View Full Version : OT F-150 -Shuts off 1/2 of cyclinders

09-12-2011, 10:04 AM
I saw the mileage post below and have my own question.

Apparently the new F-150 will shut of 1/2 of the cylinders in case of coolant loss allowing you to limp in and get repairs.

So what if I jump the coolant loss wiring and shut them off myself when I don't need them????

A.K. Boomer
09-12-2011, 10:12 AM
It may not be that simple - the system is linked to a computer and could be tossing things into a "failsafe" mode, anotherwords it may be de-tuning the "power" cylinders for optimum survival tactics, this may include retarded timing (to avoid pre-ignition) and an extreme rich mixture which aids in cooling - not quite the recipe for economy...

09-12-2011, 10:40 AM
Cadillac and Ford experimented with "cylinder management" all the way back in the 1980's. Ford soon dropped the whole thing and placed more attention toward fuel injection. Cadillac, on the other hand, actually marketed their "4-6-8 cylinder disconnect" system. which mechanically disconnected the pivots of intake rocker arms on pairs of cylinders.
We spent the next five years removing the harnesses and converting them back to 8 cylinder engines. The problem was in the disconnect system, and the rocker arms tendency to stick in either the "engaged" or "disengaged" position. This made a smooth running engine shake like a wet dog.
GM was back in the cylinder management business in the mid '90's on their pickups, but quietly decided the GEN III (LS) engines could be made more efficient without turning "dead" cylinders. Chrysler is currently using cylinder management on their "hemi" V-8's (the only way they can get any fuel economy out of them) And Cadillac has been using the technology for nearly 20 years on the Northstar 4.6L, V-8 engine. The Northstar is the only one I know of , until now, that will shut off half of the cylinders, alternating from one bank to the other in an effort to prevent engine damage should the cooling system become damaged. Fortunately, the engine doesn't use the management system for anything else. My Mother experienced this on her 1998 Cadillac when the waterpump drive belt broke. The car started running rough, and all manner of warning lights came on in the dash. But the car continued to run and got her to a safe place where she was able to call emergency road service. Even though the engine was undamaged in the incident, an unscrupulous Cadillac dealer told her the car needed a new engine ($12,000). I had her take it to a friend's garage, and he replaced a tensioner and a belt. During the repair he noticed the radiator and several minor things needed attention (the Cadillac dealer just wanted the "big ticket" stuff, not the minor repairs) Anyway, instead of paying the Cadillac dealer $12,000, she had everything done at the garage for $800. The car runs fine, with no apparent damage from the overheating incident. My friend's garage has a new customer, and the car will run for many years to come.

In answer to Abner's question; I seriously doubt if you could wire the computer to shut off the cylinders at your command, due to the architecture of today's engine electronics. Any kind of a disconnect switch or a grounding switch would be interpreted as a system failure by the truck's computer. Besides, with the cylinder management system operating the engine performance is horrible and uncomfortably rough.

09-12-2011, 11:08 AM
Agreed, Any serious (Or just verious sensore) failures that activate any kinda 'limp' mode are designed to run the engine failsafe: Absolutely crap efficency, absolute crap power. Did I mention the engine will sound like crap too?

Turning 'dead' cylinders is very inefficent due to pumping losses without somthing to lock the cams or better yet, clutch the crankshaft. Presumabley idling/underused cylinders is worse then just skiping fuel injection and running the other cylinders harder, Or some fuel injected cars would be doing that by now.

09-12-2011, 12:35 PM


Unfortunately there is a lot more involved here than just turning injectors off to save gas.
As the previous posters have already mentioned there are a multitude of varying parameters that come into play.

Although I'm rather reluctant to hand out Wikipedia links for their being incomplete or not accurate, I will leave one here as it does at least give one a general overview of cylinder deactivation.

Have a read there and do a little more reading on the subject.
Fuel economy and general automotive efficiency is a fascinating subject.

Not too long ago for instance I see where ZF is introducing a new 9-spd transaxle which they claim will result in a 16% gain in fuel mileage over their current 6-spd, all because the engine is allowed to operate in it's most efficient range.