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Turbocharger compressors are susceptible to surge – the instability phenomena that impose limitations on the operation of turbocharged engines because of undesired noise, engine torque capability constraints, and hardware strain. Turbocharged engines are typically equipped with a binary compressor recirculation valve (CRV) whose primary function is to prevent compressor surge. Calibration of the associated control strategy requires in-vehicle tests and usually employs subjective criteria. This work aims to reduce the calibration effort for the strategy by developing a test procedure and data processing algorithms. An automated calibration for CRV control is developed that will generate a baseline calibration that avoids surge events. The effort to obtain the baseline calibration, which can be further fine-tuned, is thereby significantly reduced.

Direct injection stratified charge gasoline engines are becoming increasingly popular due to their potential for improved fuel economy and emissions. However, the benefits are restricted to low speed and load conditions due to the large air requirements during stratified operation. With boost, the air flow can be increased, extending the stratified operating regime and potentially the fuel economy and emissions benefits as well. This study assesses the feasibility of this technology using a variable geometry turbocharger and a supercharger as boost devices. The effect of boost on fuel economy, delivery of recirculated exhaust gas, and exhaust gas temperature are considered.