Abstract: A fixed displacement pump including a variable capacitance flow regulator for absorbing the excess fluid flow from the pump which is not required by a hydraulic system. The variable capacitance flow regulator, in a hydraulic embodiment, includes a pair of pistons slidably movable within a housing for independent movement relative to each other. The fluid pressure in the hydraulic system is communicated to a first of the pistons to bias it to various positions within the housing depending upon the pressure level in the hydraulic system. The second or varibale capacitance piston is acted upon by the fluid pressure in the pump discharge chamber, and when the pressure in the hydraulic system exceeds the spring pre-load against the first piston, the first piston will be displaced away from the second piston.