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The effects of downspeeding and supercharging a passenger car diesel engine were studied through laboratory investigation and vehicle simulation. Changes in the engine operating range, transmission gearing, and shift schedule resulted in improved fuel consumption relative to the baseline turbocharged vehicle while maintaining performance and drivability metrics. A shift schedule optimization technique resulted in fuel economy gains of up to 12% along with a corresponding reduction in transmission shift frequency of up to 55% relative to the baseline turbocharged configuration. First gear acceleration, top gear passing, and 0-60 mph acceleration of the baseline turbocharged vehicle were retained for the downsped supercharged configuration.

Southwest Research Institute, as part of the Clean Diesel IV consortium, built a multi-cylinder HCCI engine that ran in the HCCI combustion mode full-time. The engine was used to develop HCCI fuels, demonstrate the potential operating range of HCCI, and to demonstrate the feasibility of transient control of HCCI. As part of the engine design, a hardware based method of decoupling control of air and EGR was developed and patented [ 1 ]. The system utilized a positive displacement supercharger with a controlled bypass valve for air-flow control, and a high-pressure loop EGR system with variable geometry turbocharger to control the EGR rate. By utilizing the system, the required precision from the air and EGR control in the engine controller was reduced.