Abstract

An engine ignition system comprising a signal coil for generating a first reference signal at an advanced angle and a second reference signal at a start position in synchronization with the rotation of an engine, a throttle sensor for detecting a throttle opening degree and a first ignition timing calculation circuit for calculating an ignition timing corresponding to an output signal from the throttle sensor in accordance with the first reference signal when the ignition timing is advanced from a predetermined ignition timing. The ignition timing system further comprises a second ignition timing calculation circuit for calculating an ignition timing corresponding to an output signal from the throttle sensor in accordance with the second reference signal when the ignition timing is retarded from a predetermined ignition timing. Either one of the first and the second ignition timing calculating circuits may comprise a function generator circuit having a calculating function equal to the first and said second ignition timing circuits for changing ignition timing characteristics of the first and the second ignition timing calculation circuits relative to the throttle opening degree into linear characteristics.