Use of Racing Gas

[insite]

i have run out of fuel at the track & refilled w/ VP Racing C12. it's a risky proposition since it's leaded fuel; this can foul oxygen sensors. without a doubt the car ran much better than on pump gas. i think that's because a lot of times, 93 octane at gas stations sits for awhile before it sees our tanks. octane turns into heptane (regular gas) over time, so the true octane rating of the fuel we purchase at gas station is somewhat less than 93 by the time we get it.

still, though, i don't think the computers in our car will try to optimize spark advance for anything beyond 91 octane (california fairy juice). a re-program of the ECU can widen the parameters to allow tuning to race fuel. companies like Revo will let you re-program on the fly for this. FYI, the difference is significant.

[edevlin]

So, as I said in a related thread, I filled up my base 2000 Boxster with 100 octane lead-free racing fuel when I went to VIR last weekend, an expensive experience. I have been trying to get a sense of how the car performs with the higher-octaner fuel. It seems like it is more responsive, and pulls harder at high rpm's, but it has been difficult for me to quantify.

I went to Richmond today and as I watched the gas gauge head down to a quarter of a tank of the expensive 100 octane fuel, I impulsively decided to see if there was any difference in the performance of the car. So I gave a quick call to the folks at Perfomance Autosport to see if their dyno was free this morning.

I plunked down my 75.00 and we strapped the Boxster in for a run. Dyno-pull junkies, I guess I qualify, know that they put the car in fourth gear and run it up to redline for a pull. One thing I kept track of today was the spedometer at just over the 7K redline in fourth gear. It was 138 mph, yikes. Anyway, I will try to see if I can post the dyno readout as an attachment, if not I will put it up as a sample dyno on my car webpage below.

The results were interesting, no increase in torque over the pull I did recently with normal shell premium 93 octane fuel. But there was an increase from 204 to 210 hp, a 6 hp increase, almost all at higher RPM's. I dont know how much of this increase in inherent in our cars ECU's, or if it is a result of the programming of the Autothority chip that I have put in the car. If the graph posts, the upper graph is the 100 octane fuel run, the lower graph is the 93 octane fuel run, interesting,

Ed