Pneumatic exhaust flap system
In a pneumatic exhaust flap system, vacuum is used for control. The vacuum is usually tapped off at the intake manifold and from there it goes into a pressure accumulator. This vacuum tank is equipped with a non-return valve so that the existing vacuum can no longer be lost to the engine. A reservoir is necessary because the vacuum in the intake manifold can vary greatly and you have to make sure that there is always enough vacuum to switch the exhaust flap. The vacuum is switched to the exhaust flap using a solenoid valve. As a result, the vacuum unit moves a lever rod and opens or closes the flap when vacuum is applied. If the solenoid valve switches over again, there is ambient pressure and the clock status is achieved by a return spring. The solenoid valve is switched by the internal control unit as standard. The switching position can depend on various factors. Depending on the driving mode of modern vehicles, the flap switches according to the load, throttle position, speed or pressure in the exhaust system.