Engine lubrication system is important for an Automobile Engine, as an Engine consists of various rotating and moving parts, so we need to lubricate it well otherwise they wear and tear out, and we may face Engine breakdown.
Before diving into the Lubrication System, let me give overview of what is Lubricant and What should be its property?
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, however here our main focus is in the Automobile.
In an automobile engine, lubrication is not only used for reducing friction, but it is also used for:
- Absorb Shock.
- Cleaning of the Engine cylinder.
- Sometimes used as a coolant.
- Prevent corrosion.
A lubricant is classified into the following categories:
- Animal Lubricant
- Vegetable Lubricant
- Mineral lubricant
- Synthetic Lubricant
And finally, let me discuss on the Properties what should have persisted in a Lubricant
A lubricant should have:
- Must have a high flashpoint. [i.e. it is the temperature where beyond this the lubricant vaporized and burned.]
- Viscosity should be high. [i.e. it is the attraction force acting between the molecules of the lubricant.]
- Pour Point. [i.e. it is the lowest temperature where lubricant can flow without any disturbances.]
- Chemical Stability. [i.e. it should not react with any parts of the engine]
Now get into the Lubrication System in the Automobile.
Engine lubrication system
The lubrication system is one of the most important maintenance operations of motor vehicles.
The absence of this system produces the friction between the moving parts, produces a large amount of heat which results in a serious problem like scoring of a cylinder, burning of bearings, striking of piston rings, excess fuel consumption, extra.
The main function of the system is to make the easy 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 ways:
- 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 engines like scooters, motorcycles.
- In this type of system, a certain amount of oil is mixed with petrol itself. therefore 3 to 6% of oil 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 duly used in cars extra.
- 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.
- As when the engine runs scoop splashes, the oil from oil through by centrifugal force to all engine parts.
How is Splash Lubrication System Works?
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-filled through at every revolution of the crankshaft and oil is splashed all over the interior of crankcase into the piston and cover the exposed portion of the cylinder is shown in the figure below.
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, Ashok Leyland, and others.
- Oil from the sump will be supplied to the engine parts through main galleries, via strainer and filter.
- The pressure of oil is about 2 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 between 0.4 to 1 kg/cm2.
- In this system, some parts are lubricated by the splash system and some parts are 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:
This system consists of two pumps.
- One scavenging pump placed below the sump, other pressure pump placed at the tank.
- Scavenging pumps supply lubricating oil to the main tank through the filter and, a 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 speed.
- Second, it keeps extra oil from soaking the crankshaft, which can lower horsepower.
- And, since the sump can be located anywhere, it can also be any size and shape.
- In this system, the pressure of oil is about 4 to 5 kg/cm2.
- Here sump is kept dry. Hence called a Dry sump lubrication system.
- This type of system is used in the sports car, and certain military vehicles extra.
- In brief, an engine lubrication system in which the lubricating oil is carried in an external tank and not internally in a slump.
- The sump is kept relatively free from oil by scavenging pumps, which return the oil to the tank after cooling.
- 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 4 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 called a wet sump lubrication system.
- The advantage of a wet sump system is its simplicity. And 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 build into a car.