899303 the phaeton air suspension design and function

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

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


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


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.


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 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


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


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


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


Fully Laden

Design Position

Unladen

11


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.


Rebounded

Compressed

SSP275/014a

ReboundedDiameter

Air Spring

Roll Piston

OuterGuide

Bump Stop

SSP275/014

CompressedDiameter

13


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.


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 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


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


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 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


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


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


AUTO AUTO


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


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)


16-Pin Connector T16(Diagnostic Connection)

Design and Function

34


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)


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”


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)


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

60

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:

[email protected]

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

899303 the phaeton air suspension design and function

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