it rotates the inside of the spool valve relative to the outside. Since the inner part of the spool valve is also connected to the steering shaft, the amount of rotation between the inner and outer parts of the spool valve depends on how much torque the driver applies to the steering wheel. When the steering wheel is not being turned, both hydraulic lines provide the same amount of pressure to the steering gear. But if the spool valve is turned one way or the other, ports open up to provide high-pressure fluid to the appropriate line. The Power Steering Model that we have studied for advance car is a combination of both types hydraulic and electrical power steering .This combination will provide highly precise output with less effort so that the driver should make lots of effort to drive the vehicle or turn it. This model uses lots of sensors and Microprocessors (CPU) to control this whole unit from a centralize point.