899303 the phaeton air suspension design and function
TRANSCRIPT
The PhaetonAir Suspension Design and Function
Self-Study ProgramCourse Number 899303
Rebound
Bump
Vibrating Mass
Position of Rest
Sp
rin
g T
ravel
P
Amplitude
Amplitude
cvr-outside-front-ssp275 6/30/03 1:59 PM Page 1
Volkswagen of America, Inc.Service TrainingPrinted in U.S.A.Printed 08/2003Course Number 899303
©2003 Volkswagen of America, Inc.
All rights reserved. All information containedin this manual is based on the latestinformation available at the time of printingand is subject to the copyright and otherintellectual property rights of Volkswagen ofAmerica, Inc., its affiliated companies and itslicensors. All rights are reserved to makechanges at any time without notice. No partof this document may be reproduced,stored in a retrieval system, or transmittedin any form or by any means, electronic,mechanical, photocopying, recording orotherwise, nor may these materials bemodified or reposted to other sites withoutthe prior expressed written permission ofthe publisher.
All requests for permission to copy andredistribute information should be referredto Volkswagen of America, Inc.
Always check Technical Bulletins and theVolkswagen Worldwide Repair InformationSystem for information that may supersedeany information included in this booklet.
Trademarks: All brand names and productnames used in this manual are trade names,service marks, trademarks, or registeredtrademarks; and are the property of theirrespective owners.
i
Table of Contents
The Self-Study Program provides you with informationregarding designs and functions.
The Self-Study Program is not a Repair Manual.
For maintenance and repair work, always refer to thecurrent technical literature.
Important/Note!
New!
Introduction ................................................................................................... 1
Suspension and Damping Basics ................................................................ 2
Vehicle Suspension, Types of Vibration Acting on a Vehicle,Vibrations, Definitions, Suspension System, Spring Characteristics,Spring Travel
Air Suspension Basics .................................................................................. 9
Air Suspension, Characteristics of Air Springs, Spring Characteristics,Air Spring Design
Damping System Basics ............................................................................. 15
Shock Absorbers, Twin-Tube Gas Pressure Shock Absorber,Shock Absorber Tuning
System Description..................................................................................... 19
Air Suspension with Continuously Controlled Damping, ComponentLocations, Operation and Display, Self-Leveling Suspension,Damper Tuning, Control Strategy of the Self-Leveling Suspension,Manual Deactivation and Activation, Actions of Air Suspension After“Ignition Off,” Shock Absorber Control, Diagram of Air SuspensionSystem with Continuously Controlled Damping, Schematic Diagramof the Overall System, System Overview
Design and Function ................................................................................... 34
Level Control System Control Module J197, Air Spring Struts,Air Supply Module, Compressor Unit, Pressure Accumulator,Air Supply Strategy, Self-Leveling Suspension Pneumatic Diagram,Solenoid Valves, Level Control Pump Temperature Sensor G290,Level Control Pressure Sensor G291, Vehicle Level ControlSystem Sensors, Body Acceleration Sensors, Wheel AccelerationSensors, Interfaces, Functional Diagram – Air Suspension withContinuously Controlled Damping, Additional Interfaces,Emergency Running Mode
Service.......................................................................................................... 66
Self-Diagnosis
Knowledge Assessment ............................................................................. 69
Introduction
1
Vehicle contact with the road is controlledby the suspension system components.
Conflicting requirements for maximumcomfort, optimum driving safety, andminimum noise transmission from the roadsurface to the vehicle interior place heavydemands on suspension system designers.
Vehicles like the Phaeton, which areexpected to meet high standards ofcomfort, represent a special challengethat necessitates a compromise betweenthe various requirements on thesuspension system.
One solution is a controlled suspensionsystem including:
• Full load-bearing self-levelingsuspension system.
• Continuously controlled damping.
Control is based on the “skyhookcontrol strategy.”
In a perfect world, damping would becontrolled as if the vehicle body weresuspended by a hook from the sky, floatingabove the road without interference fromthe surface of the road.
The purpose or this Self-Study Program isto introduce and describe this new system.
SSP275/20a
Suspension and Damping Basics
2
Vehicle Suspension
When a vehicle is moving, theexternal forces that act upon it producemovements in the three possible directionsof motion – the transverse, longitudinal,and vertical axes.
The aim of good suspension and dampingsystem design is to minimize the effect ofthese forces on driving comfort, drivingsafety, and operating safety by striking abalance between the suspension systemand the vibration damping system.
A basic distinction can be drawn betweenthe suspension system and the vibrationdamping system. The task of both systems
is to absorb and reduce the forces producedand, if possible, to keep them away from thevehicle body and its occupants:
Driving safety – They help maintaincontinuous tire contact with the road,which is important for steering and braking.
Driving comfort – Harmful or unpleasantvibrations are kept away from thepassengers and the cargo remains intact.
Operational safety – The vehicle body andassemblies are protected against highimpact and vibration loads.
SSP275/001
Suspension and Damping Basics
3
Types of VibrationActing on a Vehicle
In addition to the upward and downwardmovement of a moving vehicle, vibrationsoccur about and in the direction of thelongitudinal, transverse, and vertical axes.
The following terms are generally used todescribe the vibrations that can occur in amotor vehicle.
Longitudinal axis vibration terminology:
• Twitching – Vibration in the directionof the longitudinal axis (shudder,back-and-forth motion).
• Rolling – Torsional vibration (rotation)around the longitudinal axis (snaking,rolling, and tilting motion).
Transverse axis vibration terminology:
• Drifting – Vibration in the directionof the transverse axis (side slip,side-to-side motion).
• Pitching – Torsional vibration (rotation)around the transverse axis (up-and-downmotion of the front of the vehicle relativeand opposite to the motion of the rear).
Vertical axis vibration terminology:
• Bouncing – Vibration in the direction ofthe vertical axis (road surface impacts,vertical vibration, up-and-down motion).
• Yawing – Torsional vibration (rotation)around the vertical axis (side-to-sidemotion of the front of the vehicle relativeand opposite to the motion of the rear).
SSP275/009
Longitudinal Axis• Twitching• Rolling
Transverse Axis• Drifting• Pitching
Vertical Axis• Bouncing• Yawing
Suspension and Damping Basics
4
Vibrations
The tires, suspension elements, body,and vehicle seat form a system which iscapable of vibration, i.e. when an externalforce such as a bump on the road acts onthis system, it oscillates back and forthabout its position of rest. These vibrationsrepeat themselves until they die away.
The vibrations are defined by theiramplitude and frequency.
Intrinsic body frequency is a major factor invehicle occupant comfort and safety.
• An intrinsic body frequency of less than1 Hz can cause nausea, depending onone’s predisposition.
• Frequencies above 1.5 Hz are detrimentalto driving comfort.
• Frequencies higher than 5 Hz areperceived as shocks.
Intrinsic body frequency is essentiallydetermined by the spring rate and the sizeof the sprung mass.
Definitions
Sprung mass – The weight of the carsupported by its suspension including theengine, transmission and body.
Vibration – Oscillating movement of amass (e.g. bump and rebound of thevehicle body).
Amplitude – Maximum distance of anoscillating mass from its position of rest(vibration displacement, spring travel).
Period – Duration of a single, completevibration cycle.
Frequency – Number of vibration cycles(periods) per unit of time. The customarydesignation for cycles per second is Hertz,abbreviated Hz.
One complete vibration cycleper second = 1 Hz
Intrinsic Frequency – Natural vibrationfrequency (free vibrations) of a given mass.
Resonance – The physical characteristicsof a mass that allow it to vibrate easily at itsintrinsic frequency with very little excitationforce, like a lightly plucked guitar string.
Shock absorption – Describes the decayof vibrations.
Suspension and Damping Basics
5
Larger masses or softer springs producea lower intrinsic body frequency withincreasing spring travel (amplitudes).
The intrinsic frequency ofunsprung masses like the wheelsand tires with attached brake,hub, and axle components isapproximately 10 to 16 Hz.
Smaller masses or firmer springs producehigher intrinsic body frequencies withdecreasing spring travel.
SSP275/005
Time
Period
Spr
ing
Trav
el
SSP275/004
Time
Period
Spr
ing
Trav
el
SSP275/003
Damped Vibration
Time
Period
Amplitude
Position of Rest
Vibrating Mass
Rebound
Bump
Spr
ing
Trav
el
6
Suspension and Damping Basics
Suspension System
The tires, the springs, and the seats withtheir cushioning effect collectively form thevehicle suspension system.
As key components of this system, thespring and shock absorber elements arethe link between the wheel suspension andthe vehicle body.
Suspension elements include:
• Steel springs (leaf springs, helicalsprings, torsion bar springs)
• Air springs (flexible air bladder springsand toroidal bellows springs)
• Hydro-pneumatic springs (piston anddiaphragm type hydraulic accumulators)
• Rubber springs
• Anti-roll bars
• Combinations of these elements
On the vehicle, a distinction is madebetween unsprung masses andsprung masses.
Unsprung masses include items likewheels, brakes, final drive shafts, wheelbearings, and wheel bearing housings.
Sprung masses include the vehicle bodywith suspension and drivetrain parts.
The general aim of vehicle tuning is tokeep unsprung masses to a minimum. Thisminimizes interference with the vibrationcharacteristics of the vehicle body andimproves suspension response (and as aresult, driving comfort).
The following components contribute toreducing unsprung masses:
• Light-alloy suspension parts
• Light-alloy brake calipers
• Light-alloy hollow-spoke wheels
• Weight optimized tires
SSP275/002
Seat Springs Spring andShock AbsorberElement
Sprung MassSpring andShock AbsorberElement
Unsprung Mass
ProgressiveLinear Firm
Linear Soft
TravelFo
rce
7
Suspension and Damping Basics
Spring Characteristics
The characteristics of a spring are obtainedby applying a force of increasing magnitudeto a spring in a spring press and plottingthe change in spring travel against theforce applied.
The spring rate is calculated from the ratioof change in force and change in travel.
Spring rate = force : distance[pounds/inch (N/cm)]
A “firm” spring has a steeper spring ratecharacteristic than a “soft” spring.
If the spring rate is constant over the fulldistance traveled by the spring, then thespring has a linear characteristic.
If the spring rate increases over the distancetraveled by the spring, then the spring has a“progressive” characteristic.
The characteristics of a coil spring can beinfluenced as follows:
• Spring diameter
• Spring wire diameter
• Number of windings in the spring
Features of springs with progressivecharacteristics include:
• Uneven winding pitch (1).
• Conical winding shape (2).
• Conical wire diameter (3).
• Combinations of these elements (4).
Examples of Spring Characteristics
SSP275/006
SSP0275/007
1 2
43
Suspension and Damping Basics
8
Spring Travel
The necessary total spring travel (stot) of avehicle without self-leveling suspensioncomprises the static bump (sstat) and thedynamic spring travel (sdyn) resulting fromvehicle vibration when the vehicle is fullyladen and when it is unladen.
stot = (sstat (fully laden) – sstat (unladen)) + sdyn
The static spring travel (sstat) is the distancewhich the spring is compressed whenstationary depending on payload. This is thedifference between the static compressionof the fully laden vehicle (sstat (fully laden)) andthe static compression of the unladenvehicle (sstat (unladen)).
sstat = sstat (fully laden) – sstat (unladen)
Where a spring characteristic performancecurve is flat (soft spring), the difference,and so the static compression, between
the unladen and fully laden vehicle is large.Where the spring characteristic curve issteep (firm spring), the static compressionis small.
Definitions
The unladen position is the compressionof the spring when the serviceable vehicle(including a full tank of fuel, tool kit, andspare wheel, but without a driver orpassengers) is standing on its wheels.
The design position is the position whichthe serviceable vehicle adopts when loadedwith three persons, each weighing 150pounds (68 kg).
The controlled position is the positionin which the vehicle is held by theself-leveling elements of the air suspensionsystem, regardless of payload.
SSP275/008
Pay
load
Spring Travel (s)
sstat
Soft Spring
sstat
Firm Spring
UnladenPosition
Fully LadenPosition Soft Spring
PerformanceCurve
Firm SpringPerformanceCurve
Air Suspension Basics
9
Air Suspension
Air suspension is a variable-height vehiclesuspension system and can be combinedwith continuously controlled damping.
The self-leveling suspension keeps thevehicle body at constant pre-determinedground clearance level. The controlledposition is equal to a constant distancebetween the center of the wheel and thelower edge of the fender wheel opening.
The vehicle level is controlled by adjustingthe pressure acting on the air springs andthe associated change of air volume in theair springs.
Static compression is always set tosstat = 0, regardless of payload.
The advantages of a self-levelingsuspension are:
• The vehicle can be sprung comfortably.
• The static level of the vehicle is constant,regardless of payload.
• Reduced tire wear.
• No payload-dependent change of dragcoefficient (CD).
• Maximum rebound and bump travel aremaintained in all load states.
• Full ground clearance is maintained, evenat maximum payload.
• No changes of toe and camber due tochanges in payload.
Controlled Position
SSP275/010
Load
-Bea
ring
Forc
e
10
Air Suspension Basics
In addition to the basic advantages of aself-leveling, full load-bearing air suspensionsystem as described above, the system canalso be used to set different vehicle heights.
Three level settings are possible onthe Phaeton:
• The normal suspension level.• A raised suspension level for poor road
surfaces or rough terrain.• A low suspension level that is set
automatically while travelling at fasthighway speeds.
Full load-bearing air suspension
means that only air springs areused as load-bearing springelements at all wheels.
Combined suspension systemsare described as partially
load-bearing because theyconsist of a combination ofhydraulically or pneumaticallycontrolled steel and gas struts.
1124 lbs (5000 N)
899 lbs (4000 N)
674 lbs (3000 N)
450 lbs (2000 N)
225 lbs (1000 N)
SSP275/063b
+3.15 in(+80 mm)
Spring Travel
Dynamic BumpDynamic Rebound
-3.15 in(-80 mm)
-1.57 in(-40 mm)
Con
stan
t
+1.57 in(+40 mm)
0
sstat SSP275/063a
Spring Characteristics
Fully Laden
Design Position
Unladen
11
Air Suspension Basics
Characteristics of Air Springs
Spring Force and Spring Rate
The spring force or load-bearing force ofan air spring is defined by its geometricdimensions (the effective circular area) andthe excess pressure acting on the air spring.
The effective circular area is defined by theeffective circle diameter.
With the configuration of a piston in acylinder, the piston diameter correspondsto the effective circle diameter.
Load-Bearing Force
SSP275/011
Compressed Diameter
Rebounded Diameter
SSP275/012
The effective diameter of the air springis defined by the diameter at the lowestpoint of the air spring (rebounded andcompressed). Minor changes in thiseffective diameter lead to relatively largechanges in the area of the circle, and sothe load-bearing force of the air spring.
Excess Pressure
Circle Diameter
Load-Bearing Force
12
The load-bearing force of the spring can beadapted to the load situation simply bychanging the effective internal pressure inthe air spring.
The different pressures – depending onpayload – result in different springcharacteristics or spring rates.
The spring rates do not change in directproportion to total body weight.
The intrinsic body frequency, a key factorin handling performance, remainsalmost constant.
Spring compression changes the effectiveair spring diameter because it rolls back onthe roll piston.
The illustrations show the effect of rollpiston contour on effective diameter.
Air Suspension Basics
Rebounded
Compressed
SSP275/014a
ReboundedDiameter
Air Spring
Roll Piston
OuterGuide
Bump Stop
SSP275/014
CompressedDiameter
13
Spring Characteristics
In principle, the spring characteristicof an air spring with a cylindrical pistonis progressive.
The spring characteristic curve (steep orflat) is governed by the air spring volume.
The existing air volume is compressed bydynamic compression. Assuming thatbump travel is constant, the pressures in alow volume system rise more rapidly thanin a system with a large air spring volume.
• A flat spring characteristic curve(soft spring) is produced by a large airspring volume.
• A steep curve (firm spring), on theother hand, is produced by a small airspring volume.
The characteristic curve can be influencedby the roll piston contour. Modifying thecontour of the roll piston changes theeffective diameter, and so the load-bearingforce (spring force), of the air spring.
An air spring can be tuned for therequired application by adjusting thefollowing parameters:
• Size of effective circular area.
• Amount of air spring volume (air volume).
• Outer contour of the roll piston.
Air Suspension Basics
SSP275/015
Load
-Bea
ring
Forc
e of
Spr
ing
Spring Travel s
87 psi(600 kPa)
102 psi(700 kPa)
116 psi(800 kPa)
131 psi(900 kPa)
Flat Curve(Soft Spring)LargeAir SpringVolume
Steep Curve(Firm Spring)SmallAir SpringVolume
-s +s0
14
Air Suspension Basics
Air Spring Design
There are two different types of air springs:
• Partial load-bearing
• Full load-bearing
In the partial load-bearing type, acombination of steel and gas strutsgenerates the load bearing force of theair spring.
In the full load-bearing type like those usedon the Phaeton, the air springs function asthe load-bearing spring elements.
The full load-bearing air spring assemblyincludes:
• Upper housing with outer guide
• Air spring (flexible air bladder)
• Roll piston (lower guide)
• Auxiliary accumulator (where required)
• Integrated shock absorber
Flexible Air Bladder
The air spring is comprised of a specialflexible air bladder made of a high-qualitymulti-layer elastomer material withreinforcing fabric inlays of nylon cord.
The reinforcing fabric absorbs the forcesarising in the air spring. The inner layer isspecially designed to be airtight.
The combination of individual layers in theflexible air bladder provides for goodrolling characteristics of the air spring andprecise response to the movement ofthe suspension.
The materials are resistant to all externalinfluences in a temperature rangefrom -31°F to +194°F (-35°C to +90°C).
The outer guide is a metallic sleeve usedto absorb some of the internal pressure inthe air spring and control the shape of theflexible air bladder as it moves over theroll piston. This is an externally guidedair spring.
Air springs configured without the outerguide are designated “unguided.”
Typical Externally Guided
Full Load-Bearing Air Spring
Outer Guide
Roll Piston
Oil Reservoir Twin-TubeShockAbsorber
Air Spring(FlexibleAir Bladder)
Gas Cushion
Upper HousingAir Volume
SSP275/027
15
Damping System Basics
Shock Absorbers
The task of the shock absorbers is toreduce the vibration energy of structuraland wheel vibrations as rapidly as possibleby converting vibration energy to heat.
Without shock absorbers, the vibrationsintroduced into the vehicle would build upto the extent that the wheels could losecontact with the road surface. As a result,the vehicle would no longer be steerable.
There are several different types ofshock absorbers.
Single-Tube Gas Pressure
Shock Absorber
In a single-tube gas pressure shockabsorber, the working and oil reservoirsare located in a single cylinder. Changes inoil volume, due to temperature effectsand movement of the piston rod and pistonwhen the springs are compressed, areequalized by the gas in the pressurized gascushion – approximately 363 to 465 psi(2500 to 3000 kPa).
The damping valves for the compressionand tension stages are integrated intothe piston.
SSP275/081
SeparatingPiston
PressureValve
Gas Cushion
TensionValve
PistonwithValves
Oil Reservoir
PistonRod
Typical Single-Tube
Gas Pressure Shock Absorber
16
Damping System Basics
Twin-Tube Gas PressureShock Absorber
The twin-tube gas pressure shock absorberhas established itself as the automotiveindustry standard for vibration damping.
As the name indicates, this type of shockabsorber consists of two tubes, one insidethe other.
The inner tube acts as the working cylinder.It is completely filled with hydraulic fluid.
The piston together with the piston valvesand the piston rod move up and downinside the working cylinder.
The base of the working cylinder comprisesthe base plate and bottom valves.
The outer tube surrounds the oil reservoir.It is only partially filled with oil. There is agas cushion above the oil.
The oil reservoir equalizes changes in thevolume of oil in the working cylinder.
Vibrations are damped by the two dampingvalve units located on the piston and at thebase of the working cylinder. They comprisea system of spring washers, coil springs,and valve bodies with restrictor bores.
During the compression stage, damping isdefined by the bottom damper valve andpartly by the flow resistance of the piston.
During the rebound stage, vibrations aredamped by the piston damper valve alone.This valve produces a defined resistance tothe oil as it flows through it to the bottomof the working cylinder.
Piston Rod
WorkingCylinder
Oil Reservoir
Gas Cushion
Com
pres
sion
Sta
ge
BottomNon-ReturnValve
BottomDamperValve
PistonDamperValve
Typical Twin-Tube
Gas Pressure Shock Absorber
(Compression Stage)
SSP275/082
PistonNon-ReturnValve
Piston
Inner Tube
Outer Tube
17
Damping System Basics
Shock Absorber Tuning
In vibration damping, there is a distinctionto be made between the compression andrebound stages.
The damping force during the compressionstage is less than the damping force duringthe rebound stage. As a result, jolts causedby rough road surfaces are transmitted to alesser degree to the vehicle body.
Shock absorber tuning affects both drivingcomfort and safety.
Shock absorbers with adjustable dampertuning and continuous control are installedon luxury vehicles. The control moduledetermines within a matter of millisecondsthe degree of damping that is required foreach wheel.
The degree of damping indicates howquickly the vibrations must be reduced. It isdependent on the damping force of theshock absorber and the amount of thesprung mass.
Given the same shock absorber tuning,increasing the sprung mass reduces thedegree of damping and the vibrations arereduced more slowly. Conversely, areduction in the sprung mass increases thedegree of damping and the vibrations arereduced more quickly.
SSP275/017
High Degree of Damping
Time
Spr
ing
Trav
el
SSP275/018
Low Degree of Damping
Time
Spr
ing
Trav
el
18
Damping System Basics
Damping Force
The damping force of a shock absorbercan be determined using a testing devicethat can generate different compressionand rebound rates while maintaining aconstant stroke.
The values determined in this way can berepresented in force-velocity diagrams.
These diagrams clearly show thecharacteristics of the shock absorbers.
A distinction is made betweenprogressive, digressive, and linear actionshock absorbers.
Progressive Action
Damping Characteristic
Force-Velocity Diagrams
Showing Shock Absorber
Characteristic Curves
-0.85(-0.26)
1.17(0.52)
0.85(0.26)
-1.71(-0.52)
0
Velocity ft/s (m/s)
Linear Action
Damping Characteristic
Tra
cti
ve
Fo
rce
Co
mp
ressiv
e
Fo
rce
-0.85(-0.26)
1.17(0.52)
0.85(0.26)
-1.71(-0.52)
0
Velocity ft/s (m/s)
Tra
cti
ve
Fo
rce
Co
mp
ressiv
e
Fo
rce
SSP275/019c
SSP275/019a
Digressive Action
Damping Characteristic
Tra
cti
ve
Fo
rce
Co
mp
ressiv
e
Fo
rce
-0.85(-0.26)
1.17(0.52)
0.85(0.26)
-1.71(-0.52)
0
Velocity ft/s (m/s)SSP275/019b
19
System Description
Air Suspension withContinuously Controlled Damping
The full load-bearing air suspension withcontinuously controlled damping used onthe Phaeton keeps the vehicle at a constantlevel above the road, regardless of payload.
A constant static ground clearance adaptedto driver input or vehicle road speed ismaintained between the road and thevehicle floor pan.
The system includes:
• Level Control System ControlModule J197.
• Air spring and a vehicle level controlsystem sensor at each corner.
• Adjustable shock absorber integrated intothe air spring strut at each corner.
• Compressor with air drier andtemperature sensor.
• Solenoid valve block with four strutvalves, a drain valve, a pressureaccumulator valve, and an integratedpressure sensor.
• Pressure accumulator.
• Air lines from the compressor to theindividual air spring struts and to thepressure accumulator.
• Wheel acceleration sensor on each airspring strut (measurement range ± 13 g).
• Three body acceleration sensors(measurement range ± 1.3 g).
The Phaeton has three different suspensionheight settings, the first two of which aredriver selectable:
• “Normal” suspension level.
• “High” suspension level, 1 inch (25 mm)above “Normal”; intended for driving onbad roads.
• “Low” suspension level, 0.6 inch(15 mm) below “Normal”; intended fordriving at high speed on a highway.Low ride height is selected anddeselected automatically dependingon vehicle road speed.
The system also switches automaticallyto other levels depending on thedriving situation by means of a specialcontrol strategy.
Ride height adjustments are made in thebackground and are not normally noticed bythe driver.
When driving at high speeds, the groundclearance is automatically lowered from the“High” suspension level to the dynamicallymore stable “Normal” suspension level.
At even higher speeds, the groundclearance is automatically reduced to the“Low” suspension level which is notselectable by the driver.
The “Low” suspension level is automaticallydeselected when the vehicle speed dropsbelow a pre-determined speed.
The suspension damper tuning “Comfort”setting is automatically adjusted to firmersettings at higher speeds in order to ensuresafe handling and track stability.
--
43
2
1
5
6
7
100140
180
220
70
50
30
40
2010
60
1210
16
1/21/4 3/4
6030 90
8050
20110
80 120
160
200
24014260120
MAP
VEHICLE
CLIMATE
RESET
FM
AM
CD
SCAN BAL/FAD
NAV
NAV SET
AUDIO
TRIP DATA
SETTINGS
MANUAL
ON/DARK
HELP
20
System Description
Component Locations
Control Module withIndicator Unit inInstrument PanelInsert J285
Air Spring Strut,Front Axle (2)
Residual PressureMaintaining Valve
Left Front Level Control System Sensor G78Right Front Level Control Sensor G289
Left Front Wheel Acceleration Sensor G337Right Front Wheel Acceleration Sensor G338
Left Front Body Acceleration Sensor G341Right Front Body Acceleration Sensor G342
Front Information Display Control Head J523with Menu Selection Rotary Knob E460,Dampening Adjustment Button E387, andLevel Control Button E388
21
System Description
Rear Body Acceleration Sensor G343(Luggage Compartment)
SSP275/020
Left Rear Wheel Acceleration Sensor G339Right Rear Wheel Acceleration Sensor G340
Left Rear Level ControlSystem Sensor G76Right Rear Level ControlSystem Sensor G77
Air Spring Strut,Rear Axle (2)
Residual PressureMaintaining Valve
PressureAccumulator
Level Control SystemControl Module J197
Level Control PumpTemperature Sensor G290
Air Supply Module with Compressor, Air Drier,and Solenoid Valve Block with Integrated LevelControl Pressure Sensor G291
System Description
22
Operation and Display
The system features a full load-bearing airspring with self-leveling suspension at eachwheel on both the front and rear axles.Each air spring strut assembly combines anair spring integrated with a continuouslyadjustable damping shock absorber.
The system is controlled by the LevelControl System Control Module J197.
The system is operated by DampeningAdjustment Button E387 and LevelControl Button E388 as described in theoperating manual.
These buttons are located on the centerconsole behind the gear selector lever.
Display
Pressing the appropriate button opens apop-up menu in the Infotainment display.Selections can then be made using MenuSelection Rotary Knob E460 and the displayfunction keys.
The driver can then select between two ofthe three suspension levels:
• “Normal” suspension level (preset)• “High” suspension level
Four suspension damper tuning settingsare also driver selectable:
• “Comfort”• “Basic” (preset)• “Sport 1”• “Sport 2”
--
NAV SET
NAV
TRIP DATA
AUDIO
RESET
FM
AM
CD
SCAN
CLIMATE
VEHICLE
MAP
MANUAL
BAL/FAD
SETTINGS
HELP
ON/DARK
SSP275/038
Gear Selector Lever
Level ControlButton E388
DampeningAdjustmentButton E387
Menu SelectionRotary Knob E460
23
System Description
Self-Leveling Suspension
The Level Control Button E388 must bepressed to set the level. By turning theMenu Selection Rotary Knob E460, thedriver can select between “High”suspension level or “Normal” suspensionlevel. The screen corresponding to thelevel selected is displayed.
When the “High” suspension level is set,Level Control Button E388 is lit.
The driver can exit the menu by pressingthe Menu Selection Rotary Knob E460.
“Normal” Suspension Level Display
AUTO AUTO
NAV AUDIO SETTINGS ONMAPCLIMATE
AUTO AUTO
NAV AUDIO SETTINGS ONMAPCLIMATESSP275/035
“High” Suspension Level Display
SSP275/034
24
Damper Tuning
The driver can select damper tuningby pressing Dampening AdjustmentButton E387.
By turning the Menu Selection RotaryKnob E460, the driver can select one of thefollowing four damper tuning settings:
• “Comfort”
• “Basic” (preset)
• “Sport 1”
• “Sport 2”
The corresponding screen is displayed.
The driver can exit the menu by pressingMenu Selection Rotary Knob E460. In the“Comfort,” “Sport 1,” and “Sport 2”settings, the Dampening AdjustmentButton E387 is lit.
The damper tuning always resetsfrom the “Sport 2” position tothe “Basic” position when theignition is turned off.
System Description
“Comfort” Damper Tuning Display
AUTO AUTO
NAV AUDIO SETTINGS ONMAPCLIMATE
AUTO AUTO
NAV AUDIO SETTINGS ONMAPCLIMATE
SSP275/037
SSP275/036
“Sport 2” Damper Tuning Display
25
System Description
Control Strategy of theSelf-Leveling Suspension
The relative positions of the vehicle bodyand the wheels are measured by four levelcontrol system sensors located betweenthe axle carriers and the lower wishbones:
• Left Front Wheel AccelerationSensor G337
• Right Front Wheel AccelerationSensor G338
• Left Rear Level Control SystemSensor G76
• Right Rear Level Control SystemSensor G77
The reading from each sensor is comparedwith a default that is stored in the LevelControl System Control Module J197 forthe corresponding wheel. The Level ControlSystem Control Module J197 must learnthese defaults.
The air required for self-leveling is normallyprovided by the compressor up to amaximum pressure of 232 psi (1600 kPa).
At road speeds above 22 mph (35 km/h),adjustments are controlled by thecompressor. The pressure accumulator isalso replenished as required.
At road speeds below 22 mph (35 km/h),adjustments are controlled by the pressureaccumulator, which has a capacity of1.32 gallons (5 liters). A sufficient pressuredifference of approximately 44 psi (300 kPa)between the pressure accumulator and theair spring is required for this purpose.
Effect of Changes in Vehicle Payload
If the height of the vehicle in relation tothe road surface changes due to changesin vehicle payload, the Level ControlSystem Control Module J197 readjusts thesuspension to the preset default level.Level adjustments are made throughseveral valves integrated into the solenoidvalve block.
To increase the height, air is channeled tothe four air springs through the foursuspension strut solenoid valves:
• Left Front Suspension Strut Valve N148
• Right Front Suspension Strut Valve N149
• Left Rear Suspension Strut Valve N150
• Right Rear Suspension Strut Valve N151
To decrease the height, air is discharged tothe atmosphere through the Solenoid forLevel Control System N111, which isessentially a drain valve.
Activation of the compressorto replenish air pressurein the pressure accumulatoris independent of theleveling adjustments.
26
Automatic Level Adjustments
Changes in vehicle speed will triggerautomatic adjustments in the self-levelingsuspension system.
Automatic decrease in suspension leveloccurs from:
• “High” to “Normal” at speeds of 75 mph(120 km/h) or greater.
• “Normal” to “Low”:
— After 30 seconds at 87 mph(140 km/h) or greater.
— Immediately at 112 mph (180 km/h)or greater.
System Description
SSP275/021
Automatic increase in suspension leveloccurs from:
• “Low” to “Normal”:
— After 60 seconds at speeds of62 mph (100 km/h) or less.
— Immediately at 50 mph (80 km/h)or less.
0 50 62 75 87 99 112 124 mph(0) (80) (100) (120) (140) (160) (180) (200) (km/h)
60 seconds
30 seconds
“High”Level
Manual Adjustment
Automatic Adjustment
- 0.6 inch (-15 mm)
0 inch (0 mm)
Level
+1 inch (+25 mm)
“Low”Level
“Normal”Level
27
System Description
Manual Deactivation and Activation
In special situations, it may be necessaryto deactivate the self-leveling suspensionsystem. To change a wheel or to carry outwork on the vehicle while it is raised on ahoist for example.
When the vehicle is raised on a hoist orother lifting equipment at the lift points,air is allowed to escape from all four airsprings until the Level Control SystemControl Module J197 determines that thevehicle has been lifted.
The self-leveling suspension initiallydetects when the vehicle body is too highin relation to the wheels and adjusts thevehicle height accordingly by allowing airto escape from the springs.
As a result, the vehicle may have a verylow ground clearance when the liftingequipment is lowered.
To avoid this discharge of air,the self-leveling suspensionmust be deactivated beforelifting the vehicle.
The self-leveling suspension isautomatically raised to the “Normal”level again after the engine, and thereforethe compressor, has been running for ashort period of time.
Deactivating the System
The self-leveling suspension can bedeactivated by pressing both DampeningAdjustment Button E387 and Level ControlButton E388 simultaneously for aboutfive seconds.
A message indicating that the self-levelingsuspension has been deactivated willappear on the instrument panel display.
Activating the System
The suspension system can be reactivatedmanually by pressing both DampeningAdjustment Button E387 and Level ControlButton E388 simultaneously for aboutfive seconds.
The system will automatically reactivatewhen the Level Control System ControlModule J197 determines that the vehicle istravelling at a speed of 6.2 mph (10 km/h)or greater.
28
Actions of Air SuspensionAfter “Ignition Off”
System Response to
Immediate Level Changes
After “ignition off,” the Level ControlSystem Control Module J197 remainsactive for approximately one minute.During this time it can execute suspensionadjustments to compensate for changesin payload, provided that sufficient pressureis available in the pressure accumulator.The Level Control System Control ModuleJ197 always remains active for one minuteuntil no further door hood, or luggagecompartment lid operations are detected.
System Description
System Response to Gradual Level Changes
Gradual level changes can occur when theair in the air springs heats up during vehicleoperation and cools down again at the endof the trip. To compensate for gradual levelchanges, three adjustments are made toachieve optimum ground clearance after“ignition off.”
These adjustments are madeafter approximately two, five,and ten hours, provided thatsufficient pressure is availablein the pressure accumulator.
29
System Description
Shock Absorber Control
The damping control system registers thecondition of the road surface and themovements of the vehicle using four wheelacceleration sensors and three bodyacceleration sensors.The characteristics of the individual shockabsorbers are adjusted according to thecalculated damping requirements. In thiscase, the shock absorbers function asactive components during compression andrebound cycles.Continuous damping control is basedon shock absorbers whose characteristicsare electrically adjustable. These shockabsorbers are integrated in theair spring struts.Damping force can be set depending onthe characteristic map via the proportionaldampening adjustment valves built intothe shock absorbers. As a result, theycan adapt the damping force to the
driving situation and road conditionswithin milliseconds.Shock absorber damping is adjusteddepending on the vertical acceleration ratesof the wheels and the vehicle body.The Level Control System Control ModuleJ197 always attempts to set the dampingforce according to the “skyhook controlstrategy.” Ideally, this strategy wouldcontrol damping as if the vehicle body weresuspended by a hook in the sky andhovering above the road withoutinterference from the surface of the road.Maximum driving comfort is achieved byattempting to reach this ideal.
Firm damping is achievedby low control rates.Soft damping is achievedby high control rates.
78.74 59.06 39.37 19.69 0 19.69 39.37 59.06 78.74 in/s(2000) (1500) (1000) (500) (0) (500) (1000) (1500) (2000) (mm/s)
SSP275/022
Characteristic Map of Damper Force
in Phaeton Front Axle
Damper Speed in Inches per Second (mm/s)
Dam
per
Fo
rce in
Po
un
ds (
dN
)
Compression Stage Rebound Stage
lbs (dN)
13.49 (600)
11.24 (500)
8.99 (400)
6.74 (300)
4.50 (200)
2.25 (100)
0 (0)
50 mA600 mA
1200 mA1800 mA
50 mA
600 mA
1200 mA
1800 mA
30
Diagram of Air SuspensionSystem with ContinuouslyControlled Damping
This system diagram highlights therelationships with other vehicle systemsas well as display and operating elements.
System Description
Air Spring Strut with Electrically AdjustableShock Absorber
Wheel Acceleration Sensors:Left Front Wheel Acceleration Sensor G337Right Front Wheel Acceleration Sensor G338Left Rear Wheel Acceleration Sensor G339Right Rear Wheel Acceleration Sensor G340
Body Acceleration Sensors:Left Front Body Acceleration Sensor G341Right Front Body Acceleration Sensor G342Rear Body Acceleration Sensor G343
Connection via CAN Data Bus
Connection via On-Board Power Supply
SSP275/025
Front InformationDisplay Control HeadJ523 with MenuSelection RotaryKnob E460
Control Modulewith Indicator Unitin Instrument PanelInsert J285
Level Control SystemControl Module J197Inputs via CAN Data Bus:• ABS Control Module
with EDL/ASR/ESP J104• Engine Control Module• Control Module with
Indicator Unit in InstrumentPanel Insert J285
• Vehicle Electrical SystemControl Module J519
• Infotainment System
PressureAccumulator
Compressor
DampeningAdjustmentButton E387
Level ControlButton E388
31
System Description
Schematic Diagramof the Overall System
SSP275/023
Door, Hood, andLuggage CompartmentLid Signals
Infotainment
Right Rear DampeningAdjustment Valve N339
Level Control SystemControl Module J197
Driv
etra
inC
AN
Dat
a B
us
Dia
gnos
isvi
a K
Wire
Dia
gnos
is v
iaC
AN
Dat
a B
us
Convenience CAN Data Bus
Battery Management
Engine Control Module
Relay forCompressor LevelControl System J403
HeadlightRange Control
Left Front DampeningAdjustment Valve N336
Right Front DampeningAdjustment Valve N337
Left Rear DampeningAdjustment Valve N338
Level ControlPressure Sensor G291
Steering AngleSensor G85Electronic
Stabilization Program
Terminal 30 andTerminal 15Status Signals
Dampening AdjustmentButton E387 and LevelControl Button E388
Level Control PumpTemperature SensorG290
Solenoid for LevelControl System N111(Drain Valve)
Level ControlAccumulator ValveN311
Right Rear SuspensionStrut Valve N151
Left Rear SuspensionStrut Valve N150
Right Front SuspensionStrut Valve N149
Left Front SuspensionStrut Valve N148
Left Rear Level ControlSystem Sensor G76
Right Rear LevelControl SystemSensor G77
Left Front Level ControlSystem Sensor G78
Right Front LevelControl Sensor G289
Left Front WheelAcceleration SensorG337
Right Front WheelAcceleration SensorG338
Left Rear WheelAcceleration SensorG339
Right Rear WheelAcceleration SensorG340
Left Front BodyAcceleration SensorG341
Right Front BodyAcceleration SensorG342
Rear Body AccelerationSensor G343
Control Module with IndicatorUnit in Instrument Panel InsertJ285 with Data Bus On-BoardDiagnostic Interface J533
--
MAP
FM
AM
CD
SCAN BAL/FAD
CLIMATE
RESET VEHICLE
NAV
NAV SET
AUDIO SETTINGS
MANUAL
ON/DARK
HELP
32
System Overview
Sensors
System Description
Additional Signals:Door, Hood, and Luggage Compartment LidContact Signals
Left Front Body Acceleration Sensor G341Right Front Body Acceleration Sensor G342Rear Body Acceleration Sensor G343
Left Front Wheel Acceleration Sensor G337Right Front Wheel Acceleration Sensor G338Left Rear Wheel Acceleration Sensor G339Right Rear Wheel Acceleration Sensor G340
Level Control Pressure Sensor G291(Integrated in Solenoid Valve Block)
Level Control Pump Temperature Sensor G290
Left Rear Level Control System Sensor G76Right Rear Level Control System Sensor G77Left Front Level Control System Sensor G78Right Front Level Control Sensor G289
Dampening Adjustment Button E387Level Control Button E388
43
2
1
5
6
7
100140
180
220
70
50
30
40
2010
60
1210
16
1/21/4 3/4
6030 90
8050
20110
80 120
160
200
24014260120
33
System Description
Control Module withIndicator Unit inInstrument Panel InsertJ285 with Data BusOn-Board DiagnosticInterface J533
Actuators
SSP275/026
Left Headlight Range Control Module J567Right Headlight Range Control Module J568(Integrated in the Headlights)
Relay for Compressor Level Control System J403
Left Front Dampening Adjustment Valve N336Right Front Dampening Adjustment Valve N337Left Rear Dampening Adjustment Valve N338Right Rear Dampening Adjustment Valve N339(Integrated in Air Spring Struts)
Level Control Accumulator Valve N311(Integrated in Solenoid Valve Block)
Left Front Suspension Strut Valve N148Right Front Suspension Strut Valve N149Left Rear Suspension Strut Valve N150Right Rear Suspension Strut Valve N151(Integrated in Solenoid Valve Block)
Solenoid for Level Control System N111(Drain Valve Integrated in Solenoid Valve Block)
Level Control SystemControl Module J197
16-Pin Connector T16(Diagnostic Connection)
Design and Function
34
Level Control SystemControl Module J197
The Level Control System Control ModuleJ197 is located in the luggage compartmenton the left-hand side behind the side trim.It is bolted behind the backup fuse andelectronics boxes.
The Level Control System Control ModuleJ197 has the following tasks:
• Control air suspension and theshock absorbers.
• Monitor the overall system.
• Diagnose the overall system.
• Communicate via the drivetrainCAN data bus.
SSP275/083
The Level Control System Control ModuleJ197 has a redundant processor design(dual processors); the air spring algorithmruns primarily on the first processor anddamping control runs primarily on thesecond processor.
Design and Function
35
Air Spring Struts
Air spring struts with externally guided,two-layer air springs are used on the frontand rear axles of the Phaeton.
The air spring is a flexible air bladderarranged concentrically around thetwin-tube gas-filled shock absorber.
The thin wall of the air spring providesexcellent suspension response. The desiredspring rate is achieved by combining theeffects of the roll piston contour, the outerguide, and an auxiliary accumulator directlyattached to the strut.
Dampening Adjustment ValveConnecting Wires
SSP275/027a
Air Spring Cover
Air Spring
Roll Piston
Protective Bellows
Auxiliary Accumulator
Shock Absorber
Outer Guide
Shock Absorber Piston Rod
Auxiliary Spring (Bump Stop)
Compression/Rebound Bearing
Strut Support BearingFront Axle Air Spring Strut
Different auxiliary accumulators are used atthe front and rear axles.
• The cylindrical accumulators on the frontaxle struts have a capacity of 24.4 cubicinches (0.4 liter).
• The ball accumulators on the rear axlestruts have a capacity of 73.2 cubic inches(1.2 liters).
36
The air spring struts are designed tominimize the effect of transverse forces onthe shock absorbers. The special design ofthe strut support bearing on the front axleair spring struts and the controlled flexingat the fluid-cushioned top ends of the rearstruts help reduce the effects of transverseforces on the shock absorbers.
Design and Function
A residual pressure maintaining valve ismounted directly on the air connection ofeach air spring strut. It maintains a residualpressure of about 51 psi (350 kPa) in theair spring strut. This permits easy assemblyand mounting of the components.
The outer guide protects the air springagainst dirt and damage besides itsfunction of guiding the flexible air bladderand the protective bellows.
SSP275/028
Rear Axle Air Spring Strut
Dampening Adjustment ValveConnecting Wires
Shock Absorber
Air Spring Cover
Auxiliary Accumulator
Air Spring
Roll Piston
Protective Bellows
Outer Guide
Shock Absorber Piston Rod
Auxiliary Spring (Bump Stop)
Compression/Rebound Bearing
37
Design and Function
Dampening Adjustment Valves
The continuous damping control twin-tubegas-filled shock absorbers are adjustableover a wide range of damping forces viaelectrically controlled valves integrated intheir pistons:
• Left Front Dampening AdjustmentValve N336
• Right Front Dampening AdjustmentValve N337
• Left Rear Dampening AdjustmentValve N338
• Right Rear Dampening AdjustmentValve N339
The oil flow through these valves, andhence the damping force, can be adaptedto momentary demands within a fewmilliseconds by varying the electriccurrent flowing through the adjustmentvalve solenoids.
The wheel acceleration sensors mountedon each shock absorber generate signalswhich, together with the signals suppliedby the three body acceleration sensors,are used to calculate the requireddamper setting.
Since the system can rapidly detect andcontrol rebound and compression stages,it permits adjustment of the dampingforce required for the momentarydriving situation.
The driving situation dependent controlmaps for system reaction to various drivingsituations are stored in the Level ControlSystem Control Module J197.
In certain driving dynamicstates – e.g. longitudinal ortransverse dynamics –the “skyhook control” isdeactivated and the shockabsorbers are controlled byother dynamic models.
Example of a
Dampening
Adjustment Valve
SSP275/093
HollowPiston Rod
DampeningAdjustment ValveConnecting Wires
Housing
ContainerTube
CylinderTube
AuxiliaryValve
Oil Flow
MainDampingValve
ValveSpring
Armature
Solenoid
38
Air Spring Strut, Front Axle
Air Spring Components
(Blue Highlighted Area)
Design and Function
Shock Absorber Components
(Green Highlighted Area)
SSP275/084
Air Spring
SSP275/086
AuxiliaryAccumulator
FlexibleAir Bladder
Connection for DampeningAdjustment Valve
Left Front DampeningAdjustment Valve N336 orRight Front DampeningAdjustment Valve N337
Shock Absorber
Piston Rod
39
Design and Function
Air Spring Strut, Rear Axle
Air Spring Components
(Blue Highlighted Area)
Shock Absorber Components
(Green Highlighted Area)
Left Rear DampeningAdjustment Valve N338 orRight Rear DampeningAdjustment Valve N339
Connection forDampeningAdjustment Valve
SSP275/085
ShockAbsorber
Piston Rod
SSP275/087
Air Spring
Flexible AirBladder
AuxiliaryAccumulator
40
Air Supply Module
The air supply module is a compact unit.It is mounted to the underbody on ananti-vibration mount in the spare-wheelwell adjacent to the activated charcoal filter(EVAP canister).
A plastic cover with vents providesprotection from dirt.
The compressor is supplied with air fromthe luggage compartment. Air is drawninto the compressor through the silencerwith air filter, cleaned, and pumped intothe system.
The Level Control Pump TemperatureSensor G290 protects the compressoragainst overheating and ensures availabilityof the air supply for the air suspension inall climatic and driving conditions.
The air supply module includes acompressor unit with:
• Electric motor
• Dry-running compressor
• Air drier
• Residual pressure maintaining unit
• Maximum pressure limiter
• Solenoid for Level Control System N111(drain valve)
• Silencer with air filter
• Level Control Pump Temperature SensorG290 (temperature sensor foroverheating protection)
• Pneumatic drain valve with pressurerelief valve
The air supply module also includes asolenoid valve block with:
• Control valves for each air spring strut:
— Left Front Suspension StrutValve N148
— Right Front Suspension StrutValve N149
— Left Rear Suspension StrutValve N150
— Right Rear Suspension StrutValve N151
• Control valve for the for the pressureaccumulator:
— Level Control AccumulatorValve N311
• Monitor for the pressure accumulator:
— Integrated Level Control PressureSensor G291
Design and Function
41
Design and Function
SSP275/031
Solenoid Valve Block
Drain Line
PneumaticDrain Valve
Air Drier
Level ControlPump TemperatureSensor G290
Compressor
T-Connectionfor Intake Circuitand Drain Circuit
Intake/Drain Line Silencer/Filter
Electric Motor
Vibration Isolator
42
Compressor Unit
Compressed air is produced by asingle-stage piston compressor withintegrated air drier.
To prevent internal contamination ofthe air springs and the air drier cartridge,compressor design is of the dry-runningtype.
Lifetime-lubricated bearings and a pistonring made of polytetrafluorethylene ensurea long service life.
Design and Function
The Solenoid for Level Control SystemN111 (drain valve), a pneumatic drain valvewith pressure limiting valve, and threenon-return valves are integrated in theair drier housing.
To protect the compressor againstoverheating, it is turned off if excesstemperature occurs.
SSP275/032
Pneumatic Drain Valvewith Pressure Limiting Valve
Solenoid forLevel Control SystemN111 (Drain Valve)
PressureConnection
DrainConnection
Non-Return Valve 2Electric Motor
IntakeFitting
LiftingPiston
PistonRing
Diaphragm Valve“Closed”
Cylinder
Non-Return Valve 1Air Drier
Non-Return Valve 3
43
Intake/Compression Cycles
During the upward movement of thepiston, air is drawn into the compressorcrankcase through the intake fitting via thesilencer/filter. Air in the cylinder iscompressed above the piston and flowsinto the air drier via non-return valve 1.
Design and Function
The compressed and dried air flowsvia non-return valve 2 and the pressureconnection to the valves and thepressure accumulator.
SSP275/039
Air Drier
PressureConnection
Non-Return Valve 2
CompressorCrankcase
IntakeFitting
PistonMovesUpward
Non-Return Valve 1
44
Bypass Air Flow
During the downward movement of thepiston, air drawn into the crankcasebypasses the diaphragm valve and flowsinto the cylinder.
Design and Function
SSP275/040
Fill/Lift Cycles
To fill the air springs and thus raise thevehicle, the Level Control System ControlModule J197 activates the compressorrelay (Relay for Compressor Level ControlSystem J403) and the four air springsuspension strut valves at the same time.
PistonMovesDownward
BypassAir Flow
Diaphragm Valve “Open”
Cylinder
45
Drain/Lowering Cycles
(Front Axle Components Shown)
Left Front Suspension Strut Valve N148,Right Front Suspension Strut Valve N149,and Solenoid for Level Control SystemN111 (drain valve) are activated (open)
Design and Function
during the drain cycle. The air springpressure flows toward the pneumaticdrain valve and from there via the air drier,the pressure limiting valve, and thesilencer/filter into the spare-wheel well inthe luggage compartment.
Drain Cycle Pneumatic Diagram
(Front Axle Components Shown)
SSP275/042
SSP275/041
Pressure Limiting Valveand Solenoid for LevelControl System N111(Drain Valve) “Open”
To Silencer/Filter
Air Drier
Pneumatic Drain Valve “Open”
M
Signals from Level ControlSystem Control Module J197
Signal from Level ControlSystem Control Module J197
Signal from Relay for CompressorLevel Control System J403
Right Front SuspensionStrut Valve N149
Left Front SuspensionStrut Valve N148
Non-ReturnValve 2
Non-ReturnValve 3
DrainRestrictor
Air DrierNon-ReturnValve 1Silencer/Filter
Solenoid forLevel ControlSystem N111(Drain Valve)
PneumaticDrain Valve
Design and Function
Pneumatic Drain Valve
The pneumatic drain valve performstwo functions:
• Residual pressure maintenance
• Pressure limitation
To prevent damage to the air springs(flexible air bladders), a specific minimumpressure of at least 51 psi (350 kPa) mustbe maintained. This is referred to as the airspring residual pressure.
The maintenance residual pressure ensuresthat pressure in the air spring system doesnot drop below 51 psi (350 kPa) duringpressure relief during normal operation.
Residual pressure cannot bemaintained if there is a leak inthe system upstream of thepneumatic drain valve.
46
When an air spring pressure of more than51 psi (350 kPa) is applied, the valve bodylifts against the spring force of the twovalve springs and opens valve seats1 and 2.
The air spring pressure is then admittedinto the air drier via the flow restrictor andnon-return valve 3.
After passing through the air drier, theair passes the open valve seat of thepressure limiting valve and throughthe silencer/filter in the spare-wheel wellin the luggage compartment.
A sharp decrease in pressure downstreamof the flow restrictor leads to a reduction inrelative atmospheric humidity, therebyincreasing the amount of moisture that willbe absorbed by the air that is dischargedinto the luggage compartment.
SSP275/043To Silencer/Filter
Valve Seat 2
Valve Seat 1
Air Drier
Non-Return Valve 3
Flow Restrictor
Valve Body
Pressure LimitingValve “Open”
PneumaticDrain Valve
Solenoid for LevelControl System N111(Drain Valve) “Open”
Line to Solenoid Valve Block
M
Design and Function
47
Pressure Limiting Valve
The pressure limiting valve protects thesystem against excessively high pressures,as for example if the compressor fails tocut out due to a defective contact in theRelay for Compressor Level Control SystemJ403 or a defective Level Control SystemControl Module J197.
In such a case, the pressure limiting valvewill open against the spring force whenthe pressure exceeds approximately290 psi (2000 kPa), and air conveyed bythe compressor will escape through thesilencer/filter.
SSP275/044
Pressure Limiting Valve Actuation
Pneumatic Diagram
Intake Fitting
Lifting PistonPressure Limiting Valve “Open”
To Silencer/Filter
No “Drain Valve Open” Signal fromLevel Control System Control Module J197
No “Cut Out” Signal from Relay forCompressor Level Control System J403
Silencer/Filter
Pneumatic Drain Valvewith Pressure Limiting Valve
Compressor
SSP275/044a
48
Air Drier
The air in the self-leveling air suspensionsystem must be dehumidified to avoidproblems caused by the condensation ofwater in the system:
• Corrosion
• Freezing
An air drier is used to dehumidify the air.
The air drier uses a regenerative process toremove moisture from the air.
The air compressed in the self-leveling airsuspension system is routed through asilicate granulate and dried in the process.
This granulate is able to absorbatmospheric humidity amounting to over20% of its natural weight, dependingon temperature.
When the air in the system is released tolower the air springs, it flows back throughthe silicate granulate and is discharged tothe atmosphere.
During this phase, the dry air extracts themoisture from the granulate that wasabsorbed during the intake cycle.
Design and Function
As a result of this regenerative process, theair drier requires no maintenance. It is notsubject to a replacement interval.
Since the air drier is onlyregenerated by discharged air,the compressor must not beused to fill other vessels withcompressed air.
Moisture in the systemsignifies that the air drier hasfailed or the system isotherwise malfunctioning.
SSP275/045
Air Drier with SilicateGranulate Filling
SSP275/033
49
Design and Function
Pressure Accumulator
Extraction of compressed air from thepressure accumulator allows the vehiclelevel to be raised quickly with a minimumof noise. The pressure accumulator isonly filled while the vehicle is moving.As a result, compressor operation isbarely audible.
Provided that sufficient pressure is availablein the pressure accumulator, the vehiclelevel can be raised even if the compressoris not running. Pressure is sufficient whenthe pressure difference between thepressure accumulator and the air springs isat least 44 psi (300 kPa) before increasingthe level.
The pressure accumulator is made ofaluminum and has a capacity of 1.32 gallons(5 liters). The maximum operating pressureis about 232 psi (1600 kPa).
Air Supply Strategy
At road speeds below 22 mph (35 km/h),air is primarily supplied by the pressureaccumulator, provided that sufficientpressure is available.
The pressure accumulator is only filledwhen the vehicle is travelling at speedsabove 22 mph (35 km/h).
At road speeds above 22 mph (35 km/h),air is primarily supplied by the compressor.
This supply strategy ensures that thesystem operates silently and conservesvehicle battery capacity.
The compressor startsrunning when compressed airis extracted from the pressureaccumulator even if thedriver has not adjusted thevehicle’s level.
PressureAccumulator
SSP275/064
p
M
50
Self-Leveling SuspensionPneumatic Diagram
Design and Function
Signal from LevelControl SystemControl Module J197
Signal from Relay forCompressor LevelControl System J403
Right RearSuspensionStrut ValveN151
Left RearSuspensionStrut ValveN150
LevelControlAccumulatorValve N311
LevelControlPressureSensorG291
Non-ReturnValve 2
Non-ReturnValve 3
DrainRestrictor
Air DrierNon-ReturnValve 1
Motor forCompressor –Level ControlSystem V66
Silencer/Filter
Solenoid for Level ControlSystem N111 (Drain Valve)
PneumaticDrain Valve
SSP275/065
Right FrontAir Spring Strut
Left FrontAir Spring Strut
Right RearAir Spring Strut
Left RearAir Spring Strut
PressureAccumulator
Right FrontSuspensionStrut ValveN149
Left FrontSuspensionStrut ValveN148
51
Design and Function
Solenoid Valves
The air spring self-leveling suspensionsystem has six solenoid valves.
The Solenoid for Level Control System N111(drain valve) together with the pneumaticdrain valve form a functional unit that isintegrated in the air drier housing.
The Solenoid for Level Control SystemN111 is a 3/2-way drain valve and isnormally closed when de-energized.
The pneumatic drain valve has two tasks:to limit total system pressure and tomaintain residual pressure.
The following valves are combined in thesolenoid valve block:
• Level Control Accumulator Valve N311
• The four air spring suspensionstrut valves:
— Left Front Suspension StrutValve N148
— Right Front Suspension StrutValve N149
— Left Rear Suspension StrutValve N150
— Right Rear Suspension StrutValve N151
The valves in the solenoid valve block aredesigned as 2/2-way valves and are normallyclosed when de-energized. The systempressure on the air spring and accumulatorside acts in the closing direction.
To avoid confusion when connecting them,the pressure lines and their matchingconnections on the solenoid valve block arecolor coded.
SSP275/066
Green – Right FrontSuspension StrutValve N149
Black – Left RearSuspension StrutValve N150
Blue – Right RearSuspension StrutValve N151
SolenoidValve Block
ElectricalConnection
Lilac – Level ControlAccumulator Valve N311
Red – Left Front SuspensionStrut Valve N148
CompressorConnection
52
Level Control Pump
Temperature Sensor G290
To protect the compressor from overheatingand thus ensure system availability, LevelControl Pump Temperature Sensor G290 isattached to the compressor cylinder head.
Design and Function
The Level Control System Control ModuleJ197 shuts the compressor down andinhibits starting when a maximumpermissible compressor temperatureis exceeded.
Level Control PumpTemperature Sensor G290
SSP275/067
p
53
Design and Function
Level Control PressureSensor G291
The Level Control Pressure Sensor G291 isintegrated in the solenoid valve block andmonitors the pressure in the pressureaccumulator and the air springs.
Level Control Pressure Sensor G291generates a voltage signal proportional tothe pressure.
Information on accumulator pressure isrequired to make plausibility checks onthe up-control functions and performself-diagnosis.
The individual pressuresof the air springs and thepressure accumulator can bedetermined by activating thesolenoid valves accordingly.
The individual pressures are measuredwhile the air springs or the pressureaccumulator are evacuating or filling.The pressures determined in this way arestored and updated by the Level ControlSystem Control Module J197.
During vehicle operation the accumulatorpressure is determined and updated by theLevel Control System Control Module J197every six minutes.
SSP275/068
Level ControlPressure Sensor G291
PressureAccumulator
SolenoidValve Block
Left Rear SuspensionStrut Valve N150
Level ControlAccumulatorValve N311
54
Vehicle Level ControlSystem Sensors
The four vehicle level control systemsensors are wheel angle sensors:
• Left Rear Level Control SystemSensor G76
• Right Rear Level Control SystemSensor G77
• Left Front Level Control SystemSensor G78
• Right Front Level Control Sensor G289
Changes in the level of the vehicle bodyare registered and converted to angularchanges using coupling rod kinematics.
The wheel angle sensors used operateaccording to the induction principle.
The signal output provides anangle-proportional pulse-width-modulatedsignal for the self-leveling suspension.
Design and Function
SSP275/076
Coupling Rods
SSP275/075
Front Axle Vehicle Level
Control System Sensor
Rear Axle Vehicle Level
Control System Sensor
The four sensors are identical;only the mounts and the couplingrod kinematics are specific foreach side and axle.
Deflection of the sender crank,and hence the output signal, isopposed on the left and right. Asa result, during suspensioncompression for example, theoutput signal rises on one sideand drops on the other side.
55
Level Control System Sensor Design
A level control system sensor basicallyconsists of a stator and a rotor.
The stator comprises a multi-layer boardthat houses the exciter coil and threereceiver coils, as well as the control andelectronic evaluation module. The threereceiver coils are star-shaped and arrangedin an offset pattern. The stator exciter coilis located on the back of the board.
Design and Function
The rotor is connected to the actuatinglever and moves with it. A closed conductorloop is located on the rotor. The conductorloop has the same geometric shape as thethree receiver coils.
SSP275/069
ElectricalConnection
Control and ElectronicEvaluation Module
Contacts to PrintedCircuit Board
Front of Multi-Layer Boardwith Receiver Coils
Back ofMulti-LayerBoard
StatorExciter Coil
Rotor withConductor Loop
Actuating Leveron Rotor
Contacts
56
Level Control System Sensor Function
An alternating current flows through thestator exciter coil and produces analternating electromagnetic field (firstmagnetic field) around the exciter coil. Thisalternating field permeates the conductorloop of the rotor.
The electric current induced in theconductor loop of the rotor in turnproduces an alternating electromagneticfield (second magnetic field) around therotor conductor loop. The alternating fieldsof the exciter coil and the rotor act uponthe three receiver coils and induceposition-dependent AC voltages in thereceiver coils.
Whereas induction in the rotor isindependent of the rotor’s angular position,induction in the receiver coils is dependenton their distance from the rotor, and hencetheir angular position in relation to the rotor.
Design and Function
SSP275/070
Second MagneticField AroundConductor Loop
Rotor Connectedto Actuating Lever
AlternatingCurrent
RotaryMotion
Conductor LoopWith Induced Current
First Magnetic FieldAround Exciter Coil
Exciter Coil
ThreeReceiverCoils
StatorBoard
AlternatingCurrent
V1
V2
V3
57
Design and Function
Receiver Coil 1
Time0
V1
Example of Voltage Amplitudes in the
Receiver Coils Depending on Rotor Position
SSP275/071
Receiver Coil 2
Time0
V2
Receiver Coil 3
Time0
V3
Since rotor overlap in relation to theindividual receiver coils varies depending onangular position, the induced voltageamplitudes in the receiver coils varyaccording to their angular position.
The control and electronic evaluationmodule rectifies and amplifies the ACvoltages of the receiver coils andproportions the output voltages of the threereceiver coils (ratiometric measurement).After the voltage is evaluated, the result isconverted to output signals from the levelsensor and made available to the controlmodules for further processing.
58
Design and Function
Body Acceleration Sensors
The three body acceleration sensorsmeasure the vertical acceleration of thevehicle body.
• Left Front Body Acceleration SensorG341 is located in the left frontwheel housing.
• Right Front Body Acceleration SensorG342 is located in the right frontwheel housing.
• Rear Body Acceleration Sensor G343 islocated in the right front area of theluggage compartment, behind theluggage compartment lining.
Rear Body Acceleration SensorG343 in Luggage Compartment
SSP275/079
Left Front Body Acceleration Sensor G341in Left Front Wheel Housing
SSP275/080
59
Design and Function
Wheel Acceleration
Sensors
There are four wheel acceleration sensorsused in the Phaeton air suspension systemwith continuously controlled damping:
• Left Front Wheel AccelerationSensor G337
• Right Front Wheel AccelerationSensor G338
• Left Rear Wheel AccelerationSensor G339
• Right Rear Wheel AccelerationSensor G340
They are all mounted directly on theirrespective air spring struts at the front andrear axles.
They measure wheel acceleration.The Level Control System Control ModuleJ197 uses these signals along with bodyacceleration signals to calculate thedirection in which the struts are moving inrelation to the vehicle body.
Left Rear WheelAcceleration Sensor G339or Right Rear WheelAcceleration Sensor G340
SSP275/088
Left Front WheelAcceleration Sensor G337or Right Front WheelAcceleration Sensor G338
SSP275/089SSP275/080
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Design and Function
Acceleration sensor
measurement ranges:
Acceleration due to the force of gravityvaries depending upon where on the earthit is measured. The force of gravity isgreater measured at the poles and less atthe equator.
The abbreviation “g” is the accepted unitof measurement for acceleration due tothe force of gravity.
Acceleration due to gravity is normallydesignated as 1g, but the standard valueof the factor for gravitational force variesslightly between different regions ofthe world.
• The U.S. customary standard used is32.16 ft/sec2.
• The European metric standard usedis 9.81 m/sec2, which converts to32.185 ft/sec2.
For an understanding of the accelerationsensors and how they operate, these minordifferences are unimportant.
The body acceleration sensors have ameasurement range of ± 1.3 g.
The wheel acceleration sensors have ameasurement range of ± 13 g.
Function and Design
of the Acceleration Sensors
All of the body and wheel accelerationsensors used in the system are essentiallythe same and operate identically. They dohave different mechanical attachments andmeasurement ranges (sensitivity).
The acceleration sensors operate accordingto the capacitive measurement principle.
A flexibly mounted mass (m) acting as acenter electrode oscillates betweencapacitor plates and varies the capacitanceof capacitors C1 and C2 in the oppositedirection at the same rate as their oscillation.
The plate distance d1 of one capacitorincreases by the same amount as thedistance d2 decreases in the other capacitor.
The capacitance in the individual capacitorschanges as a result.
An electronic evaluation module suppliesan analog signal voltage to the LevelControl System Control Module J197.
SSP275/091
m
Capacitive Measurement Principle
of the Acceleration Sensors
d2
d1
C2
C1
Level Control System
Control Module J197
System status (OK or Not OK)
Self-diagnosis
Fault memory entry
Level status
Increase in level
Decrease in level
Information interchange withInfotainment system
Operation of Infotainment system
Information interchange withControl Module with Indicator Unitin Instrument Panel Insert J285
Engine Control Module:
Engine speed
ABS Control Module
with EDL/ASR/ESP J104:
ESP status
Front Information Display
Control Head J523
Vehicle Electrical System
Control Module J519
Driver Identification
Control Module J589
Driv
etra
in C
AN
Dat
a B
us L
ow
Driv
etra
in C
AN
Dat
a B
us H
igh
61
Interfaces
CAN Data Bus Information Exchange
Information on air suspension and dampingcontrol is exchanged between the LevelControl System Control Module J197 andthe networked control modules viathe drivetrain CAN data bus, with theexception of a few interfaces.
Design and Function
This system overview shows examples ofthe type of information provided via thedrivetrain CAN data bus and received andused by the networked control modules.
SSP275/074
Information Sent fromLevel Control SystemControl Module J197
Information Receivedand Evaluated byLevel Control SystemControl Module J197
62
Functional Diagram –Air Suspension withContinuously Controlled Damping
Components
E256 ASR/ESP ButtonE387 Dampening Adjustment ButtonE388 Level Control Button
F213 Door Contact Switch, Driver’s Door
G76 Left Rear Level Control System SensorG77 Right Rear Level Control System SensorG78 Left Front Level Control System SensorG289 Right Front Level Control SensorG290 Level Control Pump Temperature SensorG291 Level Control Pressure SensorG337 Left Front Wheel Acceleration SensorG338 Right Front Wheel Acceleration SensorG339 Left Rear Wheel Acceleration SensorG340 Right Rear Wheel Acceleration SensorG341 Left Front Body Acceleration SensorG342 Right Front Body Acceleration SensorG343 Rear Body Acceleration Sensor
J104 ABS Control Module with EDL/ASR/ESPJ197 Level Control System Control ModuleJ403 Relay for Compressor Level Control SystemJ567 Left Headlight Range Control ModuleJ568 Right Headlight Range Control Module
N111 Solenoid for Level Control System (DrainValve)
N148 Left Front Suspension Strut ValveN149 Right Front Suspension Strut ValveN150 Left Rear Suspension Strut ValveN151 Right Rear Suspension Strut ValveN311 Level Control Accumulator ValveN336 Left Front Dampening Adjustment ValveN337 Right Front Dampening Adjustment ValveN338 Left Rear Dampening Adjustment ValveN339 Right Rear Dampening Adjustment Valve
S Fuse
V66 Motor for Compressor – Level ControlSystem
Color Coding
Input Signal
Output Signal
Positive
Ground
CAN Data Bus
Design and Function
30
15
31
30
15
31
S44
10A
S19
5A
F213 Ca
n D
ata
Bu
s –
Lo
w
Ca
n D
ata
Bu
s –
Hig
h
G337 G338 G339 G340 G341 G342 G343 G76 G77 G78 G289
J567/J568S6
40A
J197
E387 E388
E256 G291 N148 N149 N150 N151 N311 N336 N337 N338 N339 G290 N111 J403V66
J104
M
t°
SSP275/073
63
Design and Function
Additional Interfaces
Door Contact Signal
This signal is a ground signal from theVehicle Electrical System Control ModuleJ519. It indicates that a vehicle door or theluggage compartment lid has been opened.
It serves as a “wake up signal” forthe transition from sleep mode tostandby mode.
Terminal 50 Signal (Via CAN Data Bus)
This signal indicates that the starter hasbeen activated. It shuts down the levelcontrol system compressor during thestart-up routine.
This safeguards the start-up routine andconserves the battery.
K Wire
Self-diagnosis information is exchangedbetween the Level Control System ControlModule J197 and the VAS 5051 via theCAN data bus connection to the ControlModule with Indicator Unit in InstrumentPanel Insert J285 (gateway), and from thereto the VAS 5051 via the K wire.
64
Design and Function
Headlight Range Control Signal
Level height adjustments are made foreach axle. This would temporarily reducethe range of vision while driving at night.The Phaeton is equipped with a headlightrange control. The automatic dynamicheadlight range control keeps the lightcone at a constant angle.
To avoid constant, unnecessaryadjustments in level height due to surfaceunevenness, such as bumps or potholes,the self-leveling suspension has longreaction times when the vehicle is travellingat relatively constant road speed and ifthere is little or no wheel acceleration.
If level height is adjusted in highway modefor example, the Level Control SystemControl Module J197 sends a voltage signalto the Headlight Range Control ModuleJ431. The headlight range control reactsimmediately and adjusts the angle of thelight cone depending on the change ofbody position.
Level change sequence:
• Raising – the level is raised at the rearaxle first, followed by the level at thefront axle.
• Lowering – the level at front axle islowered first, followed by the loweringof the level at the rear axle.
65
Design and Function
Emergency Running Mode
Both the air spring control system and thedamping control system adopt storedemergency running strategies in the eventof faults in the sensors, the actuators, orinternal faults in the Level Control SystemControl Module J197.
Control actions are limited under certaincircumstances and an entry is made in thefault memory.
In these cases, a “Level Fault”or “Damper Fault” warning isissued and a warning symbolappears in the instrument cluster.
The vehicle must be taken tothe workshop for repair.
66
Service
Self-Diagnosis
Vehicle Diagnosis, Test and InformationSystem VAS 5051 and Vehicle Diagnosisand Service Information System VAS 5052are both suitable for communicationwith the Level Control System ControlModule J197.
Self-diagnosis can be accessed with thisequipment using Address Word 34 –
Self-leveling suspension.
Resetting the Adjustment Position
If the Level Control System Control ModuleJ197, a vehicle level sensor, or the entire airsupply module are replaced, then theadjustment position must be reset.
The adjustment position is reset using the“Basic setting” function located in “Guidedfault-finding.”
Please note that repairs
group 01 is integrated in“Guided fault-finding.”
SS275/050a
SSP275/050b
43
2
1
5
6
7
100140
180
220
70
50
30
40
2010
60
1210
16
1/21/4 3/4
6030 90
8050
20110
80 120
160
200
24014260120
--
ON/DARK
HELP
SETTINGS
MANUAL
AUDIO
TRIP DATA
AM
CLIMATE MAP NAV
RESET VEHICLE
CD
SCAN
FM
AM
NAV SET
BAL/FAD
67
Service
The color coded sensors, actuators,and auxiliary signals are tested as part ofthe self-diagnosis and guided fault-findingfor the Phaeton air suspension withcontinuously controlled damping.
G76, G77,G78, G289
J403
SSP275/096
J567, J568
N336, N337,N338, N339
N311
N148, N149,N150, N151
N111
T16
J285/J533
J197
Terminal 30
Terminal 15
Door/Hood/LuggageCompartment Lid Contact
G341, G342,G343
G291
G290
E387, E388
G337, G338,G339, G340
68
Notes
An on-line Knowledge Assessment (exam) is available for this Self-Study Program.
The Knowledge Assessment may or may not be required for Certification.
You can find this Knowledge Assessment at:
www.vwwebsource.com
From the vwwebsource.com Homepage, do the following:
– Click on the Certification tab
– Type the course number in the Search box
– Click “Go!” and wait until the screen refreshes
– Click “Start” to begin the Assessment
For Assistance, please call:
Certification Program Headquarters
1 – 877 – CU4 – CERT(1 – 877 – 284 – 2378)
(8:00 a.m. to 8:00 p.m. EST)
Or, E-Mail:
Knowledge Assessment
69
Volkswagen of America, Inc.3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.August 2003
cvr-outside-back-ssp275 6/30/03 1:59 PM Page 1