The W Engine Concept

The W Engine Concept

Volkswagen of America, Inc.3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.February 2002

Self-Study ProgramCourse Number 821203

Volkswagen of America, Inc.Service TrainingPrinted in U.S.A.Printed 2/2002Course Number 821203

©2002 Volkswagen of America, Inc.

All rights reserved. Information contained in thisdocument is based on the latest informationavailable at the time of printing and is subjectto the copyright and other intellectual propertyrights of Volkswagen of America, Inc., itsaffiliated companies and its licensors. All rightsare reserved to make changes at any timewithout notice. No part of this documentmay be reproduced, stored in a retrievalsystem, or transmitted in any form or by anymeans, electronic, mechanical, photocopying,recording, or otherwise, nor may thesematerials be modified or reposted to othersites, without the prior expressed writtenpermission of the publisher.

All requests for permission to copy andredistribute information should be referred toVolkswagen 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

Introduction .............................................................................. 1

W Engines, What Does the W Stand For?,The W Principle, W Engine Modular Design,A Comparison

Engine — Mechanics................................................................. 8

W8 Engine Specifications, W12 Engine Specifications,Cylinder and Crankshaft Configuration, Engine Components,Chain Drive, Camshaft Timing Control, Belt Drive, EngineLubrication, Engine Cooling, Air Supply, Exhaust System

Service..................................................................................... 54

Engine Sealing, Engine Timing Overview,Special Tools

Knowledge Assessment ........................................................ 61

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

W Engines

The constantly rising demands regardingperformance, smooth operation, and fueleconomy have led to the advancement ofexisting engines and the development ofnew engines.

The new W8 and W12 engines byVolkswagen are representative of a newengine generation — the W engines.

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The W engines set exacting demandson design. Large numbers of cylinderswere adapted to the extremelycompact dimensions of the engine. In theprocess, more attention was paid tolightweight design.

This Self-Study Program will familiarizeyou with the mechanical components andtheir functions in the W engine family.

1

What Does the W Stand For?

With the aim of building even morecompact engines with a large number ofcylinders, the design features of the V andVR engines were combined to produce theW engines.

As with the V engines, the cylinders aredistributed to two banks. In the W8 andW12 engines, these banks of cylinders arealigned at a V-angle of 72 degrees in

relation to one another. As in the VRengine, the cylinders within each bankmaintain a V-angle of 15 degrees.

When the W engine is viewed from thefront, the cylinder arrangement lookslike a double-V. Put the two Vs of the rightand left cylinder banks together, and youget a W. This is how the name “W engine”came about.

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SSP248/002

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72°

15° 15°

Introduction

2

Introduction

3

The W Principle

To illustrate the principle of the W enginecylinder arrangement, we will first showyou conventional engine types.

Inline Engines

represent the earliest development levelin engine configuration. The cylindersare arranged in-line vertically abovethe crankshaft.

Advantage: Simple design.

Drawback: Large numbers of cylindersresult in very long engines unsuitable fortransverse mounting.

V Engines

To make engines shorter, the cylinders inthe V engines are arranged at an angle ofbetween 60 degrees and 120 degrees, withthe centerlines of the cylinders intersectingwith the centerline of the crankshaft.

Advantage: Relatively short engines.

Drawback: The engines are relatively wide,have two separate cylinder heads, andtherefore require a more complex designand a larger engine compartment volume.

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60° – 120°

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VR Engines

The need for a powerful alternative suitablefor transverse mounting for use in small tomid-size vehicles saw the developmentof the VR engine. Six cylinders, offset at aV-angle of 15 degrees, are accommodatedin a fairly slender and very short engineblock. Unlike previous designs, the engineonly has one cylinder head. This made itpossible to supply the Golf with a compactVR6 engine.

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72°

15°

15°

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Introduction

4

W Engines

The engines of the W family are acombination of two “VR banks” based on amodular design principle.

The cylinders of one bank have an angle of15 degrees relative to each other while thetwo VR banks are arranged at a V-angle of72 degrees.

Introduction

5

W Engine Modular Design

Proven components from the modules ofthe VR engine family were integrated intothe new W engine concept. The principle isvery simple.

Two compact engines from the VR seriesare combined to produce a W engine.The result is a series of compact gasolineengines ranging from the W8 to the W16.

Numerous components of the VR and Wseries are identical:

• Valves, valve springs and valve seatinserts.

• Roller rocker fingers.• Valve clearance compensating elements.

This allows Volkswagen to manufacturemany parts in high volumes.

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2 x VR6

72°

W12

6-CylinderInline Engine

6-CylinderV Engine

6-CylinderVR Engine

In the evolution of the 6-cylinder engine,the VR6 engine stands out due to itscompactness. It is much shorter than thecomparable inline engine, and narrowerthan the V engine. Combining two VR6engines with a cylinder angle of 72 degreesproduces a W12 engine.

A W16 engine is obtained by joining twocylinders to each cylinder bank of a W12engine. Splitting the W16 in the middleleaves two W8 engines. A W10 engineconsisting of two VR5 engines is also apossibility. This covers the complete rangeof W engines.

W16

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W16

W12

2xW8

Introduction

6

A Comparison

When a conventional 8-cylinder V engineof comparable displacement is compared toan 8-cylinder W engine, the latter particularlystands out due to its compact design andrelatively small external dimensions.

W8 Crankshaft V8 Crankshaft

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The V8 Engine

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The W8 Engine

This is also reflected in a comparison of thecrankshafts. The compact design of the 12-cylinder W engine is highlighted by the factthat it has even smaller externaldimensions than a conventional V8 engine.

Introduction

7

Comparing the crankshaft of a conventionalV12 engine with that of a 12-cylinderW engine emphasizes the advantage.

W12 Crankshaft

The crankshaft of a V12 engineof comparable displacement is shown.

Depending on the number of cylinders,the W principle therefore saves materialand weight.

The W12 Engine

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V12 Crankshaft

Engine — Mechanics

8

W8 Engine Specifications

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• Displacement

244 cu in (3999 cm3)

• Bore

3.307 in (84.0 mm)

• Stroke

3.550 in (90.168 mm)

• Number of cylinders

8

• Number of cylinder heads

2

• Offset

± 0.492 in (12.5 mm)

• Bank offset

0.512 in (13 mm)

• V-angle of cylinder heads

between banks

72 degrees

• V-angle of cylinders in a bank

15 degrees

• Number of valves

4 per cylinder

• Crankshaft journal offset

218 degrees

• Firing order

1-5-4-8-6-3-7-2

Torque and Power Output

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Speed (rpm)

2000 4000 6000

hp kW

268 200

201 150

134 100

67 50

lbs-ft Nm

369 500

295 400

221 300

148 200

74 100

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9

• Dimensions

16.5 in (420 mm) long;28.0 in (710 mm) wide;26.9 in (683 mm) high

• Weight

Approximately 425 lbs (193 kg)

• Maximum power output

Approximately 275 bhp (202 kW)

• Maximum torque

Approximately 273 lbs-ft (370 Nm)

Horsepower and torquespecifications are not final atthe time of printing. Pleasesee www.vwwebsource.comfor the latest specifications.

• Fuel type recommendation

Premium unleaded gasoline (91 AKI)

• Engine management system

Bosch Motronic ME 7.1

• Installation position

In-line

• Allocated transmissions

5HP19 4Motion, C90 6-speed 4Motion

To

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Ou

tpu

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W12 Engine Specifications

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10

• Displacement

366 cu in (5998 cm3)

• Bore

3.307 in (84.0 mm)

• Stroke

3.550 in (90.168 mm)

• Number of cylinders

12

• Number of cylinder heads

2

• Offset

± 0.492 in (12.5 mm)

• Bank offset

0.512 in (13 mm)

• V-angle of cylinder heads

between banks

72 degrees

• V-angle of cylinders in a bank

15 degrees

• Number of valves

4 per cylinder

• Crankshaft journal offset

+12 degrees

• Firing order

1-12-5-8-3-10-6-7-2-11-4-9


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Torque and Power Output

Speed (rpm)

2000 4000 6000

hp kW

536 400

469 350

402 300

335 250

268 200

201 150

134 100

67 50

lbs-ft Nm

590 800

516 700

443 600

369 500

295 400

221 300

148 200

74 100

11

• Dimensions

20.2 in (513 mm) long;28.0 in (710 mm) wide;28.1 in (715 mm) high

• Weight

Approximately 541 lbs (245 kg)

• Maximum power output

Approximately 420 bhp (309 kW)

• Maximum torque

Approximately 406 lbs-ft (550 Nm)

Horsepower and torquespecifications are not final atthe time of printing. Pleasesee www.vwwebsource.comfor the latest specifications.

• Fuel type recommendation

Premium unleaded gasoline (91 AKI)

• Engine management system

Bosch Motronic ME 7.1.1 (Dual ControlModule Concept)

• Installation position

In-line

• Allocated transmission

5HP24 4Motion

To

rqu

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Ou

tpu

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Cylinder andCrankshaft Configuration

Cylinder Offset

The alternate cylinders of a bank areoffset from the centerline of the crankshaftand positioned at a very narrow V-angleof 15 degrees.

The compact W engine was made possibleby arranging two banks of cylinders at aV-angle of 72 degrees.

Center ofCylinder

Center ofCylinder15°

Offset0.492 in(12.5 mm)Left

Offset0.492 in(12.5 mm)Right

Center ofCrankshaftFulcrum

Point of Intersectionof Centers of Cylinders

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To provide adequate space for the pistonsin the bottom-dead-center range, it wasnecessary to offset the crankshaft drive.This means that the cylinders are offset by0.492 in (12.5 mm) outward relative to thecenter of the crankshaft fulcrum.

This configuration was first used in theVR6 engine.

12


W12 Engine

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16

12712°

Crankpin Offset

Crankpin offset controls the relativepositions of the pistons in the cylinders foran evenly timed firing sequence.The configuration of all VolkswagenW engines is based on a 10-cylinder enginemodel. All four-cycle internal combustionengines complete their cylinder firingsequences within two completerevolutions. This amounts to a crankshaftrotation of 720 degrees.

The W10 engine needs no crankpin offset.

With 720 degrees of crankshaft rotation in a10-cylinder engine, the optimum V-anglebetween the two cylinder banks is 72degrees (720 4 10 = 72). In the 10-cylindermodel engine there is no need for crankpinoffset to achieve ideal relative pistonpositions for the equally timed firing of eachcylinder.

The W8 engine has a crankpin offset of–18 degrees.

To achieve the same kind of ideal firingsequence timing as the 10-cylinder model,an 8-cylinder W engine requires 90 degreesof crankshaft rotation between the

3

94

10

5

82

11

13

ignition cycle of each cylinder through720 degrees of crankshaft rotation(720 4 8 = 90). To determine the optimumcrankpin offset of –18 degrees for thisengine, the 90 degrees of crankshaftrotation between ignition cycles issubtracted from the 72-degree V-angle ofthe cylinder banks.

72 – 90 = –18

The W12 engine has a crankpin offsetof +12 degrees.

Similarly, a 12-cylinder engine requires60 degrees of crankshaft rotation betweenthe ignition cycle of each cylinder through720 degrees of crankshaft rotation(720 4 12 = 60). For this configuration, todetermine the optimum crankpin offset of+12 degrees, the 60 degrees of crankshaftrotation between ignition cycles issubtracted from the 72-degree V-angle ofthe cylinder banks.

72 – 60 = +12

Engine Components

W engines include the followingcomponents:

• Cylinder block

• Crankcase lower section with bearingsupport

• Crankshaft with connecting rods andpistons

• Balancing shafts


• Cylinder heads

• Oil sump and oil pump

• Crankshaft drive

• Timing chain drive

• Belt drive for auxiliary components

• Multi-part intake manifold

W8 EngineMulti-Part Intake Manifold

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Split Oil Sumpwith Oil Pump

Crankcase LowerSection withBearing Support

Crankshaft withConnecting Rodsand Pistons

Cylinder Heads

14

Combined CylinderBlock and CrankcaseUpper Section


Crankcase Lower Section

Cylinder Block and Crankcase

The W engines include two maincomponents: the combined cylinder blockand crankcase upper section, and thecrankcase lower section.

The upper section includes the cylindersand the upper main bearing caps. Thecrankcase lower section is designed as abearing support and carries the lower mainbearing caps.

Combined Cylinder Block

and Crankcase Upper Section

The “aluminum” crankcase upper sectionis made of a hypereutectic aluminum-siliconalloy (AlSi17CuMg).

Hypereutectic means that pure siliconcrystals initially precipitate out of thealuminium-silicon melt while it cools beforealuminium/silicon crystals form. Due tothe presence of these silicon crystals withinthe metal microstructure, the cooled melt isharder than a eutectic Al-Si alloy.

Use of this alloy eliminates the need foradditional cylinder liners or a plasmacoating for the purposes of cooling andlubricating the cylinder surfaces, becausethe material already has sufficient naturalstrength and thermal stability.

W12

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W8

CombinedCylinder Blockand CrankcaseUpper Section

15


Crankcase Lower Section

The crankcase lower section is a bearingsupport with integral bearing seats.

The bearing support is also made of analuminum alloy. It serves as a framestructure for the lower crankshaft mainbearing caps. These bearing caps are madeof grey cast iron and are embedded in thebearing support when it is cast.

They are located on the thrust side of thecrankshaft and give the crankshaft bearingsthe strength they require.

The bearing support is attached to thecrankcase upper section by four bolts perbearing cap.

W8 Bearing Support

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Casing Opening TowardsDrive of Balancing Shafts

W12 BearingSupport

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Cast Element in

Bearing Support

BearingCap

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16


Crankshaft

The crankshafts used in the W engines aremanufactured from forged tempered steel.Each pair of connecting rods runs betweentwo main bearings.

The drive gear of the oil pump (togetherwith the toothed belt pulley for thebalancing shafts on the W8 engine only)is pressed against the outer main bearingand held in place by the vibration damper.

The connecting rod journals are arrangedin pairs and in accordance with thecrankshaft throw.

When the connecting rods areinstalled, the bearing shells mustnot contact the radii or the edgebetween the two connectingrod faces.

W8 Crankshaft

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Connecting RodJournal withCorner Radii

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Crankshaft Journal

MainBearingJournal

Oil Pump Gear

VibrationDamper

Toothed Belt Pulley forBalancing Shafts

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Journals for Drivingthe Oil Pump and theBalancing Shaft

MainBearingJournal

ConnectingRod Journal Chain Drive Gears

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17

Connecting Rods and Pistons

The connecting rods are made of forgedsteel and are only 0.512 inch (13 mm) thick.They are of a trapezoidal construction andare cut during the production process.

To ensure better oil exchange, twogrooves are milled in the side faces ofthe connecting rod bearing caps. The pistonpin is lubricated through two inclined boresin the connecting rod head.

The pistons are made of an aluminum-silicon (Al Si) alloy. The recess in the pistontop surface is very shallow since thecylinder head provides most of thecombustion chamber volume. The angle ofthe piston top surface is necessary toaccommodate the positions of the pistonsin their V configuration.

Each piston carries two compression ringsand an oil control ring. To drain off the oilwhich collects at the oil control ring, smalldrainage holes lead from the piston ringgroove to the inside of the piston.


TrapezoidalShape

SSP248/048Bores

Grooves forOil Exchange

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DrainageHoles

Iron Coating forAluminum-SiliconPiston Skirts inCentral Crankcase SSP248/049

18

W8 Engine Balancing Shafts

The W8 engine has two balancingshafts to compensate for the forces ofinertia. The two shafts are housed in thecrankcase. The upper balancing shaftis driven by the crankshaft and a toothedbelt. A gear on the end of the upperbalancing shaft drives the lowerbalancing shaft.

The balancing shafts are installedthrough two holes on the clutch side ofthe crankcase.


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Align mark on crankshaft drivegear with the joint (TDC of 1st cylinder).

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InstallationOpenings

Drive Gear onthe Crankshaft

Bearings run in crankcasebushings.

Drive Gear on theBalancing Shaft

Align mark on balancingshaft drive gear with themark on the sealing face(TDC of 1st cylinder).

Tension Pulley

19


20

There is a groove at the gear wheel endof the balancing shaft. The lock plateengages into this groove, locating thebalancing shafts axially. During installation,the balancing shafts must be aligned

with regard to the TDC position of the1st cylinder.

The balancing shafts must be rotated sothat the marks on the balancing shafts areopposite each other.

Position ofBalancing Shaftsat TDC of1st Cylinder

Gears of theBalancing Shafts Marks

Lock Plate

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Balancing Shaft I

Balancing Shaft II

LockingGrooves

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21

The balancing shaft drive is protected onthe belt drive side by a plastic housingcover.

On the clutch side, the openings forinserting the balancing shafts, togetherwith the chain drive, are sealed by analuminium cover.

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SSP248/054

Drive

Two-Mass Flywheel with Clutch

W engines equipped with a manualtransmission generally have a two-massflywheel.

This flywheel design prevents torsionalvibration from being transmitted from the


22

Clutch Cover

crankshaft to the transmission through theflywheel. If not eliminated, this vibrationwould adversely affect performance.

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SSP248/061

Two-MassFlywheel

Clutch Disc


23

A spring damper system within thetwo-mass flywheel separates the primaryinertia mass from the secondary inertiamass so that the torsional vibrationproduced by the engine is not transmittedto the transmission. On W engines with anautomatic transmission, the two-massflywheel is replaced by a converter plate.

The two-mass flywheel also serves as asender wheel for Engine Speed (RPM)Sensor G28. Its job is to determine theengine speed and recognize cylindernumber 1 together with the CamshaftPosition (CMP) Sensor G40, CamshaftPosition (CMP) Sensor 2 G163, CamshaftPosition (CMP) Sensor 3 G300, andCamshaft Position (CMP) Sensor 4 G301.It has a larger tooth gap which serves as amarker point. This point is registered by theEngine Speed (RPM) Sensor G28 locatedin the transmission housing during eachrevolution of the two-mass flywheel.

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Two-MassFlywheel

Pulse SensorWheel

LargerTooth Gap


24

Cylinder Heads

The W engines have two aluminiumcylinder heads with two overheadcamshafts apiece.

The injectors are inserted into thecylinder heads.

CamshaftBearing —Intake

CamshaftBearing —Exhaust

Cylinder Heads of W8 Engine

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Openingfor Injector


25

RollerRockerFingers

Each of the cylinder heads in the two Wengines has an intake camshaft and an

exhaust camshaft with camshaft adjustersattached to their end faces.

CamshaftAdjusters

SSP248/067

Camshafts


26

The four valves in each cylinder areactuated by low-friction roller rockerfingers. Valve clearance is compensated byhydraulic support elements.

Due to the cylinder arrangement, shortand long valves as well as short andlong inlet and exhaust ports alternate withone another.

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SSP248/160

Camshaft

Cam Roller

Valve

RollerRockerFinger

Hydraulic Support Element


27

SSP248/170

SSP248/171

IntakePorts

ExhaustPorts

Intake Manifoldof W12 Engine

Cylinder Heads of W12 Engine

IntakeValves

Air Supply Intake

ExhaustValves


28

Secondary Air Ducting System

Besides the coolant and oil ducts in thecylinder heads, the secondary air is guidedthrough ducts and bores into the exhaustducts near the exhaust valves. Thesecondary air flows into a duct in thecylinder head through a Secondary AirInjection (AIR) Solenoid Valve N112.

From here the secondary air is guidedback into the cylinder head through groovesin the exhaust flange. The secondary airthen flows through ducts and bores to theexhaust valves.

OilReturnHoles

Bores Leading toExhaust Valve (Inboard)

ExhaustValves(Inboard)

ExhaustValves(Outboard)

Bores Leadingto Exhaust Valve(Outboard)

SecondaryAir Duct

Connection for SecondaryAir Injection (AIR) SolenoidValve N112

Coolant

Oil Ducts

Secondary Air

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Groove inExhaustFlange

SSP248/174


29

Chain Drive

The chain drive is mounted at the flywheelend of the engine. Engine power istransmitted by a gear on the crankshaft tothe gears of the central intermediate shaftby means of a double chain.

SSP248/075

At this point, each of the camshafts of thetwo cylinder heads is driven by a singlechain. Three hydraulic chain tensionersensure that an optimal chain tension ismaintained.

Chain Drive of W Engines

Slide Rail

ExhaustCamshaft

Intake Camshaft

Central Intermediate ShaftChain Tensioner

Camshaft Adjuster

Single Chain(Sleeve Type Chain)Right Bank

Tensioning RailChain Tensioner withTensioning Rail

Slide Rail

Single Chain(Sleeve Type Chain)Left Bank

Double Chain(Roller Chain)

Gear onCrankshaft

Chain Tensioner

Tensioning Rail


30

Camshaft Timing Control

Both the W12 engine and the W8 enginehave continuously adjustable intakecamshaft timing. In this case, continuouslyadjustable means that the intake camshaftcan be advanced or retarded relative to itsneutral position at any angle within a rangeof 52 degrees.

The camshafts are adjusted by hydrauliccamshaft positioners bolted to their endfaces.

The exhaust camshaft of the W12 is alsocontinuously adjustable.

Valve 1 for CamshaftAdjustment N205

Camshaft AdjustmentValve 1 (Exhaust) N318

The exhaust camshaft of the W8 engine isan exception. It can only be adjusted to the“advance” or “retard” position within arange of 22 degrees.

The Motronic Engine Control Module J220regulates the oil supply to the camshaftpositioners by controlling the Valve 1 forCamshaft Adjustment N205 and CamshaftAdjustment Valve 1 (Exhaust) N318.

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Timing Case

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Vane AdjusterIntake Camshaft

Vane AdjusterExhaust Camshaft


31

System Operation

The following examples show the operationof the intake camshaft adjuster for the rightbank (bank I).

Neutral position

When the Valve 1 for Camshaft AdjustmentN205 moves the adjusting piston into a

central position, this causes both oil ducts(a and b) — and hence the chambers(A and B) on either side of the inner rotor —to fill with oil. The inner rotor, together withthe camshaft which it is rigidly coupled to,now adopts a position in the middle of theadjustment range.


Oil Return Passage

Engine Oil Pressure

Adjusting Piston

Direction of Rotation of Drive

Oil Duct (b)

Oil Duct (a)

Exhaust Camshaft

Annular Ducts

Inner Rotor(Rigidly Coupled to Camshaft)

Chamber (A)

Chamber (B)

Outer Rotor(Coupled to Timing Chain)

Oil Duct (aa)

Oil Return Passage

Chamber (B)

Inner Rotor

Outer Rotor

StopAdvanceAdjuster

Chamber (A)

CamshaftNeutral

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Bank I

Stop RetardAdjuster

IntakeCamshaft

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Oil Duct (bb)


32

Retard adjustment

The Valve 1 for Camshaft Adjustment N205guides the oil into the oil duct (b). The oilflows from channel (b) through the annulargroove and camshaft and the bores (bb) tothe chambers (B) of the camshaft adjuster.

Exhaust Camshaft

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When the oil enters the chambers (B), theinner rotor is rotated against the direction ofrotation of the drive, adjusting the camshaftin the retard direction. The oil is forced outof the chambers (A) through the bores (aa).It flows back into the cylinder head throughthe camshaft and duct (a).

CamshaftRetard Retard Stop

Chamber (B)

Chamber (A)

Outer Rotor

Inner Rotor

Intake Camshaft

Bank I


33

Exhaust Camshaft

Advance adjustment

To rotate the inner rotor forward, theadjusting piston housed within the Valve 1for Camshaft Adjustment N205 adjustsitself so that the oil duct (a) is put under oil

pressure. As a result, the oil flows into thechamber (A), advancing the inner rotor.Chamber B is simultaneously bled throughoil ducts (bb and b) to ensure a quickresponse.

SSP248/137

CamshaftAdvance

AdvanceStop

Chamber (B)

Chamber (A)

Outer Rotor

Inner Rotor

Intake Camshaft

Bank I


34

Belt Drive

The following components are driven bythe belt drive:

• Coolant pump

• Generator C

• Power steering pump

• Air conditioner compressor

The poly-V-ribbed belt is tensioned by ahydraulic tensioning and deflection pulley.Two additional deflection pulleys ensurethat all components to be driven canbe reached.

Generator C

Belt Drive of the W8 Engine and

W12 Engine used by Volkswagen

Deflection Pulley

Deflection Pulley

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VibrationDamper

Coolant Pump

PowerSteeringPump

Hydraulic Belt Tensionerwith Deflection Pulley

Air ConditionerCompressor


35

In the W12 engine, the hydraulic belttensioner and deflection pulley are attachedto the air conditioner compressor bracket.

Generator C

Hydraulic BeltTensioner

DeflectionPulley

Deflection Pulley

Coolant Pump

Crankshaft Pulleywith Vibration Damper

SSP248/078

DeflectionPulley

PowerSteeringPump

Air ConditionerCompressor

Belt Drive of the W12 Engine used by Audi


36

Engine Lubrication

The oil is drawn out of the oil pan by the oilpump and flows to the central oil passagethrough the external oil filter/cooler module.

The main crankshaft bearings are suppliedwith pressurized oil by the central oilpassage; the central oil duct is suppliedwith pressurized oil by a riser.

The oil flows from the central oil duct to thespray jets for piston cooling, and then fromthere to the cylinder heads through risersequipped with non-return valves.

The oil also flows to the intermediate shaft,to the engine timing gear and to the chaintensioner.

In the cylinder heads, the oil flows alongducts to the camshaft adjusters and thecamshaft bearings.

The return lines guide the oil back into theoil sump.

Oil Circuit of the W12 Engine

Camshaft AdjustmentValve 1 (Exhaust) N318

Oil SumpUpper Section

Oil SumpLower Section SSP248/091

ReturnDucts

Spray Jets forPiston Cooling

CamshaftAdjuster

CrankshaftBearing

Hydraulic ElementsCamshaft Bearing

Central Oil DuctRiser

Central Oil Passage

Oil PumpDrive Gear



37

W Engine Oil Circuit Schematic Diagram

Intermediate Shaft

Chain

CentralOil Passage

SSP248/083

Spray Jet

Return Line

Oil Pump

Three ChainTensioners withChain Oil Spray


Camshaft Adjuster

TimingBelt Gear(Not Shown)

Oil Sump

Oil Filter/Cooler Module

SSP248/094

Oil Sump of

the W8 Engine

CamshaftAdjustment Valve 1(Exhaust) N318


38

The Wet-Sump Principle

The W8 and W12 engine for VW modelshave a wet-sump lubrication system.The W12 engine for Audi models has adry-sump lubrication system.

In the wet-sump lubrication system, theentire oil supply is retained in the oil sump.The single-stage oil pump draws the oil outof the wet sump through the intake line

Wet-Sump Lubrication System

of the W8 Engine

and immediately returns it to the engineafter it has cooled down and has beenfiltered.

In contrast to the dry-sump, the job of theoil sump with wet sump is to retain theentire oil supply. As a result, it has a largervolume which affects the overall height ofthe engine.

Single-Stage Oil PumpOil Filter and Cooler ModuleSSP248/137


39

The Dry-Sump Principle (Audi only)

In the dry-sump lubrication system, theentire oil supply is retained in an externalreservoir, and not in the oil sump.

To facilitate this, the oil pump is of three-stage design. Two stages draw the oil outof the oil sump at various points and pumpit into the reservoir.

Dry-Sump Lubrication System of

the W12 Engine in the Audi A8

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Reservoir

Cooler

Filter

Three-Stage Oil Pump

The third stage (discharge stage) returnsthe oil from the reservoir to the enginethrough the oil cooler and the oil filter. Theoil sump can be kept small and flat due toits lower oil volume, with the result that theengine has a smaller overall height.

This requires a slightly more complex design.


40

Oil Sump

The oil sump is comprised of two diecastaluminium parts. The oil sump lowersection forms the oil reservoir. The centraloil passage is located in the upper sectionof the oil sump.

Special baffles settle the oil in the oil sump.

The Engine Oil Level Sensor G12 whichinforms the Motronic Engine ControlModule J220 of the oil level, is inserted intothe oil sump lower section from below,near the oil drain screw, and then boltedinto place.

The oil is extracted from the sump by theoil pump through the intake line, andpumped into the oil circuit.

The single-stage oil pump is drivenby the crankshaft by a separate chain inthe crankcase.

Central OilPassage

Intake Line

Drive

Oil SumpLowerSection

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Baffles(SwashPlates)

Oil SumpUpper Section

Oil SumpLower Section

OilDrainScrewEngine

Oil LevelSensor G12

The Oil Pump


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The oil pump is mounted from below andbolted to the bearing support.

Oil Filter and Cooler Module

The oil circuit of the W engine has anexternal oil filter and cooler module. Thisallows the engine to be more easilyadaptable to the varying amounts of spaceavailable in the various vehicle models. Theoil filter is designed so that a filter elementcan be replaced by service personnel.

Oil Filter and

Cooler Module

of the W8

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Piston Spray Jets

The oil is guided from the central oilpassage of the crankcase upper section tosmall nozzles at the base of the cylinderbores. Here, the oil is sprayed below thepistons to lubricate the piston contact facesand piston pins, and cool the pistons.

Crankshaft Bearing Lubrication

The oil is routed through holes from thecentral oil passage to the crankshaft.Then it is forced through grooves in thebacks of the lower bearing shells to theupper bearing shells. There it reachesthe crankshaft through five holes in theupper bearing shell.

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Oil Supply

Bearing Support

Groove on the Backof the Bearing Shells

Upper Bearing Shell

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Crankshaft


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Connecting Rod Bearing Lubrication

The oil flows from the outer circumferentialgroove into the inner groove of the upperbearing shell through five holes. The holesensure that an even oil film forms.

TransitionalPockets Flow to

Main Bearing

Flow to ConnectingRod Bearing

Inner Grooveof Bearing Shell(In Upper Bearing Only)

Groove in Crankcase

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Hole from Main Bearing toConnecting Rod Bearing

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Integrated pockets at the transition to thelower bearing shell ensure a steady supplyof oil to the connecting rod bearingsthrough holes in the crankshaft.

G


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Engine Cooling

The coolant circuit is filled with VW G12coolant. The coolant is pumped fromthe central coolant duct in the crankcaseupper section and into the cylinder heads.Baffles ensure that all cylinders areswept evenly. At the same time, thecoolant flow is redirected from the

Generator CEngine CoolantTemperature(ECT) Sensor(On Radiator) G83

Small Cooling Circuit

Large Cooling Circuit

Ribbed V-Belt

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Map ControlledEngine CoolingThermostat F265 Radiator

ExpansionTank

Oil Cooler

Engine CoolantTemperature (ECT)Sensor (On Engine) G82

CoolantPump

Coolant Circuit of W8 Engine

exhaust side of the combustion chamberstowards the intake side.

The coolant circuit is subdivided into a smallcooling circuit, in which the coolant is onlyrouted within the engine block, and a largecooling circuit that includes the radiator andengine oil cooler.

Heating

G


45

Coolant Circuit of W12 Engine

Generator C

ExpansionTank

Engine CoolantTemperature(ECT) Sensor(On Engine) G82

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Engine CoolantTemperature (ECT)Sensor (OnRadiator) G83

TransmissionOil Cooler

Left HeatExchanger

Engine CoolantTwo-Way VacuumValve N147 Auxiliary

RadiatorRadiator

Right HeatExchanger

Map ControlledEngine CoolingThermostat F265

Small Cooling Circuit

Large Cooling Circuit

Coolant Pump

EngineOil Cooler

AuxiliaryHeater


46

Coolant Flow in the Cylinder Heads

When the coolant moves through thecrankcase and into the two cylinder heads,two thirds of the coolant volume is guidedto the outside and one third to the inside ofthe cylinder heads.

This principle helps toprovide even cooling,and is known ascross-cooling.

Coolant flows through the cylinder headsfrom the exhaust side to the intake side.This results in very good temperatureequalization as well as effective cooling ofthe outlet webs and spark plugs.

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47

Coolant Pump with Pump Gear

In both W engines, the coolant pump islocated in the cylinder block at the faceend. It is mounted directly upstream of thecentral coolant duct and is driven by theribbed V-belt.

Electronically Controlled Engine Cooling

Switching from the small cooling circuit tothe large cooling circuit is controlled by anelectrically actuated Map Controlled EngineCooling Thermostat F265 in the thermostathousing. In the W8 and W12 engine, thisvalve is installed in the crankcase uppersection from above. To replace this valve, itis necessary to remove the intake manifold.

By electrically heating the waxthermocouple in the Map Controlled EngineCooling Thermostat F265, it is possible tocontrol the switching point and coolanttemperature. Characteristic control mapsare stored in the Motronic Engine ControlModule J220. They make it possiblefor the engine to reach the desiredtemperature in accordance with theengine’s operating requirements.

Wax Thermocouple

Lifting Pin

HeatingResistor

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Map Controlled

Engine Cooling

Thermostat F265

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Air Supply

Air is supplied through a tapered intakepipe. It is of a four-part design and is madeof an aluminium alloy.

The intake manifold lower section is boltedto the cylinder heads between the twocylinder banks. The larger intake manifoldupper section is mounted to the lowersection. The intake manifold upper sectionis designed so that the manifolds for bank Iand II can be removed separately. Thismakes it easier to gain access to theindividual ignition coils and spark plugs,for example.

In the W8 engine, the intake air for bothmanifolds is guided by a Throttle ValveControl Module J338.

ThrottleValve ControlModule J338

Intake ManifoldUpper Section

Manifold, Bank I Manifold, Bank II

W8 Engine

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Intake ManifoldLower Section


49

The intake manifold used in the W12engine is made of magnesium alloy. Unlikethe W8 engine, each of the manifolds iscoupled to a separate Throttle Valve ControlModule J338.

Intake ManifoldUpper Section

W12 Engine

Intake ManifoldLower Section

Throttle ValveControl Module J338

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Manifold,Bank I

Manifold,Bank II

Crankcase Breather

The diaphragm valve limits the vacuum inthe crankcase irrespective of the intakepipe vacuum, allowing the cleanedcrankcase exhaust gases (blow-by) to berouted continuously into the intake manifold

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and burned in the cylinders during thecombustion cycle. No oil is entrained inthe process. The oil separator removesthe oil particles from the blow-by gas.The separated oil is then returned tothe oil sump.

W8 Engine

Oil Separator

Diaphragm Valve


50

Because the W12 engine has adouble flow intake manifold, eachbank has a side diaphragm valveand an oil separator.

DiaphragmValve, Left

DiaphragmValve, Right

Oil Separator

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Oil Separator

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W12 Engine


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Exhaust System

The W8 engine has an exhaust manifoldwith a catalytic converter for each cylinderhead. A total of four oxygen sensors aretherefore required for emission control.

• Heated Oxygen Sensor (HO2S) G39• Heated Oxygen Sensor (HO2S) 2 G108

Central Silencer

Exhaust System of W8 Engine

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Tailpipes

Rear Silencer PrimarySilencer

CatalyticConverter

Manifold

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• Oxygen Sensor (O2S) Behind Three-WayCatalytic Converter (TWC) G130

• Oxygen Sensor (O2S) 2 Behind Three-Way Catalytic Converter (TWC) G131

The exhaust system has a primary silencerand a rear silencer for each bank, as well asa common central silencer.


52

The W12 engine has two exhaustmanifolds for each cylinder head. Eachof these exhaust manifolds is connected toits own primary catalytic converter locatednear the engine. The two exhaust pipes ofeach bank then merge on a main catalyticconverter. The exhaust system has aprimary silencer, an intermediate silencerand a rear silencer for each bank.

Four primary catalytic converters and twomain catalytic converters help to achieve aneffective reduction in emissions.

To monitor mixture combustion andto optimize pollutant emission reduction,use is made of a total of eight oxygensensors, four each before and after theprimary catalytic converters.

• Heated Oxygen Sensor (HO2S) G39

• Heated Oxygen Sensor (HO2S) 2 G108


53

• Oxygen Sensor (O2S) Behind Three-WayCatalytic Converter (TWC) G130

• Oxygen Sensor (O2S) 2 Behind Three-Way Catalytic Converter (TWC) G131

• Heated Oxygen Sensor (HO2S) 3 G285• Heated Oxygen Sensor (HO2S) 4 G286• Oxygen Sensor (O2S) 3 Behind Three-

Way Catalytic Converter (TWC) G287• Oxygen Sensor (O2S) 4 Behind Three-

Way Catalytic Converter (TWC) G288

Manifold

Primary Catalytic Converter

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Exhaust System of W12 Engine

Tailpipes

Rear Silencer CentralSilencer

PrimarySilencer

Main CatalyticConverter

PrimaryCatalyticConverter

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Exhaust Manifold

Engine Sealing

Each of the cylinder heads is sealed offfrom the valve covers by a rubber gasket,from the contact faces of the intakemanifold by an elastomer gasket, fromthe exhaust manifolds by a two-layerembossed metal gasket, and fromthe crankcase by a multilayer embossedmetal gasket.

The gasket between the bearing supportand the oil sump upper section is alsodesigned as a single layer embossedmetal gasket.

The oil pan upper section and lowersection as well as the crankcase uppersection and the bearing support aresealed by a liquid gasket.

Multilayer Metal/Elastomer CompositeGasket between Cylinder Head andIntake Manifold Contact Face

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Liquid Gasket between Oil SumpUpper Section and Lower Section

Coated Embossed MetalGasket between Oil SumpUpper Section andBearing Support

Liquid Gasket betweenCrankcase Upper Sectionand Bearing Support

Rubber Gasket betweenCylinder Heads andValve Covers

Two-Layer Embossed MetalGasket between CylinderHeads and Exhaust Manifold

Multilayer Embossed MetalGasket between CylinderHeads and Crankcase

Service

54

Liquid Gaskets

Application of the liquid gasket sealant tomost surfaces is CNC-controlled in order toensure a constant sealant supply.

The liquid gasket between the lower timingcase cover and the upper timing case coveris applied according to a different principle.In this case, the parts are first bolted, thenthe sealant is injected into the groove in the

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upper timing case cover through zerk-typefittings (sealing injection system).

When enough liquid sealant has beeninjected, the excess sealant is dischargedfrom the openings on the end of the timingcase cover. The zerk-type fittings remain inthe housing after injecting the sealant.However, they have to be replaced whenrepairing the gasket.

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Outlet

Lower TimingCase Cover(Sealing Flange)

Upper TimingCase Cover

Upper TimingCase Cover(Covering Part)

Groove forSealant

Zerk-Type Fitting

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Zerk-Type Fitting forLiquid Gasket Installation

Service

55

Engine Timing Overview

If it is necessary to disassemble thecylinder heads, the engine timing must bereset. These are the important markerswhen the piston of the first cylinder is attop dead center.

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Adjust intakecamshaft toretard.

Adjust exhaustcamshaft toadvance.

Put copper coloredchain link on arrowof bank II.

Put copper coloredchain link on arrowof bank II.

Bank II

Place the coppercolored chain linkon the markedtooth of theintermediate shaftand the bore holein the housing.

Service

56

Insert the mandrel for holding the crankshaftinto the threaded hole in the housing: pistonin 1st cylinder at top dead center.

For a description of the exactprocedure for setting the enginetiming, please refer to therelevant Repair Manual.

Position the marker on the vibrationdamper on the housing joint: piston in1st cylinder at top dead center.

When placing on the lowertiming chain copper link, setthe colored chain link on themarked tooth and the markedtooth on the housing joint:piston in 1st cylinder at topdead center.

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Exhaust camshaftretard adjustment.

Place coppercolored chain linkon arrow of bank II.

Place coppercolored chain linkon arrow of bank I.

Marked ToothNormal ToothSSP248/178

Bank I

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Intake camshaftadvance adjustment.

Service

57

Insert camshaft rule foraligning the camshafts.

Special Tools

Camshaft Alignment Rule

For aligning the camshafts when settingthe engine timing.

T10068

Service

58

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Mandrel

For locating the crankshaft.

3242

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Engine and Transmission Holder

VAS 6095

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Notes

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60

Notes

Knowledge Assessment

61

An on-line Knowledge Assessment (exam) is available for this Self-Study Program.

This Knowledge Assessment may or may not be required for Certification. You can find thisKnowledge Assessment under the Certification tab at:

www.vwwebsource.com

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 email: [email protected]

Documents

The W Engine Concept