and with added Valvetronic (BMW) Variatore di fase Alfa Romeo (VCT) (Alfa Romeo) VarioCam (Porsche) VTEC, i-VTEC (Honda, Acura) VTi, (Citroën, Peugeot, Opel and BMW Group) VVC (MG Rover) VVL (Nissan) Valvelift (Audi) VVA (Yamaha) VVEL (Nissan, Infiniti) VVT (Chrysler, General Motors, Proton, Suzuki and Maruti Suzuki, Isuzu, Volkswagen Group, Toyota) VVT-i, VVTL-i (Toyota, Lexus) VTVT (Hyundai) Methods for implementing variable valve control (VVC) Cam switching This method uses two cam profiles, with an actuator to swap between the profiles (usually at a specific engine speed). Cam switching can also provide variable valve lift and variable duration, however the adjustment is discrete rather than continuous. The first production use of this system was Honda's VTEC system. VTEC changes hydraulic pressure to actuate a pin that locks the high lift, high duration rocker arm to an adjacent low lift, low duration rocker arm(s). Cam phasing Many production VVT systems are the cam phasing type, using a device known as a variator. This allows continuous adjustment of the cam timing (although many early systems only used discrete adjustment), however the duration and lift cannot be adjusted. Oscillating cam These designs use an oscillating or rocking motion in a part cam lobe, which acts on a follower. This follower then opens and closes the valve. Some oscillating cam systems use a conventional cam lobe, while others use an eccentric cam lobe and a connecting rod. The principle is similar to steam engines, where the amount of steam entering the cylinder was regulated by the steam "cut-off" point. The advantage of this design is that adjustment of lift and duration is continuous. However, in these systems, lift is proportional to duration, so lift and duration cannot be separately adjusted. The BMW (valvetronic), Nissan (VVEL), and Toyota (valvematic) oscillating cam systems act on the intake valves only. Eccentric cam drive Eccentric cam drive systems operates through an eccentric disc mechanism which slows and speeds up the angular speed of the cam lobe during its rotation. Arranging the lobe to slow during its open period is equivalent to lengthening its duration. The advantage of this system is that duration can be varied independent of lift (however this system does not vary lift). The drawback is two eccentric drives and controllers are needed for each cylinder (one for the intake valves and one for the exhaust valves), which increases complexity and cost. MG Rover is the only