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Technically, if the piston were to go faster than the speed of sound, it would create a shock wave in the chamber. However, this is not going to happen, for many different reasons: first of all, it would possibly destroy the inside of the piston engine, and the energy lost through friction could reach dangerous heats. Then, as the piston moves nearer the speed of sound, it would begin developing a vacuum just behind it, which would make it more difficult to pull the piston up. The air being compressed would be very thin in around the piston, changing the pressure, keeping the piston locked down.