In the S62 engine with MSS52, a controlled VANOS unit is fitted for both inlet and exhaust sides and is termed double VANOS. 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 while 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 camshafts is 30 degrees camshaft for the inlet and exhaust camshafts and 60 degrees crankshaft. This range results in possible spread of the inlet camshaft from 74 degrees crankshaft angle to 134 degrees crankshaft angle. For the exhaust camshaft, the spread range is -136 degrees to -76 degrees crank angle.
The VANOS for the S62 consists of the following for each camshaft of a cylinder bank:
- Camshaft sprocket
- Camshaft with splined sleeve
- Mechanical adjustment unit
The required position of the inlet and exhaust camshafts is calculated from the engine speed and the load signal as a function of the intake-air and engine temperatures and the VANOS adjustment unit is activated accordingly by the engine control unit. The mechanical adjustment unit operates with an oil pressure of 100 bar.
The adjustment time for the maximum adjusting path is approx. 200 ... 300 milliseconds at an oil temperature between 20 degrees C ... 80 degrees C.
The inlet and exhaust camshafts are infinitely adjustable within their maximum adjustment range. When 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 so that the camshafts remain in the corresponding positions.
A camshaft position sensor, designed as a Hall sensor, is mounted on each camshaft. The position sensors are fitted on the bulkhead end of the cylinder head on 4-cylinder and 8-cylinder engines. These sensors detect the current positions of the camshafts and transfer this data to the DME control unit A setpoint/actual-value comparison is permanently performed here.
The signal from the crankshaft sensor serves as a reference signal for this purpose.
The optimum camshaft setting is stored in several characteristic maps for different operating conditions. The input variables for determining the camshaft position are engine speed, load signal as well as intake air and engine coolant temperatures.
The VANOS system features complete diagnostic capabilities. A corresponding fault code is entered in the DME fault code 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.
For the purpose of checking operation and troubleshooting, the diagnostic program offers the option of a VANOS test procedure initiated by the tester as well as the possibility of activating the solenoid valves.