Originally Posted by 83hurstguy
I am not disagreeing with the results here, but I'm curious how much of the results are not due to just octane change, but specific gravity change. Race fuel is notably lighter (less dense) than pump gas; therefore, the same jetting causes it to run leaner. The burn curves are also different so the timing requirements could change. We found this on the dyno, but ran out of time to do a full A-B comparison with jetting and timing changes.

Quite a few NHRA stock eliminator cars are running C11 or C12 fuel (or similar) on engines that have less than 10.5:1 compression, some between 9-10:1, saying its notably quicker. For heads up racing, those same engines will have a custom carb set up for C25 (or similar Pro Stock fuel) that has octane average of 117, and timing has to get pulled to make it work. It's a ton of work to optimize a fuel for a car, but somehow the higher octane fuels work for those guys and not others. I don't have any data (yet), but plan to do more testing someday. Makes you wonder...


I ran my 10 to 1( maybe) typical low/ mid 11 sec combo on both pump 93 and 110 for extended periods of time last year to see what if any difference might be
Frankly, i noticed nothing either way regards an ET difference.
People told me it would run better on pump gas, thus the effort to try it. I ran each enough to make a valid comparison

Last edited by B3422W5; 03/31/21 01:28 PM.

69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight
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