Electronic engine control

In an electronic controller for an internal combustion engine having an ignition system responsive to ignition pulses for producing ignition sparks in combustion chambers, said controller including means for generating a reference timing signal indicative of movement of the engine to a reference position in the engine cycle, timing advance control means for producing a timing advance control signal corresponding to a respective angular displacement of said engine from said reference position, and means responsive to said reference timing signal and said timing advance control signal for producing ignition pulses at positions relative to said reference timing position systematically related to said timing advance control signal, the improvement wherein said timing advance control means comprises RPM advance means responsive to engine speed for producing an RPM timing advance signal systematically related to engine speed and corresponding to a respective timing advance systematically increasing with increase in engine speed, manifold pressure advance means responsive to manifold pressure for producing a manifold pressure timing advance signal systematically related to manifold pressure and corresponding to a respective timing advance systematically decreasing with increase in manifold pressure, output means responsive to applied timing advance signals for producing a timing advance control signal corresponding to the sum of the respective timing advances, means for applying said RPM timing advance signal and said manifold pressure timing advance signal to said output means, means for providing an engine idle reference signal corresponding to a reference air flow, means for providing a low idle timing limit signal corresponding to a respective low idle timing advance suitable for operation of the engine at idle, means responsive to rate of air flow into the engine and said engine idle reference signal for modifying said low idle timing limit signal in systematic relation to rate of flow when said rate of air flow exceeds said reference air flow to produce an idle timing limit signal corresponding to a respective timing advance increasing with increase in air flow above said reference air flow, and means responsive to said idle timing limit signal for limiting the timing advance control signal to a maximum total timing advance corresponding to said idle timing limit signal.