Backpressure compensation
The backpressure compensation function is used to counteract the air pressure in the vehicle interior at high driving speeds. Here, depending on the speed signal, the diameter of the air inlet is reduced to reduce the size of the air inlet channel.
Compensation is achieved by various flaps.
E53, E39 as from 3/2000: Backpressure flaps, left and right
E38/E46/E83 and E39 up to 3/2000: right-hand and left-hand recirculated fresh air flap
Backpressure compensation is run in a road speed range of 60 km/h to 160 km/h.