Dangerous to train down fuel trims?

[NATYPE]

Hey Jason! (And anyone really) - Figured this might be an interesting topic...

Is there any danger in training down the fuel trims? My ST was at a shop for the past few months, and for the few I had it before then had been flashed with your OTS E30 "Stage 1" tune. All great there, but I recognize I was running more ethanol than needed based on how my long term fuel trims settled in. They're very positive. I don't think I'm mistaken in thinking that 0 is really the target if you're bang on for how much ethanol you should be running. So out of curiosity I've been slowly biasing my tank back down towards E30 and monitoring things. I can see my STFT respond how I think it would, not sure I've impacted LTFT yet (how long does that take to react?) and I think I'm seeing one thing jump out at me? Seems both totally sensible or like it could be placebo since I know high AFR's exist on this platform in very specific circumstances. But should I be seeing the occasional rise to over 14.7 AFR under light throttle conditions in any gear? Full WOT and things are biasing rich and safe, it's just this light input drift to above 14.7 I don't recall ever seeing before. Feels like it makes sense if I'm forcing it to learn fueling changes. granted only to the tune of -1 off what I'd expect in STFT.

Just a curiosity really, if re-flashing and learning up rather than down so to speak is the established way to approach this that makes total sense. But with how intelligent these ECU's ultimately are in regards to following fueling changes I found myself just thinking it should work.

 

[Jason@dizzytuning]

I'm not sure what you mean by "training down".

 

[TyphoonFiST]

I'm not sure what you mean by "training down".

Trimming? maybe leaning out the system more....

 

[Jason@dizzytuning]

Trimming? maybe leaning out the system more....

I still don't understand the question, lol.

 

[NATYPE]

I still don't understand the question, lol.

Hahaa, excuse the wordy question. I'm really just talking about less ethanol = more negative short term fuel trims = learned behavior in long term fuel trim going down over time as a result. The question being is there any danger in slowly pulling back on ethanol and having the fuel trims "learn" that change rather than just re-flashing if I know I'm going to be running a tank with less than I have been.

 

[Dpro]

I think you are over thinking this having a little more ethanol on a e30 tune is better than not having enough. If you are not getting misfires you are fine. All this trying to train the ecu stuff is kinda like out thinking what the ECU is programmed to do automatically as long as you are in the mix window for the e30 tune you are fine. If you want to be more exact get a fuel content gauge and you will know automatically.

 

[NATYPE]

I think you are over thinking this having a little more ethanol on a e30 tune is better than not having enough. If you are not getting misfires you are fine. All this trying to train the ecu stuff is kinda like out thinking what the ECU is programmed to do automatically as long as you are in the mix window for the e30 tune you are fine. If you want to be more exact get a fuel content gauge and you will know automatically.

Honestly that's where my head is at too. My LTFT was just so positive on average it seemed like I must've been running closer to E40/50 and felt like that could be high enough of a learned octane level that moving back down to E30 organically could've been the cause of the slightly higher AFR I thought I was seeing. No knock, no issues, etc. Just something that caught my eye while paying attention to things. Consider this question closed though, appreciate the input.