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The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift, the valve timing is the same for all engine speeds and conditions, therefore compromises are necessary to achieve the desired result in intake and exhaust efficiency . This has been described ...
The solenoid valve regulates the amount of oil pumped by the cam action to either the valve or a bypass reservoir. When pressurized, the hydraulic line behaves like a solid body and transmits the lift schedule imparted by the intake cam directly to the intake valve. When the solenoid is disengaged, a spring takes over valve actuation duties.
A helical camshaft is a type of mechanical variable valve actuation (VVA) system. More specifically, it is a camshaft that allows the valve opening duration to be varied over a wide, continuous, step-less range, with all of the added duration being at full valve lift.
The system has the advantage that it is continuously variable rather than switching in at a set speed. Its disadvantage is the complexity of the system and corresponding price. Other systems will achieve similar results with less cost and simpler design (electronic control).
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.
Actuation may refer to: High Redundancy Actuation (HRA), a new approach to fault tolerant control in the area of mechanical actuation Variable valve actuation , any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine
The most common final control element in the process control industries is the control valve. The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point. [1]
An automatic control valve consists of three main parts in which each part exist in several types and designs: Valve actuator – which moves the valve's modulating element, such as ball or butterfly. Valve positioner – which ensures the valve has reached the desired degree of opening. This overcomes the problems of friction and wear.