Inventors:
Roger D. Sand - Kokomo IN
Assignee:
General Motors Corporation - Detroit MI
International Classification:
F02P 504
Abstract:
An encoder produces for each cylinder of an internal combustion engine a plurality of crankshaft position digital code signal groups, each being a representation of a respective different crankshaft position in degrees relative to piston top dead center. A memory circuit responsive to the last output digital code signal group thereof and an excessive cylinder combustion pressure indicating signal, produced when the combustion pressure of a selected engine cylinder exceeds a predetermined value, is preprogrammed to produce, with the presence of the excessive cylinder combustion pressure indicating signal, the digital code signal group representation of the crankshaft position in retard from that as represented by the last output digital code signal group thereof by a preselected number of crankshaft position degrees retard and to produce, in the absence of the excessive cylinder combustion pressure indicating signal, the digital code signal group representation of the crankshaft position in advance of that as represented by the last output digital code signal group thereof by a preselected number of crankshaft position degrees advance. The digital code signal group to which the memory circuit is responsive and the crankshaft position digital code signal groups are compared in a digital comparator which produces an output ignition spark initiating signal when these two signals are equal. Every two crankshaft revolutions, circuitry responsive to a clock signal applies to the input terminals of the comparator an updated digital code signal group and circuitry responsive to a reset signal erases the excessive combustion pressure indicating signal, if present.