In a typical power steering system, a hydraulic pump is driven by the engine via a belt and pulley. The pump pressurizes fluid, which is then routed to the steering gear. The pressure in the steering system assists the driver in turning the wheels.
The amount of pressure exerted by the power steering system can be varied, depending on driving conditions. For example, more pressure may be needed when making a tight turn at low speeds. Variable assist power steering systems use sensors to monitor speed and steering angle, and adjust the level of assistance accordingly.
Overall, variable assist power steering can provide a more comfortable driving experience, as it adjusts automatically to changing conditions. It can also help improve fuel economy because it only uses as much hydraulic pressure as needed – unlike fixed-assist power steering systems, which always maintain maximum pressure.