Instead of a throttle valve, the differing valve stroke is used in the Valvetronic to control the fresh gas. An eccentric shaft is operated by the engine management via an electric motor, a worm and a work wheel. The eccentric shaft controls an oscillating lever between the cam shaft and the rocker arm, with the result that the cam of the inlet camshaft opens the valve to differing extents (from zero stroke up to maximum stroke). The worm can be operated manually with the help of a small wheel!
Pic. 1: Zero stroke (vlave remains closed)
Pic. 2: Half stroke
Pic. 3: Maximum stroke