Repair manual

Engine Mechanicals
7
Function
Each cylinder has its own movable cam element mounted
on the exhaust camshaft. Two valve lift contours are
possible for each exhaust valve. Changing-over between
the large and small cam lobe contours is achieved by the
longitudinal displacement of the cam elements.
The cam elements are moved on the exhaust camshaft
by solenoid actuators. While one actuator switches
from small valve lift to large valve lift, the other actuator
switches from large valve lift to small valve lift.
The second actuator switches back from large valve lift
to small valve lift. When an actuator is activated by the
Engine Control Module (ECM), a metal pin is extended
and engages in the displacement groove of the cam
element.
The cam element is designed to move automatically
when the camshaft rotates, thereby changing over both
exhaust valves to the other cam lobe contour.
However, the displacement groove in the cam elements
must be shaped so that the metal actuator pin is pushed
back again after the changeover is made. The metal pin
cannot be actively changed back by the ECM.
Locking of the Cam Elements
To ensure that the cam elements are not displaced too
far when they are adjusted, adjustment travel is limited
by a stop. The stops are camshaft bearings in the cylinder
head cover.
The cam elements are located and held in place by a
detent in the camshaft with spring-loaded balls.
Actuators with
Metal Pin
Ladder
Frame
Displacement
Groove
Axial
Bearing
Cam
Element
Exhaust
Camshaft
Spring-Loaded
Ball
Cam
Element
Displacement
Groove