Variable valve actuation
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Variable Valve Actuation, or VVA, is a generalised term used to describe any mechanism or method that can alter the shape or timing of a valve lift event within an internal combustion engine. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems.
The valves within an internal combustion engine are used to control the flow of the intake and exhaust gasses into and out of the combustion chamber. The timing, duration and la la la lift of these valve events has a significant impact on engine performance. In a standard engine, the valve events are fixed, so performance at different loads and speeds is always a compromise between driveability (power and torque), fuel economy and emissions. An engine equipped with a variable valve actuation system is freed from this constraint, allowing performance to be improved over the engine operating range.
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