the w engine concept - 64 pg
TRANSCRIPT
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Volksw agen of Am erica, Inc.
3800 H am lin R oad
A ubu rn H ills, M I 48326
Printed in U .S.A .
February 2002
Se l f -S t udy
C o ur se N u
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Volksw agen of A m erica, Inc.
Service TrainingPrinted in U .S.A .
Printed 2/2002C ourse N um ber 821203
2002 Volksw agen of A m erica, Inc.
A ll rights reserved. Inform ation contained in thisdocum ent is based on the latest inform ationavailable at the tim e of printing and is subject
to the copyright and other intellectual property
rights of Volksw agen of A m erica, Inc., its
affiliated com panies and its licensors. A ll rightsare reserved to m ake changes at any tim e
w ithout notice. N o part of this docum entm ay be reproduced, stored in a retrieval
system , or transm itted in any form or by any
m eans, electronic, m echanical, photocopying,
recording, or otherw ise, nor m ay thesem aterials be m odified or reposted to other
sites, w ithout the prior expressed w rittenperm ission of the publisher.
A ll requests for perm ission to copy and
redistribute inform ation should be referred toVolksw agen of A m erica, Inc.
A lw ays check Technical B ulletins and the
Volksw agen W orldw ide R epair Inform ation
System for inform ation that m ay supersedeany inform ation included in this booklet.
Tradem arks: A ll brand nam es and productnam es used in this m anual are trade nam es,
service m arks, tradem arks, or registered
tradem arks; and are the property of their
respective ow ners.
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Table of Contents
Introduction.............................................................................. 1W Engines, W hat D oes the W Stand For?,
The W Principle, W Engine M odular D esign,
A C om parison
Engine Mechanics.................................................................8W 8 E ngine S pecifications, W 12 E ngine Specifications,C ylinder and C rankshaft C onfiguration, Engine C om ponents,
C hain D rive, C am shaft Tim ing C ontrol, B elt D rive, Engine
Lubrication, Engine C ooling, A ir Supply, Exhaust System
Service..................................................................................... 54Engine Sealing, Engine Tim ing O verview ,Special Tools
Knowledge Assessment ........................................................ 61
The Self-Study Program provides you w ith inform ationregarding designs and functions.
The Self-Study Program is not a Repair Manual.
For m aintenance and repair w ork, alw ays refer to the
current technical literature.
Important/Note!
New !
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Introduction
W Engines
The constantly rising dem ands regarding
perform ance, sm ooth operation, and fuel
econom y have led to the advancem ent ofexisting engines and the developm ent of
new engines.
The new W 8 and W 12 engines byVolksw agen are representative of a new
engine generation the W engines.
SS P248/101
The W engines set exacting dem ands
on design. Large num bers of cylinders
w ere adapted to the extrem elycom pact dim ensions of the engine. In the
process, m ore attention w as paid tolightw eight design.
This Self-Study Program w ill fam iliarize
you w ith the m echanical com ponents andtheir functions in the W engine fam ily.
1
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What Does the W Stand For?
W ith the aim of building even m ore
com pact engines w ith a large num ber of
cylinders, the design features of the V andVR engines w ere com bined to produce the
W engines.
A s w ith the V engines, the cylinders aredistributed to tw o banks. In the W 8 and
W 12 engines, these banks of cylinders arealigned at a V-angle of 72 degrees in
relation to one another. A s in the VR
engine, the cylinders w ithin each bank
m aintain a V-angle of 15 degrees.
W hen the W engine is view ed from the
front, the cylinder arrangem ent looks
like a double-V. Put the tw o Vs of the rightand left cylinder banks together, and you
get a W . This is how the nam e W enginecam e about.
SS P248/104
SS P248/002
SS P248/001
72
15 15
Introduction
2
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Introduction
3
The W Principle
To illustrate the principle of the W engine
cylinder arrangem ent, w e w ill first show
you conventional engine types.
Inline Engines
represent the earliest developm ent levelin engine configuration. The cylinders
are arranged in-line vertically above
the crankshaft.
A dvantage: Sim ple design.
D raw back: Large num bers of cylinders
result in very long engines unsuitable for
transverse m ounting.
V Engines
To m ake engines shorter, the cylinders in
the V engines are arranged at an angle ofbetw een 60 degrees and 120 degrees, w ith
the centerlines of the cylinders intersectingw ith the centerline of the crankshaft.
A dvantage: R elatively short engines.
D raw back: The engines are relatively w ide,
have tw o separate cylinder heads, and
therefore require a m ore com plex designand a larger engine com partm ent volum e.
SS P248/004
SS P248/005
SS P248/003
60120
SS P248/006
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Introduction
5
W Engine Modular Design
Proven com ponents from the m odules of
the VR engine fam ily w ere integrated into
the new W engine concept. The principle isvery sim ple.
Tw o com pact engines from the VR series
are com bined to produce a W engine.The result is a series of com pact gasoline
engines ranging from the W 8 to the W 16.
N um erous com ponents of the VR and W
series are identical:
Valves, valve springs and valve seat
inserts.R oller rocker fingers.
Valve clearance com pensating elem ents.
This allow s Volksw agen to m anufacture
m any parts in high volum es.
SS P248/105
2 x VR 6
72
W 12
6-C ylinder
Inline Engine
6-C ylinder
V Engine
6-C ylinder
VR Engine
In the evolution of the 6-cylinder engine,
the VR 6 engine stands out due to its
com pactness. It is m uch shorter than thecom parable inline engine, and narrow er
than the V engine. C om bining tw o V R 6engines w ith a cylinder angle of 72 degrees
produces a W 12 engine.
A W 16 engine is obtained by joining tw ocylinders to each cylinder bank of a W 12
engine. Splitting the W 16 in the m iddle
leaves tw o W 8 engines. A W 10 engine
consisting of tw o VR 5 engines is also a
possibility. This covers the com plete rangeof W engines.
W 16
SS P248/011
W 16
W 12
2xW 8
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Introduction
6
A Comparison
W hen a conventional 8-cylinder V engine
of com parable displacem ent is com pared to
an 8-cylinder W engine, the latter particularlystands out due to its com pact design and
relatively sm all external dim ensions.
W 8 C rankshaft V8 C rankshaft
SS P248/012
The V8 Engine
SS P248/014
The W8 Engine
This is also reflected in a com parison of the
crankshafts. The com pact design of the 12-
cylinder W engine is highlighted by the factthat it has even sm aller external
dim ensions than a conventional V8 engine.
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Introduction
7
C om paring the crankshaft of a conventionalV12 engine w ith that of a 12-cylinder
W engine em phasizes the advantage.
W 12 Crankshaft
The crankshaft of a V12 engine
of com parable displacem ent is show n.
D epending on the num ber of cylinders,
the W principle therefore saves m aterial
and w eight.
The W12 Engine
SS P248/150
SS P248/013
V12 C rankshaft
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Engine Mechanics
8
W8 Engine Specifications
SS P248/017
Displacement244 cu in (3999 cm 3)
Bore3.307 in (84.0 m m )
Stroke3.550 in (90.168 m m )
Number of cylinders8
Number of cylinder heads2
Offset0.492 in (12.5 m m )
Bank offset0.512 in (13 m m )
V-angle of cylinder headsbetween banks72 degrees
V-angle of cylinders in a bank15 degrees
Number of valves4 per cylinder
Crankshaft journal offset18 degrees
Firing order1-5-4-8-6-3-7-2
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Engine Mechanics
W12 Engine Specifications
SS P248/019
10
Displacement366 cu in (5998 cm 3)
Bore3.307 in (84.0 m m )
Stroke3.550 in (90.168 m m )
Number of cylinders12
Number of cylinder heads2
Offset0.492 in (12.5 m m )
Bank offset0.512 in (13 m m )
V-angle of cylinder headsbetween banks72 degrees
V-angle of cylinders in a bank15 degrees
Number of valves4 per cylinder
Crankshaft journal offset+ 12 degrees
Firing order1-12-5-8-3-10-6-7-2-11-4-9
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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 N m
590 800
516 700
443 600
369 500
295 400
221 300
148 200
74 100
11
Dimensions20.2 in (513 m m ) long;
28.0 in (710 m m ) w ide;
28.1 in (715 m m ) high
WeightA pproxim ately 541 lbs (245 kg)
Maximum power outputA pproxim ately 420 bhp (309 kW )
Maximum torqueA pproxim ately 406 lbs-ft (550 N m )
H orsepow er and torquespecifications are not final at
the tim e of printing. Pleasesee w w w .vw w ebsource.comfor the latest specifications.
Fuel type recommendationPrem ium unleaded gasoline (91 A KI)
Engine management systemB osch M otronic M E 7.1.1 (D ual C ontrolM odule Concept)
Installation positionIn-line
Allocated transmission5H P24 4M otion
Torque
Output
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Engine Mechanics
Cylinder andCrankshaft Configuration
Cylinder OffsetThe alternate cylinders of a bank areoffset from the centerline of the crankshaftand positioned at a very narrow V-angleof 15 degrees.
The com pact W engine w as m ade possibleby arranging tw o banks of cylinders at aV-angle of 72 degrees.
C enter of
C ylinder
C enter of
C ylinder15
O ffset
0.492 in
(12.5 m m )
Left
O ffset
0.492 in
(12.5 m m )
R ight
C enter of
C rankshaft
Fulcrum
Point of Intersection
of C enters of C ylinders
SS P248/186
To provide adequate space for the pistonsin the bottom -dead-center range, it w asnecessary to offset the crankshaft drive.This m eans that the cylinders are offset by0.492 in (12.5 m m ) outw ard relative to thecenter of the crankshaft fulcrum .
This configuration w as first used in theVR 6 engine.
12
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Engine Mechanics
W12 Engine
SS P248/026
1
6127
12
Crankpin Offset
C rankpin offset controls the relativepositions of the pistons in the cylinders foran evenly tim ed firing sequence.The configuration of all Volksw agenW engines is based on a 10-cylinder enginem odel. A ll four-cycle internal com bustionengines com plete their cylinder firingsequences w ithin tw o com pleterevolutions. This am ounts to a crankshaftrotation of 720 degrees.
The W10 engine needs no crankpin offset.
W ith 720 degrees of crankshaft rotation in a10-cylinder engine, the optim um V-anglebetw een the tw o cylinder banks is 72degrees (720 10 = 72). In the 10-cylinderm odel engine there is no need for crankpinoffset to achieve ideal relative pistonpositions for the equally tim ed firing of eachcylinder.
The W8 engine has a crankpin offset of18 degrees.
To achieve the sam e kind of ideal firingsequence tim ing as the 10-cylinder m odel,an 8-cylinder W engine requires 90 degrees
of crankshaft rotation betw een the
3
9
4
10
5
82
11
13
ignition cycle of each cylinder through720 degrees of crankshaft rotation(720 8 = 90). To determ ine the optim umcrankpin offset of 18 degrees for thisengine, the 90 degrees of crankshaftrotation betw een ignition cycles issubtracted from the 72-degree V-angle ofthe cylinder banks.
72 90 = 18
The W12 engine has a crankpin offsetof +12 degrees.
Sim ilarly, a 12-cylinder engine requires
60 degrees of crankshaft rotation betw eenthe ignition cycle of each cylinder through720 degrees of crankshaft rotation(720 12 = 60). For this configuration, todeterm ine the optim um crankpin offset of+ 12 degrees, the 60 degrees of crankshaftrotation betw een ignition cycles issubtracted from the 72-degree V-angle ofthe cylinder banks.
72 60 = +12
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Engine Components
W engines include the follow ing
com ponents:
C ylinder block
C rankcase low er section w ith bearing
support
C rankshaft w ith connecting rods andpistons
B alancing shafts
Engine Mechanics
Cylinder heads
O il sum p and oil pum pC rankshaft drive
Tim ing chain drive
B elt drive for auxiliary com ponents
M ulti-part intake m anifold
W8 Engine M ulti-Part Intake M anifold
SS P248/025
Split O il Sum p
w ith O il Pum p
C rankcase Low er
Section w ithB earing S upport
C rankshaft w ith
C onnecting R ods
and P istons
C ylinder H eads
14
C om bined C ylinder
B lock and C rankcase
U pper Section
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Engine Mechanics
Crankcase Lower Section
The crankcase low er section is a bearing
support w ith integral bearing seats.
The bearing support is also m ade of analum inum alloy. It serves as a fram e
structure for the low er crankshaft m ain
bearing caps. These bearing caps are m ade
of grey cast iron and are em bedded in thebearing support w hen it is cast.
They are located on the thrust side of the
crankshaft and give the crankshaft bearings
the strength they require.
The bearing support is attached to the
crankcase upper section by four bolts per
bearing cap.
W 8 B earing Support
SS P248/029
SS P248/032
C asing O pening Tow ards
D rive of B alancing Shafts
W 12 B earing
Support
SS P248/033
Cast Element inBearing Support
B earingC ap
SS P248/030
16
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Engine Mechanics
Crankshaft
The crankshafts used in the W engines are
m anufactured from forged tem pered steel.
Each pair of connecting rods runs betw eentw o m ain bearings.
The drive gear of the oil pum p (together
w ith the toothed belt pulley for the
balancing shafts on the W 8 engine only)is pressed against the outer m ain bearing
and held in place by the vibration dam per.
The connecting rod journals are arranged
in pairs and in accordance w ith the
crankshaft throw .
W hen the connecting rods areinstalled, the bearing shells m ust
not contact the radii or the edgebetw een the tw o connecting
rod faces.
W8 Crankshaft
SS P248/045
C onnecting R od
Journal w ith
C orner R adii
SS P248/043
C rankshaft Journal
M ainB earing
Journal
O il Pum p G ear
Vibration
D am per
Toothed B elt Pulley for
B alancing Shafts
SS P248/037
Journals for D riving
the O il Pum p and the
B alancing Shaft
M ain
B earing
Journal
C onnecting
R od JournalC hain D rive G ears
SS P248/056
17
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Connecting Rods and Pistons
The connecting rods are m ade of forgedsteel and are only 0.512 inch (13 m m ) thick.They are of a trapezoidal construction and
are cut during the production process.
To ensure better oil exchange, tw o
grooves are m illed in the side faces of
the connecting rod bearing caps. The piston
pin is lubricated through tw o inclined boresin the connecting rod head.
The pistons are m ade of an alum inum -
silicon (A l Si) alloy. The recess in the piston
top surface is very shallow since thecylinder head provides m ost of the
com bustion cham ber volum e. The angle ofthe piston top surface is necessary to
accom m odate the positions of the pistons
in their V configuration.
Each piston carries tw o com pression ringsand an oil control ring. To drain off the oil
w hich collects at the oil control ring, sm alldrainage holes lead from the piston ring
groove to the inside of the piston.
Engine Mechanics
Trapezoidal
Shape
SS P248/048
B ores
G rooves for
O il Exchange
SS P248/047
SS P248/016
D rainage
H oles
Iron C oating for
A lum inum -Silicon
Piston Skirts in
C entral C rankcase SS P248/049
18
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W8 Engine Balancing Shafts
The W 8 engine has tw o balancingshafts to com pensate for the forces ofinertia. The tw o shafts are housed in the
crankcase. The upper balancing shaft
is driven by the crankshaft and a toothed
belt. A gear on the end of the upperbalancing shaft drives the low er
balancing shaft.
The balancing shafts are installed
through tw o holes on the clutch side of
the crankcase.
Engine Mechanics
SS P248/057
A lign m ark on crankshaft drivegear w ith the joint (TD C of 1st cylinder).
SS P248/055
Installation
O penings
D rive G ear on
the C rankshaft
B earings run in crankcase
bushings.
D rive G ear on the
B alancing Shaft
A lign m ark on balancing
shaft drive gear w ith the
m ark on the sealing face
(TD C of 1st cylinder).Tension P ulley
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Engine Mechanics
20
There is a groove at the gear w heel end
of the balancing shaft. The lock plate
engages into this groove, locating thebalancing shafts axially. D uring installation,
the balancing shafts m ust be aligned
w ith regard to the TD C position of the
1st cylinder.
The balancing shafts m ust be rotated so
that the m arks on the balancing shafts are
opposite each other.
Position of
B alancing Shafts
at TD C of
1st Cylinder
G ears of the
B alancing Shafts M arks
Lock P late
SS P248/108
B alancing Shaft I
B alancing Shaft II
Locking
G rooves
SS P248/107
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Two-Mass Flywheel with Clutch
W engines equipped w ith a m anual
transm ission generally have a tw o-m ass
flyw heel.
This flyw heel design prevents torsional
vibration from being transm itted from the
Engine Mechanics
22
C lutch C over
crankshaft to the transm ission through the
flyw heel. If not elim inated, this vibration
w ould adversely affect perform ance.
SS P248/060
SS P248/061
Tw o-M ass
Flyw heel
C lutch D isc
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Engine Mechanics
23
A spring dam per system w ithin the
tw o-m ass flyw heel separates the prim ary
inertia m ass from the secondary inertiam ass so that the torsional vibration
produced by the engine is not transm ittedto the transm ission. O n W engines w ith an
autom atic transm ission, the tw o-m ass
flyw heel is replaced by a converter plate.
The tw o-m ass flyw heel also serves as a
sender w heel for Engine S peed (R PM )
Sensor G 28. Its job is to determ ine the
engine speed and recognize cylinder
num ber 1 together w ith the C am shaftPosition (C M P) Sensor G 40, C am shaftPosition (C M P) Sensor 2 G 163, C am shaft
Position (C M P) Sensor 3 G 300, and
C am shaft Position (C M P) Sensor 4 G 301.
It has a larger tooth gap w hich serves as am arker point. This point is registered by the
Engine S peed (R PM ) Sensor G 28 located
in the transm ission housing during each
revolution of the tw o-m ass flyw heel.
SS P248/062
SS P248/061
Tw o-M ass
Flyw heel
Pulse S ensor
W heel
Larger
Tooth G ap
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Engine Mechanics
24
Cylinder Heads
The W engines have tw o alum inium
cylinder heads w ith tw o overhead
cam shafts apiece.
The injectors are inserted into the
cylinder heads.
C am shaft
B earing
Intake
C am shaftB earing
Exhaust
Cylinder Heads of W8 Engine
SS P248/063
O pening
for Injector
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Engine Mechanics
27
SS P248/170
SS P248/171
Intake
Ports
Exhaust
Ports
Intake M anifoldof W 12 Engine
Cylinder Heads of W12 Engine
Intake
Valves
A ir Supply Intake
ExhaustValves
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Engine Mechanics
28
Secondary Air Ducting System
B esides the coolant and oil ducts in the
cylinder heads, the secondary air is guided
through ducts and bores into the exhaustducts near the exhaust valves. The
secondary air flow s into a duct in thecylinder head through a Secondary A ir
Injection (A IR ) Solenoid Valve N 112.
From here the secondary air is guided
back into the cylinder head through grooves
in the exhaust flange. The secondary airthen flow s through ducts and bores to the
exhaust valves.
O il
R eturn
H oles
B ores Leading to
Exhaust Valve (Inboard)
Exhaust
Valves
(Inboard)
Exhaust
Valves
(O utboard)
B ores Leading
to Exhaust Valve
(O utboard)
Secondary
A ir D uct
C onnection for Secondary
A ir Injection (A IR ) Solenoid
Valve N 112
C oolant
O il D ucts
Secondary Air
SS P248/172SS P248/169
G roove in
Exhaust
Flange
SS P248/174
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Engine Mechanics
30
Camshaft Timing Control
B oth the W 12 engine and the W 8 engine
have continuously adjustable intake
cam shaft tim ing. In this case, continuouslyadjustable m eans that the intake cam shaft
can be advanced or retarded relative to its
neutral position at any angle w ithin a range
of 52 degrees.
The cam shafts are adjusted by hydraulic
cam shaft positioners bolted to their endfaces.
The exhaustcam shaft of the W 12 is alsocontinuously adjustable.
Valve 1 for C am shaftA djustm ent N 205C am shaft A djustm ent
Valve 1 (Exhaust) N 318
The exhaust cam shaft of the W 8 engine is
an exception. It can only be adjusted to the
advanceor retardposition w ithin arange of 22 degrees.
The M otronic Engine C ontrol M odule J220regulates the oil supply to the cam shaft
positioners by controlling the Valve 1 for
C am shaft A djustm ent N 205 and C am shaft
A djustm ent Valve 1 (Exhaust) N 318.
SS P248/176
Tim ing C ase
SS P248/128
Vane A djuster
Intake C am shaft
Vane A djuster
Exhaust C am shaft
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Engine Mechanics
31
System Operation
The follow ing exam ples show the operationof the intake cam shaft adjuster for the rightbank (bank I).
Neutral position
W hen the Valve 1 for C am shaft A djustm entN 205 m oves the adjusting piston into a
central position, this causes both oil ducts
(a and b) and hence the cham bers
(A and B ) on either side of the inner rotor to fill w ith oil. The inner rotor, together w ith
the cam shaft w hich it is rigidly coupled to,now adopts a position in the m iddle of the
adjustm ent range.
Valve 1 for C am shaft
A djustm ent N 205
O il R eturn Passage
Engine O il Pressure
A djusting Piston
D irection of R otation of D rive
O il D uct (b)
O il D uct (a)
Exhaust C am shaft
A nnular D ucts
Inner R otor
(R igidly C oupled to C am shaft)
C ham ber (A )
C ham ber (B )
O uter R otor
(C oupled to Tim ing C hain)
O il D uct (aa)
O il R eturn Passage
C ham ber (B )
Inner R otor
O uter R otor
Stop
A dvance
A djuster
C ham ber (A )
C am shaft
N eutral
SS P248/139
Bank I
Stop R etard
A djuster
Intake
C am shaft
SS P248/135
O il D uct (bb)
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Engine Mechanics
32
Retard adjustment
The Valve 1 for C am shaft A djustm ent N 205guides the oil into the oil duct (b). The oilflow s from channel (b) through the annular
groove and cam shaft and the bores (bb) tothe cham bers (B ) of the cam shaft adjuster.
Exhaust C am shaft
SS P248/138
W hen the oil enters the cham bers (B ), the
inner rotor is rotated against the direction of
rotation of the drive, adjusting the cam shaftin the retard direction. The oil is forced out
of the cham bers (A ) through the bores (aa).
It flow s back into the cylinder head through
the cam shaft and duct (a).
C am shaft
R etard R etard Stop
C ham ber (B )
C ham ber (A )
O uter R otor
Inner R otor
Intake C am shaft
Bank I
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Engine Mechanics
33
Exhaust C am shaft
Advance adjustment
To rotate the inner rotor forw ard, theadjusting piston housed w ithin the Valve 1
for C am shaft A djustm ent N 205 adjusts
itself so that the oil duct (a) is put under oil
pressure. A s a result, the oil flow s into the
cham ber (A ), advancing the inner rotor.
C ham ber B is sim ultaneously bled throughoil ducts (bb and b) to ensure a quick
response.
SS P248/137
C am shaft
Advance
Advance
Stop
C ham ber (B )
C ham ber (A )
O uter R otor
Inner R otor
Intake C am shaft
Bank I
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Engine Mechanics
35
In the W 12 engine, the hydraulic belt
tensioner and deflection pulley are attached
to the air conditioner com pressor bracket.
G enerator C
H ydraulic B elt
Tensioner
D eflection
Pulley
D eflection Pulley
C oolant Pum p
C rankshaft Pulley
w ith Vibration D am per
SS P248/078
D eflection
Pulley
Pow er
Steering
P um p
A ir C onditioner
C om pressor
Belt Drive of the W12 Engine used by Audi
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Engine Mechanics
36
Engine Lubrication
The oil is draw n out of the oil pan by the oil
pum p and flow s to the central oil passage
through the external oil filter/cooler m odule.
The m ain crankshaft bearings are supplied
w ith pressurized oil by the central oil
passage; the central oil duct is suppliedw ith pressurized oil by a riser.
The oil flow s from the central oil duct to thespray jets for piston cooling, and then from
there to the cylinder heads through risers
equipped w ith non-return valves.
The oil also flow s to the interm ediate shaft,
to the engine tim ing gear and to the chain
tensioner.
In the cylinder heads, the oil flow s along
ducts to the cam shaft adjusters and the
cam shaft bearings.
The return lines guide the oil back into the
oil sum p.
Oil Circuit of the W12 Engine
C am shaft A djustm ent
Valve 1 (Exhaust) N 318
O il Sum p
U pper Section
O il Sum p
Low er Section SS P248/091
R eturn
D ucts
Spray Jets for
Piston C ooling
C am shaft
A djuster
C rankshaft
B earing
H ydraulic Elem ents
C am shaft B earing
C entral O il D uctR iser
C entral O il Passage
O il Pum p
D rive G ear
Valve 1 for C am shaft
A djustm ent N 205
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Engine Mechanics
37
W Engine Oil Circuit Schematic Diagram
Interm ediate Shaft
C hain
C entralO il Passage
SS P248/083
Spray Jet
R eturn Line
O il Pum p
Three C hain
Tensioners w ith
C hain O il Spray
Valve 1 for C am shaft
A djustm ent N 205
C am shaft A djuster
Tim ing
B elt G ear
(N ot Show n)
O il Sum p
O il Filter/C ooler M odule
SS P248/094
Oil Sump of
the W8 Engine
C am shaft
A djustm ent Valve 1
(Exhaust) N 318
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Engine Mechanics
38
The Wet-Sump Principle
The W 8 and W 12 engine for VW m odelshave a w et-sum p lubrication system .The W 12 engine for A udi m odels has a
dry-sum p lubrication system .
In the w et-sum p lubrication system , the
entire oil supply is retained in the oil sum p.
The single-stage oil pum p draw s the oil out
of the w et sum p through the intake line
Wet-Sump Lubrication Systemof the W8 Engine
and im m ediately returns it to the engine
after it has cooled dow n and has been
filtered.
In contrast to the dry-sum p, the job of theoil sum p w ith w et sum p is to retain the
entire oil supply. A s a result, it has a larger
volum e w hich affects the overall height of
the engine.
Single-Stage O il Pum pO il Filter and C ooler M odule
SS P248/137
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Engine Mechanics
39
The Dry-Sump Principle (Audi only)
In the dry-sum p lubrication system , theentire oil supply is retained in an external
reservoir, and not in the oil sum p.
To facilitate this, the oil pum p is of three-
stage design. Tw o stages draw the oil out
of the oil sum p at various points and pum p
it into the reservoir.
Dry-Sump Lubrication System of
the W12 Engine in the Audi A8
SS P248/088
R eservoir
C ooler
Filter
Three-Stage O il Pum p
The third stage (discharge stage) returns
the oil from the reservoir to the engine
through the oil cooler and the oil filter. The
oil sum p can be kept sm all and flat due to
its low er oil volum e, w ith the result that the
engine has a sm aller overall height.
This requires a slightly m ore com plex design.
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Engine Mechanics
41
The oil pum p is m ounted from below and
bolted to the bearing support.
Oil Filter and Cooler Module
The oil circuit of the W engine has an
external oil filter and cooler m odule. Thisallow s the engine to be m ore easily
adaptable to the varying am ounts of space
available in the various vehicle m odels. Theoil filter is designed so that a filter elem ent
can be replaced by service personnel.
Oil Filter andCooler Moduleof the W8
SS P248/095
SS P248/081
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Engine Mechanics
42
Piston Spray J ets
The oil is guided from the central oilpassage of the crankcase upper section tosm all nozzles at the base of the cylinder
bores. H ere, the oil is sprayed below thepistons to lubricate the piston contact faces
and piston pins, and cool the pistons.
Crankshaft Bearing Lubrication
The oil is routed through holes from the
central oil passage to the crankshaft.Then it is forced through grooves in the
backs of the low er bearing shells to the
upper bearing shells. There it reachesthe crankshaft through five holes in the
upper bearing shell.
SS P248/092
O il Supply
B earing S upport
G roove on the B ack
of the B earing Shells
U pper B earing Shell
SS P248/093
C rankshaft
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G
Engine Mechanics
44
Engine Cooling
The coolant circuit is filled w ith VW G 12
coolant. The coolant is pum ped from
the central coolant duct in the crankcaseupper section and into the cylinder heads.
B affles ensure that all cylinders are
sw ept evenly. A t the sam e tim e, thecoolant flow is redirected from the
G enerator CEngine C oolant
Tem perature
(EC T) Sensor
(O n R adiator) G 83Sm all C ooling C ircuit
Large C ooling C ircuit
R ibbed V-B elt
SS P248/098
M ap C ontrolled
Engine C ooling
Therm ostat F265 Radiator
Expansion
Tank
O il C ooler
Engine C oolant
Tem perature (EC T)
Sensor (O n Engine) G 82
C oolant
Pum p
Coolant Circuit of W8 Engine
exhaust side of the com bustion cham bers
tow ards the intake side.
The coolant circuit is subdivided into a sm all
cooling circuit, in w hich the coolant is only
routed w ithin the engine block, and a large
cooling circuit that includes the radiator andengine oil cooler.
H eating
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G
Engine Mechanics
45
Coolant Circuit of W12 Engine
G enerator C
Expansion
Tank
Engine C oolant
Tem perature
(EC T) Sensor
(O n Engine) G 82
SS P248/099
Engine C oolantTem perature (EC T)
Sensor (O n
R adiator) G 83
Transm ission
O il C ooler
Left H eat
Exchanger
Engine C oolant
Tw o-W ay Vacuum
Valve N 147 A uxiliary
R adiator
R adiator
R ight H eat
Exchanger
M ap C ontrolled
Engine C ooling
Therm ostat F265
Sm all C ooling C ircuit
Large C ooling C ircuit
C oolant Pum p
Engine
O il C ooler
A uxiliary
H eater
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Engine Mechanics
46
Coolant Flow in the Cylinder Heads
W hen the coolant m oves through the
crankcase and into the tw o cylinder heads,
tw o thirds of the coolant volum e is guidedto the outside and one third to the inside of
the cylinder heads.
This principle helps toprovide even cooling,
and is know n ascross-cooling.
C oolant flow s through the cylinder heads
from the exhaust side to the intake side.
This results in very good tem peratureequalization as w ell as effective cooling ofthe outlet w ebs and spark plugs.
SS P248/114
SS P248/115
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Engine Mechanics
47
Coolant Pump with Pump Gear
In both W engines, the coolant pum p islocated in the cylinder block at the face
end. It is m ounted directly upstream of thecentral coolant duct and is driven by the
ribbed V-belt.
Electronically Controlled Engine Cooling
Sw itching from the sm all cooling circuit to
the large cooling circuit is controlled by anelectrically actuated M ap C ontrolled EngineC ooling Therm ostat F265 in the therm ostat
housing. In the W 8 and W 12 engine, this
valve is installed in the crankcase upper
section from above. To replace this valve, itis necessary to rem ove the intake m anifold.
B y electrically heating the w axtherm ocouple in the M ap C ontrolled Engine
C ooling Therm ostat F265, it is possible to
control the sw itching point and coolant
tem perature. C haracteristic control m apsare stored in the M otronic Engine C ontrol
M odule J220. They m ake it possiblefor the engine to reach the desired
tem perature in accordance w ith the
engines operating requirem ents.
W ax Therm ocouple
Lifting Pin
H eating
R esistor
SS P248/179
Map ControlledEngine CoolingThermostat F265
SS P248/111
SS P248/112
SS P248/110
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Engine Mechanics
48
Air Supply
A ir is supplied through a tapered intake
pipe. It is of a four-part design and is m ade
of an alum inium alloy.
The intake m anifold low er section is bolted
to the cylinder heads betw een the tw o
cylinder banks. The larger intake m anifold
upper section is m ounted to the low ersection. The intake m anifold upper section
is designed so that the m anifolds for bank Iand II can be rem oved separately. This
m akes it easier to gain access to the
individual ignition coils and spark plugs,
for exam ple.In the W 8 engine, the intake air for both
m anifolds is guided by a Throttle ValveC ontrol M odule J338.
Throttle
Valve C ontrol
M odule J338
Intake M anifold
U pper Section
M anifold, B ank I M anifold, B ank II
W8 Engine
SS P248/118
SS P248/117
SS P248/116
Intake M anifold
Low er Section
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Engine Mechanics
49
The intake m anifold used in the W 12
engine is m ade of m agnesium alloy. U nlike
the W 8 engine, each of the m anifolds iscoupled to a separate Throttle Valve C ontrol
M odule J338.
Intake M anifold
U pper Section
W12 Engine
Intake M anifold
Low er Section
Throttle Valve
C ontrol M odule J338
SS P248/121
SS P248/120
SS P248/119
M anifold,
B ank I
M anifold,
B ank II
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Crankcase Breather
The diaphragm valve lim its the vacuum inthe crankcase irrespective of the intakepipe vacuum , allow ing the cleaned
crankcase exhaust gases (blow -by) to berouted continuously into the intake m anifold
SS P248/122
and burned in the cylinders during the
com bustion cycle. N o oil is entrained in
the process. The oil separator rem ovesthe oil particles from the blow -by gas.
The separated oil is then returned tothe oil sum p.
W8 Engine
O il Separator
D iaphragm Valve
Engine Mechanics
50
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B ecause the W 12 engine has a
double flow intake m anifold, each
bank has a side diaphragm valveand an oil separator.
D iaphragm
Valve, Left
D iaphragm
Valve, R ight
O il Separator
SS P248/129
O il Separator
SS P248/123
W12 Engine
Engine Mechanics
51
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Exhaust System
The W 8 engine has an exhaust m anifold
w ith a catalytic converter for each cylinder
head. A total of four oxygen sensors aretherefore required for em ission control.
H eated O xygen Sensor (H O 2S) G 39
H eated O xygen Sensor (H O 2S) 2 G 108
C entral Silencer
Exhaust System of W8 Engine
SS P248/125
Tailpipes
R ear Silencer Prim arySilencer
C atalytic
C onverter
M anifold
SS P248/124
O xygen Sensor (O 2S) B ehind Three-W ay
C atalytic Converter (TW C ) G 130
O xygen S ensor (O 2S) 2 B ehind Three-
W ay C atalytic C onverter (TW C ) G 131
The exhaust system has a prim ary silencer
and a rear silencer for each bank, as w ell asa com m on central silencer.
Engine Mechanics
52
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The W 12 engine has tw o exhaust
m anifolds for each cylinder head. Each
of these exhaust m anifolds is connected toits ow n prim ary catalytic converter located
near the engine. The tw o exhaust pipes ofeach bank then m erge on a m ain catalytic
converter. The exhaust system has a
prim ary silencer, an interm ediate silencer
and a rear silencer for each bank.
Four prim ary catalytic converters and tw o
m ain catalytic converters help to achieve an
effective reduction in em issions.
To m onitor m ixture com bustion andto optim ize pollutant em ission reduction,use is m ade of a total of eight oxygen
sensors, four each before and after the
prim ary catalytic converters.
Heated O xygen Sensor (H O 2S) G 39
Heated O xygen Sensor (H O 2S) 2 G 108
Engine Mechanics
53
O xygen Sensor (O 2S) B ehind Three-W ay
C atalytic C onverter (TW C ) G 130
O xygen Sensor (O 2S) 2 B ehind Three-
W ay C atalytic C onverter (TW C ) G 131
H eated O xygen Sensor (H O 2S) 3 G 285
H eated O xygen Sensor (H O 2S) 4 G 286
O xygen Sensor (O 2S) 3 B ehind Three-W ay C atalytic C onverter (TW C ) G 287
O xygen Sensor (O 2S) 4 B ehind Three-
W ay C atalytic C onverter (TW C ) G 288
M anifold
Prim ary C atalytic C onverter
SS P248/126
Exhaust System of W12 Engine
Tailpipes
R ear Silencer C entral
Silencer
Prim ary
Silencer
M ain C atalytic
C onverter
Prim ary
C atalytic
C onverter
SS P248/127
Exhaust Manifold
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Engine Sealing
Each of the cylinder heads is sealed off
from the valve covers by a rubber gasket,
from the contact faces of the intakem anifold by an elastom er gasket, from
the exhaust m anifolds by a tw o-layerem bossed m etal gasket, and from
the crankcase by a m ultilayer em bossed
m etal gasket.
The gasket betw een the bearing support
and the oil sum p upper section is also
designed as a single layer em bossedm etal gasket.
The oil pan upper section and low er
section as w ell as the crankcase uppersection and the bearing support are
sealed by a liquid gasket.
M ultilayer M etal/Elastom er Com posite
G asket betw een C ylinder H ead and
Intake M anifold C ontact Face
SS P248/148
Liquid G asket betw een O il Sum p
U pper Section and Low er Section
C oated Em bossed M etal
G asket betw een O il Sum p
U pper Section and
B earing S upport
Liquid G asket betw een
C rankcase U pper Section
and B earing Support
R ubber G asket betw eenC ylinder H eads and
Valve C overs
Tw o-Layer Em bossed M etal
G asket betw een C ylinder
H eads and E xhaust M anifold
M ultilayer Em bossed M etal
G asket betw een C ylinder
H eads and Crankcase
Service
54
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Liquid Gaskets
A pplication of the liquid gasket sealant to
m ost surfaces is C N C -controlled in order to
ensure a constant sealant supply.
The liquid gasket betw een the low er tim ingcase cover and the upper tim ing case cover
is applied according to a different principle.
In this case, the parts are first bolted, then
the sealant is injected into the groove in the
SS P248/140
upper tim ing case cover through zerk-type
fittings (sealing injection system ).
W hen enough liquid sealant has been
injected, the excess sealant is discharged
from the openings on the end of the tim ing
case cover. The zerk-type fittings rem ain inthe housing after injecting the sealant.
H ow ever, they have to be replaced w henrepairing the gasket.
SS P248/153
SS P248/152
O utlet
Low er Tim ing
C ase Cover
(Sealing Flange)
U pper Tim ing
C ase C over
U pper Tim ing
C ase C over
(C overing Part)
G roove for
Sealant
Zerk-Type Fitting
SS P248/151
Zerk-Type Fitting for
Liquid G asket Installation
Service
55
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Engine Timing Overview
If it is necessary to disassem ble the
cylinder heads, the engine tim ing m ust be
reset. These are the im portant m arkersw hen the piston of the first cylinder is at
top dead center.
SS P248/191
SS P248/144
SS P248/190
SS P248/191
A djust intake
cam shaft to
retard.
A djust exhaust
cam shaft to
advance.
Put copper coloredchain link on arrow
of bank II.
Put copper coloredchain link on arrow
of bank II.
Bank II
Place the coppe
colored chain lin
on the m arked
tooth of the
interm ediate sh
and the bore ho
in the housing.
Service
56
Insert the m andrel for holding the crankshaft
into the threaded hole in the housing: piston
in 1st cylinder at top dead center.
For a description of the exact
procedure for setting the engine
tim ing, please refer to therelevant R epair M anual.
Position the m arker on the vibration
dam per on the housing joint: piston in
1st cylinder at top dead center.
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W hen placing on the low er
tim ing chain copper link, set
the colored chain link on the
m arked tooth and the m arked
tooth on the housing joint:
piston in 1st cylinder at top
dead center.
SS P248/194
Exhaust cam shaft
retard adjustm ent.
Place copper
colored chain link
on arrow of bank II.
Place copper
colored chain link
on arrow of bank I.
M arked ToothN orm al ToothSS P248/178
Bank I
SS P248/194
Intake cam shaft
advance adjustm ent.
Service
57
Insert cam shaft rule for
aligning the cam shafts.
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Special Tools
Camshaft Alignment Rule
For aligning the cam shafts w hen settingthe engine tim ing.
T10068
Service
58
SS P248/187
Mandrel
For locating the crankshaft.
3242
SS P248/188
Engine and Transmission Holder
VAS 6095
SS P248/195
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Notes
59
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Notes
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Knowledge Assessment
A n on-line Know ledge A ssessm ent (exam ) is available for this Self-Study Program .
This Know ledge A ssessm ent m ay or m ay not be required for C ertification. You can find thisKnow ledge A ssessm ent under the C ertification 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]