Variable Assist Steering Systems
Variable assist steering systems are greatly reliant on vehicle speed. They control flow, reducing pressure at highway speeds, and increasing pressure while parking. They provide the driver with a tighter feel of the road while still providing full assist during parking maneuvers and traveling slowly.
If the steering feels sloppy at highway speeds, the variable orifice is not functioning and providing too much pressure. The orifice can become clogged, resulting in less assist during parking maneuvers.
This system is not to be confused with the standard flow control valve that regulates pressure in a standard power steering system to prevent over pressure and damage to the system. A flow control valve provides a regulated pressure but does not provide variable pressure, as an EVO does.