Highest Compression Ratio for E85 2

[PhdDave]

What is the highest compression ratio that E85 is able to run at without undue harm? What are the chances that the automotive manufacturers will make a car that can only run on E85, and gain power by using a lighter engine of smaller displacement?

 

[patprimmer]

The reduced pressure in the inlet manifold increases air flow into the manifold thereby increasing the mass of oxygen and fuel in the charge when the inlet valve closes on the inlet stroke. The extra mass of fuel and air generates more heat energy when burnt. that aspect has nothing to do with adiabatic heat.

Because of the charge cooling due to fuel evaporation, without ignition, the temperature at the top of the compression stroke will indeed be lower. This allows for a higher compression ratio or more ignition advance without detonation. Modern engines with high compression and knock sensors might gain from this. Optimising compression ratio to suite the fuel will yield gains, but requires engine modification.

Regards

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[drwebb]

"State of Minnesota tested Mileage of vehicles using e85 and conventional fuel, found no significant difference in fuel economy."
- citations for unexpected data are always appreciated.