bbturbodad

Has anyone used any Unleaded Racing gas in their TT? I put in 15 gallons of Trick 101 and WOW! However last week I put in some Unocal 100 and it ran like crap. Just put it my usual Shell 91 and it's running much better that the Unocal 100.

Can the ECU make adjustment for different gases or it all in my head?



Thanks

Jeffrey Behr

1. Porsche says the engine is designed for 93AKI (AntiKnock Index, the corrrect name in the US for the average-calculation 'octane' label) unleaded gasoline. That means it'll deliver full power and effficiency if it's fed with that.
2. Gasolines suitable for modern engines, including unleaded 'racing' gasolines, have an equal amout of energy (BTUs, calories, or whatever unit of measure you wish to use) per volume. The octane rating has NOTHING to do with ENERGY.

However, even admitting all that, it's possible for your particular engine to have some preference for the additive package that one gasoline has, over another gasoline's additives. I think your experimentation needs some broadening over your samples of one each.

I know that when I occasionally add 3 gallons of toluene* to my Turbo's tank of 91AKI gasoline, it has a little more power, but that's to be expected since the ECU no longer has to retard spark and do the other things it does to accommodate 91AKI gasoline.


* The additive all the companies already use to increase their gasolines' octane ratings. Three gallons = 11% and that presumably yields 94 octane.

bbturbodad

I didn't mean to imply that higher Octane = more power. Racing Gas tends to have a lower specific gravity, is more highly oxygenated and has a higher boiling point which = a more complete combustion of the fuel and theorically more power.

From my informal test the Trick 101 from Alliance Gas in Canoga Park gave me much better performance than 76 COMPETITION 100 fuel purchased at Brentwood 76 Service in Brentwood.

I'll be doing some testing during the upcoming months.

I'll keep you all posted.

Cayenne taking vitamins

rockitman

Is'nt that a bit riskey to the health of your engine??? From what I have heard, it is impossible to get a homogeneous mixture in your tank if you add toluene with the gas in your tank. It could also void the warranty if toluene was discovered in the tank if there was a problem and you brought it to the dealer. All the people I have spoken too that race indicate that the only safe way to boost octane is to mix 50/50 unleaded race fuel with premium unleaded. Toluene is a viscious solvent and may damage the fuel lines in high concentrations. Just my 2 cents. Besides, the additive used to boost octane for Sunoco 94 was just their 93 with MTBE added which is slowly but surely being outlawed due to pollution concerns. Sunoco 94 is no longer available in New York State because of this and the rest of the Northeast is following suit. In addition to that, Octane booster products are just bad...Many contain lead and were designed for leaded fuel only racing motors....

Cupcar#12

Actually the C's DME (as all modern P-Cars) will adjsut for the fuel quality by retarding ignition. this is a function of Anti-knock but there is a limit to how much it will retard it. since it is designed for Am- Premium lowest comman demoniator (i.e. 91 octane), your fuel map will lean as well but the C- is designed to run very rich on boost (9.5:1 if i remember correctly, which is way rich) you will see some improvement in preformance from higher grade fuel (more oxegnated) but not a huge amount. You do run the risk of killing your O2 sensors but other than that as long as it is unleaded your fine to run it - it's just not economical for the preformance recieved. Also long diets of racing gas will kill your O2's (same for additives)and since they have 4 of them it's not cheap to replace them. My 92' Cap car got about 4K miles out of an O2 sensor on a steady diet of 110 (leaded) racing gas which was needed since it was very agressively lean. anything lower and it would ping.
My 2 cents - and not a C owner

bbturbodad

Why does unleaded high grade fuel kill the O2 sensors?

Cupcar#12

the extra additives (tourene and MTBF) MTBF is the main ingredient that works in good octane boosters.

110 is leaded which is why mine went so quick.
Sorry my spelling sucks

Jeffrey Behr

Originally posted by rockitman:

"Isn't that a bit risky to the health of your engine??? From what I have heard, it is impossible to get a homogeneous mixture in your tank if you add toluene with the gas in your tank."

'Tain't impossible; one just has to be careful. The Cayenne has a 'U'-shaped tank, with 2 lower sections plus an upper. There are pumps in both lower sections and each has a vacuum-boosted drawtube in the other half. Either pump can empty the entire tank. I add the toluene (not 'tolulene' as is frequently used) towards the top where it resides intially in the top of the 'U' and not in one of the lower sections. It mixes as I drive and simply can't 'get by' the 91AKI gasoline.


"It could also void the warranty if toluene was discovered in the tank if there was a problem and you brought it to the dealer."

Maybe so, but they'd have to pay for an expensive analysis of my tank's gasoline; it smells and looks JUST like gasoline.

"All the people I have spoken to that race indicate that the only safe way to boost octane is to mix 50/50 unleaded race fuel with premium unleaded. Toluene is a viscious solvent..."

So's gasoline.


"...and may damage the fuel lines in high concentrations.

Maybe; maybe not, but I don't use it in high concentrations. As I said earlier, toluene is already used by all the gasoline refiners to boost octane; I just use a little more. I restrict concentrations to about 10% and always add to an almost-full tank. I'm simply not worried, but maybe I'm naive at best and stupid at worst.

See http://forums.audiworld.com/s4/msgs/95187.phtml for more info.