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In order to satisfy environmental regulations while maintaining strong performance and excellent fuel economy, advanced diesel engines are employing sophisticated air breathing systems. These include high pressure and low pressure EGR (Hybrid EGR), intake and exhaust throttling, and variable turbine geometry systems. In order to optimize the performance of these sub-systems, system level controls are necessary. This paper presents the design, benefits and test results of a model-based air system controller applied to an automotive diesel engine.

Control strategies for engines with multiple sources of EGR (Hybrid EGR), such as high and low pressure, have been developed and are in or near production. Next generation engines require these basic approaches be extended to take advantage of the capabilities these advanced air systems offer. This paper presents a number of the practical challenges encountered when attempting to do this control system optimization as well as proposed solutions. Engine test results showing the net improvements to emissions and transient response when using these techniques are discussed.

The paper presents the structure of an air system controller and its application to a modern boosted dual loop EGR Diesel engine. Results over a U.S. FTP cycle which show improvements in emissions and fuel consumption with future opportunities for increased performance are discussed. A recent application of the controller is also shown where standard engine sensors are eliminated to reduce cost and their function is replaced with in-cylinder pressure measurement combined with signal processing techniques.