ADAPTIVE CLOSED-LOOP ELECTRONIC FUEL CONTROL SYSTEM WITH FUEL PUDDLING COMPENSATION

An air/fuel mixture control system for an internal combustion engine uses a closed-loop controller which varies the air/fuel mixture in response to the oxygen level in the engine's exhaust emissions to achieve stoichiometry. The oxygen level sensor produces a binary signal indicating either a rich or a lean mixture. The controller responds by generating a fuel delivery rate control signal which has three components: an integral (ramp function) component, a proportional step function component which abruptly jumps the control signal to an intermediate level at the time of each oxygen level change, and a differential overshoot component which (1) injects a compensating volume of fuel into the engine intake at the onset of each lean signal, and (2) subtracts a compensating volume of fuel from the intake at the onset of each rich signal. The compensating fuel volume minimizes the effects of fuel puddling in the intake manifold to reduce the effective closed loop delay time for better control. The magnitude of the compensating volume may be altered in response to detected engine speed and/or load, or alternatively may be adaptively varied to achieve maximum closed loop cycling frequencies.