100 Octaine fuel

[cscarlson]

Anyone ever use 100 octaine fuel in their corvette? how did it do.? any problems?

[VETTEX2]

I've added 3-4 gallons per tankful before and liked it
we are stuck with 91 octane so it helps

unless you are heavily modified , anything over 93 is a waste of money

[baxsom]

Remember that octane is just resistance to pre detonation. Higher compression, advanced timing engines need more octane. if the knock sensors arent causing the computer to pull timing at 93 then 100 wont do anything.

[Hib Halverson]

Anyone ever use 100 octaine fuel in their corvette? how did it do.? any problems?

If you are talking about AVGAS LL100, don't do it. The lead in it will damage your engine.

If you're talking about unleaded 100-oct racing gasoline, there are some but not a lot of benefits to using it in a stock engine. All you really need do is mix enough 100 unleaded to get your octane up to about 94-95. That will eliminate virtually all detonation.

For more information on gasolines for Corvettes, see:
Corvette Action Center Deep Dive Series: Gasoline for your Corvette - Page 1 of 8

[Vettehead Mikey]

Hib,

are you inferring that a stock engine detonates with lower than 94-95 and that the knock sensors are actively preventing this?

[Hib Halverson]

Hib,

are you inferring that a stock engine detonates with lower than 94-95 and that the knock sensors are actively preventing this?

Yes.
I've seen it on the chassis dyno many times.

Now, obviously, this is more of a problem when using 91 octane (which is all that's available in the western U.S.) than it is when using 93-octane (common in the upper midwest and on the east coast)

For a number of years, GM has calibrated for 93 but, even using fuel with that much octane, in warm weather or with higher coolant temps, you still get detonation and the resulting KR.

I've found that going up to 94.5-95 effectively eliminates the problem so, when I'm doing chassis dyno work or road testing for numbers or racing, I mix 100 unleaded (I prefer Rockett Brand Racing Gasoline) with pump 91 at 1:2 or 2:3 depending on IAT.

[Evolution1980]

Yes.
I've seen it on the chassis dyno many times....

What about at lower RPM when most people are burbling around at 3K RPM or less? Is detonation occurring across the entire RPM band or only at higher RPM?

[Hib Halverson]

Mainly under high load near peak torque or, if the engine is really short on antiknock, from a little before peak torque up to peak power.

If the engine's rattling at light throttle in the mid-range it's unlikely you have a gasoline problem. You have either a spark curve problem or, possibly, on a 74-up, a problem with EGR.