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Variable valve lift (VVL) is an automotive piston engine technology which varies the height a valve opens in order to improve performance, fuel economy or emissions. There are two main types of VVL: discrete, which employs fixed valve lift amounts, and continuous, which is able to vary the amount of lift.
The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift, the valve timing is the same for all engine speeds and conditions, therefore compromises are necessary to achieve the desired result in intake and exhaust efficiency . This has been described ...
Valve timing and the valve profile are continuously altered according to conditions and engine load. For improved responsiveness on cold starts, VarioCam Plus raises the amount of lift and retards valve timing. At medium revs with minimal loads, the valve lift is lowered and timing advanced to help minimize fuel consumption and emissions.
For variable valve lift, competing technologies (e.g., Honda's VTEC and BMW's Valvetronic) use electromechanical concepts, achieving valve lift variation via dedicated mechanisms; it can also be combined with camshaft phasers to allow control of both valve lift and phase. In contrast, MultiAir uses managed hydraulic fluid to provide variable ...
Alfa Romeo was the first manufacturer to use a variable valve timing system in production cars (US Patent 4,231,330). The 1980 Alfa Romeo Spider 2.0 L had a mechanical VVT system in SPICA fuel injected cars sold in the US. Later this was also used in the 1983 Alfetta 2.0 Quadrifoglio Oro models as well as other cars.
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N-VTC varies valve timing by rotating the affected camshaft relative to the sprocket; valve lift and duration are not altered. This rotation is achieved when an electric solenoid, controlled by the car's ECU, allows pressurized engine oil to flow into and through the cam and into a slave mechanism, axially advancing camshaft timing relative to ...
DVVL is an acronym for Discrete variable valve lift, a mechanical component of which two types exist: DVVLd, includes dual cam phasing.