Dictionary

Knocking (Chapter 4) is a supersonic complex, which consists of a shock wave and an exothermic chemical reaction behind it. Spark-ignition internal combustion engines are rapidly destroyed by detonation, as they are designed for slow combustion of the fuel-air mixture. Rapid knocking combustion dramatically increases the pressure inside the combustion chamber, which leads to rapid engine failure. In case of strong detonation this can happen in less than a minute. Fuel with a higher octane number resists knocking better.