An ion-sense engine fine-tuner

The paper presents a real-time closed loop demonstration of spark advance control by interpretation of ionization current signals. Such control is shown to be able to handle variations in air humidity, which is a major factor influencing burn rates, and consequently pressure buildup and useful work transferred via piston to drive shaft. This leads to a clear improvement in engine efficiency compared to traditional systems using only engine speed and load. Inspired by the type of challenges and potential usefulness in interpretation of ionization current signals, the paper focuses on closed loop ignition control by ionization current interpretation. The topics discussed include: the basics of ionization currents; spark advance control, especially principles relating pressure information to efficiency; and the structure of the ion-sense spark advance controller. The experimental demonstrations and some conclusions are presented.