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...


May very well be true in my case...I ran low on 93 at the track and threw in some 110 just to make another couple passes. Wasn't going to change anything b/c the car was optimized for 93 pump gas.


CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax