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Dry sump
 
 
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A dry sump is a lubricating oil management method for four-stroke
Four-stroke cycle

Today, internal combustion engines in automobile, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle....
 and large two-stroke piston internal combustion engine
Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs in a combustion chamber inside and integral to the engine. In an internal combustion engine it is always the expansion of the high temperature and pressure gases that are produced by the combustion which apply force to the movable component of the engine, such as...
s that uses a secondary external reservoir for oil, as compared to a conventional wet sump
Wet sump

A wet sump is a lubricating motor oil management design for four-stroke cycle 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....
 system.

Four-stroke engines are lubricated by oil which is pumped into various bearing
Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle....
s and thereafter allowed to drain to the base of the engine. In most production cars, which use a wet sump system, this oil is simply collected in a three to seven litre capacity pan at the base of the engine, known as the oil pan, where it is pumped back up to the bearings by the oil pump
Oil pump

Oil pump may refer to:* A Submersible pump, often used to pump oil out of wells* A Pump jack, often used to pump oil out of wells* An Oil pump , a part of the lubrication system that transports engine oil...
, internal to the engine.






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A dry sump is a lubricating oil management method for four-stroke
Four-stroke cycle

Today, internal combustion engines in automobile, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle....
 and large two-stroke piston internal combustion engine
Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs in a combustion chamber inside and integral to the engine. In an internal combustion engine it is always the expansion of the high temperature and pressure gases that are produced by the combustion which apply force to the movable component of the engine, such as...
s that uses a secondary external reservoir for oil, as compared to a conventional wet sump
Wet sump

A wet sump is a lubricating motor oil management design for four-stroke cycle 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....
 system.

Four-stroke engines are lubricated by oil which is pumped into various bearing
Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle....
s and thereafter allowed to drain to the base of the engine. In most production cars, which use a wet sump system, this oil is simply collected in a three to seven litre capacity pan at the base of the engine, known as the oil pan, where it is pumped back up to the bearings by the oil pump
Oil pump

Oil pump may refer to:* A Submersible pump, often used to pump oil out of wells* A Pump jack, often used to pump oil out of wells* An Oil pump , a part of the lubrication system that transports engine oil...
, internal to the engine. In a dry sump, the oil still falls to the base of the engine, but rather than being collected into an oil pan, it is pumped into another reservoir by one or more scavenger pumps, run by belts from the front or back of the crankshaft
Crankshaft

The crankshaft, sometimes casually abbreviated to crank , is the part of an engine which translates reciprocation linear piston motion into rotation....
. Oil is then pumped from this reservoir to the bearing
Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle....
s of the engine by the pressure pump. Typical dry sump systems have the pressure pump and scavenger pumps "stacked up", so that one pulley at the front of the system can run as many pumps as desired, just by adding another to the back of the stack.

A dry sump affords many advantages, namely increased oil capacity and a lower center of gravity for the engine. Because the reservoir is external, the oil pan can be much smaller in a dry sump system, allowing the engine to be placed lower in the vehicle; in addition, the external reservoir can be as large as desired, whereas a larger oil pan raises the engine even further. Increased oil capacity by using a larger external reservoir leads to cooler oil. Furthermore, dry sump designs are not susceptible to the oil starvation problems wet sump
Wet sump

A wet sump is a lubricating motor oil management design for four-stroke cycle 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....
 systems suffer from if the oil sloshes in the oil pan, temporarily uncovering the oil pump pickup tube. Having the pumps external to the engine allows them to be maintained or replaced more easily, as well.

Dry sumps are common on larger diesel engine
Diesel engine

A diesel engine is an internal combustion engine which operates using the diesel cycle . Diesel engines have the highest thermal efficiency compared to any internal combustion or external combustion engine....
s such as those used for ship propulsion. Many racing
Auto racing

Auto racing is a motorsport involving racing cars. It is one of the world's most watched television sports....
 cars, sports cars, and aerobatic aircraft also utilize dry-sump equipped engines because they prevent oil-starvation at high g
G-force

The g-force of an object is its acceleration relative to free-fall. The unit of measure used is informally but commonly known as the "gee" , symbolized as g . An acceleration of 1 g is generally considered as equal to standard gravity , which is defined as precisely metre per second square...
 loads and because their lower center of gravity positively affects performance.

On the downside, dry sump systems add cost and complexity, and the extra pumps and lines require more oil, so maintenance costs go up as well.

See also

  • Sump
    Sump

    A sump is a low space that collects any often-undesirable liquids such as water or chemicals.An example is the oil pan of an Internal combustion engine....