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Bypass control valve, 4-cyl.

Bypass control valve, 4-cyl.


Accelerator depressed

When the turbocharger is working, pressure builds up in the turbocharger pressure pipe, throttle body and intake manifold. As long as the throttle butterfly is open, there is pressure on both sides of the bypass control valve diaphragm which is held closed partly by the force of the integral spring and partly by the pressure in the intake manifold.

When the accelerator is released


When the throttle butterfly closes, a vacuum is quickly created in the intake manifold due to combustion while the pressure before the throttle butterfly remains the same.

To avoid pressure surges in the intake manifold when the throttle butterfly reopens, with associated jerkiness, the overpressure ahead of the throttle butterfly must be released. The bypass valve signal duct, which under normal driving conditions is connected to the outlet before the throttle butterfly is instead connected to the outlet after the throttle butterfly by a solenoid valve that is controlled by Trionic. For further information on the solenoid valve, see Bypass solenoid valve .

Because of the vacuum in the intake manifold, a vacuum is also created on the spring side in the bypass control valve. The vacuum causes the valve to open and the pressure from the pressure pipe and throttle body escapes into the intake hose.

This connection is active until the pressure before the throttle butterfly has stabilized again. The connection between the signal line and the outlet before the throttle butterfly is then restored.