Drysump

A dry sump is a type of lubrication system used in internal combustion engines in which oil is stored in an external tank rather than in a conventional oil pan. Oil is circulated by a combination of pumps: scavenger pumps pull oil from the crankcase and return it to a separate oil reservoir, while a pressure pump draws oil from the reservoir and supplies it to the engine galleries. The external reservoir often includes baffling and oil-air separation to minimize foaming and to provide sufficient head pressure for reliable lubrication at various engine speeds and orientations.

Operation and design aspects

In a dry sump system, the crankcase oil is kept separate from the engine’s oil reservoir. Scavenger pumps actively remove oil from the bottom of the crankcase and deliver it to the external tank. A separate pressure pump moves oil from the tank to the engine’s oil passages. The reservoir’s design helps maintain oil availability during high-G conditions, hard cornering, or extreme accelerations, reducing the risk of oil starvation and improving consistent lubrication. Some configurations incorporate oil cooling and additional cooling loops for better thermal management.

Applications

Dry sump systems are commonly used in high-performance and racing applications, including sports cars, motorcycles, and some aircraft engines. They enable lower engine mounting, reduce sump depth, and improve lubrication reliability under demanding driving conditions. They are favored for engines that operate at high RPMs or in configurations where traditional wet sumps are prone to oil starvation or foaming.

Variations and considerations

Dry sump systems vary in the number of scavenger pumps and the complexity of the reservoir and lines. While offering improved lubrication reliability and packaging flexibility, they add cost, weight, and maintenance requirements, including potential external leaks and more complex installation.