Flex Fuel

[tbrtuning]

Anyone have a good flex fuel setup they care to share with me. I think I found and calculated everything that needs changed but I am not sure the best settings for a couple things I couldn't just do the math for.

Do you guys that have it working well just extend the alcohol part of the wideband voltage modifier further than the 80% it was populated to? I filled up a car with about five gallons of fuel left with E85 a few days ago testing and it learned to 85% but shouldn't have been that high.

My email address is [email protected]. Thanks

[Homer]

A member shared his E85 tune for a Demon running a whipple.
https://forum.hptuners.com/showthread.php?80370-In-the-spirit-of-sharing-My-Demon-Whipple-E85R-Nos-tune

[tbrtuning]

I don't have an issue tuning for E85. I am doing true flex fuel where it infers ethanol content using widebands

[Homer]

Ah, sorry should have read more carefully...saw the E85 and request for tune.

[rockstar9528]

wouldn't that be after the burn tho ? like using Wideband feedback to adjust fuel trims ? possibly to late for a burnt piston ? just asking, was always wondering how these guys are doing a true flex fuel tune. I can load the ethanol in the car get on the Dyno or street and tune from there but everything changes once the next fill up. I would assume a content sensor needs to be present but how is it giving feedback to the PCM to tell it which timing tables to run or what to do with the fueling based of content , so many questions loll

[tbrtuning]

I figured it out. It actually learns very quickly using the wideband feedback. There is a lot to change in these to make it work correctly but I think most of the risks can be easily eliminated. I just tell people to idle and cruise a few minutes before going WOT after changing ethanol content a lot. These go closed loop even at a low coolant temp and seem to do pretty good correcting fueling even with cold widebands.

It's kind of lucky that it ends up on the rich side going from the higher octane to lower octane fuel because it gives some safety net so the initial hit is rich not lean if someone does go WOT immediately after switching from E to 93. I think your biggest risk is there but with good knock sensor calibration you're not going to hurt something that quick.

I guess one possible risk is really bad exhaust leak before the O2 sensors. It thinks it's lean from that and starts learning higher ethanol content in response to the fuel trims, when it's actually on 93.