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Valve timing diagram for a 4-stroke engine. With traditional fixed valve timing, an engine will have a period of "valve overlap" at the end of the exhaust stroke, when both the intake and exhaust valves are open.
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.
The Alfa Romeo Twin Spark engine, introduced in the 1987 Alfa Romeo 75, also uses variable valve timing. [3] [4] The Alfa system varies the phase (not the duration) of the cam timing and operates on the inlet camshaft. [5] Alfa Romeo's variator is a cylindrical chamber that contains a pressure chamber and piston along with helical splines.
The valves are typically operated by a camshaft rotating at half the speed of the crankshaft. It has a series of cams along its length, each designed to open a valve during the appropriate part of an intake or exhaust stroke. A tappet between valve and cam is a contact surface on which the cam slides to open the valve. Many engines use one or ...
A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring. The valves in a typical four-stroke engine allow the air/fuel mixture into the cylinder at the beginning of the cycle and exhaust spent gases at the end of the cycle. In a conventional ...
One spark plug is situated in the center of the cylinder head and the other in an inverted position just below the inlet valve on the outside of the cylinder. Spark plugs are powered by two magnetos. [6] Peugeot 8Aa valve timing diagram. The Peugeot 8Aa's valve timing was considered conventional for an engine of its time period with no valve ...
The Toyota 2ZR-FE is a DOHC, 16-valve, 1.8 L (1,798 cc) [3] engine also equipped with Dual VVT-i. This new engine replaced the 1ZZ-FE engine in most applications. [ 4 ] Output for this engine is rated at 98–103 kW (132–138 hp) at 6000 rpm and 173 N⋅m (127.5 lb⋅ft) of torque at 4400 rpm for the Corolla, Matrix, and Vibe and 95 kW (128 hp ...
MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) [1] is the brand name of a variable valve timing (VVT) engine technology developed by Mitsubishi Motors. MIVEC, as with other similar systems, varies the timing of the intake and exhaust camshafts which increases the power and torque output over a broad engine speed range ...