Cut-off valve N249 03C145710E

The electrical turbocharger air recirculation valve N249 is screwed to the turbocharger housing.

Function:

The turbocharger air recirculation valve N249 prevents disturbing noises of the turbocharger and damage to the compressor wheel of the turbocharger upon switchover to boost mode and when a sharp drop in speed of the turbocharger occurs. Upon switchover to boost mode, the continuously delivered charge air accumulates in the turbocharger housing. The pressure of the accumulated charge air would rise continuously and brake the compressor wheel of the turbocharger which in turn would reduce the pressure of the charge air and lead to disturbing noises of the turbocharger. To avoid this, the turbocharger air recirculation valve N249 is opened electrically. This opens a bypass duct through which the compressed air is led back via the compressor wheel of the turbocharger to the intake side of the turbocharger. This is how the compressor wheel obtains its speed. When the throttle valve is opened, the turbocharger air recirculation valve N294 is closed and the boost pressure is immediately available again.

Effects of functional failure:

If the air recirculation valve N249 is leaking, the boost pressure is reduced and therefore also the engine output. If the valve N249 can no longer be operated, there