gpsman1 — Those energy numbers you quoted from Wikipedia are confusing (to me at least), because they are per fuel-air ratio. That is, thay are the equivalent numbers obtained by dividing the actual energy numbers by the fuel-air ratio used. For gasoline, for example, the fuel-air ratio is around 15, and the gasoline number you quoted would need to be multiplied by that ratio to obtain the (to my mind) more meaningful and more commonly quoted energy numbers for gasoline:
43.8 MJ/kg = 32 MJ/L = 121 MJ/gal US = 115 000 BTU/gal US
[gasoline has a density of ~730 g/L; 1 BTU = 1.055 kJ; 1 gal US = 3.79 L].

Stan

 

Good point Stan, noted.
Reading the whole Wiki page is quite helpful, and I hope others do.

 

Pat, I really don't understand what your saying here. The Atkinson we have is not a rotary engine. On the compression stroke, the intake valve stays open for a short bit which allows some fuel mixture back in the intake manifold. This reduces the final compression ratio for combustion. This does allow a small portion of warmer mixture to blend with the colder air before combustion again.

As far as the gas your using, looks like your best choice is 87 octane and if you can only get it with ethanol, that has to be it. If I could get gas without ethanol, I'd do it. I'm lucky here in South Florida as I get straight 87 octane year round. I have gotten Citgo gas with ethanol by mistake and it cause a 5mpg drop in MPG for about 1500 miles. After you use 10% ethanol for a while, your fuel maps will adjust to it and your mileage should improve though.

GaryG