Suction Jet Pumps, FSI Engine

Suction Jet Pumps, FSI Engine






1 Left suction jet pump

2 Left fuel delivery unit

3 Expansion tank

4 Right fuel delivery unit

5 Right suction jet pump

6 Suction jet pipe

• From the right fuel delivery unit to the left suction jet pump

7 Suction jet pipe

• From the left fuel delivery unit to the right suction jet pump

8 Overflow line

• Between the fuel delivery units

Function Description

To make sure that fuel is supplied in all driving situations, the fuel pumps must absolutely never take on air, even under hard braking and cornering situations. This risk is a possibility for any partially-filled fuel tank, when all the fuel swashes into a corner of the fuel tank.

• Therefore, the fuel delivery units - 2 - and - 4 - not only consist of the respective fuel pumps, but also an appropriately named baffle housing, into which the pumps are inserted. The baffle housing is a container that is steadily filled with fuel so that the fuel pumps are always surrounded by fuel, independent of the fuel level in the fuel tank.

• It is understandable that the trouble-free function of the fuel pumps is dependent on the filling of the baffle housing. The so-called suction jet pumps are responsible for this.

• Function of the suction jet pumps is based on a simple physical principle: A suction jet from the left and right fuel pump supply pipe - 2 - and - 4 - is pushed via the suction jet lines - 6 - and - 7 - into the suction jet pumps - 1 - and - 5 - through a nozzle and is thereby accelerated. This acceleration causes the surrounding fuel to be drawn in and be forced to the baffle housings of the fuel delivery units. The right suction jet pump - 5 - supplies the left baffle housing and the left suction jet pump - 1 - supplies the right baffle housing.

• The suction jet is distributed in the baffle housings from the fuel pumps onto the two small suction jet pumps via the 2 Y-connectors This assures the both baffle housings in the fuel delivery unit are always equally filled with fuel via the overflow line - 8 -.

• Another smaller suction jet pump is located in the reservoir - 3 - and pumps available fuel back into the fuel tank.