Diverter Valve
The diverter valve prevents backfire in the exhaust system during sudden deceleration. The valve senses sudden increase in intake manifold vacuum, causing valve to open and allowing air from air pump to vent to the atmosphere. A pressure relief valve is incorporated into the diverter valve to prevent overloading the air pump.
On 633CSi and 733i, diverter valve operation is also controlled by an electromagnetic switching valve. The switching valve opens the diverter valve when engine speed exceeds 3750 RPM, this interrupts the air injection and vents the air to the atmosphere.
NOTE:
The 633CSi and 7331 are equipped with two or three electromagnetic switching valves. The switching valve for the air injection system can be identified by a Blue cap.