I have been doing a lot of research the last couple of weeks about tuning my car on E85. I have read the how to threads on ls1tech/hptuners! The main thing that I hope someone can clear up for me is this. If you tune your boosted car on gas lets say you want an a/f of 11.5 under boost and of course 14.7 is your stoichiometric. Now stoich. is 9.7 for E85 then so 7.5 would be your afr under boost for e85 per the Eq ratio from gas. The how to says to convert your wideband to read lambda if you are running E85 to be accurate. I don't think this is necessary because there is an equivalence ratio of 1.5 between gas and e85 and if I'm right aboiu this you wont need to convert any of your readouts from the original gas setting. The way I see it is if you just leave your wideband alone (set up for gas) then you just tune the car to the same afr's that you would as if you were running it on gas then the tune would be spot on. The reason for this is a stoich of 14.7/1.5 = 9.8 and under boost 11.5/1.5 = 7.5. So if you get your E85 car tuned to a stoich of 14.7 and to a boosted afr of 11.5 per the wideband then you would be right in your correct afr on E85!

What brought all of this up was me talking with my brother which has tuned nearly 1000 cars (all imports) and he says that when he tunes a car on E85 he just tunes it with the same afr's as he does on gas of course depending on what the car likes! This got my attention quickly because there is a lot of talk around here about changing your stoich in your tune and tuning per lambda etc.etc. Hopefully this will catch someones attention that is experienced in this scenario and they can give me some insight!

Thanks
Stephen

 

That works fine, The only problem I ran into with it, was trying to autoVE tune with EFILive. Since I had just changed the Stoich in the tune to adjust for E85, my commanded AFR that showed up in the scanner was for E85, and didn't match what my wide band said cuz it was still set for gas. SO I just made a couple calculated PIDs for E85 WB and BEN factor and was able to do my autoVE tuning that way. Was pretty easy

 

Get a wideband that can display in lambda.

When you start thinking of lambda, things are a lot easier, since that is what the widebands are really measuring, not necessarily air fuel ratio.

Ryan

 

My w/b will display in lambda but how do you log your afr error % when the wideband is in lambda and the commmanded a/f reads afr?