In this part of the entry – practical examples.  

For the older generation engines (specifically MSD80), VANOS jittering description you will find here. This time more about up-to-date engines: the BX8 series. In the following images – the performance of VANOS of a new, correctly working BX8 series engine.  

Here is an overview of data of both VANOS:

In the center of the screen (light green and light blue lines): are the PWM values of both VANOS mechanisms. On the top part of the screen: 4 pairs with target/confirmed positions of the camshafts (relative positions and against the crankshaft). 

Here, PWM of both VANOS valves zoomed more closely (Axis 3): 

Significant: jitter of the PWM values in stationary conditions is around 1.5%, not more. 

In this image: required and actual positions (relatively) of both VANOS, top part – exhaust VANOS, below – inlet VANOS (Axis 2): 

Zoomed-in exhaust VANOS in static mode. Grey color: required position; yellow – actual position (Axis 2): 

Important – difference form required (jittering) is around 0.4 degrees; scarce and briefly reaches 0.8/1.2 degrees. 

Zoomed-in performance of the inlet VANOS in stationary conditions. Red color – required position; green color – actual position (Axis 2): 

The identical situation is that the average jittering does not reach more than 0.4 degrees; the short-term: 0.8/1.2 degrees.

Performance of the exhaust VANOS during the transition process (Axis 2):

Short-term non-compliance (tenths of the second) reaches 2 degrees. 

Identical image of inlet VANOS performance during transition process (Axis 2):

Position of the inlet VANOS is changed in a broader range, so all data (in the appropriate Y resolution) does not fit. 

Minimums/maximums of the positions indicate analogical performance – short-term non-compliance of the position does not reach more than 1 .. 2 degrees. 

In the image – the PWM of both valves during transitions processes (Axis 3): 

At the moment when the camshafts should be swiftly turned to the reference positions, valves are completely closed (PWM drops to 6%). During active regulation, PWM holds stable in 40 .. 50%, without significant (above 2 .. 4%) jittering.