Originally Posted by
NASIOC
Many sources make a big deal about E85 having less thermal energy per gallon that a gallon of gas. They frequently draw the false conclusion that you cannot make more power on E85 than you can on gasoline. E85 actually has a higher specific energy than gasoline, and at proper mixtures releases more thermal energy in the cylinder for a given amount of air to burn. Since an internal combustion engines power output is primarily air supply limited this means you can make 5% to nearly 30% more power on E85 than you can on gasoline.
Typical gasoline Thermal energy 19,000 BTU/lb max power fuel air mixture 12.5:1
Typical E85 Thermal energy 13,475 BTU/lb max power fuel air mixture 6.975:1
Typical ethanol Thermal energy 12,500 BTU/lb 6.429:1
If you are consuming 100 lbs of air, lets see how much fuel energy you release for each of these fuels using gasoline as the base 100% reference.
100/12.5 = 8 lbs of gasoline @ 19,000 BTU/lb = 152,000 BTU = 100%
100/6.975 = 14.337 lbs of E85 @ 13,475 BTU/lb = 193,189.9 BTU = 127% more heat energy
100/6.429 = 15.555 lbs of Ethanol @ 12,500 BTU/lb = 194431.5 BTU = 128.9% more heat energy
A 5% increase in engine power is common on NA engines with minimal conversion changes, and much higher numbers are possible if compression or boost is used to take advantage of E85's higher fuel octane.
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