http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html
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High octane fuels
produce end gases that take longer to autoignite, so the good flame front
reaches and consumes them properly.

The normal flame speed is fairly consistent for most gasoline HCs, regardless
of octane rating, but the flame speed is affected by stoichiometry.


I donÆt deny there is conflicting information about this, however after reading a number of write-ups saying flame speed is dependent on octane VS its not I found that those that said it was not were typically based research and had a lot more (lab data) data and testing to back up their claim.

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The antiknock ability is related to the "autoignition temperature" of the hydrocarbons. Antiknock ability is _not_ substantially related to:


1: The energy content of fuel, this should be obvious, as oxygenates have lower energy contents, but high octanes.

2: The flame speed of the conventionally ignited mixture, this should be evident from the similarities of the two reference hydrocarbons. Although flame speed does play a minor part, there are many other factors that are far more important. ( such as compression ratio, stoichiometry, combustion chamber shape, chemical structure of the fuel, presence of antiknock additives, number and position of spark plugs, turbulence etc.) Flame speed does not correlate with octane.


web page

SAE has good test reports on this and you may find some info on Google.

Kevin C

87 Turbo Intercooled Raider, roller cam, torsen rear diff, LSD front diff, lockup auto with modified converter, V6 brakes, low transfer case gears...