Fuel, Exhaust & Engine Electrics
Page 2.28
The DME control unit activates an electropneumatic shift valve, which
switches a vacuum to the diaphragm cell. The switching flaps for
cylinder bank 1 and 2 are actuated synchronously via a connecting link.
In the torque setting up to approx. 4150 rpm, the long intake manifold is
effective with a length of approx. 538 mm, while in the power setting, at
an engine speed of more than approx. 4150 rpm, the short intake
manifold is effective with a length of approx. 284 mm. If the electrop-
neumatic shift valve is not activated, the variable intake manifold
remains in power position.
The variable intake system is made of a shell shaped fiber reinforced
polyamide. A total of five plastic shells are welded together here. Four
switching flaps are installed on a steel shaft for each bank and are
coated with silicon for a reliable seal. The weight of the intake system in
the 4.8 l naturally aspirated engine compared to the 4.5 l engine is
reduced by approx. 10.5 oz (0.3 kg) despite the integration of the
switching flaps for the variable intake manifold system.
1 - Upper shell
2 - Effective pipe length at power position
(284.2 mm)
3 - Middle shell
4 - Sealed plastic flaps on a steel shaft
5 - Inlay
6 - Effective pipe length at torque position (538
mm)
7 - Lower shell
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