There are two calibration functions for the variable valve gear on the N62 engine:
The purpose of both functions is to improve the smooth running of the engine at low loads and low revs.
The cylinder row balancing function balances the load distribution between the two rows of cylinders. This calibration takes place continuously while the engine is running. The uneven running data from the individual cylinders is constantly gathered and compared with stored thresholds. If an uneven running figure of > 1.2 1/s is detected over an extended period, the digital engine module (DME) increases the inlet valve travel on the row of cylinders with the lower output.
Cylinder row balancing can also be initiated manually after work has been carried out on the valve gear or the balancing data has been deleted. The eccentric shaft of the Valvetronic is adjusted by increments of 1 degree at a time. Negative values affect the valve travel on cylinder row 2, positive values alter the travel of the inlet valves on cylinder row 1.
The following conditions must be met in order to carry out cylinder row balancing using the tester:
Cylinder row balancing is generally to be preferred to minimum travel adjustment for reasons of fuel consumption.
The minimum valve travel adjustment function allows the valve travel at idling speed to be increased to the fixed setting of 0.8 mm by means of tester intervention. Making this adjustment can eliminate problems with even distribution of the fuel mixture. This function should only be carried out if satisfactory results have not been obtained by cylinder row balancing.
The following requirements must be met for minimum valve travel adjustment using the tester:
After adjusting the minimum valve travel, cylinder row balancing must be carried out.
If the uneven running figures are still > 1.2 l/s after adjustment of the minimum valve travel, the valve gear, the hydraulic valve clearance adjustment system or the piston gear is damaged. At the same time, however, unsuitable fuel quality may also be the cause of uneven running. In general, further fault diagnosis should be carried out with the appropriate test modules.