TBH996

I'm doing a DE event at a track in Louisiana later this month. Is there any benefit to using the 100+ octane race fuels on a totally stock 996C2? (they sell it at the track) I know I'm not really "racing" but I was wondering if there is any benefit that helps with the wear and tear on the engine with these types of events since I'll probably be running the car pretty hard.

The 30K service interval will be done just before this event so I'll be up to date on fluids and I just bought new tires (I'm sure they won't be so "new" after the DE).

I'm just being precautionary since I haven't done any track time in this car yet.

E

s14roller

I don't see how 100 oct would give any performance versus good old 93...

Usually you run race gas if your car is running forced induction and it allows you to run higher boost safer.

Russ Murphy

^ +1

RayGT3

Computer is set up to run on 90 octane, any higher won't buy you much, if anything. Actually on a hot day the street gas will probably perform better.

TBH996

Thanks. I just didn't know if there were any other properties that had an advantage with running at high RPMs.

So here's an indirectly related question: As a novice driver, is it better to run a full fuel tank to help keep some extra weight on the front end with regards to handling characterisitics?

nick49

A lot of race gas has lead in it which will load up your combustion chamber with residual deposits. It doesn't burn as clean as unleaded. Also if the compression is such that it is not needed it will probably cause a decrease in power as it is slower burning. Most people believe super high octane fuels pack more punch when actually the opposite is true. You will obtain the highest performance and extract the most horsepower with the lowest octane rated fuel that your motor will burn without retarding the ignition timing.

Gnome

Respectfully disagree. Computer is optimized for 93 octane. Car will run on slighly lower octane (90 or 91) but the engine will detune itself to eliminate knocking. You might be right about the hot day part -- that's the limit of my knowledge.

If you have 93 octane in your area, stick with that -- any more is a waste of $$ because the car won't do anything different. If you live in an area where you can't get 93 (most stations in CA only have 91), you can mix in 100 to bring your ratio up to 93. The calculation is a straight ratio to bring the average up to 93.

I do this periodically when I'm near a gas station with race gas, and the engine runs smoother and quieter. Honestly can't tell from my butt dyno whether I'm getting any more power.

hwk72

In Europe some gas stations sell 100 octane gas - I'd call it a marketing gag. When I lived there me and some friends did some comparisons with lower octane gas with various street cars but none of us did record any power or mileage difference, so save your $$.

nick49

I think the octane ratings are different in Europe and 100 there doesn't equal 100 here. Can anyone substantiate this?

Dave Howerdel

...here you go...http://en.wikipedia.org/wiki/Octane_rating

hwk72

Right, Porsche and BMW suggest min 91 octane in the US and min 95 octane on the same engines in EU - 91 US and 95 EU are almost equal. However, 100 octane seams to be the same east and west of the Atlantic ocean.

carbonfiber

TBH,
Are you running at No Problem Raceway? If so you may want to run a half tank if you are concerned about carrying extra weight. There is a gas station only 2 minutes from the track and you could always top off in between sessions, there is always plenty of time for that. In november I ran almost a whole tank of gas during the DE in my 928. The track is not all that fast as there are lots of turns back to back but you will get to about 90-100 on the straight before turn 1. Other than the straight you will be mostly negotiating the turns and figuring out the lines so your car should do just fine on pump gas. I may be there this month, haven't made up my mind yet.
JIM

RayGT3

Just got back from Techtactics and had this same discusion. Actual program value 90. Minimum suggested 91. This is the area that some or all tuners get some performance from, they program to take advantage of higher octane gas. Some actually have dual fuel settings.

I have to correct my statement regarding temperature, on a cold day re:winter it is better to use low octane fuel as it burns quicker, on a warm/hot day use a higher octane as it burns a bit slower. But I agree with the previous Nick49 post that using the lowest possible octane without knock is the best senario.

Orient Express

There is a Unocal station about 4 miles from my house that sells 100 octane Race gas. For the last 4 years, I have added 4 gallons of 100 race gas to every fill-up I do on my 996, and I can tell a difference over straight 91 gas. A 1:4 ratio of 100 and 91 gives you an average of 95 octane.

The car is smoother, gets better fuel economy, and has much better performance, especially in the low end. It is also quieter.

The local price of 100 octane Race gas is about $5 and Premium is about $3.10, so the average price of a blend is about $3.60/ gallon. Not bad in these days, and worth it for the improvement you can see in your 996.

Galun

How quickly does our computers learn that there is higher octane gas in the engine, and adjust things accordingly?