The electronic variable orifice (EVO) system increases or decreases the amount of fluid leaving the power steering pump. This provides the driver with a comfortable balance of steering wheel feel and power assist.
At vehicle standstill or at very low speeds, the system allows full hydraulic fluid flow for maximum power assist and reduced steering effort. As the vehicle gains speed, a variable orifice closes at the steering pump which reduces the pump fluid flow. This action provides a stiffer steering wheel response for an improved road feel and a greater directional stability at highway speeds.
A sensor mounted on the steering column detects the steering wheel movements associated with defensive driving maneuvers. A control module uses this sensor input and the vehicle speed in order to adjust the amount of current to the solenoid.
The EVO system consists of the following components:
| • | The EVO solenoid (actuator) is located on the power steering pump discharge fitting. |
| • | The module that controls EVO will be located in one of two areas depending on option content: |
| • | On vehicles equipped with Real Time Damping (RTD), EVO is controlled through the Suspension Control Module which is located behind the right rear quarter trim panel. |
| • | On vehicles which are not equipped with RTD, EVO is controlled through the Body Control Module which is located under the Instrument Panel, below the steering column. |
| • | The steering handwheel position speed sensor is located in the lower bearing of the steering column. |
| • | The vehicle speed sensor is located on the transfer case output shaft. |
| • | The powertrain control module (PCM) is located in the engine compartment on the left front inner wheelhouse. |
