Spark ignition systems for internal combustion engines

Claim 1

A spark ignition system for an internal combustion engine comprising the combination of an engine having at least one spark plug, an engine driven transducer producing a pulse train at a frequency dependent on the speed of the engine, speed computing means connected to said transducer and periodically operating to produce a first multi-bit digital signal, sensor means for producing a second multi-bit digital signal, corresponding to another engine operating parameter, an empirically programmed read only digital memory device having input terminals connected to said speed computing sensor means and to said means and having output terminals for producing a third multi-bit digital output signal determined by the first and second multi-bit digital input signals supplied thereto, an engine shaft position computing means connected to said transducer and producing a fourth multi-bit digital output signal varying with the displacement of the transducer from a datum position, a comparator connected to the read only digital memory device and the position computing means and producing a single pulse trigger signal output when the instantaneous value of the fourth multi-bit digital output signal from the position computing means is equal to the third multi-bit digital output signal from the read only digital memory device, and ignition control means connected to said comparator and to said spark plug so as to be triggered into producing a spark at said spark plug by said trigger output from the comparator.