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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.
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 ...
VarioCam varies the timing of the intake valves by adjusting the tension on the timing chain connecting the intake and exhaust camshafts. VarioCam was first used on the 1992 3.0 L engine in the Porsche 968. Porsche's more recent VarioCam Plus combines variable valve timing with two-stage lift on the intake side. The two-stage valve-lift ...
First-generation Valvetronic systems can decrease the valve lift to a minimum of 0.3 mm, while second- and third-generation Valvetronic can decrease the lift to as little as 0.18 mm. On first-generation Valvetronic, the contact point on the intermediate arm for the camshaft was a contact pad; later systems use a roller which is less prone to wear.
The Porsche patent used an oscillating cam to increase the valve lift and duration. The desmodromic cam driven via a push/pull rod from an eccentric shaft or swashplate. It is unknown if any working prototype was ever made. Fiat was the first auto manufacturer to patent a functional automotive variable valve timing system which included ...
The VTi Engine (Variable Valve Lift and Timing injection) is a variable valve timing (VVT) system for Prince engine created jointly by both PSA (Peugeot, Citroën, DS Automobiles) and Mini from the BMW Group.
Nissan Ecology Oriented Variable Valve Lift and Timing (commonly known as VVL & VVT) is an automobile variable valve timing technology developed by Nissan. VVL varies the duration, and lift of valves by using hydraulic pressure switch between two different sets of camshaft lobes. VVT varies the valve timing throughout the RPM range.
DVVL is an acronym for Discrete variable valve lift, a mechanical component of which two types exist: DVVLd, includes dual cam phasing.