[quote=WhiteFwdsm;4385334]Just a quick note .. the octane of the gas will not change your airfuel ratio.quote]


Sorry, David is wrong. Ive laid this out 100 times on here, ill do it again.

Octane is a measure of a fuels resistance to detonation, as measured by the MOTOR octane number (increasing the compression till detonation is reached) or RESEARCH octane number (advandcing timing until detonation)

Higher octane fuel usually have a richer a/f ratio due to a lighter specific gravity. (in gasoline)

The additives put in to increase octane, mbte and the like, decrease burn rate and have less energy that the gas. This slows burn rate and make the fuel more detonation resistant. It also means 93 has less btu/lb than 87.

87 also has a higher latent heat vaporization rate, which means it ignites quicker due to increased off-gassing.
If a car can run without detonating on 87, it will be more efficient in every aspect besides thermal efficiency. This is the reason we can start a Top Fueler on 87, not 93.

Putting 100 in you street car is worthless unless you have the compression, timing, or boost to require it. And that bring you to tuning.

The more timing, the more pumping losses=less efficieny

Boost is a measure of restriction. With the right cam ive seen 15 less indicated lbs of boost and 70 more hp. That get into proper dynamic compression for the fuel and cylinder design.

Compression ratio is a chapter in itself, just know in a street-ish car, I can make more power with 93 octane at 10:1 than with 110 octane at 12:1.

If I missed something lemme know, until then I will no longer bore you with this nonsense