Scavenge efficiency :-
It is the ratio of mass off air in the cylinder at the beginning of the compression (closing of exhaust ports or valves ) to the mass of air represented by the swept volume by the piston.
If if the scavenge efficiency will increase then the mass of air will be available and fuel can be burnt to produce more power.
Trapping efficiency :-
● The Scavenge air supplied to the cylinder is split into two parts :-
the short circuiting air which lives through the the exhaust ports /valves.
the retained air which is trapped in the cylinder and take parts in the subsequent combustion.
● it is used to indicate the ability of the cylinder to retain the fresh air.
● it is the ratio of amount of charge retained in the cylinder to the total charge delivered by the engine.
● Trapping efficiency is a measure of the success of trapping the supplied air with minimum waste. it is mainly controlled by the geometry of the ports and the overlap time.
charging efficiency :-
● It is the ratio of useful fresh charge in the cylinder to the displacement volume.
● The amount of fresh charge in the cylinder is a measure of power output of the engine.
● It is important index as it most directly affect the power output.