Camshaft adjustment function - GF07.61-P-4021L

ENGINE 137.970 

Fig 1: Camshaft Adjustment Function Diagram

Task 

Improving idle speed, boosting torque curve and power output.

Design / function 

The camshaft adjustment is map-controlled and is dependent on the following parameters:

• Engine speed
• Load
• Coolant temperature
• Intake air temperature
• Engine oil temperature
• No camshaft adjustment is performed in selector lever position P and N
• Requirements of cylinder shutoff which deactivate the camshaft adjustment

If the camshaft adjustment is activated in the speed range from approx. 1500 - 4000 rpm, the camshaft adjustment valves are actuated at the ground side by the ME control module. Their voltage is supplied by circuit 87.

The valves open and engine oil flows into the working chamber. The engine oil pressure pushes the adjustment piston against a compression spring. As a result of the helical gearing, a rotation of approx. 7.5° is performed between camshaft sprocket and camshaft in the "advanced" direction, which corresponds to an adjustment of approx. 15° crank angle.

If the camshaft adjustment valves are de-energized and closed, the adjustment piston is moved back by spring force. When this happens, the engine oil is able to flow along a return flow in the camshaft adjustment valve out of the working chamber.