Autotune – game changer

(for me anyway)




The story so far

So as you may or may not know I wasn’t really having that much luck with my previous attempts at mapping manually with the wideband, largely because for whatever reason, the wideband I was using didn’t work much of the time, so never really got to get stuck in. Even when it did work I wasn’t exactly bowled over with successes though.

Either way, doesn’t really matter why, point is it didn’t work as an approach so back to the drawing board. So I was chatting to another R125er on twitter and they suggested an autotune box as an option to sort my mapping situation out, having had success with one on their other bike, and seemingly picked up a bunch of power.

I’d heard of them but wasn’t sure if it would work, and new they’re like another £250, so yikes. This mapping thing has been an expensive exercise.

They do come up used on ebay now and then and when one did I pounced and got it.

The Autotune is basically an additional little box which you can plug into your PCV (not PCFC, PC3 as far as I’m aware, only the PCV), and comes with its own little wideband sensor (LSU 4.2). It uses the CAN bus (a wire/serial cable) to talk to the PCV, and tells it to correct the fuel mixture by however much to hit a specific Air/fuel (AFR) target.. e.g. 12.6 or 13.2 AFR. If you want to get really fancy you can also plug the POD300 panel into the same CAN bus and get realtime info on your stuff, and adjust things. Very cool, but I’m not quite there yet (financially haha).

I don’t know how quickly it reacts or at what point it decides that a value in The Map is wrong enough to need a trim adjustment, or how it compares that new trim value to any value already in the tim table. My guess would be that they smooth/damp the figure slightly with some sort of average of each value and then values would trend towards the current ideal.

WHICH MEANS: that you can kinda leave it in learn mode and use that as a “ok well try harder” sorta thing, or revert back to the more “conservative”/economical Base Map which we know is generally great.

Tuning for Max Power - AFR vs. Ignition Timing? - Pelican Parts Forums

I was mostly running the base map recently and then a couple of times when flat out I thought “hmm wonder if learning mode would be faster”, clicked over and picked up a few mph.

It may not sound like much but till recently the current vmax was 81 mph, so if you’re sat at 79 and click over to learning mode and now you’re at 82 (also setting a new vmax)…that’s actually pretty impressive.

*Please note – in case you’ve missed it, something’s weird with my motor – either I’m a tooth off on the timing chain or the timing chain is stretched which is affecting the valve timing, or [something I haven’t realised yet]. This means the power band has “slipped” down bit about 500rpm, so where normally you’d be hitting peak power around 10k, she’s strong through the lows and mids (hella fun!), but it means she’s out of breath at wide open (boo), so top speed isn’t particularly impressive, even though she’s on a 15t sprocket so has the gearing for 85+. she used to do 82mph on the 14t on the 125 cylinder, she just never got there so quickly or reliably 😉 Kinda of a bummer re the top speed but if that’s the cost of my timing chain mistakes last year then fair enough for now. This is one of the things i want to remedy with the B-motor build, and a longer duration cam, but for now it is what it is.

My impression so far is that it’s like a “short term moving average”. So it’s not quite instant (would be too jittery), but it reacts quickly enough that it should adapt to new conditions pretty quickly. Slightly damped I guess.

Forex Better Tillson Moving Average Indicator Unlimited Download -  ForexShop24
short term moving average – a bit like the blue line

Cool! so does this work on the PCFC and PC3 too?

Sadly – No. As far as I’m aware this only works with the PCV. Only the PCV can handle 2 maps at once and only the PCV has the CAN bus to even let it talk to other boxes like Autotune (and the POD-300).

The special trick the PCV can do which the PCFC and PC3 can’t (as far as I know), is that it can do two maps in memory at once, and the map switching thing I’ve mentioned previously. Here it’s basically using the same feature, but instead of an A-map and a B-map, you have your Base Map and a “trim table” which is basically the corrections it needs to make (to your base map) to hit the AFR you’ve specified.

Simpsons Knifey Spooney GIF - Simpsons KnifeySpooney Australia - Discover &  Share GIFs

So basically you plug it in and ride around, and when you switch it to “learning mode” (via your A/B map switch) it makes notes on where you need more or less fuel to hit your target AFR, and then after your run you can apply those “trims” to your base map and then that’s The New Map.

(as far as I can tell) it seems to leave off more or less where you left it, which is quite convenient. So you can effectively switch between “Base Map” and “Live tune” (learning mode).

You still have your map switch button but now it toggles between “The Map” and “Learning mode” (i.e. where it makes notes and tries to hit your target AFR).

This also means you can selectively tune – so you might be happy with your map in general but perhaps think the top end needs a bit more work. You can clear your trims and then go out, staying on Base Map most of the time, and then only when you’re in the situation you want to tune for (e.g. flat out/WOT), you switch to learning mode and then let it do it’s thing for a while. At the end of the run, switch back to Base Map, go home and see what the trims say. You shoul dhave just a few adjustments in the part of the graph you were trying to tune, in the situation you were trying to tune for. Very gran turismo, very good for tinkerers. Love it.

What’s interesting though, is that I found there was a sweet spot with refining the map. I’d gone out riding for a good couple of hours to train it and and there was a point where the bike just came *alive* and it became like an excitable puppy on a lead. fantastic! you could just *feel* it kick in and it was like “ah ok, nice, that’s what we came for”, like clear as day (to me anyway).

So when I tried refining the map further it didn’t really improve beyond that point. That map still seemed sharper and more responsive than the subsequent revisions.

So do you still need learning mode anymore then?

Actually, kinda…

I like my Base Map for *most* conditions. but I haven’t yet figured out how to do the gear indicator thing so I can have per-gear fuel maps (which the PCV can do apparently, very cool). That means The Map is still effectively a bit of an “average” of the fuelling/rpm conditions needed for ALL the different gears.

(BTW: Please correct me if you know different, I’m just expaining it the way I understand it, that may not be accurate, or not entirely accurate).

The way I understand it: as far as my PCV is concerned, fuelling for (for example) 100% throttle and 10k rpm is value X%, regardless of the gear since it doesn’t know which gear it’s in. Same goes for all the other values too.

But imho the load conditions between 100%/10krpm in 2nd gear, and 100%10krpm in 5th are quite different… you’ve got gearing and wind resistance and all sorts of goodness coming into play with speed, so the system could perhaps benefit from individual fuelling per gear (idk, this is theory currently. once I know you’ll know).

I suppose if there were no potential benefit then wny bother adding the feature. The fact that per-gear-mapping is even A Thing suggests perhaps there is something to it.

My point is that at this stage even The Best Map is a compromise between what works best for that Throttle-vs-RPM in *ALL** the conditions in ALL *the* gears, and hence probably not *exactly* right for any/each gear individually.

For me once the map passed its ‘sweet spot’ it sorta started feeling muddy… idk if the injector was maxing out but it kept trying to pile more and more fuel in there each time I added the trims. it was over 100% extra duty in places (on the orig injector). Probably because I was flat out everywhere and it was just trying to keep up. idk.

So at that point I went back to the map which felt sharp and responsive and that’s now my Base Map. I stopped trying to “refine” it beyond there…so learning mode is now redundant, right? do you even need the O2 sensor etc anymore?

Well, no but kinda yes. As long as your map is reasonably well refined you *could* take the O2 sensor out and insert a bung to seal it off, even remove the autotune box and sell the unit. If you’d bought your autotune unit used you’d probably recover most of your investment and your map lives on the PCV by now (and hopefully backed up on your computer) and would still be good for evermore.

Well..until you change something that is (e.g. new exhaust, different baffle, new intake…new cam…you name it… which point you’d want to go trhough the process to just see if the map can be sharpened up a bit to the new setup. Besides, learning mode lets you do other cool stuff.

Thing is the trims probably weren’t wrong for me, if I had been flat out everywhere and really working the bike when she was fully warmed up, then perhaps it did need shitloads more fuel at the time, but that doesn’t mean I want it drowning in fuel all the time.

What learning mode let’s you do:

So say you build a nice “sweet spot” map around a 13.2 AFR target. Good power, nice and responsive, not bad economy either. A good all rounder, esp if you have to commute or have even a modicum of occasional chill.

That’s your base map.. but you can have your target AFR for *learning mode* set to 12.6 (for max power) so if you find you’re in a situation where the bike feels a bit flat or today you’re just going fuckign banzai, you can switch over into learning mode and you know whatever abuse you dole out to your beloved little deathmachine, at least the fuelling should be about right, and also means you’re getting the absolute most amount of bang for your liquefied dinosaurs.

Stuff changes

Also the conditions *change*…cold air can hold more oxygen so can take more fuel potentially. Those days where you think “wow she’s really on one today” or “meh feeling a bit flat”…could be (to some extent anyway) down to atmospheric conditions intersecting well or poorly with the “average-ness” of your map vs the warmup/state of the engine at the time. Apparently this is especially noticable with small engines, which seems plausible.

So perhaps for “responsiveness” you might find you want your base map a tiny bit leaner. I tuned that base map to 13.2 AFR whereas recently learned that for max power you want more like 12.6, and whilst yes the top speed did go up a little, I think for responsiveness I sorta prefer it a little leaner in general. So we might end up changing the target AFR map to be more like 12.6 in the 8-10k rpm range, but shoot for 13.2 below that.


I’ve been riding on the autotune box wiht this arrangement now for about a month or two and I’ve gotta say I absolutely love it. It’s an interesting and kinda flexible setup which has let me set the bike up how *I* want it set up, which makes riding really fun. I’ve been going on longer and longer rides and really enjoying them. Such a fun setup.

I was sorta getting to the point where I was a bit pissed off I’d spent the extra on the PCV when the PCFC has like 10 map slots which would make it better for trail+error tuning (as covered on this page), where the PCV can only hold 2. So if you’re trial+error tuning it’s slow going since you have to go back to the laptop each time or take it with you and do roadside stops.

But when I finally got my paws on the autotune box and just plugged the O2 sensor it came with right into the bung I’d added to my exhaust, and off she went. I was a bit on the fence till we were a few revisions in and then the bike just *came alive*… and I was grinning non stop. Still am.

So I really love it, a LOT.

New at £250, on *top* of the £370~ for the PCV, plus I had mine dyno tuned when it was fitted so extra £££.. makes is quite an expensive exercise, but if you keep a saved search on ebay for “YZF R125 autotune”, they do come up now and then and tend to go for around £130, which is much more palatable. It comes with the wideband sensor but YOU NEED TO HAVE AN O2 BUNG ON YOUR EXHAUST.

(this is something we’ll get into in a future part, already working on it).

What I really wanna know though…is how well does the autotune cope with a situation with more unknowns. When I added the autotune box to my bike it was already running pretty good. What happens if you give it more of a blank page to work with. Does it still Figure It Out to the same degree?

The next part is already filmed and partially written and gets into exactly that…

Please like, comment and subscribe, share the shit out of this your preferred doomscrolling platform.

Leave a Reply