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Once the engine spins to starting speed, centrifugal force causes the lever to move out of the way, and the exhaust valve is allowed to seat fully. [4] Older compression release systems used a small bump on the cam that would bump the valve very slightly at low speeds. Once the engine gained speed, the pressure would push the exhaust valve ...
In theory, the closing of all rear bank valves produces an ‘air spring’ effect. However, the reciprocating effect of the piston with closed valves reportedly produces a vacuum condition where oil can get pulled past the piston rings to flood the cylinder. When VCM disengages, the engine then misfires if needing to clear the cylinder of oil.
These blow-by gases, if not ventilated, inevitably condense and combine with the oil vapor present in the crankcase, forming oil sludge. Excessive crankcase pressure can furthermore lead to engine oil leaks past the crankshaft seals and other engine seals and gaskets. Therefore, it becomes imperative that a crankcase ventilation system be used.
The oldest engine technological predecessor for the variable-displacement engine is the hit and miss engine, developed in the late 19th century.These single-cylinder stationary engines had a centrifugal governor that cut the cylinder out of operation so long as the engine was operating above a set speed, typically by holding the exhaust valve open.
The oil pump forces the motor oil through the passages in the engine to properly distribute oil to different engine components. In a common oiling system, oil is drawn out of the oil sump (oil pan, in US English) through a wire mesh strainer that removes some of the larger pieces of debris from the oil.
Oil under constant pressure is supplied to the lifter via an oil channel, through a small hole in the lifter body. When the engine valve is closed (lifter in a neutral position), the lifter is free to fill with oil. As the camshaft lobe enters the lift phase of its travel, it compresses the lifter piston, and a valve shuts the oil inlet. Oil is ...
A blowoff valve is designed to release pressure in the intake system when the throttle is closed. A "recirculating" type blowoff valve releases the pressurised air back into the non-pressurized section of the intake (i.e. upstream of the turbocharger), while an "atmospheric venting" type blowoff valve dumps the air directly into the atmosphere.
Desmodromic poppet valve in a Ducati engine. 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 ...