Quote:
Originally Posted by snowfish
It seems logical that with more power one should get better FE .
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Ethanol has far fewer BTU's per pound, which is why you have to burn more of it to accomplish the same work.
But ethanol also has a higher resistance to predetonation (octane) which allows more aggressive ignition timing, and provides smoother/more even burn - as well it brings a lot of its own oxygen to the party so it increases the volumetric efficiency of the engine.
As a side note, gasoline burns
most completely at its stoich. ratio of around 14.7:1 at sea level. But it
releases the most BTU's per pound at around 12:1 so on paper,
you should be able to return better fuel efficiency when running rich than when running lean. 