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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.
SSP248/101
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.
SSP248/104
SSP248/002
SSP248/001
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.
SSP248/004
SSP248/005
SSP248/003
60° – 120°
SSP248/006
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.
SSP248/010
SSP248/009
72°
15°
15°
SSP248/008SSP248/009
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.
SSP248/105
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
SSP248/011
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
SSP248/012
The V8 Engine
SSP248/014
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
SSP248/150
SSP248/013
V12 Crankshaft
Engine — Mechanics
8
W8 Engine Specifications
SSP248/017
• 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
SSP248/018
Engine — Mechanics
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
SSP248/021
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
rqu
e
Ou
tpu
t
Engine — Mechanics
W12 Engine Specifications
SSP248/019
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
Engine — Mechanics
SSP248/020 SSP248/022
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
e
Ou
tpu
t
Engine — Mechanics
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
SSP248/186
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
Engine — Mechanics
W12 Engine
SSP248/026
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
Engine — Mechanics
• 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
SSP248/025
Split Oil Sumpwith Oil Pump
Crankcase LowerSection withBearing Support
Crankshaft withConnecting Rodsand Pistons
Cylinder Heads
14
Combined CylinderBlock and CrankcaseUpper Section
Engine — Mechanics
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
SSP248/027
SSP248/028
W8
CombinedCylinder Blockand CrankcaseUpper Section
15
Engine — Mechanics
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
SSP248/029
SSP248/032
Casing Opening TowardsDrive of Balancing Shafts
W12 BearingSupport
SSP248/033
Cast Element in
Bearing Support
BearingCap
SSP248/030
16
Engine — Mechanics
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
SSP248/045
Connecting RodJournal withCorner Radii
SSP248/043
Crankshaft Journal
MainBearingJournal
Oil Pump Gear
VibrationDamper
Toothed Belt Pulley forBalancing Shafts
SSP248/037
Journals for Drivingthe Oil Pump and theBalancing Shaft
MainBearingJournal
ConnectingRod Journal Chain Drive Gears
SSP248/056
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.
Engine — Mechanics
TrapezoidalShape
SSP248/048Bores
Grooves forOil Exchange
SSP248/047
SSP248/016
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.
Engine — Mechanics
SSP248/057
Align mark on crankshaft drivegear with the joint (TDC of 1st cylinder).
SSP248/055
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
Engine — Mechanics
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
SSP248/108
Balancing Shaft I
Balancing Shaft II
LockingGrooves
SSP248/107
Engine — Mechanics
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.
SSP248/058 SSP248/059
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
Engine — Mechanics
22
Clutch Cover
crankshaft to the transmission through theflywheel. If not eliminated, this vibrationwould adversely affect performance.
SSP248/060
SSP248/061
Two-MassFlywheel
Clutch Disc
Engine — Mechanics
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.
SSP248/062
SSP248/061
Two-MassFlywheel
Pulse SensorWheel
LargerTooth Gap
Engine — Mechanics
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
SSP248/063
Openingfor Injector
Engine — Mechanics
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
Engine — Mechanics
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.
SSP248/161
SSP248/160
Camshaft
Cam Roller
Valve
RollerRockerFinger
Hydraulic Support Element
Engine — Mechanics
27
SSP248/170
SSP248/171
IntakePorts
ExhaustPorts
Intake Manifoldof W12 Engine
Cylinder Heads of W12 Engine
IntakeValves
Air Supply Intake
ExhaustValves
Engine — Mechanics
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
SSP248/172SSP248/169
Groove inExhaustFlange
SSP248/174
Engine — Mechanics
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
Engine — Mechanics
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.
SSP248/176
Timing Case
SSP248/128
Vane AdjusterIntake Camshaft
Vane AdjusterExhaust Camshaft
Engine — Mechanics
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.
Valve 1 for CamshaftAdjustment N205
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
SSP248/139
Bank I
Stop RetardAdjuster
IntakeCamshaft
SSP248/135
Oil Duct (bb)
Engine — Mechanics
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
SSP248/138
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
Engine — Mechanics
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
Engine — Mechanics
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
SSP248/137
VibrationDamper
Coolant Pump
PowerSteeringPump
Hydraulic Belt Tensionerwith Deflection Pulley
Air ConditionerCompressor
Engine — Mechanics
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
Engine — Mechanics
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
Valve 1 for CamshaftAdjustment N205
Engine — Mechanics
37
W Engine Oil Circuit Schematic Diagram
Intermediate Shaft
Chain
CentralOil Passage
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Spray Jet
Return Line
Oil Pump
Three ChainTensioners withChain Oil Spray
Valve 1 for CamshaftAdjustment N205
Camshaft Adjuster
TimingBelt Gear(Not Shown)
Oil Sump
Oil Filter/Cooler Module
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Oil Sump of
the W8 Engine
CamshaftAdjustment Valve 1(Exhaust) N318
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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
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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.
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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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SSP248/079
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
SSP248/095
SSP248/081
Engine — Mechanics
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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
SSP248/175
Integrated pockets at the transition to thelower bearing shell ensure a steady supplyof oil to the connecting rod bearingsthrough holes in the crankshaft.
G
Engine — Mechanics
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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
Engine — Mechanics
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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
Engine — Mechanics
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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.
SSP248/114
SSP248/115
Engine — Mechanics
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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
SSP248/111
SSP248/112
SSP248/110
Engine — Mechanics
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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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SSP248/117
SSP248/116
Intake ManifoldLower Section
Engine — Mechanics
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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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SSP248/120
SSP248/119
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
SSP248/122
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
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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.
Engine — Mechanics
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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
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• 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
SSP248/126
Exhaust System of W12 Engine
Tailpipes
Rear Silencer CentralSilencer
PrimarySilencer
Main CatalyticConverter
PrimaryCatalyticConverter
SSP248/127
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
SSP248/148
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
SSP248/140
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.
SSP248/153
SSP248/152
Outlet
Lower TimingCase Cover(Sealing Flange)
Upper TimingCase Cover
Upper TimingCase Cover(Covering Part)
Groove forSealant
Zerk-Type Fitting
SSP248/151
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.
SSP248/191
SSP248/144
SSP248/190
SSP248/191
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.
SSP248/194
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
SSP248/194
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
SSP248/187
Mandrel
For locating the crankshaft.
3242
SSP248/188
Engine and Transmission Holder
VAS 6095
SSP248/195
Notes
59
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]