Charge Air Bypass Valve

Charge air bypass valve







With accelerator depressed
When the turbocharger is working, overpressure builds up in the turbocharger delivery pipe, throttle body and intake manifold. As long as the throttle valve remains open, overpressure will be present on both sides of the bypass valve's diaphragm which is held closed by the force of the integral spring and overpressure from the intake manifold.

With accelerator released







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

To prevent the pressure in the inlet manifold increasing too quickly, which will cause jerking, the excess pressure before the throttle butterfly valve must be released when the butterfly reopens.

Due to the vacuum in the inlet manifold, a vacuum is also obtained on the spring side of the charge air bypass valve. Since the bypass valve cannot resist the overpressure on the other side of the diaphragm by spring force alone, the valve opens and the overpressure from the delivery pipe and throttle housing is admitted to the intake manifold.

Charge air bypass valve (B235R)







1 Overpressure in the intake manifold
2 Throttle valve open
3 Charge air bypass valve closed

With accelerator depressed
When the turbocharger is working, pressure builds up in the turbocharger delivery pipe, throttle body and intake manifold. As long as the throttle is open, there will be pressure on both sides of the bypass valve diaphragm, which is kept closed partly by the force of the integrated spring, partly by the pressure from the intake manifold.

With accelerator released







1 Vacuum in the intake manifold
2 Throttle valve closed
3 Charge air bypass valve open

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

To prevent pressure surges in the intake manifold resulting in jerky running, the pressure in front of the throttle must be evacuated when the throttle opens again. The bypass valve signal line, which is normally connected to the outlet in front of the throttle, is instead connected to the outlet after the throttle by a solenoid valve controlled by Trionic. For further information on the solenoid valve, see Air Bypass Valve.

The vacuum in the intake manifold causes a vacuum on the spring side of the bypass valve as well. The vacuum opens the valve and allows the pressure from the delivery pipe and throttle body to evacuate to the inlet hose.

This connection is active until the pressure in front of the throttle is stable again, after which the connection is switched back between the signal line and the outlet in front of the throttle.