Abstract: An internal combustion engine crankshaft reference signal pulse corresponding to a selected one engine cylinder pair and a series of crankshaft position signal pulses are generated during each crankshaft revolution and a crankshaft reference signal pulse corresponding to each other engine cylinder pair is synthesized during each crankshaft revolution. In response to each crankshft reference signal pulse and the subsequent crankshaft position signal pulses there is produced an ignition dwell signal effective to initiate ignition coil primary winding energization and later an ignition spark event signal that is effective to terminate ignition coil primary winding energization to thereby produce an ignition spark potential at the engine crankshaft angle at which an ignition spark event is to occur as calculated by an associated external data processor unit.