Originally Posted by SeanC

Below is a very good video that will help you understand how valvetronic works. My understanding is that there is actually a smaller "camshaft" that is attached to the servotronic motor which controls valve timing together with the older Vanos technology. A good view of it is at around 8:00 minute mark.

https://www.youtube.com/watch?v=3gRhDKE8vKU