A control system and method for obtaining power on demand from a diesel engine in order to operate vehicle functions and accessories. The method comprised of: (1) determining a flow rate necessary to operate each of a plurality of function hydraulic pumps and an vehicle drive pump associated with the engine; (2) comparing the flow rates of the various hydraulic pumps to determine the greatest flow rate; (3) establishing an engine speed necessary to deliver the greatest flow rate; (4) comparing the engine speed necessary to deliver the greatest flow rate with a current engine speed; and (5) adjusting the current engine speed to provide the greatest flow rate required.