Method of controlling a four stroke Otto engine and reduction of knocking

The internal combustion engine control system may delay the closing of the inlet valve when the engine is under full load, changing engine operation from an Otto cycle to an Atkinson cycle. When the engine is under part load, the exhaust and inlet valves are moved from their normal timings (11,12) to retarded timings (15,16) with later opening (EVO,IVO) and closing (EVC,IVC). When knocking or detonation is detected by a sensor, the engine control system performs the following actions:- (a) reduces cooling fluid temperature to below 90[deg]C; (b) changes fuel-air mixture from stoichiometric or rich to lean; (c) changes phase of camshaft to delay opening and closing of inlet and exhaust valves; and (d) partially closes throttle valve to reduce pressure of mixture in induction manifold.