Cylinder Deactivation Exhaust Flow Control Valve System

As a means to improve fuel economy, the engine management systems in some vehicle applications include provisions to deactivate half of the engine cylinders under certain operating conditions. For example, under a light load. The cylinder deactivation exhaust flow control valve subsystem is used to mitigate the impact that powertrain engine cylinder deactivation (active fuel management) has on the quality of the exhaust sound. When the active fuel management system is in operation, the cylinder deactivation exhaust flow control valve subsystem takes over control of the exhaust tailpipe flow control system. When active fuel management is operating, the exhaust tailpipe flow control valves are commanded shut resulting in a quieter exhaust note until the active fuel management system deactivates with increased throttle demand at which time the exhaust tailpipe flow control returns to the operational status determined by the vehicle specific mode that is being used.

The cylinder deactivation exhaust flow control system controls the undesirable exhaust noise generated during the cylinder deactivation process. This is achieved through the use of up to two electronically actuated cylinder deactivation exhaust flow control valves in the vehicle exhaust system. The cylinder deactivation exhaust flow control valves are commanded to the closed position by a pulse width modulated signal from the chassis control module in response to active or pending engine cylinder deactivation. When the cylinder deactivation exhaust flow control valves are in the closed position, the engine exhaust flows through a hole machined in the plates integral to the valves. When the engine is operating on all cylinders, the cylinder deactivation exhaust flow control valves are commanded to the open position in order to minimize exhaust restriction. To provide some control hysteresis, once the cylinder deactivation exhaust flow control valves have been commanded to the closed position, they are not reopened until the engine torque reaches a calibrated minimum value that is determined as a function of the driver selectable performance mode.