the w engine concept - 64 pg

8/10/2019 The W Engine Concept - 64 Pg

1/64

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

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A ll requests for perm ission to copy and

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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,

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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

19


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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


27/64

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


28/64


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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


36/64

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


39/64

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


A djustm ent N 205


40/64

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


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


41/64

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


42/64

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.


43/64


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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


45/64

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


46/64


47/64

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


48/64

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


49/64

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


50/64

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


51/64

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


52/64

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


53/64

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


54/64

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


55/64

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


56/64

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-




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-


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


57/64

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


58/64

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


59/64

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.


60/64

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.


61/64

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


62/64

Notes

59


63/6460

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]

the w engine concept - 64 pg

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