Starrynight: Many rally cars are turbocharged. However, your mentioned turbo-lag is a real pain in the ass for them as they are constantly speeding up and slowing down. Someone came up with a neat workaround for this: as the car slows down, the turbocharger is kept up to speed by the injection of fuel directly into the exhaust pipe, which is then ignited. The resultant explosion mimics the effect of exhaust at high speed, driving the turbine. This is why you hear a lot of banging noise as a rally car slows down to take a corner.

To do this on a normal road car would be outright insanity. Not only would you probably cause severe injury to anyone walking past your car, but the exhaust pipes wear out really fast; I don't know exactly how long they last, but I think its tens of miles.

I don't actually know anything about this sort of stuff. I was told all this by an "engines-hacker" friend of mine and thought it was cool. /msg me with corrections.