Related Manuals for Audi A8 292
Summary of Contents for Audi A8 292
- Page 1 Service adaptive air suspension in the Audi A8 Home study program 292 For internal company use only...
- Page 2 However, this sporty tuning necessarily entails limi- tations when it comes to comfort. In the Audi A8 MY 2003, a newly developed, fully bearing air suspension system is used. In conjunction with the CDC status-dependent electronic damping control, this ensures that the main - and partly conflicting - requirements are satisfied in an optimum manner within the limits of the laws of physics.
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Page 3: Table Of Contents
Contents Page Introduction Basics ............. . 4 New technology. -
Page 4: Introduction
Introduction Basics The basics for understanding air suspension systems are contained in home study pro- grams 242 and 243 and are of course also valid for the system to be introduced in the A8 from model year 2003. New technology The new A8 heralds a new system in terms of technical content and range of functions. - Page 5 Encased pneumatic springs: The air bellows are encased in an aluminium cylinder. The result is a considerable improve- ment in the response characteristic. (See description "Pneumatic springs" in the "System components" section.) 292_003 Operation: Integration in the MMI means that operation is user-friendly, logical and easy to learn.
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Page 6: Operation And Display
Operation and display Vehicle levels The A8 comes either with a standard running gear (adaptive air suspension) or a sporty run- ning gear (adaptive air suspension-sport). Standard running gear: The following programs can be selected either manually or automatically: "automatic" mode: Basic vehicle level, comfort-oriented suspension with appropriately adapted damper map. - Page 7 "dynamic" mode: Vehicle level is 20 mm lower than in "automatic" mode. The damper map is automatically set to sporty. After 30 seconds at speeds of 75 mph (120 km/h) or more, the car is lowered by another 5 mm ("motorway lowering"). - 20 mm 292_004 "dynamic"...
- Page 8 Operation and display Sporty running gear: "automatic" mode: Basic vehicle level corresponds to "dynamic" mode in the standard running gear, sporty suspension with appropriately adapted damper map (more comfortable than "dynamic" mode). The vehicle is lowered by another 5 mm after 30 seconds at speeds of 75 mph (120 km/h) or more ("motorway lowering").
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Page 9: Operation And Display System
Operation and display system The process of switching from one mode to another and the display/monitoring of the system status all form part of the MMI operat- ing system. The adaptive air suspension menu is opened directly in the MMI display in the centre con- sole when the "CAR"... -
Page 10: System Components
System components Vehicle overview Dash panel insert Front operator/display unit (MMI) Adaptive air suspension control unit Body acceleration sender Pneumatic struts, FA Vehicle level sender, FA Solenoid valve block with pressure sender Air supply unit... - Page 11 Body acceleration sender Pneumatic struts, RA Accumulator Vehicle level sender, RA 292_012...
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Page 12: Control Unit J197
System components Control unit J197 The control unit is the central element of the The principal result of this processing work system. It is installed in the vehicle in front of are the signals to actuate the compressor, the the glove box. solenoid valves and the shock absorbers. -
Page 13: Suspension/Shock Absorber Strut
Suspension/shock absorber strut All four suspension/shock absorber struts are constructed in the same way. Pneumatic spring Construction: The pneumatic spring is encased in an alu- Aluminium minium cylinder. In order to prevent dirt from cylinder getting between the cylinder and the air bel- lows, the area between the piston and the cyl- Pneumatic inder is sealed by a sleeve. -
Page 14: Shock Absorber
System components Shock absorber Construction: Function: A twin-tube gas-filled shock absorber with For general information on the function of a continuous electrical control is used (ccontin- twin-tube gas-filled shock absorber, see uous damping control =CDC shock absorber). SSP 242. The main damping valve 3 in the piston 1 is The damping force is determined to a consid- mechanically pre-tensioned by a spring 4. -
Page 15: Air Supply Unit
Air supply unit The air supply unit is installed at the front left of the engine compartment. This prevents any impairment of the acoustics in the passenger compartment. Furthermore, more effective cool- ing can be achieved. This increases the amount of time the compressor can be switched on, and thus the quality of control. -
Page 16: Solenoid Valve Block
System components Solenoid valve block Solenoid valves Construction/function: The solenoid valve block contains the pres- The construction and function of the solenoid sure sender and the valves for actuating the valves are largely the same as in the allroad pneumatic springs and the accumulator. It is quattro (see SSP 243). - Page 17 Notes...
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Page 18: Pneumatic Diagram
System components Pneumatic diagram Air supply unit Solenoid valve block 292_020 Compressor V66 Valve for strut RL N150 Air drier Valve for strut RR N151 3a, 3b Non-return valves Valve for accumulator N311 Exhaust throttle Pressure sender G291 Electrical exhaust solenoid valve Accumulator N111 Pneumatic spring FL... -
Page 19: Pressure Build-Up
Pressure build-up The valves 9a, 9b and 9c, 9d are electrically When the pneumatic springs are filled by the actuated in pairs (front axle and rear axle). accumulator, the valve 10 and the valves 9 for The compressor takes in the air through the the appropriate axle open. -
Page 20: Senders (Sensors)
System components Senders (sensors) Compressor temperature sender G290 Construction: An NTC resistor is housed in a small glass case. Function: The sender records the temperature of the cylinder head compressor. Its resistance decreases sharply as the tem- perature rises (NTC: negative temperature coefficient). - Page 21 Acceleration sender In order to achieve optimum damping for Two of these are situated on the front axle every driving condition, knowledge of the MacPherson strut towers, the third in the rear body movement (sprung mass) and axle com- right wheel housing. The acceleration of the ponents (unsprung mass) characteristic over axle components (unsprung masses) is deter- time is required.
- Page 22 System components Rest condition: The seismic mass is situated exactly in the middle between the counter-electrodes. The two capacitors C1 and C2 have the same capacitance. Metal-plated electrodes Silicon spring Capac- itor C1 Seismic mass Capac- itor C2 292_026 Accelerated condition: The supply voltage is provided by the pneu- Mass inertia causes the seismic mass to be matic spring system’s control unit.
- Page 23 Vehicle level senders G76, G77, G78, G289 Function: Construction: The senders record the distance between the The sender construction and the PIN designa- links and the body, and thus the level of the tion are the same as those of the allroad quat- tro (description in SSP no.
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Page 24: System Functions
System functions General control concept Changes in level are effected by axle, with correction of differences in level between the left and right-hand sides (e.g. caused by one-sided loading of the vehicle) At vehicle speeds of 22 mph (35 km/h) or less, the accumulator is the preferred energy source. A prerequisite for this is a pressure difference of at least 3 bar between the accumulator and the pneumatic springs. - Page 25 Notes...
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Page 26: Control Concept For Standard Running Gear
System functions Control concept for standard running gear "automatic" mode (basic level) The suspension is oriented towards a more comfortable ride. Automatic motorway lowering of 25 mm takes place after 30 seconds at speeds of 75 mph (120 km/h) or more. The vehicle is automatically lifted back up to basic level once the speed drops below 44 mph (70 km/h) for 120 seconds or if the speed drops below 22 mph (35 km/h). - Page 27 292_053 "lift" "automatic" "dynamic" "comfort" Acceptance level for selecting "lift" mode 50 mph (80 km/h) System automatically leaves "lift" mode at v > 63 mph (100 km/h), vehicle is not lifted back up automatically Automatic lift to revert to sporty/basic level (dependent on speed/time) Automatic motorway lowering after >...
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Page 28: Control Concept For Sporty Running Gear
System functions Control concept for sporty running gear – Same levels but different damping maps Differences from the standard running gear: for "dynamic", "automatic" and "comfort" modes at speeds of less than 75 mph – Different, sporty suspension and damping (120 km/h) –... -
Page 29: Control Concept For Special Operating Conditions
Control concept for special operating conditions Cornering Suspension adaptation is interrupted during The damping forces are adapted to suit the cornering manoeuvres and continued after- current driving situation. wards. This effectively eliminates undesirable body The system recognises that cornering is tak- movements (e.g. - Page 30 System functions Braking manoeuvres Damping control is employed, particularly This keeps nose diving, squatting and rolling during ABS/ESP braking manoeuvres. Damp- of the vehicle body to a minimum. ing is regulated as a function of the current braking pressure. Longitudinal axis Transverse axis Squatting/ nose diving...
- Page 31 Pre-travel and after-run mode Any difference from the specified height Any difference in height caused, for example, by climbing out of or unloading the vehicle before driving commences or before ignition after switching off the ignition, is corrected in on is corrected. after-run mode.
- Page 32 System functions Using a jack (service mode) There is no automatic recognition. Adaptive air suspension must be deactivated if a jack is to be used. This is done by actuating the MMI control knob in the CAR -> SETUP menu. This mode is deactivated either by resetting in MMI or by driving at a speed of >9 mph (15 km/h).
- Page 33 Extreme low level Extreme low level (65 mm or more below nor- mal level) is shown by the low level indicator lamp and the warning lamp flashing. Extreme low level can occur after the vehicle has been at a standstill for a very long period. 292_045 Extreme high level Extreme high level (50 mm or more above...
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Page 34: Interfaces
Interfaces System overview of components with bus link (CAN, MOST) J197 Adaptive air suspension control unit Diagnosis J533 Gateway J345 Trailer recognition control unit J285 Control unit with display unit in dash panel insert J220 Motronic control unit J518 Access and start CAN drive authorisation control unit... -
Page 35: System Overview Of Components Without Bus Link
System overview of components without bus link N111 Exhaust solenoid CAR button valve for adaptive air SETUP button suspension (integrated in air supply unit) N148, N149, N150, N151 Strut G76, G77, G78, G289 FA and RA valves vehicle level senders (integrated in solenoid valve block) G290 Compressor temperature sender... -
Page 36: Can Information Exchange
Interfaces CAN information exchange J197 Adaptive air suspension control unit – System status (all) – Actuate warning lamp (5) – Actuate low level indicator (5) – Advance warning of level adjustment (4) – Advance warning of compressor start- up (4) –... - Page 37 J220 Motronic control unit (1) CAN drive – Engine speed – Driver’s desired torque – Current position of brake light switch CAN multi-function – Current position of brake test switch CAN comfort MOST bus J104 ESP control unit (2) Information which is transmitted –...
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Page 38: Function Diagram
Interfaces Function diagram G76 Vehicle level sender, rear left G77 Vehicle level sender, rear right G78 Vehicle level sender, front left G289 Vehicle level sender, front right G290 Temperature sender for adaptive air suspension compressor G291 Adaptive air suspension pressure sender J393 Central control unit for comfort sys- tem (for door signal) - Page 39 292_051 Ancillary signals CAN High CAN Low...
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Page 40: Other Interfaces
Interfaces Other interfaces The wake-up signal to wake the adaptive air suspension control J393 transmits a signal even if terminal 15 is unit from sleep mode is transmitted by the detected but the doors and/or boot lid are comfort system central control unit J393. not opened or closed. - Page 41 The signal for headlight range control The adaptive air suspension control unit The headlight range control unit uses this sends the headlight range control unit a CAN information to calculate the required head- message about the momentary body level on light setting in each case.
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Page 42: Service
Service Control unit code The code for both the standard and the sporty running gear is 15500. System initialisation The system initialisation process includes cal- The height of each wheel is measured from ibration of the vehicle level senders. the centre of the wheel to the lower edge of This is required whenever a sender or the the wheel housing. -
Page 43: Final Control Diagnosis
Final control diagnosis Final control diagnosis checks the function of Final control diagnosis is implemented when the compressor, the solenoid valves and the the vehicle is stationary and the ignition is on. struts/shock absorbers. The engine may be running. During final con- trol diagnosis, the yellow warning lamp in the Diagnosis is executed automatically in three dash panel insert flashes. - Page 44 Notes...
- Page 46 All rights reserved, including the right to make technical changes Copyright* 2002 AUDI AG, Ingolstadt Department I/VK-35 D-85045 Ingolstadt Fax +49 (0)841/89-36367 000.2811.12.20 Technically correct as at 007/02 Printed in Germany...