Technician A says mechanical efficiency is a comparison between brake horsepower and indicated horsepower. Technician B says volumetric efficiency is a measurement of the amount of air-fuel mixture that actually enters the combustion chamber compared to the amount that could be drawn in. Who is correct?

Both are correct

Explanation:

Both are correct because

Mechanical efficiency is the dimensionless term which is the ratio of brake horsepower to the Indicated horse Power

Where brake power is the Power obtained at the crankshaft  and  

Indicated horsepower is the power obtained in the combustion chamber and this power is the loss in the form of friction.    

Volumetric efficiency is the ratio of actual fuel intake to the maximum air fuel that could be taken.  

50 inches should be the resultant vector

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