What is the relationship between the diameter of a plunger and the capacity of the pump

I think there is no relationship between the diameter of a plunger and the capacity of a pump.Actual relation ship is between the volume of the plunger and the capacity of a machine.The volume the plunger is responsible for the force of the stroke and thus the force(capacity) of a pump.
Generally 1 cc(cubic centimeter) volume of a plunger creates 1 hp(horse power) capacity.

Bijay Krishna Pandey,Gorakhpur(India)
bijaykrishnapandey@ymail.com
bijaykrishnapandey@gmail.com

For a given stroke, the diameter of the plunger is proportional to the square of the displacement/capacity

doing some grundle pumping i see