kcshaner

This is regarding the 100-103 octane race gas available at some tracks and gas stations.....

I know that running higher octane allows less risk of detonation therefore allowing to run more timing, boost, or both resulting in more power.

My question is if a car is tuned at 91 octane and all things staying the same (same tune, no more boost, etc) will running race fuel add power because it burns more efficiently?

In Lahmens terms (spell? ) If a person dyno's at 400rwhp on pump gas, what would you think they would dyno on race fuel if all else stays the same

Sorry, I had some beers over lunch and started thinking about this...

kcshaner

Anyone....anyone....Bueller....Bueller

eviltwins

No, you will not make any more power with the same tune unless the PCM is pulling out timing due to knock. You might lose some power though.

y2khawk

iTrader: (5)

High octane results in a slower burn rate/flame front. Leaving everything the same will put peak cylinder pressure later in the power stroke, yielding less work done.

Pro Stock John

iTrader: (34)

Well if you make 400rwhp with 91 octane, what power might you make with more timing and 104 octane is your question.

I'd say that you'd make 450rwhp at least, maybe more. Making 400rwhp with 91 might be with timing in the mid teens, whereas with 104 you might be able to run stock timing advance. Timing makes power.

I make 738rwhp with 110L and 23 degrees of timing at peak HP. To run 93 pump gas I might need to cut timing back to like 15 degrees, not that I have tried.

qqwqeqwrqwqtq

Though octane and burn rate are not really related, generally most race fuels will have a faster burn rate, as most race engines operate at a high rpm, which have less time for a complete burn.

Actual burn rate is effected by much more than just fuel type however. Engine type, combustion chamber design(shape, quench), a/f ratio and the homogeny of the a/f, temperature, etc,etc,etc.


I think if you run 93 octane on the street, and mix in some race fuel at the track, power level will be similar, but you will have an extra margin of safety.

z98

Wrong.

Put race fuel in an 85 Chevy pickup for a demonstration.

S_J_H

I agree with INTMD8 . There is a common misconception that higher octane = slower burn rate. An engine that turns 10,000 rpm needs a faster burn than A 4500RPM motor.
But going back to the original question-I have read more than one published dyno test where an engine was changed from pump gas to a good race fuel and did in fact gain power with no other changes to the tune up which surprised the testers.
So the answer is yes it is possible to gain power.There is more to the race fuels than just higher octanes.
But it is also possible to gain nothing. Just don't expect much gain without tuning changes.

Pro Stock John

iTrader: (34)

But that gain might be due to the fact that the test car was still getting knock with pump gas.

Higher octane is going to reduce knock earlier in the combustion stroke which has been stated a number of times. Going from 15 to say 25 degrees of timing with a 9 psi blower is huge.