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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. It is increasingly being used in combination with variable valve lift systems.
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 ...
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 the sprocket. Valve to crank angle timing varies depending on whether engine speed is high or low and changes at fixed intervals.
Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
Cutaway view of Variable Valve Timing with intelligence on a ZR engine in Techniquest Glyndŵr. VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing petrol engine technology manufactured by Toyota Group and used by brands Groupe PSA (Peugeot and Citroen), Toyota, Lexus, Scion, Daihatsu, Subaru, Aston Martin, Pontiac and Lotus Cars.
The active valve control system (AVCS) is an automobile variable valve timing technology used by Subaru. It varies the timing of the valves by using hydraulic oil pressure to rotate the camshaft, known as "phasing", [1] in order to provide optimal valve timing for engine load conditions. The system is closed loop using the camshaft sensors ...
Engines that always run at a relatively high speed, such as race car engines, will have considerable overlap in their valve timings for maximum volumetric efficiency. Road car engines are different because they are required to idle at less than 1000rpm, and excessive valve overlap would make smooth idling impossible because of the mixing of ...
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.