How the semiactive Eberspächer silencer system works

With the aid of an innovative exhaust flap the semiactive Eberspächer silencer system tunes the outlet noise and the exhaust backpressure intelligently to the driving situation.

Noise reduction in urban traffic

In urban traffic, especially in overrun mode (such as when decelerating before traffic lights), the low frequency outlet noises predominate. Therefore at low engine speeds the exhaust flap closes one of two exhaust tailpipes. The consequence is that around two thirds of the low-tone exhaust noise disappears. The loudness sensed is halved.

Noise reduction at high speed

At higher road speeds the pitch of the exhaust noise rises. Silencing the low tones would now be ineffective. Instead of this, it is necessary to reduce the exhaust backpressure. The flap opens to do this. The gas flows though both tailpipes. The exhaust backpressure is reduced, the engine can develop its full performance.

Control of the exhaust flap

The exhaust flap is controlled by a vacuum transducer that is installed outside on the tailpipe. A hose line (run in the cable harness) supplies the necessary suction pressure. The engine control unit controls the exhaust flap according to engine speed, load and temperature by an electric switching valve.