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There are many systems for VVT, which involve changing either the relative timing, duration or opening of the engine's inlet and exhaust valves. One of the first practical VVT systems used a variator to change the phase [note 1] of the camshaft and valves. This simple system cannot change the duration of the valve opening, or their lift.
For twin-cam or DOHC engines, VCT was used on either the intake or exhaust camshaft. (Engines that have VCT on both camshafts are now designated as Ti-VCT.↓) The use of variable camshaft timing on the exhaust camshaft is for improved emissions, and vehicles with VCT on the exhaust camshaft do not require exhaust gas recirculation (EGR) as retarding the exhaust cam timing achieves the same ...
Cylinder head of Honda K20Z3.This engine uses continuously variable timing for the inlet valves. Variable valve timing (VVT) is the process of altering the timing of a valve lift event in an internal combustion engine, and is often used to improve performance, fuel economy or emissions.
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.
It has a 10.2:1 compression ratio, Sequential multi-port fuel injection, and a bore and stroke of 94 mm × 85.6 mm (3.70 in × 3.37 in). Lower-powered versions only have variable cam phasing on the inlet cam (LE0). Selected models also include variable exhaust. The engine weighs 370 lb (170 kg) as installed.
This engine features upgrades to the variable valve timing (VVT) system, two-stage variable valve lift (VVL), a new intake manifold, new valve springs, new piston rings, new fuel injectors, new ignition coils, a cooled Exhaust gas recirculation system, lower internal friction and lower weight. It also features a higher compression ratio ...
Fiat 875 cc two cylinder TwinAir engine featuring Multiair technology. MultiAir or Multiair is a hydraulically-actuated variable valve timing (VVT) and variable valve lift (VVL) engine technology enabling "cylinder by cylinder, stroke by stroke" [1] control of intake air directly via a gasoline engine's inlet valves.
The camshaft consists of a cylindrical rod running the length of the cylinder bank with a number of cams (discs with protruding cam lobes) along its length, one for each valve. As the cam rotates, the lobe presses on the valve (or an intermediate mechanism), thus pushing it open. Typically, a valve spring is used to push the valve in the ...