The Audi valvelift system, or AVS, is a two-stage variable-valve-lift system. Instead of changing only a camshaft’s angular position, AVS changes the lobe that operates the intake, exhaust or both valves. A small or short-duration profile reduces pumping losses at partial load; while a larger profile improves cylinder filling or exhaust flow under load. Some versions add a zero-lift profile for cylinder deactivation.
AVS first appeared globally on Audi’s 2.8-liter FSI V6 and reached North America on the 3.2-liter FSI V6 for 2008. Audi subsequently used it on some 2.0 TFSI EA888 four-cylinders; the 2.5 TFSI EA855 evo; 2.9- and turbocharged 3.0-liter EA839 V6 engines; 4.0 TFSI V8s; the second-generation 5.2 FSI V10; and the 6.3 FSI W12. European applications include the 1.4 TFSI cylinder-on-demand engine and 4.0 TDI V8. The supercharged EA837 3.0 TFSI is an important exception: Audi states that it does not use AVS.
Volkswagen-brand applications include the intake-side system on the EA888 Generation III B 2.0 TSI introduced in the 2018 Tiguan and related B-cycle applications. European 1.4- and 1.5-liter TSI engines use the sliding-cam principle for Active Cylinder Technology, or ACT. Equipment varies by output, market and engine code, so never identify AVS by displacement or badge alone.
AVS can be installed on either side. The longitudinal Audi EA888 2.0 TFSI originally used AVS on its single exhaust camshaft. Volkswagen’s EA888 Generation III B uses it on the intake camshaft. A V6 may have it on one intake camshaft per bank, or two camshafts. Cylinder-deactivation V8 and V10 versions switch both intake and exhaust valves on the affected cylinders, sealing them with all valves closed.
How the Cam Pieces Move
The basic camshaft carries external splines. Cylindrical cam pieces, sometimes called cam sleeves, fit over those splines and carry two or more adjacent lobe profiles. Electromagnetic actuators are mounted in the cam cover or camshaft frame above the sleeves.
When the ECM commands a change, it briefly energizes an actuator and extends a metal pin into a helical groove in the rotating cam piece. The groove converts rotation into axial movement, sliding the sleeve until the alternate lobe aligns with the follower. A spring-loaded detent holds the sleeve, and a return ramp pushes the actuator pin back, inducing a voltage pulse that confirms the shift. A second actuator and groove move the sleeve in the opposite direction.
Working With Variable Valve Timing
AVS and variable valve timing are separate systems. AVS changes lift and duration by selecting lobes. A hydraulic camshaft adjuster rotates the entire camshaft relative to the crankshaft, changing when the valves open and close. The ECM coordinates both with throttle angle, load, speed, boost and temperature.
On an intake-side B-cycle engine, the small profile provides a shorter opening period and earlier closing point. Cam phasing positions that event. Under higher load, AVS selects the longer profile and the phaser moves toward an Otto-cycle strategy. Exhaust-side systems coordinate lift, duration and cam position to manage residual gas, turbine energy and cylinder filling.
Turbocharger Response and Engine Oil
On exhaust-side applications, it selects the valve event that preserves exhaust-pulse energy and gas velocity at lower speed, helping the turbine respond sooner. At higher airflow, the larger, longer-duration profile reduces restriction. The ECM coordinates AVS with cam phasing, ignition, throttle and wastegate control; the benefit comes from the complete charge-management strategy.
Lubrication
The sleeve is not shifted by engine oil. The actuator is electrical, and camshaft rotation supplies the force that moves the sleeve. However, oil is still essential for lubricating the cam pieces, splines, followers and bearings. More importantly, the conventional cam phasers paired with AVS are hydraulically operated. Incorrect viscosity, low oil pressure, sludge or aeration can therefore cause timing faults or poor operation that may be mistaken for an AVS failure.
Service Problems and Bulletins
Common complaints include a MIL or EPC lamp, rough operation, reduced power and valve-lift actuator codes. Depending on the application, technicians may encounter P11A1 through P11B8 electrical or implausible-signal faults. Likely causes include an open or shorted actuator coil, connector or harness damage, incorrect actuator-to-cam clearance, a sticking actuator pin, or a cam piece that cannot slide because of wear, damage or contamination.
Audi TSB 2031085/1 addresses implausible cam-actuator signals on 2009-2012 3.2 FSI applications. It calls for measuring actuator-pin clearance and specifies a revised actuator at 0.9 mm or greater; Audi also noted an optimized camshaft frame from July 2011.
When working on this, start diagnosis with a full scan, freeze-frame data and the appropriate output test or basic setting. Confirm power, ground and coil integrity before condemning the camshaft, and separate AVS codes from cam-phaser or oil-pressure faults.
