Quote:
Originally Posted by bryn
the reason e85 gives such poor mpg is that it has a lower energy density, as ethanol has less BTU's than regular gasoline.
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Not quite, ethanol blends' effects on FE are not in line with its energy content. That's because FE drive cycles can actually improve volumetric efficiency with lower heating content fuel.
Some data:
http://www.ethanol.org/pdf/contentmg...yStudy_001.pdf
http://www.ethanol.org/pdf/contentmg...inal_12507.pdf
You can bet that the max. torque line fell in pretty much proportion to the lower heat content (unless the ECU allowed more spark with the ethanol, then the torque loss would be at least partially offset). But FE is a different issue -- lower heat content can improve things even if spark advance is constant.