Does race gas really improve 1/4-mile times at all?

Can it be mixed safely with pump gas or do you need to have basically an empty tank and fill up with it for it to be effective?

I've been comtemplating filling up with some of it at the track, but was skeptical if it really works.

Can it harm the engine at all?

 

Race gas won't harm the engine however since race gas has lead in it, it will kill your O2 sensors.

There's no more BTU energy in VP C12 than there is in your local 92 octane pump gas. All the race gas does is burn slower to prevent detonation.

If your engine isn't pinging and/or your computer isn't detecting any knock then using a higher octane fuel is a waste of money. You only need enough octane to prevent detonation.

 

WRT to "energy content", the above statement may (or may not) be correct. Depends how you define "energy content". If you define it as BTU/lb than it would be an essentially correct statement. However, defined as BTU/volume, it is probably far from correct. There is a fairly large difference in density between different gasolines. For example, the specific gravity of VP race fuels varies from .696 to .760, a difference of nearly 10%. An EFI sytem delivers a given volume of fuel/time. The energy content of a given volume of gas with a s.g. of .696 will be a lot less than the same volume of gas with a s.g. of .760. If the car was tuned for the heavier gas and you simply substituted the lighter gas you would run quite lean and lose power, all else being equal.

Also, octane and burning rate are not directly related. Fuel chemists can, and do, vary burn rate to suit the intended rpm range of the motor. A higher revving motor needs a faster burn rate than a lower speed motor, and so on.

However, the conclusion "If your engine isn't pinging and/or your computer isn't detecting any knock then using a higher octane fuel is a waste of money. You only need enough octane to prevent detonation" is essentially correct. And as Stephen 87 IROC suggested, leaded race gas will kill your O2 sensors and you car will run like crap if this occurs. There are unleaded race fuels available, up to ~104 motor octane. If you need more octane, these are the way to go unless you have a dedicated race car that doesn't need to run in closed loop.

BTW: a stock tune is plenty rich enough that you don't need to worry about fuel density or additional small amounts of oxygenates in the fuel. Because of this, if you use a fuel with a higher level of oxygenates (such as some unleaded race fuels) you may gain hp. The AF ratio will be closer to optimal. Think of the oxygenates as a "chemical supercharger" in that context. So, you may want to try some unleaded race gas, especially if you have a stock tune and are seeing some timing retard. Setups like mine, tuned for a specific AF ratio with a wideband and on the edge of detonation should always be run on the fuel they were tuned for.

Rich Krause

 

I forgot to add:

If performance increases from using 87 octane to 92 octane or from using 92 pump gas to 100 unleaded race gas it isn't really because of the higher octane. Chances are using the lower octane was creating detonation that the knock sensor picked up and told the computer to retard the timing. If the timing is constantly being retarded under WOT operation then performance won't be what it could be. Using a higher octane fuel will reduce or eliminate the detonation and it will make the car run faster.

On a non computer car, chances are you won't see any difference. Maybe a slight increase since if the engine isn't detonating, it will make more power but at least the timing isn't being retarded by a computer.

 

Simple answer: At your level (or mine), don't bother. The only thing it will help with is emptying your wallet.