Quote:
Originally Posted by RonC
Some GM truck and car engines are designed to run on E85. Their computers are specifically setup to moniter the ethanol blend % in the tank and adjust the air fuel ratio required for that blend in the tank at the time. 100% gasoline AFR is set to 14.68 to 1 and 100% ethanol is 9.0 to 1 AFR. E85 is set at 9.7 AFR and 10% is 14.0 to 1 in the flex-fuel truck tuning. The 5.3L truck engines set up for flex-fuel use 36 lb per hour injectors vs. 24 lb per hour without FF. They have to flow much more fuel per hour to produce the same amount of energy (power) in the same length of time. Real world result; a truck that gets 15 mpg on gasoline gets about 11 mpg on E85. My real world results using 10% ethanol blend gets about .5 mpg less than 100% gasoline in my truck with it's computer optimized for best mileage with each fuel.
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What diarmadhi is saying is that a car designed to run specifically on E85 will have a higher compression ratio allowing it to run as efficiently as it can. Trying to use gasoline in one of these engines will cause it to knock and ping.