View Single Post
Old 11-01-2011, 06:04 PM
Fudman's Avatar
Fudman Fudman is offline
Officially Welcomed to the 'Fest
Location: Sudbury, MA
Join Date: Apr 2007
Posts: 6,823
Mein Auto: '02 530i Sport auto
RDL: A very informative .pdf! I've seen BB's posts regarding the sucking jet pump and I had no clue as to what a sucking jet pump was or did. It certainly had a strange name.

It is not a pump at all. It is simply a brake booster that uses intake manifold pressure to boost the master cylinder. When the car is started, the pressure on the intake manifold side of the jet pump is less than the intake boot side, so air flows from the intake boot into the intake manifold. The pump uses the Venturi principle to constrict the flow of air which increases the velocity of the airflow. This in turn creates a vacuum on the brake booster inlet side, which improves braking power. It's just a clever way to scavenge pressure differential to achieve an improvement to braking with no electrical component or parasitic loss.
Reply With Quote