Exhaust System: Description and Operation

Electric Changeover Valve Exhaust Flap

Electric changeover valve exhaust flap
The exhaust flap is integrated within the rear silencer. The exhaust flap reduces the noise level when the engine is idle and when the engine speed is close to idle. This reduces the outlet noise to improve comfort for the customer. The reduction in outlet noise is approx. 8 dB.

Functional description
The engine control activates the electric changeover valve. The partial vacuum applied opens the exhaust flap. The degree of opening depends on gear, engine load and engine speed. The partial vacuum applied opens the exhaust flap. When air impacts against the diaphragm in the aneroid capsule (vacuum system depressurised) a spring closes the exhaust flap.







Structure and inner electrical connection
A diaphragm box is fixed on the exhaust tailpipes of the rear silencer. The diaphragm box is linked to the exhaust flap via an adjustment mechanism. From the electric changeover valve the vacuum hose leads to the diaphragm boxes.







Activation and setpoint values
When the engine is off no power is supplied to the exhaust flap and the exhaust flap is closed. Only the two conditions, open and closed, occur while driving. Control of the exhaust flap is governed by:
- Load
- Gear engaged
- Rotational speed







Observe the following setpoint values for the electric changeover valve of the exhaust flap:

Size Value
Voltage range 9 to 16 volts
Power consumption 1 A
Temperature range -30 °C to 140 °C

Diagnosis instructions

Failure of the component

If the electric changeover valve of the exhaust flap fails, the following behaviour is to be expected:
- Fault entry in the engine control unit

General notes
If the exhaust flap is defective the exhaust system will emit a hissing noise at high engine speeds when it is closed. If the exhaust flap is defective and partially open a humming noise will be generated at idle.
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