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Hello, I own a 1999 Carrera and have been doing lots of track events lately. The car has not been "chipped". The cats were removed and headers and mufflers replaced with FabSpeed. At the track they sell 98 and112 octane fuel (at a very high premium). My question is, can this fuel be safely used without any modifications on the engine or electronics and if so, will it improve performance to justify paying 8 dollars per gallon? I live at sea level in Florida. I searched the site and could find nothing on this topic, just references to low octane fuel. Thanks for any help.

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98 octane is as high as you would need to go. Anything higher is a waste in your car. Like Logray was saying, there is an improvement but you would probably need a dyno to see it. Seat of the pants I doubt it. The best thing to do at the track is get a proper corner balance and ride height. Also strip as much weight as you can. You will see a much bigger improvement on the track.

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Thank you very much. The corner balancing has been done as well as the ride height (H&R coilovers dropped it by 1.5 inches). Got worried when I saw a guy in a BMW put racing fuel and then experiencing engine trouble at the race track. The race fuel is expensive but conveniently available at the track. It will save me a drive out of the track to refuel on extended track weekeends.

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I was told that it take about half a tank of fuel run through the car before the DME builds a new map to take advantage of the higher octane. I'm not sure how true this is or if it's the same with the older cars. Maybe someone else can confirm this. Either way just make sure that it is unleaded and you shouldn't have any problems.

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98 octane is a standard here,it is available at every petrol station. Some filling stations ( ARAL and SHELL ), especially on the highways, also sell 100 octane. They claim, at full acceleration and especially turbo engines, better performance. Anyway i've instinctively at least never encountered any advantage.

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We run Sunoco 110 in our kart race engines and it is leaded. If your catalytic converters are out of the car, why would you need to avoid leaded fuel? Kart engines do not have anti-knock technology and often produce more power on lower octane rated fuel. Some engine builders are recommending high oil to fuel ratios as a claimed way to reduce the effective octane rating of the 110 fuel. If your ignition timing is being retarded by an anti-knock system you may see higher output when using higher octane fuel. Is there a way to monitor throttle position, RPM, and ignition timing? We use MyChron4 telemetry from AIM. Maybe there's an iphone application for that?

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You will se little to no advantage running higher octane unless the car is actually remapped to handle the appropriate firing (timing) to take advantage of the less combustible fuel. Unfortunately the "self learning" aspect of the ECU is more about driver idiosyncrasies (and perhaps to a lesser extent, environmental) than actual fuel differences.

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Regarding fuel octane--US pumps display (R+M)/2 octane, whereas European pumps display just RON (the "R" in the US octane rating). For most pump gasolines, "R" is about 10 points higher than "M". Bottom line is that the 93 octane US premium unleaded is essentially the same as the 98 octane premium unleaded available in Europe, at least from an octane rating perspective.

As for the car's performance on racing fuel--it may increase slightly over time. I would personally spend the extra $$ on more track time; that will lower lap times more quickly and effectively than boutique racing fuel for anyone other than a pro (or near pro) driver, IMHO.

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  • 11 months later...

If your car is designed to run on 93 max and if it isnt programmed to adjust timing to anything higher then 93 then going higher in octane will loose you hp. The higher the octane the slower it burns. This is why turbos and very high compression engines can take advantage of higher octane. You will be wasting money by adding expensive high octane fuel and you will have slightly less hp. Save your money and spend it on tires, brakes, track time and things that are fun.

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