Tài liệu đào tạo động cơ V TDI trên ô tô Audi

Audi 4.0l V8 TDI engine
of EA898 series
Self Study Programme 652

For internal use only

Audi Service Training


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Ξ Contents

As a source of superior driving power in the premium segment, the
V8 TDI engine offers high traction and ample power reserves in any
driving situation. The new V8 TDI continues to follow this course.
An electric powered compressor (EPC) contributes to good driveaway performance.

In addition to the main development targets, a key aim was to
create a standard engine for all markets. The different emission
standards are differentiated by the vehicle exhaust system.
The state-of-the-art technologies described in this self study
programme have been implemented with the following aims:

The derivatives of the new engine generation will be available with
the following features:
• Power spread from 310 kW to 320 kW
• Maximum torque of up to 900 Nm
• Certification to EU6 (ZG) emission standard

• Certification to EU5 and ULEV125 emission standards for
export markets

• High engine power output and high torque for sporty positioning in an S model
• Low fuel consumption for high efficiency in the high-performance segment
• Low and sustainable emissions certified to EU6, EU5 and
ULEV125 exhaust emission standards for world-wide use
• Spontaneous power delivery and optimal drive-away performance as well as a high level of comfort

Learning objectives of this self study programme:
This self study programme describes the design and function of
the 4.0l V8 TDI engine of the EA908 engine series.
After you have completed this self study programme you will be
able to answer the following questions:

2

652_002

• What is the structure of the components located in the
inner V?
• How is the coolant pump driven and how can it be switched
off?
• What is the voltage applied to the electric powered compressor (EPC)?
• How does the charge pressure control system work?


Contents
Introduction
Brief description and special features _ ____________________________________________________________________________________________________________________ 4

Specifications _________________________________________________________________________________________________________________________________________________ 6
Engine concept with "inner hot side" _ _____________________________________________________________________________________________________________________ 7

Engine mechanicals
Engine block __________________________________________________________________________________________________________________________________________________ 8
Timing gear __________________________________________________________________________________________________________________________________________________ 10
Cylinder head ________________________________________________________________________________________________________________________________________________ 12
Audi valvelift system (AVS) _________________________________________________________________________________________________________________________________ 13
Crankcase ventilation system ______________________________________________________________________________________________________________________________ 14

Oil supply
System overview ____________________________________________________________________________________________________________________________________________ 16
Oil circuit _____________________________________________________________________________________________________________________________________________________ 18
Oil filter ______________________________________________________________________________________________________________________________________________________ 18
Oil pump _____________________________________________________________________________________________________________________________________________________ 19
Oil cooling _ __________________________________________________________________________________________________________________________________________________ 19

Exhaust gas recirculation
Overview _____________________________________________________________________________________________________________________________________________________ 20
EGR cooler ___________________________________________________________________________________________________________________________________________________ 21

Cooling system
System overview ____________________________________________________________________________________________________________________________________________ 22
Coolant module _____________________________________________________________________________________________________________________________________________ 24

Air supply and turbocharging
Combined design cover with integrated air filter ________________________________________________________________________________________________________ 27
Intake system _______________________________________________________________________________________________________________________________________________ 28
Intake manifold header ____________________________________________________________________________________________________________________________________ 29
Electric powered compressor (EPC) _______________________________________________________________________________________________________________________ 30

48-volt electrical subsystem _______________________________________________________________________________________________________________________________ 33
Charging group ______________________________________________________________________________________________________________________________________________ 34
Charge-air pressure control ________________________________________________________________________________________________________________________________ 35

Fuel system
System overview ____________________________________________________________________________________________________________________________________________ 38
High-pressure fuel system _________________________________________________________________________________________________________________________________ 40
SCR system __________________________________________________________________________________________________________________________________________________ 41

Exhaust system
Overview _____________________________________________________________________________________________________________________________________________________ 42
Exhaust gas treatment module ____________________________________________________________________________________________________________________________ 42
Ammonia slip catalyst (version for NAR) _________________________________________________________________________________________________________________ 43

Engine management
System overview ____________________________________________________________________________________________________________________________________________ 44

Service
Special tools and workshop equipment ___________________________________________________________________________________________________________________ 46

Appendix
Self study programmes _____________________________________________________________________________________________________________________________________ 47

The self study programme teaches a basic understanding of the design and mode of operation of new models,
new automotive components or new technologies.
It is not a repair manual! Figures are given for explanatory purposes only and refer to the data valid at the
time of preparation of the SSP.
This content is not updated.
For further information about maintenance and repair work, always refer to the current technical literature.

Note

Reference

3


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Ξ Contents

Introduction
Brief description and special features
Synergy with the 3.0l V6 TDI Gen2 evo

CO2 reduction measures

•
•
•
•

• Innovative Thermal Management (ITM) 2
• Concept of a fully variable oil pump
• Friction reduction through the use of coated piston rings and
reduced preload
• Friction reduction in the exhaust turbocharger rotor
• Use of engine oil 0W-20

Concept of the timing gear
Concept of the cylinder heads
Concept of the thermal management system
Concept of the single-scroll
high-pressure exhaust gas recirculation system

Oil pump

Audi valvelift system (AVS)

• Combined oil/vacuum pump integrated in the oil pan
• Fully variable oil pump flow rate control

• Located at the intake and exhaust ends

Chain drive for
oil/vacuum pump

652_032

oil/vacuum pump

652_021

Integrated oil filter
• Installed in the oil pan behind a cover

Oil filter

652_022

Active engine mountings
• Engine oscillation reduction

652_088
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High-pressure fuel system
• Common rail injection system which delivers injection pressures of up to
2500 bar

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Combined exhaust aftertreatment system
• Common NOx oxidation catalyst (NOC) and SCR-coated diesel
particulate filter installed in the inner V, i.e. near the engine

652_017
652_023

Turbocharging
• Combination of active and passive turbochargers
• Inner hot side
• Switching of passive turbocharger via

AVS on exhaust valve side

Active turbocharger

Passive turbocharger

652_019

Electric powered
compressor (EPC)
• Complementary to conventional exhaust turbochargers
• Powered by 48-volt electrical subsystem

652_015

652_024
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Specifications
Torque-power curve of 4.0l V8 FDI engine EA898
(engine code CZAC)
  Power output in kW
  Torque in Nm

652_050

The engraved engine code is located at the front left below the
cylinder head on the protruding edge of the engine block as seen in
the direction of travel.

Features

Specifications

Engine code

CZAC

Type

8-cylinder engine with 90° V angle

Displacement in cm

3956

Stroke in mm

91.4

Bore in mm

83.0

Number of valves per cylinder

4

Firing order

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

Compression ratio

16.0 : 1

Power output in kW at rpm

320 at 3750 - 5000

Torque in Nm at rpm

900 at 1000 - 3250

Fuel type

Diesel to EN 590

Turbocharging

VTG, active and passive turbochargers, e-actuator,
electric powered compressor (EPC)

Engine management

Bosch CRS 3.25

Maximum injection pressure in bar

2500 bar

Exhaust gas treatment

NOC (NOx oxidation catalyst), SCR-coated diesel particulate filter
with integrated ammonia slip catalyst

Emission standard

EU 6 (ZG)

CO2 emissions in g/km

189 – 1981)

3

1)

6

Engine speed [rpm]

Depending on tyre size.

652_007


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Engine concept with "inner hot side"
The exhaust turbocharger and the exhaust gas recirculation system
are integrated in the inner V of the engine. This compact layout
follows a strict multi-level architecture which, thanks to a twinscroll exhaust manifold system, allows short gas flow paths and
close-coupling of the exhaust gas aftertreatment system. This
concept, with a "hot side" in the inner V, provides the basis for

meeting fuel economy and emission targets. The exhaust gas
recirculation system is located on the lowest level of the inner V.
The EGR cooler with U-shaped throughflow, pneumatic EGR bypass
valve and electric controlled EGR valve (exhaust gas recirculation
valve GX5) has been optimised for minimal pressure loss.

Components in the inner V
Exhaust manifold

Charging group

Active turbocharger

Passive turbocharger

Exhaust gas recirculation

652_044

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Engine mechanicals
Engine block
Engine block GJV450 is a completely redesigned sand-core package
casting. The positioning of the "hot side" in the inner V and the
separate head-block cooling system have to a large extent defined
the geometry of the engine block.
The engine block has been designed with a systematic focus on
reducing wall thickness The complex part of the media supply
system to the oil/coolant heat exchangers is now separate from
the engine block and integrated in a lightweight aluminium transfer plate.
The split head block cooling configuration allows the coolant to
stand inside the engine block at cold start, which results in ever
faster warming up thanks to the low volume of the water jacket.
The cylinder liners are plate-honed to attain an optimal cylinder
shape during engine operation. This process is a basic requirement

for reliable functioning of the piston rings with a low preload and
is a key factor contributing to an optimal friction balance.

Oil filter integrated
in the oil pan

Pistons
For reasons of friction and strength, the aluminium pistons with
salt-core cooling port are designed as sleeve pistons with a DLC1)coated gudgeon pin. After casting and premachining, the highly
stressed bowl rim is re-melted by means of laser energy to produce
the finest and strongest possible aluminium microstructure.
The piston ring assembly was designed with a special emphasis on
reduced friction. For example, lower piston ring preloads and
piston ring heights are used. A combined system of PVD (physical
vapour deposition) and DLC1) layers provides the required wear
resistance of the first ring (control ring).

Re-melted bowl
rim

Salt-core cooling
duct

DLC1) coated
gudgeon pin

1)

8

 LC stands for Diamond like Carbon, an amorphous carbon.
D
These strata exhibit very high hardness and are noted for having
very low dry coefficients of friction. They can be identified by
their glossy, black-gray surface.

Pin bore bushing

652_026


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Engine block

Coolant pump drive sprocket

Oil cooler
(oil/coolant heat exchanger)

Oil/vacuum pump

652_025

Transfer plate
The area to the oil/coolant heat exchangers has been separated

from the engine block and integrated into a lightweight aluminium
transfer plate.
Transfer plate

Oil/coolant
heat exchanger 2

Oil/coolant
heat exchanger 1

652_008
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Timing gear
The layout for the new V8 TDI engine has been taken from the V6
TDI engine family. The timing drive is, therefore, located on the
flywheel side. To meet the high dynamic requirements of the
high-pressure pump during use of the 2500 bar injection system,
the chain drive for the high-pressure fuel pump is configured as a
torsionally rigid twin-shaft drive which eliminates resonance and
high chain forces across the entire rev band.

In this engine the oil/vacuum tandem pump flange-mounted to

the oil pan is driven directly from the front end of the crankshaft
via a separate chain track.

Previous
chain drive

New-generation
chain drive

652_027

High pressure fuel pump

Chain drive
Fuel pump

Drive shaft
Coolant pump
Timing gear
Chain drive
Oil/vacuum pump

Oil/vacuum pump

652_028
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Camshaft drive
An intermediate gear mounted in the cylinder head provides a 2:1
ratio without the need for large camshaft sprockets. Taking this
intermediate gear as the starting point, camshaft drive is provided
by a downstream double gear-wheel stage with each gear wheel
having backlash compensation for acoustic reasons. To minimise

friction in these additional bearing points, the intermediate gear
mounting takes the form of a needle bearing. To provide greater
robustness in terms of oil quality and different oil viscosities, the
Audi V configuration diesel engines exclusively use bush chains
with chrome-plated pins.

Spur gear step with
backlash compensation

Support for
omega spring
connecting to
fixed gear
Idler gear

Sprocket
Omega spring

Needle bearing

Fixed gear
652_029

Idler

Backlash compensation
Recess in the fixed gear

Backlash is compensated by the omega spring, which engages the
recess in the fixed gear and is preloaded by a spring guide in the
idler.
When the camshaft gear is installed, it is relieved of stress by an
excentric bolt and engages the drive wheel with a degree of play.
On completion of assembly, the excentric bolt is removed. The
spring force rotates the two gears towards each other, and the
gear runs without backlash in the drive sprocket.

Omega spring

Hole for insertion of the
excentric bolt during
assembly

Snap ring
Camshaft

Fixed gear

Idler

652_074
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Cylinder head
The high demands imposed on the cylinder head in terms of power
output and maximum cylinder pressure have been met by means of
an axle-parallel, symmetrical valve star and a two-part water
jacket.
In order to eliminate micro-notching effects in high-stress zones,
the coolant jacket and the intake ducts have been optimised with
respect to their parting burr characteristics. The objective was to

eliminate mould parting burrs from highly stressed areas and to
allow these areas to be deburred reliably and automatically.
The structural design of the cylinder head has been adapted to the
engine concept with the "hot side" of the cylinder head located in
the inner V. In conjunction with other structural improvements,
this makes both cylinder heads about 7.0 kg lighter than in the
predecessor engine.

Intake cam adjuster

Fuel injector

Movable cam
element

Roller-type cam
follower
Exhaust duct to
passive turbocharger
Glow plug

Exhaust duct to
active turbocharger

652_030

Cooling jacket
Upper coolant jacket

Thanks to very fast flow rates, the lower water jacket ensures
intensive cooling of the combustion chamber plate and the highly
stressed valve webs. Despite the gain in performance, web temperatures have been reduced by as much as 30° C compared to the
predecessor engine with a single-part water jacket.
In the upper water jacket requiring less cooling, slow flow rates
prevail in order to minimise the water-side pressure losses.

Lower coolant jacket
652_031

Vent duct

If leaks occur in the area of the injector ring seal, a vent duct
allows the combustion pressure to escape. This duct is integrated
in the cylinder head above the intake module.
It prevents excess pressure from the combustion chamber escaping via the crankcase ventilation system to the compressor side of
the turbocharger and causing the turbocharger to malfunction, or
damaging the ring seals or blowing them out of the crankcase.

Vent duct
12

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Audi valvelift system (AVS)
The Audi valvelift system (AVS) is the core element of the multistage turbocharging system. The system had been used previously
in the petrol engines of the VW Group and has been improved to
meet the general operating requirements of the diesel engine.
Due to the position of the injectors and the alignment of the valves
perpendicular to the combustion chamber plate, the basic shaft of
the AVS is mounted between the individual cylinders. The basic
shaft has a spline which accommodates the individual, axially
displaceable cam elements. The pins of the electromagnetic
actuator (cam adjuster) engage the gate of the cam element and
move it axially between the two cam shift positions. Two different

cam contours are used on the intake side to vary event duration

with the aim of maximising drive-way performance while generating the required power output by means of long valve opening
times, short valve timings for drive-away performance (opening
angle of 160 crank angle degrees) and long valve timings for
power (opening angle of 185 crank angle degrees).
Thanks to variable intake valve timing, it has been possible to
achieve an optimised intake valve lift curve which provides good
response at low engine speeds and volumetric efficiency at high
engine speeds. This combination, together with leakage-free
switch-over between the two exhaust turbochargers and variable
exhaust valve timing, results in significantly better spontaneity.

Intake end

Exhaust end
Intake cam adjuster
Injector
Cam element

Cam element

Exhaust cam adjuster

Glow plug

Active exhaust valve
for multi-stage
charging

163 crank
angle deg.

652_075

652_032
185 crank
angle deg.

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Crankcase ventilation system
The 4.0l V8 TDI engine is equipped with an efficient crankcase
ventilation system consisting of a crankcase breather module and
blow-by gas ducts leading into the cylinder head covers.
The blow-by gases rising up out of the crankcase are collected at
the centre of the cylinder head covers and ducted through the
coarse oil separator. This separator consists of multiple ascending
steps (settling chambers) which are responsible for initial separation of the oil and air in the blow-by gases. The blow-by gases
subsequently reach the fine oil separators, of which there is one in

the left cylinder head cover and two in the crankcase breather
module. The blow-by gases are ducted through a labyrinth into the

two fine oil separators with swirls, which are installed horizontally
and vertically in an enclosed housing. The remaining oil residues
are thereby separated.
The separated oil flows along several discharge ducts and into the
oil pan above the oil level. The oil-free blow-by gases flow through
the pressure control valve to the intake end of the active turbocharger and are admitted into the combustion chamber.

Overview
Treated blow-by gases to the intake end
of the active turbocharger

Fine oil separator

Crankcase breather module
with 2 fine oil separators

Oil return

Vent tube with
fixed connection

Cylinder head cover with
integrated fine oil separator

652_009
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Crankcase breather module
The crankcase breather module is located at the back of the
engine. In it are integrated the two fine oil separators for the right-

hand cylinder bank, the pressure control valve and the oil return
line from the fine oil separator of the left-hand cylinder bank.

Treated blow-by gases to
the intake end of the
active turbocharger

Non-return check valve

Fine oil separator for the left cylinder bank

Blow-by gases from
the left cylinder bank

A non-return check valve, installed in the oil return line from the
crankcase breather module, ensures that oil cannot be drawn into
the intake area from the oil pan in situations such as icing-up of the
crankcase breather.

Oil return from the left
cylinder bank

Blow-by gases
from the right
cylinder bank

Pressure control
valve
Fine oil separator for
the right cylinder bank
Oil return to oil pan

Non-return check valve

652_014

Fine oil separator
In terms of their working principle, the fine oil separators are
centrifugal separators - or what are known as axial swirls
(PolyswirlTM). Each of these separators consists of 8 permanently
open swirls and 2 packs of 8 swirls which are activated and deactivated depending on volumetric flow. The two packs are activated

Action springs

and deactivated by action springs with different spring characteristics. The fine oil separator is opened by the blow-by gas flow in
dependence on engine speed. The spring force of the action
springs is used for closing.

Permanently open swirls

Cleaned blow-by gas
Swirl

Separated oil

Blow-by gas inlet
(raw gas)

Pack of 8 swirls
(flow-dependent opening)

Permanently open swirls
652_016
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Oil supply
System overview
Key:
A
B
C

Camshaft bearing
Support element
Main bearing

1
2
3
4
5
6
7
8
9
10
11
12
13

Exhaust turbocharger 1
Exhaust turbocharger 2
Flow restrictor
Oil/coolant heat exchanger 1
Oil/coolant heat exchanger 2
Oil filter module
Chain tensioner pinion A:
Chain tensioner pinion D:
Piston cooling nozzle
Non-return valve
Oil pressure control valve N428
Controlled oil pump
Vacuum pump

A

A

B

A

B

B

A

B

A

B

A

B

B

A

B

B

A

B

B

A

B

B

B

A

B

B

Cylinder head 2

3

4
6

5

10

High pressure circuit
Low pressure circuit

10

10

16

12

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A

A

B

1

A

B

B

A

B

B

B

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Ξ Contents

A

B

B

2

A

A

B

A

B

B

A

B

B

B

A

B

B

Cylinder head 1

3

7
8

9

C

9

C

9

C

9

C

C

11
Engine block

Oil pan
652_005

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Oil circuit
Passive turbocharger

Active turbocharger

Chain tensioner

Oilways for supplying the
camshafts and the support
elements

Main oil gallery

Piston cooling jets
Oil pressure switch
F22
Oil/coolant
heat exchanger 2
Oil filter module
(in oil pan)
Oil/coolant
heat exchanger 1

Oil pressure control valve
N428

Oil/vacuum pump

652_047

Oil filter
Due to the constraints on space, the oil filter has been installed

inside the oil pan. The oil filter is accessible through a sevice cover
on the oil pan.

Oil filter cartridge

Service cover on the oil filter
with seal

Service cover on the oil pan
with seal

652_010
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Oil pump
The oil circuit uses the fully variable oil pump of the V6 TDI engine,
which has been adapted to the oil demand of the V8 TDI engine.
The vane pump, continuously controlled by way of an eccentric
ring, permits optimum adaptation of the pressure/volume flow

depending on engine load and speed. Additionally, the throughput
of the piston jets can be influenced, or shut off, by way of the
pressure map in order to optimise friction.

Design
Flutter valve

Rotor with vane cells

Valve

Vacuum pump
cover

Rotor with vacuum
pump vane
Input shaft

Cold start valve

Adjustment ring
with control spring

Oil pump cover

Intake manifold
Oil strainer

652_052

Oil cooling
To allow the oil to heat up oil quickly after a cold start, volumetric
flow to the oil/coolant heat exchangers takes place on the coolant

side. There is no coolant flow through the oil/coolant heat
exchangers during the cold start phase and at low engine loads. It

is not until a certain, evelated oil temperature is reached that
coolant flow through the oil/coolant heat exchangers is enabled by
switching the oil cooler valve.

Transfer plate

Oil/coolant
heat exchanger 2

Oil/coolant
heat exchanger 1

652_008
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Exhaust gas recirculation
Overview
In a combustion process involving surplus air, unwanted nitrogen
oxides form at high combustion chamber temperatures in any
internal combustion engine. The formation of nitrogen oxides can,

to a large extent, be avoided by recirculating the exhaust gases.
The exhaust gas recirculation system directs a portion of the

Exhaust gas extraction point
on active turbocharger

exhaust gases back into the combustion chambers. This reduces
the amount of fresh, oxygen-rich air in the exhaust gases thereby
inhibiting the chemical reactions within the combustion chamber.
The resultant reduction in combustion temperatures in turn means
significantly lower NOx emissions.

Active turbocharger

Exhaust gas
recirculation pressure sensor
G691

Exhaust gas
recirculation valve
GX5

Charge air pipe

EGR cooler

652_062

Exhaust gas inlet
in the charge air pipe

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EGR cooler
Coolant flow
Due to the gas flow configuration in the EGR cooler, double the
distance of the EGR cooler is utilised. The exhaust gases from the
exhaust manifolds flow in a U shape from the bottom to the top
section of the exhaust gas recirculation cooler. The gases flow
through the coolant tubes and dissipate their heat to the coolant.
To enlarge the cooling surface area, the gas-carrying pipes are
embossed. The cooled coolant flows into the EGR cooler at the hot
exhaust gas inlet. This results in so-called "continuous flow
cooling" at the bottom end of the EGR cooler and "counterflow
cooling" at the top end of the EGR cooler.

EGR cooler

Exhaust gas outlet Exhaust gas inlet

Coolant outlet

Coolant inlet

Gas-carrying pipes
with embossings

Exhaust gas
recirculation valve
GX5
652_066

Bypass mode

Cooling mode

A key feature of the external exhaust cooling system is that the
exhaust gases on the exhaust side of the engine are extracted from
the exhaust manifold and returned to the combustion process.
When the engine is cold, the hot exhaust gases are channelled
directly into the charge air system via the bypass duct. This ensures
rapid heating of the oxidising catalytic converter and of the engine.

To reduce nitrogen oxide emissions still further, the exhaust gases
are additionally cooled via the liquid-controlled exhaust gas recirculation cooler. The EGR bypass valve, activated by the EGR cooling
bypass valve N386, opens the inlet to the EGR cooler. The exhaust
gases are now channelled through the cooled pipes and dissipate
their heat to the coolant. This allows the combustion chamber
temperature to be reduced thereby ensuring lower NOx levels in the
exhaust gases.

Pneumatic
EGR bypass valve

Exhaust gas inlet

Pneumatic
EGR bypass valve

Exhaust gas
recirculation valve
GX5

To
EGR inlet on
charge air pipe

Exhaust gas inlet

Exhaust gas
recirculation valve
GX5

To
EGR inlet on
charge air pipe

Cooler bypass valve closed

Cooler bypass valve open

EGR cooler

Coolant outlet

652_045

EGR cooler

Coolant outlet

652_046

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Cooling system
System overview

1

2

V488
N509
3

4
N474

8

6
5

9

7
10

12

G812

G8

11
13

14

15

16/F265

15

17

G62

18

15

G83

19

J671

20

V645

J293

21
15
652_004

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Key to figure on page 22:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

Front heater heat exchanger
Rear heater heat exchanger
ATF cooler
Exhaust turbocharger 1

Coolant expansion tank
Cylinder head, bank 1
Cylinder head, bank 1
Cylinder head, bank 2
Cylinder head, bank 2
EGR cooler
Exhaust turbocharger 2
Oil/coolant heat exchanger 1
Oil/coolant heat exchanger 2
Coolant pump
Non-return valve
Rotary slide valve with electrically heated
wax expansion element
Oil cooling circuit control valve
Electric powered compressor (EPC)
Head block cooling circuit control valve
Flow restrictor
Radiator

F265 Thermostat for mapped engine cooling
G8
Oil temperature sensor
G62 Coolant temperature sensor
G83 Coolant temperature sensor at radiator outlet
G812 Coolant temperature sensor 3
J293 Radiator fan control unit
J671 Radiator fan control unit 2
N474 Reducing agent injector
N509 Gearbox oil cooling valve
V488 Heating assistance pump

V645 Electric compressor coolant pump

Cooled coolant
Warm coolant

Components on the engine
Passive turbocharger

EGR cooler

Active turbocharger

EGR valve
GX5

Vent

Thermostat for mapped
engine cooling
F265
Return line
Coolant cooler

Coolant module

Coolant pump

Oil cooler circuit
control valve
Head block cooling circuit

control valve
Radiator
supply line

652_040
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Coolant module
The innovative thermal management concept permits autonomous
supply to the interior and gearbox oil heating, the EGR cooler and
the exhaust turbocharger via the cylinder head circuit, regardless
of the coolant standing in the engine block.
Coolant flows through the engine block and cylinder heads in two
parallel cooling circuits. The coolant flow for both circuits runs
from the hot inner V intake across the engine block or cylinder
head to the cold outer side.
The water pump located in the inner V now has a covered impeller
with three-dimensionally curved blades, and continuously supplies
the two sub-circuits. The coolant pump is driven by a drive shaft
integrated in the timing gear via a sprocket.
The coolant module, in which key functional components of the
coolant circuit are integrated, is installed at the front end of the
engine. The volute casing of the coolant pump forms the coolant

module. The map-controlled thermostat with rotary slide valve and
electrically heated wax expansion element for switching the large
cooling circuit is flange-mounted to the coolant module on the
supply side. Also integrated in the coolant module are the head
block control valve, activated by the pressure reducing valve N155,
and the oil cooler bypass valve, activated by the EGR cooling
bypass valve 2 N387 in a pulse width modulated fashion using
vacuum.

Design

Supply line to
engine

652_060

Coolant module with coolant pump

Coolant pump

Oil cooling circuit
control valve

Head block cooling circuit
control valve

Rotary slide valve
(open)

Return from engine

Intake to
radiator

Thermostat for mapped engine cooling
F265

Return from radiator

24

652_039


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Ξ Contents

Map-controlled thermostat with rotary slide valve and electrically heated wax expansion element
The temperature level of the cylinder head cooling circuit is controlled via a mapped thermostat with a heated wax expansion
element. The thermostat is de-energised during the warm-up
phase and opens at 90 °C. Thus, no thermal energy is dissipated to
the main radiator in order to achieve this temperature. Hot coolant

is provided for heating the ATF oil and for heating as necessary.
The temperature level of the cylinder head cooling circuit can be
reduced – within the physical bounds of the radiator – by energising the map-controlled engine cooling thermostat.

Actuation of the rotary slide valve

Deflection point
Rotary slide valve
open

Guide rod

Coolant flow is enabled
Sliding element with
spring
Wax expansion element

Electrical connection
for heating the wax
expansion element

Control piston actuates
the sliding element
against the pressure of
the spring
652_070

The wax expansion element is a pressure-resistant cell filled with a
wax-like expanding material. An integrated heater melts the
expanding material in the wax expansion element, causing the
volume of the latter to increase significantly. As a result, the
control piston pushes outwards and the sliding element moves
against the pressure of the spring. The sliding element connected

to the rotary slide valve is now guided along a guide rail. The linear
movement of the sliding element is translated to a rotational
movement of the rotary slide valve at a deflection point. This
causes the rotary slide valve to open or close. The expanding
material contracts when it cools down again and the spring-loaded
control piston closes the rotary slide valve.

Thermostat closed

Thermostat open

652_041

652_042

Coolant temperature sensor
at radiator outlet
G83

Coolant temperature sensor
G62

25