A New Methodology for Use in Engine Diagnostics and Control, Utilizing “Synthetic” Engine Variables: Theoretical and Experimental Results

This paper describes new methodologies and algorithms for use in engine diagnostics that simplify and improve combustion quality monitoring and closed-loop engine control in order to meet stringent emission standards. The “synthetic” variables these algorithms produce can be used to indicate the work produced by each cylinder combustion event at all engine speeds, and can be effectively used for on-board combustion quality measurements, engine diagnostics, and closed-loop control. The algorithms are very simple in form, run in real time, and the methodologies can be applied to compression ignition or spark ignition, 2-stroke or 4-stroke gasoline or diesel engines. Both simulation and experimental results are given for a two-stroke, two-cylinder in-line engine. The rotational dynamics and firing sequence of this configuration of engine is very similar to a four-stroke, four cylinder in-line engine, and nearly identical results will be seen with these two designs. Even more dramatic improvements can be seen with engines of fewer cylinders because of greater variations in their inertial forces. The algorithms can be successfully applied to many other engine configurations as well. Therefore, benefits can be derived from the application of these algorithms and their “synthetic” variables to control strategies for almost all modern small and medium size automotive and marine engines, as well as utility engines used for lawn care, snow removal, and other similar applications.