Method and apparatus for controlling the operation of an internal

Abstract

A method for operating an internal combustion engine under varying load conditions includes different controls which are used in first, second and third load ranges of the engine. In the first, lowest load range, including idle operation, a constant lean fuel-air ratio and constant mixture volume are supplied to the engine while the ignition timing is varied to provide a more advanced timing with increased engine load. In the second, intermediate load range, the lean fuel-air ratio is again maintained constant, the ignition timing corresponding to the most advanced ignition timing of the first range is maintained constant, and the mixture volume is varied from the volume corresponding to the first range to a higher volume with increased engine load. In the third, highest range of engine load, the mixture volume is maintained constant, the ignition timing is varied only as required to prevent knocking of the engine, and the fuel-air ratio is varied to supply a richer mixture with increased engine load. In one embodiment of the invention, the fuel-air ratio and ignition timing are controlled by the use of an electronic control circuit which responds to signals representative of a control lever position and the engine speed. The mixture volume is controlled by a conventional throttle flap which is linked in a special manner to the control lever.