A pump system includes a fixed or variable capacity pump and a speed-related control mechanism to alter the capacity of a variable capacity pump or to alter the relief pressure of a fixed capacity pump in response to changes in the operating speed of the pump. A pressure generator comprising a volume of working fluid is rotated at a speed related to the operating speed of the pump and creates a forced vortex in the working fluid. The pressure induced in the working fluid of the forced vortex is used as a speed related control to alter the discharge pressure of the pump as desired.