Quote Originally Posted by Joe_Black
Converting to flex-fuel, or E85, appears to be more difficult than going pure ethanol. With the pure ethanol you just ensure your fuel pump and system is compatible and upgrade as needed (viton o-rings, improved pump, stainless rail) and get injectors that flow about 30% more fuel. Reset the ECU and adjust from there. With flex-fuel the ECU needs to easily figure out and adjust if you're running E85, gas or a blend.
Most new vehicles (ie mid 90's + and definitely OBDII systems) can adjust to the blended fuel automatically by reading the O2 sensors. The vehicles I have run or directly seen run various blends of ethanol have adapted fine. AFOAF reported his Ford ranger set a code running E85...don't remember the specific code, but it reportedly had something to do with the fact that the long term fuel trim was maxed out and the computer didn't like that. But the ECU was still easily responding to the change in fuel, though Larger injectors, or a boost in fuel pressure would help cure the issue.

I believe the two main issues with running straight ethanol are low volatility/cold starting issues and the fact that our government (US) would rather poison you to death rather than have you skip out on taxes on a fifth of booze - hence denaturing. Regular gasoline added to the ethanol in small amounts solves both of these issues very nicely and relatively cheaply.

I have read that most car manufacturers that make any FFV's offer it as a no cost option. Based on that, I have to wonder just how much they are changing on the fuel systems to cope with ethanol. Bigger injectors - probably, change in ECU programming - probably, stainless steel fuel system - doubtful. Next time I see a FFV locally, I will have to climb under it and see what the tank looks like!