2016 OVTune Tacoma 3.5L Manual Transmission / Engine ECU Reflash

Disclaimer: I'm an engineer, but not an automotive powertrain engineer. I do lots of reading research on dyno experiments, but I don't work at a tune shop or anything like that.

There are many reasons why. Usually, it's down to the combination of intake manifold, head design, and cam specs (airflow characteristics) relative to displacement (airflow demand) that determines the way an engine runs and feels. VTEC, VVTI, MIVEC, etc. all give more flexibility with those specs, but ultimately, if an engine is built to make power up top, it's very hard to make it pull off idle. I suspect that these engines would be strictly superior to the 4L in the 2nd gen trucks if we had the extra displacement to demand more air at low RPM. As it is, playing with the VVTI will help under 3500 RPM, but there probably simply isn't enough displacement to take advantage of our available airflow capabilities. A stroker kit, or a camshaft change to cams with lower duration and higher lift combined with very thorough tuning would help too, but that's $$$$$$, and there simply isn't enough demand for it. @OVTune can probably expand on these points, as he's an experienced tuner.

 

I was under the impression that the power surge at 3500 rpm was from a mechanical change in cam timing and variable length intake runners. I think Atkinson switches to Otto at lower rpms depending on load, not necessarily a specified rpm.

 

I'l explain the Tacoma cam system in detail with an example image tonight so it's clear how it works.

 

there's more to it. why does it transition perfectly smoothly at times, and at times like a off/on switch?

maybe your tune never transitions smoothly? seems like some of the reports i see around here are from folks with the tune but they never see that smooth transition?

 

Thank you! I've been looking for a while and wasn't really sure the exact specifics of our system.

 

once you see the vvt system and maps you'll understand why only so much can be done. The cams go from almost complete retard to complete advance with load changes that = small throttle changes at low rpm.

so it's quite literally 15% throttle atkinson, 25% throttle full advance

 

i was just about 100% sure it was from this calculated load deal. that's the one thing that seems to change while i'm driving, and yet one time it's a smooth transition and, with apparently the same driving dynamics (gear, speed, wheel angle, etc) the transition is like a switch. it looks to me that load is the thing that's different. i guess it's related to throttle position as well?

 

I get a smooth power transition at that rpm but it has to be at full operating temperature and light load.

 

Look forward to it - and that was kind of the point I was getting to in that everyone keeps saying "give me the power that exists above 3,500 down low" and I'm not convinced this is all tunable to that degree necessarily (at least not safely). that said the lower end has always been more responsive and powerful with the tunes than stock but I certainly still feel the rocket ship take off in the 3500 range as most do.

 

I believe this is exactly the case. "Load" in this case is not determined only by the actual loading of the engine. It takes into consideration your request for power (throttle position) as well as the engine loading.

Edit, I guess what I mean is the VVT adjustments are definitely not based only on engine parameters/conditions. It definitely takes throttle position into account. I'm pretty sure this was also related to the bucking during moderate acceleration on early manual tunes (1.01 I think).

 

The 87 tune is getting worse and worse on my truck. It has alot of hesitations and stutters. I have had it on there for about 200 miles now and it is getting worse. The 91 version on 1.03 did it randomly but not near as much.

 

I’ve got almost 500 miles on mine now and it hasn’t changed at all for me.

 

was your car part of the crank sensor recall?

 

No but I changed it when I was getting stutters on 1.01a. 1.01b fixed it. 1.02c was fine too. The 91 version of 1.03 did it some with in the first 300 miles and was very random. The 87 version is doing it alot. I was in city traffic today, one time when it hesitated, it backfired a couple of times.

 

can you PM me your ECU version (the number / name of file we sent)

 

The 2GR-FKS uses a system called ACIS (Acoustic Control Induction System). A bulkhead valve is either open or closed, which changes the effective intake runner length. Not sure if that can ever be smoothed out perfectly.

 

Pm sent.

 

Mine has been stuttering more in the last week or so as I put mileage on the tune, especially under moderate/heavy load (1500-2500 RPM). It doesn't happen all the time though. I hate to say it, but the throttle response (clutch in) has also degraded. Still way better than stock, but rev matching is worse than when I first flashed.

I run 91 Octane fuel and my ECU version is 04B10. I wasn't on the recall, but replaced my CKP anyway.

I must add that my truck has ALWAYS had some stuttering, right out of the showroom. 1.01B seemed to be the best version to alleviate this.

 

I also doubt something like this could be smoothed out perfectly, if it’s an “on-off” function then the change in power delivery is going to be felt with the “on” and the “off”.

 

yes, i think the calculated load takes the throttle position into account too, of course. i need to test this, but it appears to me that if the driving dynamics are the same (gear, speed, wheel angle, etc) then:
- if partial throttle --> transition is like a switch
- if full throttle --> transition is smooth

i just haven't had time and an open road to verify. when i can i will. in the meantime I'm using full throttle more, more smooth, more gas. but this would suggest calculated load is the main wild card... not that Mat isn't aware.

edit: it doesn't seem so simple. wondering if it calculates load (or requested load etc) based in part on throttle position, but it calculates it too early, so if you weren't at full throttle back when the sample was taken to calculate load, then it doesn't engage the transition immediately.