Explained-Audi Valvelift System
AVS, quite simply, lifts valves higher and for a longer period of time to improve breathing and therefore engine performance at high revs.
Instead of securing the bigger lobe via a side-pin, the lobe in question is pushed onto the valve by moving a whole cam lobe unit (consisting of a smaller and bigger lobe) sideways on the camshaft.
When it’s time for the smaller lobe to take over again, the selfsame unit simply glides back along the camshaft to its original position.
This side-ways motion (facilitated by oil, of course) is controlled by an electrically-activated ejector pin positioned above the cam lobe unit.
When this pin retracts, the cam lobe unit operates in its normal position, via the smaller lobe.
When the pin is ejected, it catches a spiraling groove in the cam lobe unit. As the groove spirals out of a straight line, its one side-wall runs against the stainless-steel tipped pin which pushes the whole unit up along the camshaft, to position the bigger lobe over the valve.
When the ejector pin is retracted, there is nothing to hold the cam unit in this new position any more, so it will glide back to its original position to resume valve lift via the smaller cam lobe.
Quite ingenious, actually, this system, which operates on the outlet-side only of Audi’s brilliant new 2.0-liter TFSI (with 155 kW and 350 Nm), but on both sides (inlet and outlet) of the 3.2-liter V6.