An interesting thing about nitromethane is that it does not burn as quickly as gasoline. In fact, there is not enough time to burn all of the nitromethane between when the spark plug fires and when the exhaust valve opens. So the engine is pumping still-burning nitromethane into the exhaust pipe. That's why you see flames shooting out of the exhaust of a Top Fuel Harley.
Before there run, racers often preform a burnout in order to clean and heat tires. Additionally, the burnout applies a layer of fresh rubber to the track surface, which greatly improves traction during launch.
Before there run, racers often preform a burnout in order to clean and heat tires. Additionally, the burnout applies a layer of fresh rubber to the track surface, which greatly improves traction during launch.