Exhaust System: Description and Operation

Electric Changeover Valve For The Exhaust Flap

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

Functional description
The engine management system activates the electric changeover valve. The partial vacuum applied opens the exhaust flap. Opening depends on the gear, engine speed as well as load. The partial vacuum applied opens the exhaust flap. On venting the diaphragm canister (vacuum system at static pressure), the exhaust flap is closed by a spring.







Structure and inner circuit
A diaphragm canister is fixed onto the rear silencer exhaust pipes. The diaphragm canister is linked to the exhaust flap via an adjustment mechanism. From the electric changeover valve, the vacuum hose leads to the diaphragm canister.







Activation and target values
The flap is closed without current when the engine is not running. While the vehicle is being driven, only the two states open or closed are present.
Activation of the exhaust flap depends on:
- Load
- Gear engaged
- Engine speed







Observe the following target values for the electric changeover valve for the exhaust flap:

Variable Value
Voltage range 9 to 16 Volts
Current consumption 1 A
Temperature range -30 °C to 140 °C

Diagnosis instructions

Failure of the component

If the electric changeover valve for the exhaust flap fails, the following behavior is to be expected:
- Fault code memory entry in the engine control unit

General information
If a closed exhaust flap is defective, the exhaust system hisses at higher engine speeds. If a partially opened exhaust flap is defective, a humming noise is generated at idle speed.
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