Abstract: An engine performance optimizing system is described that requires only a single engine parameter (shaft revolution time) to be measured. By simultaneously dithering spark timing, air/fuel ratio and/or EGR rate in accordance with a predetermined cyclic pattern, and measuring shaft speed during each discrete phase of the dither cycle, correction factors can be computed and used to adjust the spark setting, the air flow and/or the recirculation rate in a way that causes engine performance to be enhanced in terms of fuel economy and lowered emissions.

Abstract: A digital electronic control system for optimizing the performance of an energy consuming system wherein a given parameter, such as the air supply in a furnace, the spark setting in an internal combustion engine, or the pitch of a propeller in an aircraft is perturbated and the resulting effect on the machine or system performance is computed for producing a control signal which is then used to adjust the setting in a way which improves the performance. The process continues until an incremental change in setting no longer is accompanied by an improvement in the system's output, thus indicating operation at the optimum. The control apparatus of the present invention permits the selective introduction of desired bias values so that operation can be established off the optimum by a predetermined amount.