Adding flex fuel capability to L67

[muecker]

Wanted to get some thoughts on adding flex fuel, E85 to Gasoline and every ethanol % in between, to an L67 engine. The engine/trans is from an '03 Bonneville SSEI.

The way I planned to go about it was to add a flex fuel sensor, connected to a microcontroller that would then basically act like a scalable AFC that would alter the MAF signal based on ethanol content. The base tune would be on E85, and as the ethanol content dropped, the micro would begin scaling down the MAF frequency so the PCM would inject less fuel. However the issue I see with this is the spark table. As there is no flex fuel provisions in this PCM, reducing the MAF signal would then alter the point at which the PCM is pulling timing values from the table. Would it also make sense to make use of the IAT timing table in this case and have the micro spoof the IAT and have it pull additional timing as the ethanol content decreases?

Any ideas on how to do this or if I should cut bait are appreciated. Really don't want to have to reflash the PCM if I go somewhere E85 isn't available.

[5FDP]

I don't see any way to make it work the way you want it, those computers are just so limited on their functions. Everyone I know in the 3800 community either has to run straight E85 (more like E50-E70) or regular gas and create a tune around that.

It's that or go full stand alone with a mega squirt or similar but then you lose transmission control.