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Old Dec 05, 2012, 11:15 AM
Nav_Aids is offline
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Canada, MB, Winnipeg
Joined Nov 2011
348 Posts
Actually all 3 of you (S3NFO, ChillPhatCat, and DarZeelon) are somewhat correct in what you are saying about higher octane fuels. All pump gas has a certain amount of natural octane rating but, a lot of fuel companies use additives to raise the octane rating of their fuel. Speaking from experience I can tell you that if you use a high octane fuel like 110 in a 9.5:1 compression engine it will fire the mixture but, it will not burn the fuel fully. It will run like it has a miss. In our racecar we have 16.5:1 compression and run VP C16 (117 octane) with 26 degrees timing. I tried to run this fuel in my car with 9.5:1 compression and could barely keep the engine running. IMHO =<9.5:1 use 85 - 87 octane, >9.5 but <10.5:1 use 92, >10.5:1 use alcohol or racing fuel starting at 100 octane.

The Reid Vapor Pressure is totally different between 87 octane and 117 octane, the C16 RVP is almost 5 times lower than 90 octane, and the evaporation temperatures are higher in the C16. Takes a lot more compression to get the C16 to burn right (Combust and Deflagration) but, to an open flame or spark the C16 is easier.

Reid Vapor Pressure Wiki:

Volatility Wiki:

Deflagration Wiki:

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Last edited by Nav_Aids; Dec 05, 2012 at 11:17 AM. Reason: missed an equal sign
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