Piston

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For the American composer, see Walter Piston.

For the use of the term in optics, see piston (optics).

piston + connecting rod

Components of a typical, four stroke cycle, DOHC piston engine. (E) Exhaust camshaft, (I) Intake camshaft, (S) Spark plug, (V) Valves, (P) Piston, (R) Connecting rod, (C) Crankshaft, (W) Water jacket for coolant flow.

In general, a piston is a sliding plug that fits closely inside the bore of a cylinder.

Its purpose is either to change the volume enclosed by the cylinder, or to exert a force on a fluid inside the cylinder.

1 Ways of making power
2 External combustion engine
3 See also
4 External links

[edit] Ways of making power

There are two ways that a piston engine can make power. These are the two-stroke cycle and the four-stroke cycle. A single cylinder two-stroke engine produces power every crankshaft revolution, while a single cylinder four-stroke engine produces power every other crankshaft revolution. Older designs of small two-stroke engines produced more pollution than four stroke engines, however modern two-stroke designs, like the Vespa ET2 Injection utilise fuel-injection and are as clean as four-strokes. Large diesel two-stroke engines, as used in ships and locomotives, have always used fuel injection and produce low emissions. One of the biggest internal combustion engines in the world, the Wärtsilä-Sulzer RTA96-C is a two-stroke; it is bigger than most two-story houses, has pistons nearly 1 metre in diameter and is one of the most efficient mobile engines in existence. In theory, a four stroke engine has to be larger than a two stroke engine to produce an equivalent amount of power. Two stroke engines are becoming less common in developed countries these days, mainly due to manufacturer reluctance to invest in reducing two-stroke emissions. Traditionally, two stroke engines needed more maintenance, even though they have less moving parts and tended to wear out faster than four stroke engines, however fuel-injected two-strokes achieve better engine lubrication and cooling and reliability should improve considerably.

[edit] External combustion engine

A steam engine is another type of piston engine. In most steam engines, the pistons are double acting: steam is alternately admitted to either end of the cylinder, so that every piston stroke produces power. .