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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.

At present, combustion pressure sensors find widespread use in basic engine research and development. In the future they could provide the essential information for closed loop engine control (of both fuel mixture and ignition timing) and diagnostics. The quartz piezoelectric device is the most familiar; its concept has been extended to piezo-ceramic configurations seated beneath or inside a sparkplug. This paper presents preliminary results for a novel fiber-optic pressure sensor incorporated into a spark-plug. Head-stud transducers are also described.