Abstract: An exhaust valve system for an internal combustion engine including a turbocharger is provided for effectively increasing the turbocharged boost pressure at low load engine conditions thereby effectively improving engine transient response. The exhaust valve system includes an exhaust valve control device operable in a normal timing mode for permitting normal opening of one or more exhaust valves at a normal opening crank angle, and in an advanced timing mode for advancing the timing of the opening of the exhaust valve to an advanced opening crank angle prior to the normal opening crank angle while maintaining the timing of normal closing of the exhaust valves at a normal closing crank angle.

Abstract: A turbocharger wastegate control system is responsive to electrical control signals to control the position of a wastegate valve positioned within an exhaust bypass conduit of the turbocharger. In one embodiment, the control system includes an air pressure control device having an inlet port receiving boost air pressure from an intake manifold connected to the turbocharger, an outlet port providing wastegate air pressure to a wastegate actuator and a vent to atmosphere. A number of air flow control switches are responsive to electrical control signals to control the levels of boost air pressure and vented air to thereby provide a plurality of discrete wastegate air pressure levels to the wastegate actuator. In another embodiment, the control system includes an electrically controllable wastegate actuator responsive to boost air pressure and electrical control signals to modulate the position of the wastegate actuator plunger.