Valve Timing Gear

Valve Timing Gear

Valve train
The cylinder head is equipped with a conventional valve gear with 2 overhead camshafts. In addition, friction optimizing roller cam followers and a hydraulic valve clearance adjustment are used. The valve have a shaft diameter of 5 mm, whereby the exhaust valves are filled with sodium. A fully variable spread of the inlet camshaft (VANOS) ensures optimized power output and torque.

Brief description of components
The following components are described for the valve gear:

Intake camshaft sensor
The valve gear is equipped with the variable camshaft control unit (VANOS) for the inlet camshaft. The camshaft sensors pick up the adjustment of the inlet camshaft. To do so, a camshaft sensor is fitted on the camshaft. The camshaft sensor works according to the Hall effect. The DME control unit supplies the camshaft sensor with voltage.







VANOS solenoid valve, intake
The variable camshaft control serves to enhance the torque in the lower and middle engine speed range. The VANOS solenoid valve activates a VANOS adjustment unit on the inlet side. The VANOS solenoid valves are activated by the digital engine electronics control unit.







System functions
The following system functions are described for the valve gear:

Variable camshaft timing control VANOS
The variable camshaft improves the torque in the lower and middle engine speed range. A greater valve overlap results in lower amounts of residual gas at idle speed. The internal exhaust-gas recirculation in the part-load range reduces the nitrogen oxides.

The following are also achieved:
- faster heating of the catalytic converters
- lower pollutant emissions after a cold start
- reduction in the fuel consumption

A regulated VANOS adjustment unit is fitted to the inlet camshaft.
A regulated VANOS adjustment unit is fitted to the inlet camshaft. A VANOS solenoid valve activates the VANOS adjustment unit. The required positions of the inlet and exhaust camshafts are calculated from the engine speed and the load signal (depending on the intake-air temperature and engine temperature). The DME control unit activates the VANOS adjustment unit accordingly. The inlet camshaft can be variably regulated within its maximum adjustment range. When the correct camshaft position has been reached, the VANOS solenoid valve keeps the oil volume in the actuating cylinder in both chambers constant. This holds the inlet camshaft in this position. The variable camshaft control requires acknowledgement of the current position of the camshafts for the adjustment. A camshaft sensor on the inlet side picks up the position of the camshaft. On engine start, the inlet camshaft is in the end position ("late").

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