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Old 07-30-2009, 06:18 PM   #28 (permalink)
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Originally Posted by nemesis View Post
[Higher-octane] fuel burns slower ...
Not strictly true. In fact, I know several petrochemical engineering types who insist that the flame-front speed is more dependent upon cylinder pressures and mixture than upon the fuel composition. At least, in any gasoline we would see sold for street use. (Ethanol will change things; I am not sure how much.)

As a counter-example, there are known cases of aviation engines who suffered burned exhaust valves from running 110-octane Av Gas when they were designed specifically for 80-octane Av Gas. Those seem to have been caused by the mixture still burning as it exited through the exhaust port. But that's a much larger change in octane than we see in streetable motor fuels, and Av Gas is not really the same as automotive-grade gasoline.

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