Audi V6 2009 User Manual

Self-Study Program 941803

Audi 3.0-liter V6 TDI

With Clean Diesel System

Service Training

Audi of America, LLC
Service Training
Printed in U.S.A.
Printed 03/2009
Course Number 941803

©2009 Audi of America, LLC

All rights reserved. All information contained in this manual is
based on the latest information available at the time of printing
and is subject to the copyright and other intellectual property
rights of Audi of America, Inc., its affiliated companies and its
licensors. All rights are reserved to make changes at any time
without notice. No part of this document may be reproduced,
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the publisher.

All requests for permission to copy and redistribute
information should be referred to Audi of America, LLC.

Always check Technical Bulletins and the latest electronic
repair information for information that may supersede any
information included in this booklet.

Trademarks: All brand names and product names used in
this manual are trade names, service marks, trademarks, or
registered trademarks; and are the property of their respective
owners.

Table of Contents

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

Engine Mechanical .................................4

Fuel System ......................................25

Engine Management ...............................48

Exhaust Treatment ................................68

Service ...........................................92

Appendix .........................................94

Knowledge Assessment ...........................99

The Self-Study Program provides introductory information regarding the design
and function of new models, automotive components or technologies.

The Self-Study Program (SSP) is not a Repair Manual!
All values given are intended as guidelines only and refer
to the software version valid at the time of publication of the SSP.

For maintenance and repair work, always refer to the current technical literature.

Reference Note

i

Notes

ii

Introduction

Introduction

This Self-Study Program (SSP) describes the design and function of the 3.0 liter Clean Diesel TDI Engine and exhaust gas
after-treatment system.

When you have completed this SSP, you will know the following:

Design and function of the 3.0 liter TDI engine –
The limits established by the emission standards for diesel engines in various countries throughout the world –
Which components are used in the exhaust gas after-treatment system –
The location and function of these components –
The influence of combustion chamber pressure –
The reason for heating the tank elements of the reducing agent at low ambient temperatures –

1

Introduction

2

Audi Introduces the Cleanest Diesel Technology World Wide into
Standard Production

The systematic evolution of the TDI resulted with the development of the world’s cleanest diesels. The core components
of this current TDI combustion system development include:

The fuel injection system –
Comprehensively improved exhaust gas recirculation system –
Optimized turbocharging –
Integrated cylinder pressure control system –

As a first step, improvements to these systems help to significantly reduce the engine’s untreated emissions. In the
second step, an active exhaust gas after-treatment system reduces the oxides of nitrogen emissions to a minimum. Thus,
by combining engine modifications with a new exhaust gas after-treatment system, the Clean Diesel system makes it
possible to efficiently minimize emissions while at the same time reducing fuel consumption.

The objective is the further development of TDI technology to achieve emissions below the future EU6 limits, as well as
below the most stringent LEV II/BIN5 limits, and to be ready for world-wide use.

AdBlue® is a registered trademark of the Verbands der Automobilindustrie e. V. (VDA)

Introduction

3

Emission Standards

The guidelines specify the following emission limits for gasoline and diesel engines:

Diesel engine particulates –
Unburned hydrocarbons (HC) –
Oxides of nitrogen (NOx) –
Carbon monoxide (CO) –

Emission Limits

Particulates

PercentagePercentagePercentage

Limits g/km

HC+NOx

CO

428_036

LEV = Low Emission Vehicle

ULEV = Ultra Low Emission Vehicle

SULEV = Super Ultra Low Emission Vehicle

BIN5 = Exhaust standard for California and other US states

The term “BIN” comes from the fact that the exhaust gases are collected and analyzed in bags during the exhaust tests.
Depending on the specified emission standard, calculations go from BIN10 to BIN5.

Engine Mechanical

4

Engine-Related Measures

Engine Mechanical

The 3.0 liter V6-TDI was based on and developed from the
EU5 (European) engine. It is a modular extension of an
existing engine with the following changes:

An optimized two-stage chain drive that lowers the –
chain forces, reducing frictional losses

An oil pump with flow rate-control and two pressure –
stages to reduce drive output required for lubrication

High exhaust gas recirculation cooling performance is
achieved by using a new EGR system with aluminum
module technology. This measure also reduces the
pressure loss in the exhaust gas recirculation path, which
has a positive effect on the charge cycle and on fuel
consumption.

The injector system with a maximum injection pressure
of 29,000 psi (2000 bar), optimized turbocharging, as
well as a charge-air path with an integrated charge-air
cooler bypass permits the optimized temperature
management of the air path. The combustion chamber
pressure sensor for cylinder pressure-based combustion
is also a new feature.

Engine Mechanical

5

268 (200)

241 (180)

215 (160)

188 (140)

160 (120)

134 (100)

HP (kW)

80 (60)

479 (650)

443 (600)

406 (550)

369 (500)

332 (450)

295 (400)

lb ft (Nm)

221 (300)

1000 2000 3000 4000 5000

Torque Curves

BIN5

Engine Speed in RPM Engine Speed in RPM

Output in HP (kW) Torque in lb ft (Nm)

Specifications

Engine Code Letters

Design

Displacement cu in (cm3)

Output HP (kW)

Torque lb ft (Nm)

Valves per Cylinder

Bore in (mm)

Stroke in (mm)

Compression Ratio

Firing Order

Engine Management

Fuel

Exhaust Standard

BIN5

CATA

6-cylinder V Engine

181 (2967)

225 (165) @ 3500 – 4000 rpm

406 (550) @ 1750 – 2250 rpm

4

3.27 (83)

3.6 (91.4)

16.8 : 1

1–4–3–6–2–5

Bosch EDC 17 CP 24

US Diesel

ULEV II/BIN5

428_002-3

Engine Mechanical

6

Mechanics

325_005

Crankcase

The engine block is made of GGV-40 (vermicular graphite
cast iron) with a cylinder gap of 90 mm.

The cylinder bores undergo UV-photon honing for friction
optimization and to minimize initial oil consumption.

Note:
UV photon honing involves using a laser

beam to smooth the cylinder bores
following honing.

The laser beam, which is applied at high
force, melts down the remaining metal
nibs in the one-billionth range. A smooth
cylinder bore is achieved immediately in
this way rather than through the break-in
process.

Crankshaft

The crankshaft is forged from temper-hardened steel and
is supported by 4 main bearings.

The upper end of the connecting rods are a trapezoidal
design. The lower end of the connecting rods are cracked
to ensure a precision fit and reduce movement of the
bearing cap under load.

The upper and lower bearing shells are not identical
in composition. The upper bearing shell is a two­component composite while the lower shell is a three­component composite bearing.

325_030

Pistons

Cast pistons with a centrally arranged piston trough are
used. They are cooled by injected engine oil via a ring
channel. The pistons do not have valve pockets.

325_032

Engine Mechanical

7

Balance Shaft

The balance shaft is located in the inner V of the engine
block. The shaft goes through the engine and the
balancing weights are secured at the ends.

Driven by chain drive D, the balancer shaft turns at
crankshaft speed opposite the direction of engine
rotation.

325_076

325_010

Bolts/Main Bearing Assembly

Top Section of Oil Pan

The division between the crankcase and the oil pan is at
the middle of the crankshaft.

The two-section oil pan is made up of an aluminium
pressure-cast top section and a bottom section made of
steel plate.

Retaining Frame

A retaining frame made of GGG 60 (spheroidal graphite
cast iron) supports the crankshaft and serves to reinforce
the crankcase.

325_011

Engine Mechanical

8

Cylinder Head

Four valves per cylinder ensure optimum charging of
the combustion chamber. In the V6 TDI, the valves are
actuated by roller-type cam followers with hydraulic valve
clearance compensation.

Cylinder Head Cover

Cylinder Head Cover Seal

The acoustics of the unit benefits from the use of the
roller-type cam followers. These, together with the
tensioned and play-compensated camshaft drive gears,
reduce the mechanical noise of the valve train.

Retaining Frame

Camshafts

The camshafts are manufactured from precision steel
tubing using the IHU method.*

The exhaust camshafts are driven by the intake
camshafts by straight-toothed spur gears.

* IHU – Internal High-pressure recasting

Camshaft

Valve Train

Cylinder Head

325_034

Engine Mechanical

9

Tooth Profile Clearance Compensation

The spur gear of the exhaust camshaft (driven spur gear)
comes in two parts. The wide spur gear is held on the
camshaft through spring actuation and has three ramps
at the front.

The narrow spur gear has the corresponding grooves
and is capable of both radial and axial movement. This is
done to eliminate backlash between the gears.

Spur Gears

Belleville Spring
Washer

325_039

325_038

Note:

Please refer to the current service literature
for assembly instructions.

A defined axial force is produced via a Belleville spring
washer, where the axial movement is converted at the
same time into a rotary movement with the help of the
ramps. This offsets the teeth of the two driven spur gears,
which in turn affects tooth clearance compensation.

Installation Position Clearance Compensation

325_066325_065

Engine Mechanical

Chain Drive Valve Train Assembly

The chain drive has been designed to minimize the loss
to inner friction. Chain Drive B on the camshaft drive
of Cylinder Bank 1 has been reshaped to increase the
contact ratio of the camshaft gear that is now larger.
At the same time, the gear ratio of the drive is modified
making it possible to reduce the effort required for
operation.

New Camshaft
Drive B

New Chain Drive D

Chain Drive D is modified in the balance shaft area
making it possible to enlarge the engagement of the
chain on the gear wheel.

Chain Drive D drives the balance shaft at crankshaft
speed against the normal rotation of the engine.

Camshaft Drive C

Oil Pump Drive

Gold Chain = Old Chain Drive from previous EU5 Engine

Silver Chain = Current Chain Drive

Balance Shaft

Crankshaft

428_004

10

Notes

11

Engine Mechanical

12

Flow Rate-Controlled Oil Pump

The use of a flow rate-control system reduces the
required drive output of the oil pump.

A vane pump is used in the new 3.0 liter V6-TDI engine;
its delivery characteristics can be changed via a pivoted
adjustment ring. This adjustment ring can be loaded with
oil pressure via Control Surfaces 1 and 2 and swiveled
against the force of the control spring. The ECM connects
ground to the energized Oil Pressure Regulation Valve
N428 in the lower rpm range, and the solenoid valve
opens the oil duct leading to the second control surface
of the adjustment ring.

Both oil flows are now acting with identical pressure
upon both control surfaces.

The forces resulting from this are higher than those of
the control spring and they cause the adjustment ring to
swivel counterclockwise.

The adjustment ring turns into the center of the vane
pump and reduces the supply space between the vanes.
The lower pressure level is switched depending on the
engine load, engine speed, oil temperature, and other
operating parameters, reducing the drive output of the
oil pump.

Oil Pressure Regulation Valve N428

Oil Pressure Switch

Crankshaft Oil Duct

428_005

Applied oil pressure
from the crankshaft
oil duct

Delivery Chamber

Vanes

Control Surface 2

Control Spring

Low Delivery Rate

Control Surface 1

Adjustment Ring

Mounting Flange

428_006

Engine Mechanical

13

High Delivery Rate

72.5 (5.0)

65.2 (4.5)

58.0 (4.0)

50.8 (3.5)

43.5 (3.0)

36.3 (2.5)

29.0 (2.0)

750 1000 1500 2000 2500 3000 3500 4000 4500 4750

Starting at an engine speed of 2500 rpm or a torque of
300 Nm (wide open throttle acceleration), Engine Control
Module J623 disconnects Oil Pressure Regulation Valve
N428 from the ground connection thus closing the oil
duct to Control Surface 2.

The applied oil pressure is now acting on Control Surface
1 only and acts with a lower pressure against the force of
the control spring.

De-energized Solenoid

The control spring swivels the adjustment ring clockwise
around the mounting flange. The adjustment ring now
swivels out of the center position and increases the
delivery space between the individual vanes.

More oil is delivered by increasing the spaces between
the vanes. A resistance builds up against the higher
oil volume flow due to the oil bores and the bearing
clearance of the crankshaft, which lets the oil pressure
increase. This makes it possible to implement a flow rate­controlled oil pump with two pressure stages.

Oil Pressure Curve @ 212°F (100°C)

Oil Pressure psi (bar)

428_007

Delivery Chamber

Control Surface 2

Engine RPM

Solenoid Valve Closed

Solenoid Valve Open (current applied)

High Delivery Rate

Control Surface 1

428_009

Adjustment Ring at
Maximum Delivery

Mounting Flange

428_008

Engine Mechanical

14

Air Intake

Intake Manifold with Butterfly Valves

Butterfly valves that can be regulated smoothly are
integrated into the intake tract. These can be used to
adapt the air movement according to the current engine
speed and load with regard to emissions, consumption
and torque/power.

Exhaust Gas Recirculation Flow

Intake Pipe

The butterfly valve adjuster with potentiometer reports
the current position of the butterfly valve back to the ECM.

Exhaust Gas Recirculation Unit

Throttle Position Adjuster

Intake Air

Butterfly Valves

Exhaust Gas Recirculation:

This involves high-pressure exhaust gas recirculation.

The entry of exhaust gasses into the intake tract counters
the intake air flow, resulting in a constant mixture of fresh
air and exhaust gas.

Note:

The throttle and butterfly valves are opened
in coasting mode to check the air flow
sensor and balance the oxygen sensor.

Electric Butterfly Valve
Adjuster

Throttle Position Adjuster:

The throttle is closed in order to stop the engine. This
reduces the compression effect and achieves softer
engine coasting.

In addition, the exhaust gas recirculation rate can be
increased through targeted, map-controlled closure.

325_031

Engine Mechanical

15

Butterfly Valve Closed Butterfly Valve Open

Tangential Pipe

Swirl Duct

325_047 325_048

To optimize the torque and combustion, a closed swirl
duct increases the swirl at low loads.

When the engine is started, the butterfly valves are
open and are only closed again at idle speed (duty cycle:
approximately 80%).

Continuous opening is performed from idle speed to
approximately 2,750 rpm (duty cycle: approximately 20%).

To optimize performance and combustion, an open swirl
duct allows a high level of cylinder charging at high
loads.

The butterfly valves are always completely open at a
speed of approximately 2,750 rpm or higher.

The butterfly valve is also open both at idle speed and
during coasting.

Note:

A replacement adjuster must be adapted
with the Scan Tool to synchronize it with
the butterfly valves.

Engine Mechanical

16

Exhaust Gas Recirculation (EGR)

The EGR system combines the EGR coolers, EGR valve,
and EGR bypass in a single component.

Due to the higher exhaust temperatures in the upper
partial load range, increased EGR cooling performance
becomes necessary.

The exhaust gas recirculation path consists of the
following: micro-catalytic converter, additional cooler,

A separate cooling channel is integrated into the housing
on the valve side to cool down the bypass flap and the
EGR valve.

To prevent deposits in the EGR path, especially during
operation with low-quality fuels with high aromatic
hydrocarbon contents, a metal micro-oxidation catalytic
converter is located at the beginning of the EGR path.

and cooler for exhaust gas recirculation temperature
sensor, and electric water-cooled exhaust gas
recirculation valve.

To obtain the lowest possible temperatures for the recirculated exhaust, the exhaust gas recirculation cooler is connected
to a separate low temperature coolant circuit (described on the following pages). The coolant is extracted directly at
the radiator outlet and delivered to the exhaust gas recirculation cooler by an electric pump. The additional cooler is
connected to the engine cooling circuit and makes it possible to nearly double the cooling performance.

Both the EGR Cooler and the additional EGR Cooler connected in series have bypass flaps. This allows the demand
controlled adjustment of the EGR cooling performance at specific load points. To reduce the carbon monoxide and
hydrocarbon emissions, the flaps are set to bypass position (the exhaust gas does not go through either cooler) during the
engine warm-up phase.

Throttle Valve

Exhaust Gas Recirculation (EGR)
Motor V338

EGR Temperature Sensor G98

Bypass Flap

Bypass Flap

Exhaust Gas
Recirculation Cooler

Metal Micro-Oxidation
Catalytic Converter

428_010

Additional Exhaust Gas Recirculation Cooler
Connected in Series

Engine Mechanical

17

0 5 10 15 20 25 30 35

Switchable Exhaust Gas Recirculation Actuator

The cooling performance of the exhaust gas recirculation cooler leads to a clear reduction in particle and nitrogen
emissions. The diagrams below and on the next page show the efficiency of the exhaust recirculation system in two
selected partial load points.

Flow Through Exhaust Gas Recirculation Cooler – Additional EGR Cooler Bypassed

When the engine is in partial load operation, the bypass of the additional EGR cooler is open (exhaust gas does not flow
through it). The bypass of the EGR cooler is closed and exhaust gas is directed through the cooler.

The bypass flap for the EGR cooler is opened at
approximately 1750 rpm. It is controlled by the ECM,
based on mapped values.

Particles

Bypass Flap

428_047

Earlier EU4 Standard EGR with Cooler EU6

NOx (g/h)

Engine Mechanical

18

0 50 100 150 200 250

Flow Through Additional EGR Cooler – Flow Through EGR Cooler

The additional cooler is opened with increasing load and resulting higher exhaust temperatures; thus both EGR coolers
are in cooling mode. This allows an increase of the EGR rate. The exhaust gas temperatures are lower and nitrogen oxide
emissions are further reduced.

Exhaust Gas
Recirculation Cooler

Additional EGR Cooler

428_048

Bypass Flap

The bypass flap for the additional EGR
cooler is opened at approximately
2200 rpm. It is controlled by the ECM,
based on mapped values.

Earlier EU4 Standard EGR with Cooler EU6 EGR Cooler and Additional EGR

NOx (g/h)

Cooler (EU6)

Engine Mechanical

19

t

o

t

o

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

Cooling System

Legend

Engine Coolant Temperature (ECT) Sensor G621.

Bleeder Screw 2.

Additional Exhaust Gas Recirculation Cooler3.

Exhaust Gas Recirculation Cooler 4.

Change-Over Flap For Exhaust Gas Recirculation5.

Heater Core6.

From The Heater Core7.

To The Heater Core8.

Cylinder Head Bank 2 (Left)9.

Fuel Cooler (Fuel/Water)10.

Bleeder Screw11.

Coolant Regulator For Exhaust Gas Recirculation12.

Water Pump13.

Cooler For Fuel Cooling (Water/Air)14.

Heated Coolant Cooled Coolant

Fuel Cooler Pump V16615.

Check Valve16.

Radiator 17.

Engine Coolant Temperature (ECT) Sensor (on Radiator) G8318.

Bleeder Screw 19.

Coolant Regulator For Exhaust Gas Recirculation20.

Coolant Thermostat21.

Exhaust Gas Recirculation (EGR) Cooler Pump V40022.

Alternator23.

Engine Oil Cooler24.

Cylinder Head Bank 1 (right)25.

Coolant Expansion Tank26.

Cap For Coolant Expansion Tank27.

428_018

Engine Mechanical

20

Exhaust Gas Recirculation Cooling

Exhaust Gas
Recirculation (EGR)
Cooler Pump V400

Exhaust Gas Recirculation
Cooler Thermostat
(Opens when Cooler Output
Temperature Exceeds 158°F (70°C))

Exhaust Gas Recirculation Cooler

Additional Exhaust Gas
Recirculation Cooler
Connected In Series

428_062

Coolant Regulator
for Engine Circuit
(Thermostat)

Coolant Regulator for
Exhaust Gas Recirculation
(Opens at 131°F (55°C))

Blue – from the engine
cooling circuit

Red – to the heater core

The high efficiency of the radiator for exhaust gas recirculation is reached through its own low-temperature cycle in the
cooling system.

Exhaust Gas Recirculation Cooler Pump V400 activates after engine start up and supplies the EGR cooler with cold water
directly from the main radiator. The coolant regulator for the EGR controls the temperature in the EGR cooler at a constant
131°F (55°C) independently from the outside temperature.

The additional EGR cooler is connected in series to the main cooler. This additional EGR cooler is integrated into the
engine cooling system circuit which is controlled at a temperature of 188°F (87°C).

Fuel Cooling

Fuel Return Line from
the Injector System

Coolant Supply from the Expansion Tank

Cooler for Fuel Cooling (Water/Air)

Fuel Cooler
(Fuel/Water)

Fuel Return to the Tank

At high loads, the diesel fuel must be cooled to ensure
injection quantity accuracy and to stay within exhaust
emission limits.

The fuel cooling pump starts to run at engine start.

Fuel Cooler Pump V166

428_028

Engine Mechanical

21

Variable Vane Turbocharger Operation

The adjustable turbocharger uses air guide vanes to
regulate the flow of exhaust gas into the turbine. In
contrast to the exhaust gas turbocharger fitted with a
wastegate bypass, the adjustable turbocharger produces
pressure not only at the top end of the speed range but
also across the full speed range.

The fundamental principle here is that a gas will flow
through a narrowed pipe more quickly than through a
pipe without a restriction, provided that the pressure in
the two pipes is equal.

Advantages

High engine output is available at the bottom end –
of the speed range since the exhaust gas flow is
regulated by the adjustable vanes.

The lower exhaust gas back-pressure in the turbine –
reduces fuel consumption at the top end of the speed
range and also improves bottom-end power output.

Exhaust gas emissions decrease because an optimum –
charge pressure and improved combustion is attained
across the full speed range.

Low Engine Speed and High Charge
Pressure are Required

The cross-section of the exhaust gas flow is narrowed
upstream of the turbine wheel by means of vanes. Since
the exhaust gas is forced to pass through the restricted
cross-section more quickly, the turbine wheel rotates
faster. The high turbine speed at low engine speed
generates the required charge pressure. The exhaust gas
back-pressure is high.

High Engine Speed

The turbocharger cross-section is adapted to the exhaust
gas flow. In contrast to the wastegate bypass, the entire
exhaust gas flow can be fed through the turbine in this
way. The vanes free a larger inlet cross-section, thereby
ensuring that the required charge pressure is not
exceeded. The exhaust gas back-pressure drops.

The vanes are fitted together with their shafts onto
a supporting ring. The pilot pins of each vane are
engaged in an adjusting ring, which moves all vanes
simultaneously. The adjusting ring is controlled by
Turbocharger (TC) 1 Control Module J724 via a guide pin.

Support
Ring

Vanes

Adjusting Ring

190_010

Pilot

Shaft

Control Linkage

Control Linkage
Guide Pins

190_007

Engine Mechanical

22

To allow a quick build-up of charge pressure at low speed
and under full load, the vanes are set to a narrow inlet
cross-section. The effect of the restriction is to speed up
the exhaust gas flow, thus increasing turbine speed.

The vanes are set at a steeper angle with increasing exhaust
gas flow rate or if a lower charge pressure is required.

Shallow Vane Angle

=

Narrow inlet cross-section

of exhaust gas flow

When the inlet cross-section is enlarged, the charge
pressure and the turbine output remain virtually constant.

In emergency operation, the vanes are at their maximum
angle, providing the largest possible inlet cross-section.

Steep Vane Angle

=

Large inlet cross-section

of exhaust gas flow

Direction of rotation
of adjusting ring

190_011 190_012

190_008

The small size of the compressor and turbine allows
a high level of response with only a slightly reduced
maximum output.

Optimized mounting of the turbine shaft reduces
frictional losses with cold engine oil during the warm up

Air Guide Vanes

190_009

phase and causes, especially at high elevations and at
cold ambient conditions, a more spontaneous response
behavior.

A flow silencer on the suction side and a dual-chamber
flow silencer on the compressor outlet prevent flow noise
associated with high supercharging pressures.

Turbocharger (TC) 1 Control Module J724

Dual-Chamber Flow Silencers

428_029

Exhaust Temperature Sender 1 G235

Engine Mechanical

23

Charge-air Cooling with Integrated Charge-air Cooler Bypass

Controlling the charge-air temperature contributes to
ensuring consistently low emissions at varying ambient
temperatures.

Three-way Tube

Since the charge-air coolers are highly efficient and
they cool the compressed charge-air to near ambient
temperatures (at low outside temperatures), a bypass is
integrated into the air path for bypassing the charge-air
cooler.

Turbocharger Throttle Valve

Right Charge-air Cooler

The bypass flap element consists of the flap housing
and two flaps that are mounted at 90° angles on a
common shaft.

They permit continuous mixing of cooled air from the two
charge-air coolers and heated air from the turbocharger.

In the final positions of the flap, either only the heated air
from the turbocharger or the cooled down air from the
charge-air coolers is delivered into the intake manifold.

Left Charge-air Cooler

Charge-air Cooler Bypass

428_015

The advantage of variable charge-air mixing is that the
intake air temperature can be regulated to the desired
specified value depending on the characteristic map
through a variable mixture ratio.

This permits constant thermodynamic boundary
conditions for low-emission and low-consumption
combustion.

The Charge-air Pressure Sensor G31 with integrated
Intake Air Temperature (IAT) Sensor G42 senses the
charge-air temperature. It is installed just upstream of the
throttle valve in the pressure hose.

Engine Mechanical

Cold Engine, Low Outside Temperature

The heated charge-air, coming from the turbocharger
over the three-way tube, is delivered directly through the
bypass flap to the intake manifold.

This allows the oxidation catalyst, the particle filter, and
the exhaust cleaning systems to activate quickly.

Heated Air from
the Turbocharger

To the Intake Manifold

Bypass Flap Element

428_017

Engine Under Load, High Outside
Temperature

Starting at approximately 1750 rpm, depending on the
characteristic map, the amount of cooled charge-air
is delivered to the intake manifold through a defined
position of the bypass flaps.

By closing the bypass flap, the direct path of the charge­air to the intake manifold is closed. The charge-air is
directed to the intake manifold through the charge-air
cooler.

To the Intake Manifold

Cooled Air from the
Intake Manifolds

428_016

24

Common Rail Fuel Injection System

Fuel System

Fuel System

The common rail fuel injection system is a high-pressure
accumulator fuel injection system for diesel engines.

The term “common rail” means that all of one cylinder
bank’s injectors have a common, high-pressure fuel
accumulator or rail.

In this injection system, pressure generation and fuel
injection are separate. The high pressure required for
injection is generated by a separate high-pressure
pump. This fuel pressure is stored in a high-pressure
accumulator (rail) and is made available to the injectors
via short injector pipes.

High-Pressure Accumulator (Rail),
Cylinder Bank 1

This fuel injection system’s characteristics include:

The injection pressure can be selected almost –
infinitely and can be adapted to the engine’s operating
status

A high injection pressure up to a maximum of 29,000 –
psi (2000 bar) enables optimal mixture formation

A flexible fuel injection process, with several pilot and –
secondary injection processes

The common rail fuel injection system offers many
options for adapting the injection pressure and the
injection process to the engine’s operating status. It
is designed to meet the ever increasing requirements
for low fuel consumption, low exhaust emissions, and
smooth running characteristics.

Connecting Pipe Between the
High-Pressure Accumulators (Rails)

Cylinder 1 – 3
Fuel Injectors
N30, N31, N32

High-Pressure Pump

Cylinder 4 – 6 Fuel Injectors
N33, N83, N84

High-Pressure
Accumulator (Rail),
Cylinder Bank 2

351_064

25

Fuel System

26

Fuel System

Fuel Metering Valve N290

High-pressure Pump CP 4.2

Fuel Temperature Sensor G81

Auxiliary Fuel Pump V393

Pressure Holding Valve

Temperature-Dependent
Switch-over

Fuel Filter

High Pressure (300 - 2000 bar)

Low Pressure Return from the Injector (10 bar)