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Old 04-07-2009, 06:42 PM   #20 (permalink)
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Originally Posted by snowfish View Post
It seems logical that with more power one should get better FE .
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.
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