Race gas?

[drifting]

This might be the stupidest question I've asked.

I've been talking to a few turbo builders in the states they all go on about "race gas" I've googled this but don't seem to get a good answer. Here in the uk or at least the uk drift scene just seem to use normal 97-99 ron petrol. So the term meaning nothing to me.

So is there a set rating for race gas or can it be anything from 98 - 118 ron?

Any help is appreciated

[MotherTucker]

Well, here on this side of the pond, race gas seems to be anything of higher octane than what you can buy at the the common gas station. 93 octane is the highest you can buy here at "normal" gas stations, so race gas is generally 97 or above.

BUT, there is a big caveat. The ECU controlling modern engines such as in the R8 do their very best to make up for variations in octane, air temperature, air pressure, etc. So using a high-octane "race gas" is very effectively negated by the ECU. I have used 117 octane race gas on the track, and noticed absolutely nothing different. The ECU undoes the power gain inherent in high-octane gasolines, to keep the performance of the engine as consistant as possible. You can't get increased performance from high octane fuels without matching changes in ECU settings. Somebody correct me here if you think I'm wrong, but this is my understanding and experience as well.

mt

[StanleyFord]

What is the lowest octane rating the engine will work with effectively? In California, most gas stations max out at 91 octane.

[AJR8]

Good to know MotherTucker...I've never heard of that...but that modulation happens with the FSI engines or all kind of new engines? Because I once used Panta 115 octane racing fuel on my 996 4S (MY2004) and it was like supercharging...it took 2-3 minutes to the ECU to elaborate the new fuel and get a proper set up but them it was awsome...

[drifting]

Thanks MT
Its for my R34 project I'm a bit stuck with turbos due to garrets just melt so means a custom borg warner or holset but for the power I want its hard to find a quick spooling turbo for the job. A lot of the state side guys seem to use race gas they tell me it spools up quicker.

other than fitting a supercharger and a turbo i'm out of ideas

[KfabR8]

Race gas is for race engines.

The whole idea of the higher octane rating is to slow down the ignition/burn rate of the fuel and allow for higher compression engines to burn the fuel/air mixture more efficiently - and extract more energy from the fuel.

Putting anything over "X" octane in an engine designed for "X" does nothing other than waste money (race fuel's not inexpensive) and can actually hurt horsepower output. The engine's not able to use the energy stored in the fuel if it can't compress it enough. It doesn't fully burn.

One of the biggest misnomers in the motocross world is "It's a high performance bike, it needs race fuel!" Nah, it needs high octane pump fuel. I've seen many people at the track with a bike that runs like crap and has a jug of Brand X 100 octane sitting beside it. "But it's a race bike!". No, it's a high performance machine designed to work with pump fuel. They put pump gas in and suddenly the bike runs! Gee, go figure...

Now, if you've done work - i.e. upping the compression, advancing the ignition, etc, then you might start looking into race fuel.

Another example is the old Honda Pilot off road buggy. - 400cc two stroke power plant. Bone stock they run about 135-140 psi of compression. They run regular old low octane fuel with a stock engine. A little engine work, say get the compression up to the 155-160 psi range and then you start needing the higher octane pump fuels. The breaking point for having to switch to race fuel is 165 psi. 100 octane works well to about 175 psi, then you need to bump up to the 107-110 range. Above 185-190 you have to look for 115. Probably the most finicky and straight forward (on numbers) engine I've ever met. Just 5 psi makes a huge difference on this machine.

Fuel is not going to affect the spooling up of your turbos that much - once again, the octane rating is how quickly the fuel burns - lower octane, lower flash point, quicker to go boom under pressure. 115 octane race fuel burns slowly compared to 89 pump gas.

Also, many of the race fuels are not necessarily 'petroleum' based as are pump fuels. Usually they're more of the hydrocarbon (yea, it's similar to pump fuel) bias. They often have lead in them too - which is really hard on the catalytic converter and the O2 sensor - it kills them both quickly. They don't generally have the lubricity that pump fuel has either.

One thing that might be something to look into are the oxygenated fuels. I believe that VP sells a roughly 100 octane rated fuel that's high in oxygen content. It's not traditional "race fuel", but does supposedly give an increase. I'm not familiar with it, though as I set all my stuff up to run on good old pump gas. I've done the race fuel setup and it's a total pain in the butt to deal with.

@StanleyFord - use the highest octane rated fuel you can get - Shell is one of the better ones (there's a thread on this somewhere, but I'm too lazy to search for it at present). The car will adjust accordingly.

We're lucky that here in Ohio we can get 93 at pretty much any pump and there are a few that carry 94.

[Yspokes]

MT and KFABR8 are right. You DO NOT need 100 octane unleaded in your R8. It will not increase performance unless you increase the compression ratio, or re-tune the ECU for it, or preferably both. The most you can hope for is 2-3 degrees more timing advance due to absence of knock (pre-ignition), but that's about it. Today's ECU's are tuned for pump grade fuel between 91 and 93 octane, and you will just waste your hard earned money. I actually tested this on my Dyno with about 5 different cars in a before and after scenario with matching weather specs. There was NO increase. (KFABR8....you make me jealous with your fab shop. I miss mine, and I MISS my Dyno!)

[Monkey boy UK]

MT and KFABR8 are right. You DO NOT need 100 octane unleaded in your R8. It will not increase performance unless you increase the compression ratio, or re-tune the ECU for it, or preferably both. The most you can hope for is 2-3 degrees more timing advance due to absence of knock (pre-ignition), but that's about it. Today's ECU's are tuned for pump grade fuel between 91 and 93 octane, and you will just waste your hard earned money. I actually tested this on my Dyno with about 5 different cars in a before and after scenario with matching weather specs. There was NO increase. (KFABR8....you make me jealous with your fab shop. I miss mine, and I MISS my Dyno!)

& is higher octane better for the V8 / V10, forgeting the price should we opt for higher? we usualy opt for over 100 cct when in France, Germany ect as we dont get it in the UK! all thinking we would go quicker!!!

[harrison]

How much better is the gas over in the other countries?? Or how does the U.S. gas compare ?? We are approaching 5.00 gal now. I know how expensive fuel is in Europe - but I assumed the quality was a little better over there. I am just a fuel burner. NOT a fuel Tech. But I love fuel that is explosive/fast burning.

[KfabR8]

& is higher octane better for the V8 / V10, forgeting the price should we opt for higher? we usualy opt for over 100 cct when in France, Germany ect as we dont get it in the UK! all thinking we would go quicker!!!

I believe that in Europe they use the Research octane number (RON). Here in the States we use the average of Research and Measured octane number.

Look on the inside of your fuel filler door - Europe they list 98RON and here in the States is says 95RON, which turns out to be 93 (if what I understand is correct).

Anything over what they list for your car is really just a waste of money. The car's tuned for what they list.