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# What is difference between volumetric efficiency and compression ratio in ic engine?

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What is difference between volumetric efficiency and compression ratio in ic engine?

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Compression ratio is the ratio between the volume in the cylinder, when the piston is in bottom dead centre, and the volume, when the piston is in the top dead centre. So: CR=Vbdc/Vtdc

Then you have the swept area, the engine displacement, which is: SA=Vbdc-Vtdc

Volumetric efficiency is the amount of air/fuel mixture that gets to the piston compared to the swept area - if the same volume of the mixture goes in, you have a 100 % efficiency. Usually it's a bit less, since you are creating a small vacuum when the piston is going down (with naturally aspirated engines) and that doesn't even out with the surrounding air pressure before the intake valve closes, but with proper tuning (think racing engines, F1 for example) it is possible to get over 100 % volumetric efficiency in a naturally aspirated engine.

volumetric efficiency :- amount of volume of air deliver into cylinder / total capacity of volume of air in cylinder

compression ratio = sweet volume /(sweet volume+clearance volume)

Volumetric efficiency in Internal combustion engine  is defined as the ratio of the volume of the air-fuel mixture drawn into the cylinder at atmospheric pressure (during the intake stroke) to the volume of the cylinder

The static compression ratio of an Internal combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity

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