Retrofit Feedback Control of A/F Ratio and Ignition Timing for Fuel Economy

An electronic engine management system has been developed to control both ignition timing and air-fuel (A/F) ratio to maximize fuel economy. Both controls employ feedback techniques and are therefore intrinsically adaptable to a wide variety of models, as required for a universal retrofit market. The ignition control loop monitors the position of the combustion pressure peak while the mixture control loop senses the lean limit as defined by a roughness threshold. Test results demonstrate fuel economy and transient operation. A brief background to the New Zealand energy conservation program is in included as background to the system’s specification.