I know race gas will do wonders in a turbo car, but has anyone filled their tank with race gas before? Any noticeable difference in performance? Will it negatively impact the car in any way? My 991 is stock with PSE.

Thanks.

 

be careful, some race fuels will damage catalytic converters

 

Make sure it's UNLEADED. A lot of race fuel is leaded and will do damage.

I've used Sonoco 260 GT Unleaded 100 octane.

Look up Sonoco to see where your nearest dealer is. Unfortunately you might have to buy 5 gallon pails. The place I found has the one I listed above on a pump thank goodness. It has ethanol and they are allowed to have it on a pump in my great "ethanol mandated" part of the state.

The difference is very noticeable! The car sprints, way more responsive, and takes off like a rocket. I plan on getting it whenever I can even though it's like a 30-40 min drive from my house.

Haven't priced it since last fall, since the car is in winter storage. Was over $7.00 a gallon last time I filled up.

 

http://www.racegas.com/fuel/unleaded

 

Higher octane is merely more stable at higher compressions it has no greater energy potential than lower octane fuel.- there is therefore no greater energy to be had from higher octane gasoline.

 

Not sure what you mean by "energy", but I'll tell you when I put that 100 octane in my tank my C2S takes off like a bat out of hell.

Hit the gas and there's no stumble, lag, blurb, or time to blink. It runs 100% better than 93 octane.

 

It's funny a lot of companies pushing aftermarket exhausts, parts, etc. get accused of running higher octane gas on the "after" to boost their dyno charts.

 

The only way to determine whether there is an increase in performance is to schedule two dyno sessions. One using 93 octane followed by a test where you have filled the tank entirely with the 100 octane fuel.

Octane is a merely a measure of the fuel's resistance to combustion resulting from pressure. A low octane fuel will pre-ignite in a high compression engine, that is, it will explode prior to the completion of the compression stroke, the point of highest compression.

I do not know, but I suspect that you are mistaken when you say that your car performs better with 100 than 93 octane unless the station where you are buying 93 is putting 87 into its tanks. If the fuel used is proper for the vehicle, higher octane will not cause better performance...for example, my old 66 VW would still go 0-60 mph in 26 seconds even if its tank was filled with rocket fuel.

 

So there is a difference from 87 to 100 octane, but not 93 to 100?

I have never put in 87 octane nor has a station switched fuels on me.

I'm sure someone will chime in that has more info than me, or I'll just look up the technicalities myself. I have a keen eye for small details and it's never failed me.

 

I agree with rnl. Higher Octane race gas simply adds to the pre-detonation preventative of a high performance engine. If you're driving conditions are not likely to result in pre-detonation even on lower octane fuels, you're highly unlikely to notice the difference.

Perhaps on a really hot summer day at the track the race gas would give a noticeable improvement in a street legal car as the engine is less likely to experience pre-detonation, detected by the knock sensors which results in a retarding of the timing...and more sluggish throttle response.

I always thought race gas was specifically for engines which were tuned to run high compression and very aggressive timing. The extra octane making that possible without pre-detonation that might occur with typical pump gas.

 

Good input. Thanks for the replies. I passed by a gas station in Pasadena that was charging $10 a gallon for race gas. Not sure what octane. Given the performance gain may be negligible I will pass.

 

Wouldn't this be a function of the vehicles ability to take advantage of higher octane fuels, ie. advancing timing?

 

Unless you are actually tuned for racegas, you will not see any advantages. Most likely the car will run like crap...

I used to play with racegas when i had my EVO IX fuly built block on a 63mm T3 turbo... The car would would gain a ton compared to pumpgas but with DIFFERENT mapping... leaner, mort boost and more timing...

 

High compression engines require higher octane fuel. Advancing ignition timing alone, were it is not warranted, may cause an engine to overheat. 991 engines automatically sense "knock" and will retard or advance timing accordingly.

Fuel companies have done a good job of labeling and advertising to create the impression that "premium" fuel is better fuel. Lower compression engines can burn either. The anti pre-ignition properties of premium gas is wasted on low compression engines.

Any real performance qualities experienced by the use of 100 octane in a 991 engine may be the result of a comparison with mis-labeled 93 gas. Unscrupulous vendors may be selling 87 octane as 93. Use of 87 octane will result in poor performance. Clearly, the use of 100 octane after a tank of 87 will result in significant performance differences.

My suggestion, start buying 93 from another vendor and see what happens.

My 991 provides "rocket ship" performance with 92 or 93 octane gas.

 

old school racers used %toluene, not sure how it affects cats