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Old 09-10-2011, 02:44 PM   #9
blue2000s
Porscheectomy
 
Join Date: Mar 2006
Location: Seattle Area
Posts: 3,011
Quote:
Originally Posted by pk2
Typically a higher ethanol percentage gives a false octane reading. 93 oct spiked with ethanol can still give a rating of 93 oct. The diff is, when it "delivers" the heat and how fast.

PK
The octane rating is only a measurement of the energy required to combust the air/fuel mixture or activation energy of the mixture. All it does is keep the fuel from igniting off a hot piece of carbon within the combustion chamber before the spark plug fires, preignition. Lower octane fuel takes less energy to light off.

It has nothing to do with the burn rate or energy content of the fuel. Because of the mixture that is typically used to increase octane, it is usually a lower energy content than lower "grade" fuels.

Slower burn rates aren't necessarily a bad thing, by the way.

Last edited by blue2000s; 09-10-2011 at 02:49 PM.
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