Control system and method for an internal combustion engine

A method for controlling an internal combustion engine having a compression ratio control mechanism capable of varying a compression ratio of the engine by varying a top dead center position of a piston, an ignition timing control system capable of varying an ignition timing of the engine, a detector for detecting engine rpm and engine load, and a detector for detecting a warm-up condition of the engine, the method comprising:

• controlling the compression ratio control mechanism and the ignition timing control system so that the compression ratio is varied depending upon variations of the engine rpm, the engine load and the warm-up condition and that when the engine is cold, the ignition timing is retarded from a MBT point and the piston top dead center position is made lower in level than that obtained when the engine is hot and operated at corresponding engine rpm and engine load.