So I'm getting ready to run my SL55 at the dragstrip in a few weeks and I'm wondering if 100 octane will knock a tenth or so off my 1/4 time over 93 octane which is what I normally use. I have a Renntech ECU upgrade. Will the ECU advance the timing more for 100 octane right away or will it take a tank or two of 100 before the ECU adapts?

Hartmut, recommended 1/2 tank of Super and 1/2 tank of 100 Octane to me. Seems to be an issue with gas and the Ethanol in it, 93 Octane may not end up being 93 Octane. I hear over and over BAD GAS...

I know some guys that run a 15% blend of CAM2 (110 octane I think) racing fuel and 93 octane. They swear it creates better throttle response. CAM2 is leaded so I'm not sure it is a good idea for the cats. They run a quarter to half tank or so to lighten the car a bit.

Yea, don't use the leaded gasoline with your SL. Beyond ruining the cats, it will also mess up the finish on your exhaust tips as well as (possibly) building a residue on your cylinder heads. (As engine metals are now designed differently than when leaded gasoline was legal.) I'd just go with 1/2 Super and 1/2 100 unleaded octane, running with about 3/8ths to 1/4 of a tank of gas to save weight. Saving weight is one of the quickest, easiest and safest ways to better your ET at the strip. I'm sure you're already doing it, but remove everything from the trunk (including the spare) to lower the weight, run with less fuel weight, and you may want to try running 3-4 psi less on your tires as well. All this should net you at least as much or more than running huge octane leaded gas.

Also working on your reaction time can lead to a great ET!

Rook

We have done testing with different fuels and programming. I can't speak to what Renntech does, but we set up the ECU's to take maximum advantage of high octane fuel.

Depending on the fuel, as well as outside air temp, and a few other factors your car WILL make more hp with higher octane fuel.

I'm pretty sure Renntech does the same because they asked me if I had 91 or 93 available. I can get 93 and that is all I run.

This should happen instantly instead of the ECU needing to adapt, correct?

I am thinking the higher octane will allow the ECU to advance the timing without knock or pre-ignition and that's were the extra power is coming from.

Once the fuel is mixed together, the results should be instant.

Reaction time can win the race but it does not lower your ET