What is wet sump lubrication?

Short Answer:

Wet sump lubrication is a system in which the lubricating oil is stored in the oil sump located at the bottom of the engine crankcase. The oil is pumped from the sump by an oil pump and supplied to various engine parts for lubrication. After circulating through the engine, the oil drains back into the sump by gravity.

This system is commonly used in most automobile engines because of its simple design, low cost, and easy maintenance. It provides effective lubrication for general-purpose vehicles where extreme operating conditions are not present.

Detailed Explanation :

Wet Sump Lubrication

The wet sump lubrication system is the most common and widely used method for lubricating internal combustion engines. In this system, the lubricating oil is kept in an oil sump (reservoir) located at the bottom of the crankcase. The oil is pumped from the sump to different moving parts of the engine to reduce friction, remove heat, and prevent wear. After lubrication, the oil returns to the sump by the force of gravity, where it is reused in the next cycle.

This system is called a “wet sump” because the sump always contains a sufficient amount of oil during engine operation. It is simple, compact, and economical, making it suitable for small and medium-size engines like those used in cars, motorcycles, and small trucks.

The main purpose of this system is to ensure that all moving parts such as crankshaft bearings, connecting rods, camshaft, and pistons are continuously lubricated with clean oil. It also helps in cooling, cleaning, and sealing the engine components.

Components of Wet Sump Lubrication System

  1. Oil Sump:
    The oil sump is the container located at the bottom of the crankcase that stores the lubricating oil. It collects the returning oil and serves as the oil reservoir for the system.
  2. Oil Pump:
    The oil pump draws oil from the sump and sends it under pressure to different parts of the engine through the oil galleries. The pump ensures continuous oil circulation throughout the system.
  3. Oil Filter:
    The oil filter removes dirt, metal particles, and carbon deposits from the oil, ensuring that only clean oil reaches the moving engine components.
  4. Oil Pressure Gauge:
    This gauge monitors the oil pressure inside the engine and ensures that it remains within a safe range.
  5. Oil Galleries:
    These are the passages through which the oil is delivered to various engine components such as bearings, pistons, and camshafts.
  6. Return Passages:
    After lubrication, the oil flows back to the sump through these passages by gravity.

Working of Wet Sump Lubrication

When the engine starts, the oil pump draws oil from the sump through a strainer and delivers it under pressure through the oil filter. The clean, filtered oil then flows through oil galleries to different engine parts. It reaches bearings, crankshaft, connecting rods, and camshaft to reduce friction between moving surfaces. Some of the oil also splashes onto cylinder walls and piston rings to ensure smooth operation.

After lubricating the parts, the oil drains back into the sump by gravity. This cycle continues as long as the engine is running. The oil temperature is maintained at an acceptable level due to continuous circulation and heat dissipation through the engine body.

To ensure the oil remains clean and effective, it is necessary to change the oil periodically and replace the filter at regular intervals. The proper functioning of the oil pump and maintaining the right oil level in the sump are also important for efficient lubrication.

Types of Wet Sump Systems

There are mainly three types of wet sump lubrication systems used in different types of engines:

  1. Splash System:
    In this system, a small scoop or dipper attached to the connecting rod splashes oil onto the engine parts. It is simple and used in small engines.
  2. Splash and Pressure System:
    This system combines splash lubrication with pressure feed. Some parts receive oil by splash, while others get it directly through pressure. It is commonly used in modern engines.
  3. Pressure Feed System:
    Here, oil is delivered to all critical parts through pressure created by the oil pump. It ensures uniform lubrication and is used in most automobile engines today.

Advantages of Wet Sump Lubrication

  • Simple and economical design.
  • Easy to maintain and repair.
  • Compact construction requiring less space.
  • Reliable for normal driving conditions.
  • Provides adequate cooling and lubrication for general engines.

Disadvantages of Wet Sump Lubrication

  • Not suitable for high-performance or racing engines.
  • During sharp turns or steep slopes, oil may move away from the pickup pipe, causing oil starvation.
  • Cooling efficiency is lower compared to dry sump systems.
  • Oil aeration and foaming may occur at high speeds.
Conclusion :

Wet sump lubrication is the most widely used system for lubricating internal combustion engines due to its simplicity and cost-effectiveness. It provides continuous lubrication by storing oil in the sump and circulating it through the engine. Although it is not suitable for extreme conditions or high-speed racing, it serves efficiently for everyday vehicles, ensuring smooth operation, reduced wear, and longer engine life.