[kellyjames]

Two main variables: 1) oxygenated or not; 2) Octane rating

I understand that oxygenated gas, you need to run richer (larger mains on carbed sled).... this makes sense.

i always thought that all things being equal, it was better to run 91 than 87. Now I'm hearing the firecat doesn't handle 91-93 octane very well, and that we should stick with 87.

SO MY QUESTION IS: What is effect of higher octane (burns hotter?) and how does that impact things...what are you guys using in your F7s.

THanks
KJ

 

[Earl McCreary]

running Chevron 92 oct. My dealer recommends it, as the higher octane is normally better quality gas... Claims less chance of water and so forth. So I have always run super unleaded.

 

[firecatsnopro]

OK heres the deal, F7's are made to run on 87 oct. fuel.
92 oct. burns slower ,NOT HOTTER and will slow you down, unless you are running increased compression or timing!
You need to burn the faster burning HOTTER 87 oct. to make the most power!!!!!!!!!!!
It's not true that 92 oct. is cleaner or contains less chance of water
92 oct. is used when there is a chance of detonation, on high compression engines
and that's the fact jack!

 

[fast f7 firecat]

thats the way i understand it too.

 

[firecatsnopro]

ttt

 

[alleycat]

i allways thought that higher ment my motor would run cooler,
was told that hightest run cooler then reg,
i never new it burned slower <_<
thank's for the info guy's, B)

 

[Earl McCreary]

Talk to the service manager this morning. does all my sled work, he said he is running 92 in his sled and that he recommends that I run the 92 also..

I will have to stick with his recommendations, but I do appreciate the feedback and information


Maybe my brother and I will do a comparsion this winter, fill his F7 with Regular and mine with 92 and see which runs faster.

 

[rob]

the info I got from Cat said 89 octane is best. But given a choice between 87 and 93, go with the 87. And I see in the latest bulletin it says to run the fuel switch in ethanol if using fuel with MTBE, and a lot of 93 octane in new england does.

 

[firecatsnopro]

Earl, it won't hurt a bit to run the 92, but after 22 years of engine building this is my findings.
It may not sound right to use the lower oct. fuel, but you will make the most power if you use the LOWEST oct. fuel your engine engine can stand, based on the compression and timing requirements!

 

[kellyjames]

This is very interesting... I never thought running lowest octane sled could handle was best... most power. This also means lowest octane it can handle is also closest to the edge of burndown...that's probably why I've always heard it is safest to run higher octane fuel. 92 vs 87.

Thanks guys. I think I'll try to stick with 89 this year... split the difference!
kj

 

[Thumper]

Originally posted by Earl McCreary@Dec 7 2002, 01:39 PM
Talk to the service manager this morning. does all my sled work, he said he is running 92 in his sled and that he recommends that I run the 92 also..

I will have to stick with his recommendations, but I do appreciate the feedback and information


Maybe my brother and I will do a comparsion this winter, fill his F7 with Regular and mine with 92 and see which runs faster.

There is no reason to reccomend running 92 unless you have engine mods. In fact. as stated the 87 can make more hp on a stock motor. Something else to condsider is that when you buy 92 unless it is from a high volume station it maybe old and have less octane. If two F7's with stock motors raced AND both were equal to start with you would be hardprerssed to see a difference between 87 and 92 octane fuels. Take all that money you save on buying 87 vs 92 octane fuel and buy a clutch kit. Then go out and blow away your buddy running 92 octane fuel.