longer and closing later.
If I'm starting to sound like a scratched record, then you've noticed the overriding theme
of getting more power - getting more fuel-air mix into your cylinders by any method
possible. As they say on naff informercials But wait - there's more! Let the scratched
record continue......


As weird as this sounds, you can actually make most engines perform better in some
circumstances by injecting water directly into the fuel-air mixture. It sounds
counterintuitive but the principal is really simple. Vapourising water into the fuel-air mix
will cause the air to become denser and cooler. Cool, dense air results in a better
charge into the cylinder head, which results in a more powerful burn during combustion.
This naturally results in more power. Water injection is used on WRC (World Rally
Championship) cars but is detrimental to power when the charge air temperature is
below 42C and boost pressure is below 0.6BAR. Because of this a triggering / shut off
system is used on some WRC cars that triggers on at 42C and shuts back off at 38C,
only triggering when boost is above 0.6BAR.

Intercooling takes a slightly different poke at the "cooling the fuel-air mix" equation.
Intercoolers are normally found on turbo engines and are designed so that atmospheric
air flowing around the outside of them cools the air charge from the turbo inside them.
The cooler air for the outside can be direct- or indirect-flow. Direct flow designs have the
intercooler mounted at the front of the car in the airflow. Indirect-flow units are mounted
somewhere in the engine bay with hoses and scoops to get the air to them.

An enhancement to standard intercooling is water-assisted intercooling as found on the
Subaru WRX STi. Rather than using water injection into the fuel-air charge, it has an
intercooler water spray system that sprays water onto the outside of the intercooler to
improve the efficiency of the charge air cooling. The auto version found on the top spec
models is ECU-controlled to give 5 second bursts of cooling water when boost is high
enough to warrant it. The lower spec versions have a manual switch on the dash that
triggers a 5 second burst every time you press the button.

Charge coolers are a more sophisticated derivative of water-assisted intercooling.
Rather than just spraying water around the outside of the intercooler, they have a water
jacket around the core with an external water pump and independent radiator. The
pump constantly circulates water through the chargecooler jacket and then out to the
radiator, keeping the whole unit cool. Chargecoolers work well until the engine starts
being more demanding about power - once they get to a certain point, they're
overwhelmed by the amount of air being drawn into the engine.


Rather than injecting water directly into the air flow, or cooling the body of the
chargecooler or intercooler, refrigerated systems force the incoming air over a radiatorlike device to cool the air. This heat exchanger is filled with a compressed-gas based
and works just like your refrigerator at home. The gas is compressed into a liquid then
piped into the heat exchanger. As it turns back into gas, it cools down and hence cools
the air flowing over the heat exchanger. The now-gaseous coolant is re-compressed
outside the intercooler where it gives off the heat via a secondary radiator positioned in
the airflow.
Picture credit: Nitrous Oxide Systems


Anyone in the street racing scene, or anyone who sawThe Fast and the furious will be
familiar with nitrous oxide (N 2O), also known by one of the trademarks NoS (Nitrous

Oxide Systems - a division of Holley). NoS takes the idea of cooling the inlet charge to
extremes. These systems involve an injector unit in the intake system connected via a
solenoid release valve to a tank of compressed NoS somewhere else in the car usually in the boot or trunk. When you push the 'boost' button, the solenoid opens and
liquid NoS rushes to the injector. As it vapourises into a gas, it absorbs a phenomenal
amount of heat, resulting in a supercooled airflow. At the same time, because it absorbs
heat, it splits into oxygen and nitrogen. The normal oxygen content of air is around 20%.
With NoS that is pushed up to about 33%. Adding that much oxygen to the intake
means you need to also add more fuel otherwise the fuel-air ratio is way off so all NoS
kits come with a fuel solenoid and injector too. When you apply the boost, NoS and fuel
are forced into a y-nozzle in the airflow just in front of the throttle body. As well as all
that plumbing, NoS kits can be enhanced with blow-off valves. If you're sitting at the
lights on a drag strip with the NoS system pressurised, it will slowly be evaporating in
the system and gaseous NoS is nowhere near as dense as the liquid, compressed form.
To get the gaseous stuff out of the line, the blow-off valve is opened by a manual switch
in the car to let it out and keep the lines full of liquid NoS. So now you have a highly
oxygenated fuel-air mix which is supercooled and thus super dense, being blown into
the combustion chamber under pressure, thus forcing more of it in there. The resulting
burn is so highly potent that you can easily see a 50hp increase in instantaneous power



engine. Easily.

There are however three obvious downsides. The first is that if your boost pressure is
too high, you get way too much NoS into the system and the resulting fuel-air mix can
burn so violently that it will blow out your head gaskets and/or melt something important
inside the engine. You can safely assume about 20hp increase in power per cylinder
before you need to start upgrading to racing parts. The second downside is that the very
sudden increase in power from the engine can destroy a non-racing clutch, or if you
have a racing clutch, it can torque the drive wheels so much that your tyres simply can't
grip and more and you start to skid - not good at speed. The third is that the boost is
finite. Once your NoS tank is empty, that's it, no more go-go juice. This is why it's
typically only used in street or drag racing because the increase in power is very steep,




One last thing: however photogenic the neon purple and green gas was coming from
the exhausts in The Fast and the furious, that was just Hollywood eye-candy. Your NoS
system will not do that.


A lot of people think only about power. They want more and more power but they
overlook one thing. The speed and acceleration of your car is directly related to the
power-to-weight ratio. This is a measure of how powerful your engine is compared to
the weight of the vehicle. So a massive V8 lump in a beefy 60's American muscle car
might seem like a good idea, but it might easily be outrun by a highly-tuned 2 litre 4cylinder engine in a super lightweight Japanese car. The actual units of power-to-weight
ratio don't really matter, as long as you use the same units when comparing any two
vehicles. So you can't use bhp and weight in kilos to measure one vehicle and hp and
weight in pounds for the other. So to illustrate power-to-weight ratio, consider the
following example. Subaru do several vehicles in their Impreza lineup. From their 2007

















(Kerb weight is the total weight of a vehicle with standard equipment, all necessary
operating consumables (such as motor oil and coolant), a full tank of fuel).
You can see as you go up the range, the weight of the vehicles increases, but so does
the horsepower. Power-to-weight ratio is a two-sided equation. A vehicle will go faster
with less weight, or more or a combination of the two. With the Subaru example, the
















The figures are easy to come by - divide the power by the weight to get the ratio. The
'to' in 'power to weight' is like the dividing line in a fraction. So 173hp / 3067lbs =






You can see that despite the higher-end cars getting heavier, the increase in engine
power brings the power-to-weight ratio down so the car becomes quicker. This explains
why motorbikes are so quick compared to cars. For example if you compare the 2007
Honda CBR600RR to the 2007 Subaru WRX STi, it becomes readily apparent why the





Impreza WRX STi = 293hp, 3351 lbs kerb weight = 1:11.43 power-to-weight ratio






= 1:2.93 power-to-weight


So it's not that the bike is more powerful - it's not. The engine is only 600cc and it
produces almost a third the horsepower of the car. But the bike weighs so much less
that the weight side of the equation drops to the point where the ratio plummets.

So in a car, weight is everything. It can be expensive to start beefing up the engine to
give you more power, but it can be really cheap to reduce the weight. As a rough guide,
for every 100lbs (45kg) of weight you remove from the average car, you will drop 1/10
second from a timed quarter mile. For the ultimate sports car or street racer, beef up the
engine and reduce the weight; increase the power side of the equation and decrease
the weight side of the equation and the power-to-weight ratio becomes more favourable.
So how do you reduce the weight of your car. Well again it depends on how far you

want to go. If you don't care about carrying passengers, toss out the rear and passenger
seats. Don't mind getting a flat and calling a tow-truck? Get rid of the spare tyre and
jack. If you're going for a true drag-strip car, take out the glass windows and replace
them with plastic ones. Remove the dashboard, carpet, headliner, etc.etc.etc. Beginning
to get the idea? There's really no limit to how far you can go. One of the most popular
weight-saving mods is a carbon fibre hood. If you're interested enough in this topic to
have reached this point on the page, then you'll likely have seen cars with carbon hoods
- they're very obvious because the hood is almost always black.

But why this particular item? Well, the hood of your car provides no structural strength,
and it has no crash-absorbing properties in a front-end wreck. It's basically an engine
cover. Swapping your factory hood for a carbon fibre one can save something like 4kg
(8.8lbs) of weight. Doesn't sound like much? Put 4 bags of sugar in a plastic bag and








People really underestimate the value of weight in a car. It's why race cars are made of
sheet aluminium and carbon fibre. It's why they don't have passenger seats. If you're
serious about racing your car, shedding weight every bit is as good as adding power.
Swap steel wheels for alloys - less unsprung weight and they look better. Swap steel
brake discs for carbon-fibre reinforced ceramic ones (standard equipment on some
Porsches) and save weight there. Or if you're totally loaded with cash and don't know
what to do with it, get pure carbon-carbon discs instead for even more weight saving.
Although if you do that, you'll need a healthy disposable income. Carbon-ceramic and

carbon-carbon brake rotors do wear annoyingly quickly but you absolutely will stop on a

Thank you.


In an ideal world, the engine in your car would do one thing - propel you forward. In real
life of course it's doing a lot more than that. It's driving the alternator to charge your
battery and in most cars now, it's also driving the air conditioning compressor (when
active). Both of these items increase the load on the engine. As a rough guide, every
25amps of load on the alternator equals 1hp of load on the engine, whilst running the
a/c can typically sap 5% of the engine's power. Automobile blog dyno'd a BMW Z4 with
the a/c on and off and registered 232hp / 212lb-ft torque with the a/c off and 221hp /









So imagine you have a 150hp engine in a vehicle in the summer with the a/c on,
running the radio and the seatback DVD player and LCDs for the ankle-biters. You're
dropping a couple of horsepower for the electronics in the vehicle (electric power
steering, power seats, radio, LT circuit, lights etc) and 7hp because you're running the
air conditioner. Your 150hp engine is now performing like a 140hp engine - you've lost a
lot of power there. But what can you do? Well the most obvious thing is turn off the a/c.
Unless it's genuinely hot outside, don't use it. For example, in the winter, when you're
defrosting the windows on a cold morning - don't turn the a/c on - leave it off. Ok the air
won't be so dry but you'll also not be sapping that power from your engine. After that
you can look at separate charging and battery circuits for things like the radio or ICE
install that only load the engine when they need to charge. Upgrade your alternator to a
super lightweight item with professional grade ballbearings on the alternator shaft; this

makes the alternator easier to turn and induces less drag on the alternator belt


You could also look at grounding kits although the jury is still out on whether these
actually work or not. The idea with a grounding kit is that you beef up the ground straps
in your vehicle to ensure an uninterrupted current flow with less resistance. I'm honestly
not sure that this would produce a measurable decrease in load on the alternator but
you'll find a lot of these kits being flogged on e-bay. The one thing grounding kits are
good for are sorting out the electrics on older cars. For some reason the Mazda RX-7
always seems to benefit from revamping the grounding straps. Bear in mind this isn't
going to magically increase the performance of your vehicle though - on an older vehicle
you're simply making the electrical system closer to how it was when the car was new.
The other kit you'll see a lot of are noise attenuators. The claim with these is that they
'clean' the 12v electrical signal of the inherent high-frequency electrical noise, to give
the engine management system a better chance to read a clean signal from its various
sensors. Most of these systems are simply a large capacitor in a plastic box. A
capacitor will remove high frequencies, but the frequencies are dependant on the value
of the capacitor and the resistance of the circuit path. Generally speaking, most modern
cars already have a suppressor capacitor on the alternator. There's not much harm in
adding more, but it would probably be better to fit power filters to each sensor. Without
knowing what's inside these devices it would be hard to say if any of them will do what's
claimed. Apart from that, if the engine management system is any good it should be
able to filter out noisy readings in its software.


Most people know that a turbo or supercharged engine is more powerful, but do you
know why? In simple, sexual innuendo terms, they give more suck before the squeeze,
bang and blow of your engine. The basic idea behind both devices is a turbine that sits
in the intake airflow. As it spins, it physically sucks more air in than the normal induction

of the engine and compresses it further down the line resulting once again in more air in
the intake charge, which means better burn which means more power. Both devices are
known by the common description of forced induction systems. The difference is the
way the two devices are driven.


First built in 1925 by Swiss engineer Alfred Buchi, a turbo is normally driven from the
exhaust gasses. The faster the exhaust gas passes through one side of the turbo, the
faster the exhaust turbine spins and the more air it can force in to the engine using the
intake turbine on the other side. This is the source of "turbo lag". When you put your foot
down, the engine spools up and produces more exhaust pressure, which spins the turbo
and accelerates the incoming air. The lag is the time between putting your foot down
and the exhaust gasses getting up enough pressure to make a difference. The
advantage of a turbo over a supercharger is that the turbo essentially runs on "waste
product". The exhaust leaves the car anyway, so why not make use of it on the way
out? A turbo can spin up to 150,000rpm and because it's in the exhaust flow, can reach




The picture here shows a cutaway of a typical turbo. The exhaust gasses flow through
the brown section at the back, passing over the blades of the centrifugal turbine and
turning the shaft connected to the centrifugal intake compressor in the silver section at
the front.


As I mentioned above, turbo lag is an omnipresent problem. Anti-lag systems help to

minimise this by keeping a turbo spinning whilst the throttle is closed - a condition which
would normally make the turbo spool down. Anti-lag works by bleeding a little air past
the throttle and dumping unburned fuel into the turbine housing to keep it spinning.
When the power is required, the initial spool-up is already done and the turbo can
provide power more quickly, with reduced lag. ALS can add over 200C to the
temperature of the turbo forcing it up over 1000C.

Most turbo cars have dump valves in the intake system. This is a spring-loaded
pressure-release valve. Because of turbo lag, you can take your foot off the accelerator
intending to slow down, but the turbo can still be spooling up because of the lag. When
this happens, the pressure in the intake manifold rises rapidly because the turbo is now
trying to jam more air into the engine than it can handle. When the pressure gets to a
certain point, the dump valve pops open and relieves the pressure. It's what gives that
satisfying "pffssshhhhhhh" sound when you rev a turbo engine with the car standing still.


Superchargers work slightly differently in that they're normally driven directly from the
crank either via a belt or via direct connection to one of the camshafts. With a
supercharger, there is little or no lag because you don't have to wait for the exhaust
pressure to build up. As soon as the engine starts to spin faster, the supercharger spins
faster because of the direct mechanical connection. That advantage is also a
disadvantage. Unlike the turbo, a supercharger is imposing a mechanical load on the
engine itself, so a percentage of the increase in power is actually taken up simply in
driving the supercharger itself. Modern superchargers are quite compact and can sit
either on top of, or next to the cylinder head. The most common type, called a twinscrew supercharger, uses a pair of interlocking Archimedes screw compressors (shown
on the right) that suck air in and compress it at the same time. Centrifugal
superchargers are almost a hybrid between turbos and twin-screw superchargers.
They're still driven via a direct mechanical connection, but rather than having the two
screws that mesh together, they have a single centrifugal compressor that looks like the
intake turbine in a turbo (above). "Classic" superchargers are what you see poking out
of the hoods of souped-up 70s Americana with huge air scoops and giant belt-driven
compressors. The picture to the left shows a top-mounted belt-driven supercharger.


This little section almost needs to be considered along with turbos, above, because the
two typically go hand-in-hand. When gas gets hot, it gets less dense. Less dense
means less resistance to flow. It figures, then, that people who are looking at every tiny
minutae of performance would want to wrap their exhaust headers. Why? Well exhaust
gas exits the combustion chamber extremely hot (duh!) but it cools rapidly as it travels

through the exhaust system. In doing so, two things happen. First, the gas becomes
more dense and begins to resist flow, and second, as it does this, it disperses heat into
the metal exhaust pipes, which in turn radiate the heat into the engine bay, raising the
under-hood temperatures. The problem with the gas cooling down is obvious - it begins
to slow down and provide resistance in the exhaust system. The problem with the
under-hood temperatures going up is that it makes it more difficult for the engine to get
a good, cold charge of air. (Colder air is more dense, which means better, more
powerful combustion.) This is why you sometimes see vented hoods on cars; they're
designed to let the hot air out and keep the under-hood temperatures down. So
wrapping the exhaust headers with exhaust wrap helps because it basically insulates
the metal exhaust pipes. This means they retain the heat better which in turn means the
exhaust gas remains less dense and keeps up it's high flow rate. For turbos, this is a
good thing because it means the exhaust reaching the turbo is travelling faster, which
means the turbo spins faster, which means more air forced into the engine. Everything
is connected, you see? So the ideal system would be a turbo, with wrapped exhaust
headers, a vented hood, a cold-air unduction and an intercooler. That combination,
whilst expensive, will give the coldest (and thus densest) fuel-air charge into the engine,
whilst insulating the exhaust and ventilating the engine bay at the same time.
It's worth pointing out that not all exhaust wraps are made equal. If the wrap insulates
too well, then the exhaust pipes get too hot and that can cause all it's own problems












Point to note: It's only a rumour that exhaust wrap absorbs water and can encourage
your mild steel headers to crumble away prematurely. If anyone tells you this, they're


"A fool and his money are easily parted". No saying holds more truth than in the
motoring world. There are tens, perhaps hundreds of companies out there all claiming

to manufacture devices which give better fuel economy, cut down on emissions, add to
engine longevity etc. For the most part, these products are elaborate cons. And in some
cases, not-so-elaborate. For as long as people are gullible, and can be led by






What you need to consider is one very important question : If these devices work, why
do the manufacturers not put them on their cars as standard? Surely selling a
Subaru equipped with a device that gives 8% better economy than the equivalent
Nissan would be a killer sales pitch?. Well the answer is blindingly simple: these
devices don't work as advertised. There's an important distinction there because a lot
these devices dosomething but just not necessarily to the level promoted in the






For the lawyers out there, I'm not attempting to be defamatory about these products.
I'm attempting to educate. If your company can prove to me that these devices work, I'll
happily change my articles. Contact me for where to send free samples to for testing.
Without further ado, then.....




: Tested
: and

MPG Caps, or any of the other "pill in your fuel tank" products are the cheapest and
easiest-to-find miracle cures for increased power and gas mileage. The products are
simple. They're normally pills, in a pop-out wrapper just like medical pills, or in a bottle.

They smell foul and the manufacturers claim that one pill per 20 gallons of fuel will give
you increased power and performance whilst at the same time cutting your mpg (in
some cases they claim up to 30%). Explanations range from "organic engine
conditioner that improves fuel economy and power by creating a micro-thin coating on
the combustion chamber allowing fuel to burn better" all the way up to the
fantastical "nanotechnology particles that seek out and change the molecular structure
of refined gasoline to make it burn more efficiently". Wow. Impressive stuff. Typically
these pills are biodegradable plant or sugar compounds laced with food colouring and
some odd petrochemical to give them an official smell. They don't work.
ABC reported on a AAA test of the MPG Caps and found their claims to be invalid.ABC
Texas recently closed down Bioperformance Inc. for fraud linked to their magic fuel
For my test of the MPG Caps fuel pills head over to my Product Reviews page.



: Untested
: and/or

If I started this paragraph by telling you that a device projected"holographic frequencies

into the gas tank and changes the molecular structure of the gasoline" what would you
think? Well it seems that plenty of people think enough of that statement to cough up
$299 for a plastic disc with some fancy silk-screen printing on it. The idea is, apparently,
that the molecularly-changed fuel burns more efficiently thus giving you better gas
mileage and less emissions. It's about the size of a US quarter or a UK 10p piece and is

supposed to - wait for it - be taped to the underside of your gas tank. The website even









"It doesn't work," says Dr. Terry Parker, a physics professor at the Colorado School of
Mines. Parker and graduate student John Dane of the chemistry department tested the
device for 9News. "It's clear that it's just a sticker and nothing else," Dane said.
What should set alarm bells ringing with this device is that it's sold through multi-level
marketing, the new buzzword for pyramid selling. The more of these units you sell, the












OceanCity Network, Inc. is proud to offer a 30 day 100% money back guarantee if not
completely satisfied. To qualify for a full refund, the MPT SmogBuster must remain










So if you unstick it and use it, you can't get your money back. However, they add that to
test it, you can simply duct-tape the thing to the gas tank, complete with it's backing
paper. So even if the device was electrical (which the silk-screen printing might lead you
to believe), putting a piece of paper in the way would prevent it from making any contact
with the metal of your tank. I also suspect that trying to remove the duct tape from the
fuel disc without removing the fuel disc from the backing paper is going to be next to
impossible. One last point to note : most fuel tanks are covered in a rubberised
underseal protection - there's no metal to stick this thing to in the first place.....



: Tested



This thing is known by many, many different names, including the Cyclone-Z Fuel Saver
and the Dynamix Fuel Saver. The basic premise is to make you believe that by swirling
the air in your intake manifold, you'll get a better fuel-mix which will result in cleaner
burning, longer-lasting, more emission-friendly engines, that at the same time give more
It's a great theory, and for $69, who could resist? The theory is sound. So sound in fact
that carburetors and fuel systems have been swirling the air in the intakes for decades.
It's called the venturi effect and it's why carburetors can freeze up in the winter.
John Matarese of the "Don't Waste Your Money" website has a good writeup of a
Tornado review. You can find it at this link. His results? Less than a 1% increase in fuel






The US E.P.A has not tested the tornado fuel saver, but after testing more than 100
similar products including the Cyclone-Z (report PDF) and the Dynamix (report PDF),
the E.P.A says it"has not found any product that significantly improves gas mileage."
Let's face it. If these things really worked, GM, Ford, Volvo, BMW and all other
manufacturers would be buying them by the millions, and cars would come out of the
factory with them on. And speaking of the factory, bear in mind that most car
manufactures can and will use an engine add-on as a reason not to honour your
For my test of the Tornado, head over to my Product Reviews page.



: Tested





If you drive a car, you're absolutely guaranteed to have heard this claim before : "put a
magnet on the fuel line and it will increase your fuel economy by making the fuel burn
more efficiently." There's many reasons that these devices typically don't work. Here's
just a few of them:

The magnets are tiny, and pretty weak. A magnet cannot provide oxygen and
neither can it change the amount of heat released from burning the fuel. It
can effect the fuel through diamagnetic influence but that's never been proven
to have any measurable effect on gas mileage.

Liquids cannot "retain" any magnetic effect when they leave the magnet, even
if affected when within it. Hence you cannot "charge up" a liquid in the way
that a dust particle can be charged.

There is no truly independent lab analysis which could give evidence that
combustion can be improved nor that you'll get better power output or lower



: Untested



This is an interesting device that takes a different, but similar doublespeak approach to
making you believe you can get better fuel economy. Their device consists of a jumble
of wires connected to plastic blocks which clamp around your spark plug cables. This is




When a spark plug fires, the capacitor block attached to each spark plug wire picks up a
high voltage, low amperage charge (sometimes called a "Corona Charge"). This charge

is transferred from the firing cylinder to the other non-firing cylinders via the harness
wire. These charges cause a partial breakdown in the larger hydrocarbon molecules in
all the non-firing cylinders, resulting in increased combustion efficiency. This translates
into better fuel mileage (economy), more horsepower, easier starting, less pollution




Let me decode that for you : they claim to fire the spark plugs in the cylinders that don't
need firing. The spark is supposed to cause a breakdown in the gas left in the cylinder










First of all there's the deviously misused definition of "corona charge". That's actually a
wire which emits a static electric charge in a halo around itself. It's normally used in
reference to laser printers (!) If spark plug wires did this, you wouldn't be able to hold
them whilst the engine was running, nor would you be able to have them touch or be
near anything metal in the engine bay. If they were constantly generating static electric
charge, you'd also not be able to listen to your radio either. So seeing that caused me to
want to work through the rest of the description one step at a time.

A capacitor block picks up a charge from the spark plug cable. Hmm. Well a
capacitor stores charge - it doesn't pick it up. For a capacitor to get any
charge at all, it would need to be physically wired in to the spark plug circuit.
So instead you'd need an inductive loop. Inductive loops generate current
because of Faraday's law - it's all to do with magnetism. The brief pulse of
current through the spark plug cable generates a magnetic field. The coil of
wire sitting inside the magnetic field induces current in its own circuit.

The charge is transferred to the non-firing cylinders via the harness

wire. Actually it isn't. The induced current is transferred along the harness
wires to the other inductive loops. The result is a brief inducance back into the
other spark plug wires, but at a reduced amount due to resistance in the
wiring. The current induced in the other spark plug cables would be nowhere

near enough to fire the spark plugs. But lets' give them the benefit of the
doubt again and assume the other plugs to spark.............

These charges cause a partial breakdown in the larger hydrocarbon

molecules in all the non-firing cylinders. (sigh). Ok - the charge isn't doing
anything to the cylinders at all. The spark plug might be sparking, but even if
it is, given the basic design of a 4 stroke engine, there is nothing to burn in
the cylinders unless the fuel-air mix is in there. In fact, trying to initiate a spark
too early could result in detonation, which would actually damage your

Honestly if this idea had any merit, it would be a lot simpler to just wire all the spark plug
cables together so they all fired every time one of the cylinders reached it's firing










Sadly for EngineIonizer, there's a reason why engine manufacturers only fire one spark
plug at once. Although having said that, one reader did contact me with the following



On the subject of The Electronic Engine Ionizer, you say "there's a reason why engine
manufacturers only fire one spark plug at once". As a small note, some manufacturers
have simplified ignition systems (Yamaha's YZF-OW01 and YZF-R1 come to mind)
which fire cylinders in pairs - one near TDC of the compression stroke and one near
TDC of the exhaust stroke. When I did a little work with Kingston Kawasaki (a BSB
privateer team) we switched over to this system: there was no power gain, about 1.5 kg
weight saving and the spark plug life dropped by about a quarter. I've only ever seen
this in 4-cyl engines, although I think some early British twins did this too.










I used to own a 1979 Yamaha XS650 (twin cylinder Triumph ripoff, if you don't know
them) with electronic ignition. It had a 360 degree crank, so Yamaha figured there was
no harm in having the sparks go off each rotation so that's what they did - every time
the cylinder went past TDC there was a spark, whether it was a compression or exhaust
stroke. Cheap to manufacture but it had no effect on fuel consumption or power.



: Untested

Ecotek PLC are marketing a device in England which clamps on to your intake manifold.
According to the doublespeak on their site, this device improves performance by
collapsing the manifold vacuum so that when the throttle is reapplied, there'll be slightly
more fuel in the air-fuel mix and that will improve the throttle response. The hype also
claims that the device creates greater turbulence and swirl, which promote better
suspension of fuel molecules. And finally, the all-encompassing claims of better fuel
economy, better acceleration and more power are all present and correct.
One slight problem. This device claims to work during overrun - when you take your foot
of the accelerator and the car uses engine-braking. In those conditions, 100% of
modern fuel-injected cars cut off the fuel supply. And on older carburettor engines,
there's no proof this device does anything at all. In fact there's so little proof that this
product has been complained about enough in England to reach the advertising
standards authority. You canread their report on it here. In short : waste of money. Once
again ask yourself the same question : (all together now) "If it's so good, why don't
manufacturers fit it to their cars as standard?"



: Untested

This is a great scam doing the rounds of ebay in Europe. Search for "mod + 20 bhp"
and you'll see literally hundreds of these things going very cheaply. (Better still click
here to pop up a new browser window with the search in it). If you are suckered into
buying one of these, you'll get a kit containing a resistor that you connect to the positive
line of your air intake temperature sensor. The idea is that it fools the ECU into thinking
the air charge is colder than it actually is. So why does they claim this works? The claim
is that the ECU will be fooled into increasing the fuel in the fuel-air mixture making the










Of course like all these scams, that's not quite the case. First of all, it's the air which
would make the engine run better, not the fuel. That's why turbos and superchargers
push more air into the cylinders. By running more fuel, you basically run a richer engine
which makes the engine run cooler. As well as that, all EFI engines have lambda
sensors to measure the actual fuel-air ratio and the ECU takes this reading and adjusts
the fueling accordingly. It doesn't simply do it from the intake air temperature. So if you















2. The Ecu then gets the actual fuel-air ratio info from the lambda sensor, realises it's











3. The cycle repeats until the excess fuel totally destroys your expensive catalytic
4. The ecu will also adjust the igniton timing everytime it gets new info. This means the
ignition map is constantly changing which could eventually cause the engine to










As with most of these scams, there's a Q&A associated with them designed to make
you believe the device will work. In this case, it looks something like this. I've debunked
each Q&A on a per-item basis.
What is this Device? It is a resistor chip that gives out a constant reading of air




Sorry, it isn't. It's a 40 resistor that lowers the voltage coming from the sensor. A chip is
made of silicon and has many layers of circuitry laid out in it, and it requires a special














Will my car accelerate faster with this electronic device? Yes! This is the whole
point! It has been dyno proven that this device will add up to 20 HP to your vehicle!
Really? Because the dyno graphs on e-bay are so obviously faked that I'd believe an
untrained 3-year-old could do a better job. I'd like to see actual proof of this from a




Will this device damage my car? Absolutely not. Since the altered signal will always
stay within the manufacturer's specifications, there is no way for your engine to get




Yeah - not technically true. You are fooling the engine into thinking it has a cooler air
charge, therefore the fueling will be altered beyond the manufacturers specification for





that could damage



Like I've said above in this page - if this really worked, why wouldn't the car
manufacturers simply re-map their ECUs to perform like this? Or add this resistor to
their circuits themselves? Simple - because it does not work.




: Untested, but I've







I've seen a few websites kicking around that advertised massive benefits in fitting their
voltage stabilisers and grounding kits to vehicles. Votech Performance is one such
company. Their doublespeak (in very poor English by the way) is technically correct. If
you connect a car alternator directly to the battery and run all the electrical circuits off it,
then you're going to be subject to high-frequency noise in the power supply as well as
fluctuations in voltage due to engine loading. They're also correct in asserting that a

voltage stabiliser kit and some decent grounding connections will help minimise these
issues. What they fail to mention on their website is that almost every new car on the
market today (and probably since the mid 90's) has a voltage stabiliser in it. Basically
it's a collection of passive components (ie. that draw no power) like capacitors, arranged
such that any voltage spikes can be capped off, and the high frequency noise can be
reduced. For the grounding wires, check under the hood of your car. Those gigantic
copper braided cables connecting the battery and engine to the body of the car and the
fusebox are your grounding cables. Pretty significant sized cables too. The reason for
these bits is the ECU - vehicle manufacturers don't want random power fluctuations
reaching the sensitive electronic components in the engine management system. By
default, the inclusion of any sort of chip-based engine management means the
manufacturer must include voltage stabilisation in their electrical system. So - outfits like
Votech are entirely correct in their assertions, but miss out the important fact that your







However in July 2006, Votech contacted me directly to address some of my comments

here. What wasn't clear from their website, but has been made clear since, is
that Votech's target market is for local Malaysian-built cars, Korean cars (except for Kia
and the Hyundai Sonata which has voltage noise suppression from the factory) and
Japanese cars for the Asian market. It seems the standards of manufacture with their
vehicles are so poor that the electrical systems are all over the place, and there's a lot
of difference between Japanese cars for the west versus those for the Asian markets.
What Votech are selling is basically what the Malaysian manufacturers don't put in their
vehicles as standard but what we in the "west" take for granted. Their marketing guru
told me "We advise our customers before we sell to them. Customers who driving
BMW, Merc, Audi, Fiat, VW and other continental cars are advised that our product isn't
necessary. If a customer insists they want it, then we will proceed with the installation."
OK so now with that in mind, when we look at the claims, whilst they read pretty poorly
to anyone with an American, Japanese or European car, I can imagine for Votech's
target market they might actually make sense. Votech tell me that they can provide
anyone who asks with independent lab results gained from dyno testing.

Increased Torque - how? Votech claim that the better voltage response in the
low tension circuit results in better response in the high tension circuit. This
could result in a more powerful spark which might give a better burn in the
combustion chamber. It's possible on Malaysian-built cars then that this would
result in more torque.

Better throttle response - this is all to do with how the engine sensors read
their data and send it back to the ECU. If they're getting crappy, noisy voltage,
then the readings being sent back to the ECU could be all over the place,
meaning it could have trouble generating good throttle position information
from the engine map. If the sensors are allowed to do their work properly, the
ECU might be able to do a better job of mapping it all out, and the result could
be better throttle response.

Brighter headlights - this could be true except their product would need to be
generating either more than 12v or higher current. Well again you need to
look at it from the perspective of their target market. If their cars have
headlights that get brighter the more you rev the engine, then Votech's
product could stabilise the voltage and give a more consistent light output.

Improved audio quality - now this one I could go with, especially if you listen
to AM radio. But again, most modern Euro, Japanese and American cars
have stabilisation and noise-suppression built into the factory 12v system.

Improved Fuel Efficiency. Fuel efficiency would seem to have nothing to do

with the 12v electrical system. But technically, the alternator is in the 12v
electrical system, and load on the alternator can affect fuel efficiency by
adding mechanical drag to the engine. The more load on the electrical
system, the more drag in the alternator. The difference between a shoddy 12v
system and a decent one can be up to 3% in fuel efficiency.

Colder air-con - this is a bit of a wild claim. The a/c compressor is belt-driven
off the engine crank. The only electrical component is the fan that blows the
air into the car, and that doesn't make the air colder, it just moves it around.
However Votech reported to me that they did get a 2C drop in temperature

coming out of the vents on their Alfa test vehicles. Quite why this would be, I
don't know.

I was contacted in 2011 by Ricky Willems, a senior electrical engineering and product
design major at Rensselaer Polytechnic Institute, a member of SAE and IEEE. (His
extracurricular work includes designing hybrid electric race cars and vehicle ECUs). He






I own a Pontiac Montana van that has gone through 3 separate stock voltage
stabilizers. The electrics were poorly implemented, and water has repetitively damaged
the electronic controls. In addition, I have been in situations where the jiggling of
grounding wires brings the voltage back into regulation temporarily. Because of these
failures, Ive had opportunity to judge the effects of having or not having a voltage
stabilizer on a modern EFI car that was designed to operate with one. I imagine this
would be a similar situation to asian market cars that did not include one, despite








The only claim I cannot support that you list is the colder AC, which I have not noticed,












I can support increased torque, Better throttle response, and Improved Fuel Efficiency.
The voltage variations send rippling voltages to the cars sensors, which then report
back flawed data to the internally regulated ECU. The engine can normally adjust for
errors, but since the errors are transient and continuous, the ECU cannot adapt. As
such, according to my OBDII connection, the values reported vary from what they
should and impact fuel mixture negatively, causing a loss in torque, loss in fuel








Audio quality on my vehicle has not been impacted, as it is also internally regulated, but
I have had stereos on vehicles with no regulation that suffer severely for it. Many
vehicles, even with a solid voltage stabilizer system still have too much noise for after-










As for brighter headlights, the claims are half true. When my regulation is off, the
headlights flicker severely with the pulsing of the alternator. The appear dim, although
each flash is actually brighter than the headlights would regularly be. The flashing
makes it appear otherwise though. (your eyes adjust to the brighter light output, only to








My only -guess- on the air conditioning is that it may make it cooler at idle, when the
more properly running engine would smooth out its idle, and have a more consistant AC
output. Mind you its only a guess.


There is an excellent site which covers all the above and a lot more with engineering
and scientific analysis of all these products. If you really think they work, then drop in and find out how clever the marketing hype is, and how little any of




The FTC have a page dedicated to warning the public about these scams. Click here for

FTC's "Gas-Saving"




Fuelishness? page.

The Environmental Protection Agency (E.P.A) has evaluated or tested more than 100 of
these alleged gas-saving devices and has not found any product that significantly
or cause substantial increases in exhaust emissions. Click over to and put "gas





One of the best sources of information on the E.P.A site is their page on Gas Saving
and Emission Reduction Devices Evaluation.. Here you can find downloadable PDF
reports on everything from the FuelXpander to the sexually deviant-named Analube




EPA Motor











Environmental Fact Sheet: Aftermarket Gas Saving Products and EPA Product
Evaluations (PDF)

If you've got a device you've bought and tested, or you'd like to know more, drop me a
line. The more of you that contact me, the more complete this page will become.