US Patent 7484368 Clutched super turbo control strategy

A method of controlling an internal combustion engine boosting system of the type including an exhaust-driven turbocharger and a mechanically-driven supercharger. The supercharger includes rotors and a clutch operable in a first condition to transmit torque from a mechanical drive source to a supercharger input in response to a positive input, and operable in a second condition to interrupt the transmission of torque from the source to the input. The method is characterized by determining possible operation of the clutch in a first condition; and commanding a bypass valve toward a closed position, forcing air through the supercharger. The airflow causes the supercharger rotors to rotate, thus rotating the input of the supercharger prior to the clutch operating in the first condition.