Electronic ignition system

Claim 1

An ignition system for a spark ignition combustion engine having a rotatable driven output shaft comprising: means for sensing the rotational position and speed of said shaft and for generating output signals, representative thereof, at least one spark plug, means for cyclically activating said spark plug in synchronism with the rotation of said shaft comprising: a source of electrical energy, means for storing electrical energy, switch means responsive to said sensing means for electrically connecting said source of electrical energy to said storing means for a predetermined period of time regardless of the rotational speed of said shaft and for thereafter discharging the energy stored in said storing means to said spark plug at a preselected rotational position of said shaft, means for manually varying said rotational position at which said spark plug is energized by a user selected value, said manual varying means generating a spark advance output signal representative of the user selected value, wherein the voltage of said source of electrical energy varies between an upper limit and a lower limit, and comprising means responsive to the voltage of said source of electrical energy for varying the duration of said predetermined time period inversely with respect to the voltage of said electrical source and for generating a voltage output signal representative of the voltage of the electrical source, a computer having a data input and program means for periodically reading either of said voltage output signal or said spark advance output signal on said data input at predetermined time intervals.