The VANOS system serves the purpose of increasing torque in the lower and medium engine speed ranges. Reduced valve overlap results in lower residual-gas quantities during idling. Nitrous oxide components are reduced by internal exhaust-gas recirculation in the partial load range. This achieves faster heating of the catalytic converters, lower untreated emissions after cold starting and reduced fuel consumption.
The total adjustment range of the the inlet and exhaust camshafts is 40 degrees of crankshaft rotation or 20 degrees of camshaft rotation.
The VANOS system consists of the following components for each row of cylinders:
- Inlet camshaft
- VANOS gear unit with sprockets
- Oil distributor intermediate flange
- Solenoid valve
- Non-return valve
- Pulse-generator gear for camshaft sensor
The required position for the inlet and exhaust camshafts is calculated from the engine speed, the load signal and other measured engine data. The VANOS adjuster units are controlled accordingly by the DME control unit. For this purpose, the VANOS system is pressurized directly by engine oil pressure. Solenoid valves timed by the DME control unit open the oil channels to advance or retard the camshafts. The camshafts are infinitely adjustable within their range of adjustment. As soon as the relevant optimum camshaft position is reached, the solenoid valves maintain a constant oil volume in the adjustment cylinder on both sides of the chamber. In this way, the camshaft remains in the corresponding position.
When the engine is started, the inlet camshaft is in the ”retard” limit position.
The VANOS system features complete diagnostic capabilities. A corresponding fault code is entered in the DME fault memory if a fault occurs during engine operation. An engine limp-home program is nevertheless still possible if the VANOS system can no longer be activated in the event of damage.