Power steering systems and methods

Power steering systems and methods to improve efficiency and performance of vehicle power steering systems. In one embodiment, there is provided an engine driven positive displacement hydraulic pump, a rotary valve coupled to a steering shaft for receiving hydraulic fluid under pressure in a rotary valve inlet and providing a differential pressure to a steering rack piston for a steering boost responsive to a torque exerted on the steering shaft, valving coupled between an output of the hydraulic pump, the rotary valve inlet and the hydraulic pump input for controllably coupling the output of the hydraulic pump to the rotary valve inlet or an input of the hydraulic pump, and a controller coupled to valving to maintain a flow rate of hydraulic fluid coupled to the rotary valve responsive to a pressure sensor output. Other embodiments are disclosed.