Valvetronic

The Valvetronic system is a BMW variable valve lift system[1] which, in combination with VANOS, allows infinite adjustment of the intake valve timing and lift.

[2][3] The system claims to improve fuel economy and emissions, and negates the need for a throttle body in regular use.

Unlike a traditional engine where the camshaft acts onto a rocker arm that actuates the valves, an engine with Valvetronic has an intermediate arm between the rocker and the camshaft, which allows the valve lift to be varied depending on the position of an eccentric shaft adjacent to the intermediate arm.

The eccentric shaft, whose position is controlled by the DME using an electric motor, rotates through a range of 225 degrees to push the intermediate arm towards, or away from, the camshaft.

[5] First-generation Valvetronic systems can decrease the valve lift to a minimum of 0.3 mm, while second- and third-generation Valvetronic can decrease the lift to as little as 0.18 mm.