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The 4 level air suspension system in the Audi allroad quattro The 4 level air suspension system in the allroad quattro is a logical development of the self levelling system in the Audi A6. The principles of the suspension/air suspension system and the description of those system components which are identical in the 4 level air suspension system are described in SSP 242. The contents of this self study program are supplementary to the contents of SSP 242. Introduction Designing a vehicle this perfect for on and off road use sounds like squaring the circle. Usually the strengths of an off road vehicle are decided weaknesses when it comes to road use. A high ground clearance, crucial for rough terrain, gives the vehicle a correspondingly high centre of gravity. 243 001 When it comes to fast cornering, however, this is as disadvantageous as it is for driving stability at higher speeds. In addition, the air resistance is increased, which significantly affects fuel consumption. In contrast, the shorter spring travel and the firmer running gear matching of an “on road running gear” offer inadequate driving comfort off road. 243 002 A variable ground clearance is the solution for all road use and it’s called 4 level air suspension. The air suspension realised in the allroad quattro is based on the familiar self levelling system of the Audi A6. 243 003 2 Contents Page System description 4 Operation and display Operation 7 Display . 8 Control strategies Control strategies, control unit 4Z7 907 553A . 10 Control strategies, control unit 4Z7 907 553B . 12 ESP safety switching 13 System components Air springs 14 Air suspension . 17 Diagram of pneumatic system 20 Solenoid valves . 21 Temperature sensor G290 .. 22 Pressure sensor G291 22 Level senders G76, G77, G78, G289 . 23 Warning lamp K134 27 Operating unit E281 .. 28 Interfaces CAN information e