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LUBRICATION SYSTEM

  • The moving parts of an I.C engine are likely to wear off due to continuous rubbing action of one part with another.
  • In order to avoid an early wearing of the engine parts, a proper lubrication arrangement is provided in I.C. engines.
  • Lubrication is an art of admitting a lubricant (oil, grease, etc.) between two surfaces that are in contact and in relative motion

The main parts of an automotive engine require lubrication are:

    • Main crankshaft bearings
    • Big end bearings
    • Gudgeon pin bearings 
    • Piston rings and cylinder walls
    • Camshaft and camshaft bearings
    • Timing Gears
    • Valve mechanism 

Purpose of Lubrication:

  • It reduces wear and tear of the moving parts.
  • It damps down the vibrations of the engine.
  • It dissipates the heat generated from the moving parts due to friction.
  • It cleans the moving parts.
  • It makes the piston gas-tight.

Properties of Lubricant:

  • Suitable viscosity
  • Should not react with lubricating surfaces
  • No tendency to form deposits by reacting with air, water, fuel or the products of combustion
  • Cleaning ability
  • Non foaming characteristics
  • Non toxic and non inflammable

Types of Lubrication:

The various systems used for internal combustion engine may be classified as:- 

    • Mist lubrication system
    • Wet sump lubrication system
    • Dry sump lubrication system

Wet sump Lubrication:

  • In the wet sump lubrication system, the bottom of the crankcase contains an oil pan or sump from which the lubricating oil is pumped to various engine components by a pump.
  • After lubrication these parts, the oil flow back to the sump by gravity.
  • Again it is picked by a pump and re-circulated through the engine lubricating system.

There are three varieties in the wet sump lubricating system.

  • The splash system
  • The splash and pressure system 
  • The pressure feed system

The splash system


  • This was employed for the engines of early motor cycles.
  • A scoop is made in the lowest part of the connecting rod and the oil is stored in the oil trough, it being pumped there from the crankcase oil sump.
  • When the engine runs, the scoop causes the oil to splash on the cylinder walls each time it passes through its BDC position. 
  • This affects the lubrication of engine walls, gudgeon pin, main crankshaft bearings, big end bearings etc.

The Pressure feed system

The basic components of the pressure feed lubricating system are
    1. Pump
    2. Strainer
    3. Pressure regulator
    4. Filter

  • Oil is drawn from the sump by a gear or rotor type of oil pump through an oil strainer. 
  • The strainer is a fine mesh screen which prevents foreign particles from entering the oil circulating system.
  • A pressure relief valve is provided which automatically keep the delivery pressure constant.
  • An oil hole is drilled in the crankshaft from the Centre of each crankpin to the Centre of an adjacent main journal, through which oil can pass from the main bearing to the crankpin bearing. 
  • From the crankpin it reaches piston pin bearing through a hole drilled in the connecting rod.
  • The cylinder wall, tappet roller, piston and piston rings are lubricated by oil spray from around the piston pins and the main and connecting rod bearings.
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