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In four-stroke cycle engines and some two-stroke cycle engines, the valve timing is controlled by the camshaft. It can be varied by modifying the camshaft, or it can be varied during engine operation by variable valve timing. It is also affected by the adjustment of the valve mechanism, and particularly by the tappet clearance.
Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
Animation of a two-stroke engine. A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston (one up and one down movement) in one revolution of the crankshaft in contrast to a four-stroke engine which requires four strokes of the piston in two crankshaft revolutions to complete a power cycle.
To minimise vibrations, most engines use an evenly spaced firing interval. This means that the timing of the power stroke is evenly spaced between cylinders. For a four-stroke engine, this requires a firing interval of 720° divided by the number of cylinders, for example a six-cylinder engine would have a firing interval of 120°. [5]
A "twingle" is a four-stroke twin-cylinder engine with an altered firing order designed to give power pulses similar to a single-cylinder four-stroke engine. Inline twins with a 360° crankpin offset or flat-twins can be easily converted into twingles by firing both of the cylinders at the same time and installing a camshaft or camshafts that ...
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 ...
A stroke is the action of a piston travelling the full length of its cylinder.In a two-stroke engine, one of the two strokes combines primarily the intake stroke and the combustion stroke, while the other stroke primarily combines the compression stroke and the exhaust stroke, though technically since both ports are exposed during both the combustion and compression strokes, some reversion ...
Cutaway model of a MAN B&W two-stroke marine diesel engine with the piston rod attached to a crosshead. In the two-stroke cycle, the four stages of internal combustion engine operation (intake, compression, ignition, exhaust) occur in one 360° revolution of the crank shaft, whereas in a four-stroke engine they take two complete revolutions.