A dry sump oil system is a method of managing the lubricating motor oil in four-stroke and large two-stroke piston-driven internal combustion engines. In a dry sump system, 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 system - 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, and the oil capacity of a dry sump can be as big as desired. Dry sump systems have several advantages over wet sumps, including:
-
Lower center of gravity: 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.
-
Reduced oil sloshing: In a wet sump, turning, braking, and acceleration can cause the oil to pool on one side of the engine, which can dip the crankshaft into the oil as it turns or uncover the pumps pick-up tube. Excess oil around the crankshaft in a wet sump can get on the shaft and cut horsepower. Dry sump systems reduce these issues.
-
Increased engine power: In a wet-sump engine, oil sloshing against spinning parts causes substantial viscous drag, which creates parasitic power loss. A dry-sump system removes oil from the crankcase, reducing friction inside the engine.
Dry sump systems are common on larger diesel engines, as well as gasoline engines used in racing cars, aerobatic aircraft, high-performance personal watercraft, and motorcycles. They are more expensive, complex, and heavier than wet sump systems due to the extra pump and tank.
