Dynamic steering (Audi Q5-8R)

In standard steering systems, there is a direct mechanical connection between the steering wheel and the steering gear. This results in a clearly defined correspondence between the values of the steering angle and the steering angle of the steered wheels. In this version, only one gear ratio can be implemented on the vehicle. The selection of the appropriate gear ratio is always a compromise that must satisfy various, sometimes contradictory, requirements. Essential requirements can only be optimally met by means of a variable gear ratio. This gear ratio changes the actual steering angle of the wheels depending on the vehicle speed and the steering angle. The dynamic steering system provides primarily 2 variable gear ratios with a comfortable and sporty characteristic. The implementation of the variable gear ratios is carried out by means of an additional electromechanical drive of the steering pinion, which converts the steering wheel rotation by the driver. In an emergency, i.e. if the drive fails, the steering works in the same way as the standard steering. The mechanical connection between the steering wheel and the front axle is not disconnected. However, the advantages of the dynamic steering system are much more extensive. The system is also activated in critical driving conditions, thanks to interaction with the stability control system and the sensors of this system. By deliberately changing the steering angle of the front wheels, the dynamic steering system maintains the stability control system in the range of the limit values of the dynamic driving condition. The "regulator" installed on the steering column is a non-removable part of the steering column. If the "regulator" is faulty, the steering column must be replaced. The "valve" installed on the vane pump is a non-removable part of the pump. If the "valve" is faulty, the vane pump must be replaced. The correct basic setting is a prerequisite for the flawless operation of the dynamic steering.

Note: A prerequisite for successful basic adjustment is preliminary calibration of the steering angle sensor "G85" using the steering wheel calibration device "U4S 6458".

Basic adjustment is required if: the dynamic steering control unit "J792" is replaced; adjustable front wheel toe angle; rear wheel alignment angles are adjustable; changes were made to the car's chassis, for example, replacing the standard chassis with a sports one; the steering wheel angle sensor "G85" was calibrated; the steering column was replaced; when driving straight, the steering wheel is not level.

Note: Before the basic setting of the dynamic steering system, the fault memory must be read and, if necessary, the faults must be corrected. The basic setting of the dynamic steering system may only be performed on the wheel alignment stand recommended by VW/AUDI. The following figure shows the arrangement of parts "2" and "3" on a left-hand drive vehicle, on a right-hand drive vehicle parts "2" and "3" are arranged in mirror image.

Removal the Active Steering Control Unit "J792"

The used dynamic steering system "J792" is located in the footwell, under the driver's seat. Before removing the control unit, read the coding via "Guided Fault Finding" in the "Replace Control Unit" function. Loosen the driver's seat bolts and move it to the back with the wires connected. Remove the door sill trim. Remove the footrest. Bend back the floor covering and support it with a suitable wooden block "6". Loosen the nuts "7". Loosen the nuts "1" and remove the ground wire "2" from the grub screw. Carefully disconnect the wiring harness retainer "3" from the bracket "4". Disconnect the plug connectors of the wiring harness "3" from the control unit "8". Unscrew the bolts "5" from the control unit "8" and remove the holder "4".

Installation

Installation is carried out in reverse order. Please note the following: Observe the sequence of installation of the control unit. Tighten bolts "5" of bracket "4" on control unit "8" to 8 Nm. Connect the plug connectors of wiring harness "3" to control unit "8". Carefully insert the retainer of wiring harness "3" into bracket "4". Install the control unit with the holder. Install the ground cable "2" on the threaded pin and tighten the nuts "1" to 6 Nm. Tighten nuts "7" to 6 Nm. When replacing the dynamic steering control unit "J792", the system must be recalibrated.

Tightening torques

Bracket "6" and ground cable "5" (connector "4" is installed in the wiring harness) using nut "1" to the threaded pin:	6N·m
Bracket "6" with bolts "2" to control unit "3":	8N·m

[This publication is borrowed from the resource audimanual]