US Patent 7370634 Internal combustion engine spark timing control system

A method for controlling spark timing in an internal combustion engine. The method includes determining, in response to a knock sensor mounted to the engine, a spark offset to the scheduled spark timing for the engine at relatively low engine speed which is applied to the scheduled spark timing at relatively high engine speeds. This offset is applied in conjunction with a time-varying spark retardation bias. The offset is removed at a rate proportional to the time varying spark retard bias. The bias increases if either a relatively large torque is demanded from the engine or the engine is at the relatively high speed and relatively high air charge condition; otherwise, the bias is decreased with time.