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      05-16-2012, 12:55 PM   #17
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Originally Posted by Joshboody View Post
Nice write up! Question about heat of vaporization and how it relates to power. You state that energy per volume is greater... Yes, but I am guessing that fuel will vaporize during the compression stroke once the intake valve is closed and thus no additional air added.

I think heat of vaporization is mainly part of the octane calculation cooling the mixture reducing detonation.
Octane and heat of a vaporization are separate ratings, but the cooling effect definitely influences the fuels octane rating. Unfortunately I do not have a chart here, but heat of vaporization is only a measure of the fuel's ability to cool the intake charge. A cooler, denser charge is good for making power and it also helps for keeping engine components cool thus helping them to live a long a healthy life. So yes, the fuels ability to cool the charge will help combat premature ignition. Heat of vaporization is expressed in British Thermal Units per Gallon of fuel with a higher value representing a better capacity to cool. Off the top of my head I think E85 for example is at least 100 BTU/Gal greater than regular pump gasoline. That's part of the reason why you see cars like the Koenigsegg make crazy power on that fuel.


Last edited by EFI Logics; 05-16-2012 at 02:25 PM.