Exhaust Tail Pipe Flow Control System Description and Operation

Exhaust Tail Pipe Flow Control System Description and Operation

The exhaust tailpipe flow control system is used to tune the exhaust note for high performance vehicles. The vehicle is equipped with two tailpipe exhaust valves - a left one and a right one. Each exhaust tailpipe valve is installed in the low restriction exhaust path of a dual outlet muffler, near the exhaust tip. When a tailpipe exhaust valve is open, the low restriction exhaust path is exposed to atmosphere, and the exhaust note becomes more characteristically high performance.

An output circuit from the fuel pump control module is used to operate a relay-controlled solenoid valve that regulates vacuum to the left and right exhaust tailpipe valves. When the exhaust flow control valve relay is energized (turned on), the exhaust flow control valve solenoid opens and applies vacuum to the exhaust tailpipe valves, causing them to close. When the exhaust flow control valve relay is de-energized (turned off), the exhaust flow control valve solenoid closes, which isolates the exhaust tailpipe valves from vacuum and causes them to open.

To provide a more aggressive exhaust note when the vehicle is started, the exhaust tailpipe valves are opened during an engine cranking event. Once the engine is running, accelerator pedal position, transmission gear and engine speed are used to determine the commanded state (open or closed) of the exhaust tailpipe valves.