"VANOS" variable camshaft control

The variable camshaft control improves torque in the low and medium engine speed range.

Due to a larger valve overlap, the volume of residual fumes at idle speed is reduced. A recirculation of internal exhaust gas in the part-load range reduces the volume of nitrogen oxide.

The following is also achieved:

• Faster heating of catalytic converters
• Reduced exhaust emissions following a cold start
• Reduced fuel consumption

A controlled VANOS adjustment unit is mounted at both intake and exhaust camshafts (controlled using oil pressure).

A VANOS solenoid valve is used to control the VANOS adjustment unit. The required position of the intake and exhaust camshaft is calculated using the engine speed and load signal (dependent on intake temperature and engine temperature). The DME control unit activates the VANOS adjustment unit accordingly.

The control of the intake and exhaust camshaft is variable within their maximum adjustment range.

Once the correct camshaft position has been reached, the VANOS solenoid valves ensure that the oil volume in the servo control cylinders in both chambers remains constant. This keeps the camshafts in this position.

To perform the adjustment, the variable camshaft control requires information on the current position of the camshaft.

Camshaft sensors on the intake and exhaust end record the position of the camshafts.

When the engine is started, the inlet camshaft is in the end position ("retarded" position). When the engine is started, the exhaust camshaft is pretensioned by a spring and held in the "advanced" position.