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A valvetrain is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. [1] The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combustion chamber, while the exhaust valves control the flow of spent exhaust gases out of the ...
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. The intake valve is opened before the exhaust gases have completely left the cylinder, and their considerable velocity assists in ...
Valves can be categorized also based on their function: Check valve or non-return valve, allows the fluid to pass in one direction only; Flow control valve, to maintain and control a variable flow rate through the valve; Poppet valve, commonly used in piston engines to regulate the fuel mixture intake and exhaust; Pressure-balanced valve
In piston engines, the valves are grouped into 'inlet valves' which admit the entrance of fuel and air and 'outlet valves' which allow the exhaust gases to escape. Each valve opens once per cycle and the ones that are subject to extreme accelerations are held closed by springs that are typically opened by rods running on a camshaft rotating ...
Diagram of a typical gas turbine jet engine. Air is compressed by the compressor blades as it enters the engine, and it is mixed and burned with fuel in the combustion section. The hot exhaust gases provide forward thrust and turn the turbines which drive the compressor blades. 1. Intake 2. Low pressure compression 3. High pressure compression ...
Its function is the same, using a vacuum at the intake to trigger a valve that pulses atmospheric air into the exhaust. The original "iron barrel" style engine did this with a hose from the PAV going to the exhaust pipe, the newer (2003–2009) AVL aluminum engine pulses the gas directly into the exhaust port on the head of the engine itself.
When the exhaust valve opens, the high pressure exhaust gas escapes into the exhaust manifold or header, creating an "exhaust pulse" comprising three main parts: The high-pressure head is created by the large pressure difference between the exhaust in the combustion chamber and the atmospheric pressure outside of the exhaust system
In an overhead valve engine the tappets (on right) are sandwiched between pushrods and the camshaft. In an internal combustion engine, a tappet (also called a 'valve lifter' or 'cam follower') [3] [4] [5] is the component which converts the rotation of the camshaft into vertical motion to open and close an intake or exhaust valve.