Lubrication System: Petroil, Splash, Pressure, Semi-Pressure, Dry & Wet Sump [PDF]

Introduction

Lubrication System is important for an Automobile Engine. Because an Engine consists of various rotating and moving parts, we need to lubricate it well otherwise they wear and tear out. Because of this we may face Engine breakdown problems. Before diving into the Lubrication System, let us first understand what is a lubricant and what are it’s properties?

What is a Lubricant

A lubricant is an artificial or natural fluid that has high viscosity, greasy and oily. It is used to reduce the friction between the moving parts. It is not only used in the Automobile industry, but it also used in the various fields where we need to reduce the friction between two bodies.

In an automobile engine, lubrication is not only used for reducing friction, but it is also used for the following purposes:

1. Absorb Shock.
2. Cleaning of the Engine cylinder.
3. Sometimes used as a coolant.
4. Prevent corrosion.

Types of Lubricants

1. Animal Lubricant
2. Vegetable Lubricant
3. Mineral lubricant
4. Synthetic Lubricant

Lubricant Properties

1. Must have a high flashpoint. It is the temperature beyond which the lubricant vaporizes and get’s burnt.
2. Viscosity should be high. Viscosity is the attraction force acting between the molecules of the lubricant.
3. Pour Point. It is the lowest temperature where lubricant can flow without any disturbances.
4. Chemical Stability. It should not chemically react with any parts of the engine

Lubrication system

The lubrication system is one of the most important maintenance operations of motor vehicles. The absence of this system increases the friction between the moving parts, produces a large amount of heat which results in serious problems like scoring of a cylinder, burning of bearings, striking of piston rings, excess fuel consumption, etc.

The main function of the system is to allow the smooth running of an engine and to reduce the rate of wear and tear on the vehicles. This system reduces power loss due to friction. It absorbs the heat from the engine part, thereby acts as a cooling agent in the engine of the vehicle. It also provides the sealing action between moving parts.

Types of Lubrication System

The lubrication system can be classified into the following types:

• Petroil system
• Splash system
• Pressure system
• Semi-pressure system
• Dry sump system and
• Wet sump lubrication system

Petroil Lubrication System

This system is generally used in the two-stroke petrol engine like scooters and motorcycles. In this type of system, a certain amount of oil is mixed with petrol itself (Approximately 3% to 6% of oil is mixed with fuel). This proportion should be proper. If this proportion is less, the danger of oil starvation causes damage to the engine. If this proportion is more, the engine gives dark smoke and excessive carbon deposits on the cylinder head.

Splash Lubrication System

This is the most popular type of lubrication system used in cars. This is one of the cheapest methods of the lubrication system. It consists of a scoop, which is fitted at the lower end of the connecting rod as shown in the diagram. When the engine runs scoop splashes the oil by centrifugal force to all engine parts.

Splash lubrication system is used on small, stationary four-stroke engines. In this system, the cap of the big end bearing on the connecting rod is provided with a scoop which strikes and dips into the oil at every revolution of the crankshaft. Oil is splashed all over the interior of crankcase including the piston and covers the exposed portion of the cylinder.

A hole is drilled through the connecting rod cap through which the oil passes through the bearing surface. Oil pockets are provided to catch the splashed oil over all the main bearings and also the camshaft bearings. From these pockets, oil passes to the bearings through a drilled hole. The surplus oil dripping from the cylinder flows back to the oil sump in the crankcase.

Pressure Lubrication System

This system is used, because the splash system is not sufficient for larger engines like Ambassador, Jeep, Trucks, etc. Oil from the sump is supplied to the engine parts through main galleries, via strainer and filter. The pressure of oil is about 2kg/cm² to 4kg/cm². For camshaft and timing gears, oil is supplied by a separate line through the pressure reducing valves. In this type of system, oil is pressurized by using a gear pump.

Semi-Pressure Lubrication System

In this type of system the oil pressure is between 0.4kg/cm² to 1 kg/cm². In this system, some parts are lubricated by the splash system and some parts by a pressure system. The parts such as cylinder wall, piston, piston pin, connecting rod extra are lubricated by splash system and remaining parts are by a pressure system.

Dry Sump Lubrication System

The Scavenging pump is placed below the sump. The Pressure pump is placed at the tank. Scavenging pumps supply lubricating oil to the main tank through the filter and pressure pump supplies oil to the different parts of an engine through the oil cooler. A dry-sump system gets you a couple of bonuses: First, it means the engine can sit a little lower, which gives the car a lower center of gravity and improves stability at high speed. Second, it prevents extra oil from soaking the crankshaft, which can lower horsepower. And, since the sump can be located anywhere, it can also be of any size and shape.

In this system, the pressure of oil is about 4kg/cm² to 5 kg/cm². The sump is kept dry. Hence it is called a Dry sump lubrication system. This type of system is used in sports cars, and certain military vehicles etc. In brief, an engine lubrication system is a type of lubricating system in which the lubricating oil is carried in an external tank and not internally in a sump. The sump is kept relatively free from oil by scavenging pumps, which return the oil to the tank after cooling. It is the opposite of a wet sump system. The pumping capacity of scavenging pumps is higher than that of the engine-driven pumps supplying oil to the system.

Wet Sump Lubrication System

In this system, the oil is delivered from the sump strainer to different engine parts. In this system, the pressure of oil is about 4kg/cm² to 5kg/cm². After lubrication oil is drawn back to the oil sump. In this case, the oil is always present in the sump. Hence it is called a wet sump lubrication system. The advantage of a wet sump system is its simplicity, the oil is close to where it will be used, there aren’t too many parts to engineer or repair, and it’s relatively cheap to install into a car.

FAQ’s

Conclusion

So we saw the various properties, purposes and types of lubrication systems in Automobile. However, there are also other important systems in Automobile, which are also important for the safe and smooth running of an Engine, like Cooling systems in the Automobile, Fuel supply System and more.