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A gasoline compression-ignition combustion system is being developed for full-time operation over the speed-load map. Low-temperature combustion was achieved using multiple late injection (MLI), intake boost, and moderate EGR for high efficiency, low NOx, and low particulate emissions. The relatively long ignition delay and high volatility of RON 91 pump gasoline combined with an advanced injection system and variable valve actuation provided controlled mixture stratification for low combustion noise. Tests were conducted on a single-cylinder research engine. Design of Experiments and response surface models were used to evaluate injection strategies, injector designs, and various valve lift profiles across the speed-load operating range. At light loads, an exhaust rebreathing strategy was used to promote autoignition and maintain exhaust temperatures. At medium loads, a triple injection strategy produced the best results with high thermal efficiency.

This paper addresses the longstanding problems of residual gas measurement during engine dynamometer testing, and of real-time residual modeling for engine control applications. A new method is described which is simple to apply, requiring only currently standard calibration test cell instrumentation. Experimental validation against measurements using direct in-cylinder CO2 sampling is presented, and a comprehensive error sensitivity analysis is included. A real-time capable, controls-oriented model is also described. Its accuracy is assessed by comparison to engine-simulation-generated residual values after using these values to determine the model parameters.