In engines, frictional losses are mainly due to slide as Well as rotating parts Engine friction is expressed in terms of frictional power Friction all losses is mainly attributed to the following mechanical losses

• Direct frictional losses
• Pumping losses
• Power loss to drive the components to change and scavenge Power loss to drive other auxiliary components

A good engine design should not the total frictional losses to be more than 30%of energy input in Reciprocating engine. It should be the aim of a good designer to reduce friction and wear of the parts subjected to relative motion. This is achieved by proper lubrication system

1. Direct Frictional Losses:

It is the power absorbed due to the relative motion of different bearing surfaces such as

• Piston rings,
• main bearings,
• Cam shaft bearings etc…

2. The frictional losses are comparatively higher in the reciprocating engine.

3. Pumping Loss For4-stroke engines Considerable amount of energy is spent during the exhaust

Processes. The pumping loss is the net power spent by the engine (piston) on the working medium (gasses) during intake and exhaust strokes. For2-stroke engines this is negligible since the incoming fresh mixture is used to scavenge the exhaust gasses Power Loss to drive the components to change and scavenge 4-strokeengine. In turbo/supercharged engines the intake charge is supplied at A higher pressure than the aspirated engines For this purpose mechanically driven compressor or turbine driven compressor used accordingly the engine is called Supercharged or turbocharged engine.