DRY SUMP
A dry sump is a lubricating oil management method for four-stroke for four-stroke and large two-stroke piston internal combustion engines that uses a secondary external reservoir for oil, as compared to a conventional wet sump system. 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, which use a wet sump system, this oil is simply collected in a three to seven liter 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, 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, pumps, run by belts from the front or back of the crankshaft. crankshaft. Oil is then pumped from this reservoir to the bearings of the engine by the pressure pump. Typical dry sump systems have the pressure pump pu mp and scavenger pumps "stacked up", so that one pulley at the front of the system can run as many pumps as desired, desired, just by adding another to the back of the stack. A dry sump affords many advantages, namely increased oil capacity, decreased parasitic decreased parasitic loss and a lower center 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 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 larger diesel engines such as those used for ship propulsion. Many race cars, super cars, cars, and aerobatic aircraft also utilize dry-sump equipped engines because they prevent oil-starvation at high G loads and because their lower center of gravity positively affects performance. A tank assembly for a dry sump lubrication system for an internal combustion engine is disclosed. The tank assembly includes a tank having an upper tank portion and a lower tank tank porti portion on.. An inte interf rfac acee asse assemb mbly ly is disp dispos osed ed at the the lowe lowerr tank tank porti portion on and is configured to operable deliver and receives a lubricant to and from the engine. A first end of a return tube in fluid communication with a second end is configured to receive lubricant from the engine at the interface assembly. The second end opposite the first end is in fluid communication with the upper tank portion. In this manner, a return hose and a feed hose may be connected to a same portion of the tank assembly.
How Does a Dry Sump System Work?
Dry Sump oiling systems are the safest, most dependable oiling systems available. They are popular in all forms of racing, especially where low chassis height is important for good handling. Horsepower gain is maximized because there is virtually no oil in the pan and no internal pump, so the windage tray or screen can run the full length of the pan. Other advantages of a dry sump system include a remotely mounted oil tank for increased capacity, the ability to easily add remote oil coolers, more consistent oil pressure, adjustable oil pressure, improved scavenging and increased ring seal due to greater pan vacuum.
Multi-Stage Pumps
The three-stage dry sump pump has one pressure section and two scavenge sections, while the four-stage pump has one pressure and three scavenge sections. The pressure section of each feeds oil to the block, while the scavenge sections pull oil from special pickups in the dry sump oil pan. The four-stage dry sump pump is plumbed like the three stage, but the line from the additional scavenge section can be routed to pull excess oil from the lifter valley. This keeps oil from sloshing around in the top of the engine and running down onto the rotating assembly, reducing windage and increasing horsepower. Recently, the need for five-stage pumps with four scavenge stages has arisen for large displacement drag race engines. Razor’s new five-stage pump is capable of creating the higher crankcase vacuum needed by today’s "mountain motors". Why do some engines use a dry sump oil system?
Most production cars have a wet sump oil system. On car engines the sump is located at the area below the crank shaft. In a wet sump, the oil that you put into the engine is stored beneath the crankshaft in the oil pan. This pan has to be large and deep enough to hold four to six quarts of oil. In a wet sump, the oil pump sucks oil from the bottom of the oil pan through a tube, and then pumps it to the rest of the engine. In a dry sump, extra oil is stored in a tank outside the engine rather than in the oil pan. There are at least two oil pumps in a dry sump -- one pulls oil from the sump and sends it to the tank, and the other takes oil from the tank and sends it to lubricate the engine. The minimum amount of oil possible remains in the engine.
Dry sump systems have several important advantages over wet sumps: •
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Because a dry sump does not need to have an oil pan big enough to hold the oil under the engine, the main mass of the engine can be placed lower in the vehicle. This helps lower the center of gravity and can also help aerodynamics (by allowing a lower hood line). The oil capacity of a dry sump can be as big as you want. The tank holding the oil can be placed anywhere on the vehicle. In a wet sump, turning, braking and acceleration can cause the oil to pool on one side of the engine. This sloshing can dip the crankshaft into the oil as it turns or uncover the pump's pick-up tube. Excess oil around the crankshaft in a wet sump can get on the shaft and cut horsepower . Some people claim improvements of as much as 15 horsepower by switching to a dry sump.
The disadvantage of the dry sump is the increased weight, complexity and cost from the extra pump and the tank. 3 STAGES DRY SUMP SCHEMATIC DIAGRAM
4 STAGES DRY SUMP SCHEMATIC DIAGRAM
The 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 p umped into various bearings and thereafter allowed to drain to the base of the engine. In most production, which uses 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, light weight 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 harder to replace, but that is dependent on the engine design.
However, the wet sump design is entirely unsuitable because it has a limited oil capacity of the sump size and it is difficult to cool the oil since it is contained within the engine which is a source of heat. 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. Wet sump systems can be modified to ensure a supply of oil to the pump. In the oil pan baffles direct oil through gates in pickup boxes using those same vehicular forces to move the oil. Scrapers and windage screens scour oil out of the crankcase, directing it into the sump.
Block modifications help oil return to the sump as q uickly as possible. The internal pump can often cope with the increased demands of larger bearing clearances, higher RPM, higher horsepower levels and additional oiling tasks. When those limits are reached an external pump can be fitted to match engine requirements for greater volume and/or pressure.
References •
Howstuffworks.com
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http://en.wikipedia.org/wiki/Dry_sump
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Jeppesen Sanderson – Powerplant Textbook
UNIVERSITI KUALA LUMPUR MALAYSIAN INSTITUTE OF AVIATION TECHNOLOGY Engine lubrication system (wet sump & dry sump)
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