Originally Posted by white_n_slow
sure, most regular premium gas is more than 5% ethanol. But these Chevy's can run on regular gas or 85% ethanol... same motor, same injection system, tank to tank.
From what I've read, these new FlexFuel cars have a second fuel and ignition map for E85. What I don't know is how the car senses what fuel is being used. I assume the ECU looks at knock sensor input and switches maps accordingly.
In terms of the chemistry, E85 has less potential energy than normal petrol, so the fuel consumption increases (marginally) with E85.
At any rate, it's undoubtedly a process that is dependent on more than the ECU alone. :hs: