The bias-ply tires also dramatically change diameter over a run, which has the effect of altering the overall gearing. Specially constructed Goodyears have the intimidating task of transferring all that rotational energy to forward speed. The discs get so hot that at least two of them are welded together by the run's end. If it engages too quickly, the tires will spin, but if it's too lazy, the car won't accelerate as fast as possible. The clutch is tuned according to track conditions. A hydraulically motivated throw-out bearing operates off a simple timer (computer controls are illegal). 'The clutch is the lifeline of the car,' Oberhofer says, because it regulates wheelspin by gradually engaging and slipping as the car moves down the track. ClutchĪ five-disc dry clutch is the only link between the engine and the locked rear end-there's no transmission. That kind of flow requires a firehose-like fuel line. The 58 nozzles in the intake tract are always open, dumping about 5 gallons of fuel in a 4-second run. But nitro is an oxygen-rich compound that requires less air to burn, so the engine can consume more of it, thereby producing greater power.
Interestingly, a gallon of nitromethane, which costs $58, has less energy content than gasoline (14 kilowatt-hours versus 34). Top-fuelers burn a mixture that's 90 percent nitromethane and 10 percent alcohol.
