A dry sump car engine utilizes a lubrication system that stores engine oil in a separate external reservoir rather than in the oil pan located directly below the crankshaft.
Unlike a traditional "wet sump" system where the crankshaft rotates through the oil stored in the pan, a dry sump system actively removes oil from the crankcase using one or more scavenge pumps. This process removes oil from the crankcase, along with the possibility of such viscous drag that can occur when the crankshaft is partially submerged in oil.
How a Dry Sump System Works
A dry sump system is more complex than a wet sump setup and involves several key components:
- Scavenge Pump(s): These pumps remove oil that drains into the bottom of the crankcase (the sump) and other areas where oil might pool, such as in the valvetrain. The reference highlights that more complex dry-sump systems may scavenge oil from other areas where oil may pool, such as in the valvetrain. The scavenged oil is then sent to the external reservoir.
- External Oil Reservoir: This is a separate tank, often located elsewhere in the engine bay or vehicle, where the oil is stored. It allows for a larger oil capacity.
- Pressure Pump: This pump draws clean oil from the external reservoir and circulates it under pressure throughout the engine to lubricate moving parts like bearings, pistons, and the valvetrain.
- Oil Cooler: Often integrated into the system, an oil cooler helps manage the oil temperature, especially under demanding conditions.
Dry Sump vs. Wet Sump: Key Differences
| Feature | Dry Sump System | Wet Sump System |
|---|---|---|
| Oil Storage | External reservoir | Oil pan below the engine |
| Crankcase Oil | Oil is actively scavenged out (dry) | Oil pools in the pan (wet) |
| Pumps | Separate scavenge and pressure pumps | Single pressure pump drawing from pan |
| Complexity | Higher | Lower |
| Cost | Higher | Lower |
Benefits of a Dry Sump System
Dry sump systems offer several advantages, particularly beneficial in performance and racing applications:
- Improved Lubrication Under High G-Forces: In high-speed cornering or acceleration, oil in a wet sump can slosh away from the oil pickup, leading to oil starvation. A dry sump system, with its scavenge pumps and external reservoir, ensures a consistent supply of oil regardless of vehicle orientation or forces.
- Reduced Viscous Drag: By removing oil from the crankcase, the rotating crankshaft doesn't have to churn through oil, which reduces parasitic losses and improves engine efficiency. The reference specifically mentions the removal of oil from the crankcase along with the possibility of such viscous drag.
- Lower Engine Height: Since the oil pan no longer needs to store all the engine oil, it can be significantly shallower, allowing the engine to be mounted lower in the chassis for a lower center of gravity.
- Increased Oil Capacity: The external reservoir allows for a larger volume of oil, which helps manage oil temperature and extends the oil's life under strenuous use.
- Improved Oil De-aeration: The reservoir design often aids in separating air bubbles from the oil, which improves lubrication efficiency.
Applications
Dry sump systems are typically found in:
- Race cars (e.g., Formula 1, GT racing)
- High-performance sports cars (e.g., some Porsche, Ferrari, Corvette models)
- Aircraft engines
- Motorcycles
In summary, a dry sump engine utilizes an advanced lubrication system that stores oil externally and actively removes it from the crankcase and other areas like the valvetrain, mitigating viscous drag and ensuring reliable oil supply under demanding conditions.
