Abstract: A spark timing control system for an uneven firing engine utilizes a microprogrammed engine controller which produces a spark timing control system based on internal calculations using spark advance and dwell variables supplied by a microcomputer. A crankshaft position transducer produces a reference signal having alternate long and short pulses from which the firing cycle may be determined. The microcomputer is interrupted at each falling edge of the reference signal and based on a determination of the existing firing cycle, calculates and supplies appropriate spark advance and dwell numbers to the controller.

Abstract: The values of dwell and ignition timing signals from which ignition dwell and spark timing are provided are controlled to minimize power dissipation in an electronic ignition system and to ensure that adequate dwell times are provided during engine acceleration conditions and large advance angle increases. The dwell signal is increased from a static dwell value during steady state engine operation to a higher value in response to sensed engine accelerating conditions and the change in the spark advance between ignition events is limited to ensure that an adequate dwell period is provided.