Wet sump

Wet sump

A wet sump is a lubricating oil management design for four-stroke piston internal combustion engines which uses a built-in reservoir for oil, as opposed to an external or secondary reservoir used in a dry sump design.

Four-stroke engines are lubricated by oil which is pumped into various bearings and thereafter allowed to drain to the base of the engine. In most production cars and motorcycles, which use a wet sump system, the oil is collected in a three to seven quart (3 to 7 L) capacity pan at the base of the engine, known as the oil pan or sump where it is pumped back up to the bearings by the oil pump, internal to the engine.

A wet sump offers the advantage of a simple design, using a single pump and no external reservoir. Since the sump is internal, there is no need for hoses or tubes connecting the engine to an external sump which may leak. An internal oil pump is generally more difficult to replace, but that is dependent on the engine design.

However, the wet sump design is entirely unsuitable for a racing application, for example, as the large g force pulled by drivers going around corners causes the oil in the pan to slosh, starving the system of oil for a small period of time. This can damage the engine. Early stationary engines employed a small scoop on the extremity of the crankshaft or connecting rod to assist with the lubrication of the cylinder walls by means of a splashing action. Modern small engines, such as those used in lawnmowers, use a "slinger" (basically a paddle wheel) to perform the same function.

See also

The Porsche 996 3.4 and 3.6 are not wet sump engines. Porsche has internally created an integrated oil compartment but not external to the engine. The 3.4 and 3.6 engines use multiple return oil pumps along with a pressurization pump.


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Look at other dictionaries:

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  • Dry sump — A dry sump is a lubricating motor oil management method for four stroke and large two stroke piston internal combustion engines that uses external pumps and a secondary external reservoir for oil, as compared to a conventional wet sump system.… …   Wikipedia

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  • dry sump — noun A type of engine sump where oil that flows down from the crankshaft etc is sucked up into an external reservoir (as opposed to a wet sump where it simply pools in a pan at the bottom of the engine) …   Wiktionary

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