Diesel Air Intake and Exhaust System

Aftersales Training Product information. Air Intake and Exhaust System Diesel.

BMW Service

The inform informati ation on contai contained ned in the Produc Productt Inform Informati ation on and the Workbo Workbook ok form form an integr integral al part part of the training literature of BMW Aftersales Training. Refer to the latest relevant BMW Service information for any changes/supplements to the technical data. Information status: July 2007

Contact: [email protected] [email protected] © 2007 BMW AG München, Germany Reprints of this publication or its parts require the written approval of BMW AG, München VS-12 Aftersales Training

The inform informati ation on contai contained ned in the Produc Productt Inform Informati ation on and the Workbo Workbook ok form form an integr integral al part part of the training literature of BMW Aftersales Training. Refer to the latest relevant BMW Service information for any changes/supplements to the technical data. Information status: July 2007

Contact: [email protected] [email protected] © 2007 BMW AG München, Germany Reprints of this publication or its parts require the written approval of BMW AG, München VS-12 Aftersales Training

Product Information Air Intake and Exhaust System Diesel. Peakperformancewithoptimizedfreshair supply Minimum pollutants Perfect sound

Notes on this Product Information Symbols used The following symbols are used in this Product Information to improve understanding and to highlight important information:

3 contains information to improve understanding of the systems described and their function. 1 identifies the end of a note.

Information status and national variants BMW vehicles satisfy the highest requirements of safety and quality. Changes in terms of environmental protection, customer benefits and design render necessary continuous development of systems and components. Discrepancies may therefore arise between specific details provided in this Product Information and the vehicles available during the training course. This document relates exclusively to left-hand drive vehicles with European specifications. On right-hand drive vehicles, some controls or components are arranged differently from the illustrations in this Product Information. Further differences may arise as the result of the equipment variants used in specific markets or countries. Additional sources of information Further information on the individual subjects can be found in the following: - Owner's Handbook - BMW diagnosis system - Workshop systems documentation - BMW Service Technology

Contents. Air Intake and Exhaust System - Diesel Objectives

1

Product Information and reference material for practical applications

1

Introduction

3

General requirements

3

System overview

9

Overview System overviews of current engines

9 15

System components

27

Unfiltered air duct Intake silencer Exhaust turbocharger Intercooler Sensors - air intake system Throttle valve Intake air manifold Exhaust manifold Exhaust gas recirculation Exhaust turbocharger Sensors - exhaust system Oxidation catalytic converter Diesel particulate filter Particulate trap catalytic converter Silencer Vacuum system

27 28 29 35 38 41 42 44 45 53 61 70 74 79 81 89

Service information

101

System overview System components

101 102

Summary

103

Points to remember

103

Test questions

109

Questions Answers to questions

109 113

Objectives. Air Intake and Exhaust System - Diesel.

Product Information and reference material for practical applications This Product Information provides detailed information on the design and function of the various air intake and exhaust systems used in BMW diesel vehicles. The Product Information is designed as a work of reference and supplements the contents of the BMW Aftersales Training course. The Product Information is also suitable for private study.

As a preparation for the technical training course, this publication provides an insight into the air intake and exhaust systems of the current BMW diesel models. In conjunction with practical exercises carried out in the training course, its aim is to enable course participants to carry out servicing work on the air intake and exhaust systems in BMW diesel vehicles.

Please remember to work through the SIP (training and information program) on this topic. Basic knowledge ensures confidence in theory and practice.

Technical and practical background knowledge of the current BMW diesel models will simplify your understanding of thesystems described here and their functions.

1

2

Introduction. Air Intake and Exhaust System - Diesel.

General requirements The air intake system supports the charge cycle process. Thehigher the delivery rate, the more effective the charge cycle. The term delivery rate refers to the ratio between the actual and theoretically possible cylinder charge. A large volume of air additionally means a higher oxygen content in the cylinder charge. The oxygen content is also higher in air that has been compressed to some extent thus shortening the combustion paths. The introduction of the transverse flow cylinder head was key in achieving an improved cylinder charge. In this cylinder head, the intake and exhaust are not arranged on one side (counterflow cylinder head) but rather on different sides of the displacement engine. The incoming fresh gasses are able to exit the combustion chamber in virtually the same direction with no flow-back. This design layout also made possible the use of multivalve technology with optimum cross sections for the valves and ideal central arrangement of the injection nozzles.

Formerly, the counterflow cylinder head still had the advantage of effective mixture preheating for cold start by the exhaust manifold arranged below it. However, this advantage proved to be a disadvantage once the engine reached operating temperature. For this reason, intake air preheating (subsequently also thermostatically controlled) has become less and less prevalent. The only remaining disadvantage of the cross-flow cylinder head is the division of the engine into a warm exhaust side and a cold intake side. Design measures and corresponding material selection are required to compensate for this disadvantage.

It is necessary to implement appropriatedesign measureson the air intake and exhaust system in order to be able to meet the emission limitsspecifiedthroughout the world. The design of the air intakeand exhaust systemdiffersfor different types of engine.

Ever greater significance is being attached to the typical sound a specific model makes. In recent years, the significance of the sound made by the different models can be measured by the attention paid to this topic in the motor press.

Exhaust emission legislation Pollutants Many countries limit the levels of emitted pollutants by way of corresponding exhaust emission legislation. The regulations stipulated by the respective countries are based on test procedures, measuring technologies and limits that may vary for ecological, economic, climatic and political reasons. Limits are specified for following exhaust emissions: • Hydrocarbons (HC), country-specific • Non-methane hydrocarbon compounds (NMHC), country-specific • Carbon monoxide (CO)

Sulphur compounds in the exhaust gas are the result of the sulphur contained in the fuel. The limits for the sulphur content in diesel fuel have therefore been reduced throughout the world. The pollutant emissions from the crankcase are relatively low as only clean filtered air is compressed in the diesel engine. The gasses that enter the crankcase during expansion (combustion stroke) contain only approx. 10 % of the pollutant mass that occurs in petrol engines. Nevertheless, a sealed crankcase ventilation system is required by law. There is no need to monitor evaporative emissions on diesel engines as the diesel fuel contains no volatile components.

• Nitrogen oxides (NOx) • Particles (PM) These pollutants are the result of: • Combustion in the engine • Sulphur content in fuel • Crankcase ventilation • Fuel evaporation 3

Consequently, this means that an engine and therefore also the air intake and exhaust system need to be adapted to the respective conditions. The pollutants hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOx) and particle emissions (PM) are measured as part of the EURO type approval test procedure. The vehicle to be tested must have covered a running-in distance of 3000 km.

• Sulphur compounds

In the USA, the Federal State of California limits the emission of non-methane hydrocarbon compounds (NMHC) to the average model range of a vehicle manufacturer. The vehicle manufacturer can use different vehicle concepts that divided into the following categories depending on their emission values for NMHC, CO, NO x and particle emissions:

• Water

• TLEV (Transitional Low Emission Vehicle)

1 - Exhaust gas composition of a diesel engine before exhaust treatment

The particles (PM) consist of: • Carbon • Hydrocarbons • Metal abrasion

Type approval testing Exhaust emission inspections are the prerequisite for granting the general type approval for a specific type of vehicle and/or engine. For this purpose, test cycles must be run under defined marginal conditions and emission limits met. The test cycles and emission limits are specific to the respective country. The following graphics show the different exhaust emission limits based on the example of the EURO specification, US specification and Japan specification. The tables are not directly comparable as the corresponding test conditions for determining the pollutant emissions differ in part quite significantly from each other.

4

• LEV (Low Emission Vehicle) • ULEV (Ultra-Low Emission Vehicle) • SULEV (Super Ultra-Low Emission Vehicle) • ZEV (Zero Emission Vehicle) For the type approval of a vehicle model, the manufacturer must verify that the pollutants HC (or NMHC), CO, NOx, particles and smoke emission (turbidity) do not exceed the emission limits over a distance of 50,000 and/ or 100,000 miles. The vehicle manufacturer must make available two vehicle fleets from production for this type approval test.

Type approval test values, EURO specification

2 - Exhaust emission limits, EURO specification

Valid from

Regulation

CO in mg/km

NOx in mg/km

HC + NOx in mg/km

Particles (PM) in mg/ km

01.07.1992

EURO 1

2720

970

970

140

01.07.1996

EURO 2

1000

700

700

80

01.01.2000

EURO 3

640

500

560

50

01.01.2005

EURO 4

500

250

300

25

planned 01.09.2009

EURO 5

500

180

230

3

planned 01.09.2014

EURO 6

500

80

170

3

5

Type approval test values, Japan

3 - Exhaust emission limits, Japan

6

Valid from

Regulatio n

CO in mg/km

NOx in mg/km

HC + NOx in mg/km

Particles (PM) in mg/ km

01.10.1998

-

2100

400

400

80

01.09.2000

-

2100

400

400

80

01.09.2004

-

630

300

120

56

01.09.2007

LEV 2005

630

150

24

14

planned 01.09.2010

-

630

80

24

5

Type approval test values, US specification in comparison with EURO specification and Japan specification

4 - Exhaust emission limits, comparison of EURO specification, US specification and Japan specification

Valid from

Regulation

CO in mg/km

NOx in mg/km

HC+NOx Particles (PM) in mg/km in mg/km

planned 01.09.2009

EURO 5

500

180

230

3

01.09.2007

LEV 2005 Japan

630

150

24*

14

Model year 2005

LEV II, Tier 2 Bin5

2110

31

47*

6

* NMHC is regulated in the USA. NMHC = Non-methane hydrocarbon

7

Preconditions Intake system

Exhaust system

The task of the intake system is to supply the engine with as much cool fresh air as possible. The lower the flow losses, the higher the output yield and torque.

The task of the exhaust system is to provide the necessary noise damping, low exhaust backpressure and the necessary exhaust gas treatment.

The intake system consists of the following individual components:

The exhaust system consists of the following components:

• Unfiltered air duct

• Exhaust manifold

• Intake silencer

• Exhaust gas recirculation

• Hot-film air mass meter

– Exhaust gas recirculation valve

• Filtered air duct

– Exhaust gas recirculation cooler

• Blow-by gas connection

– Exhaust gas recirculation bypass actuator

• Exhaust turbocharger • Intercooler • Charge air temperature sensor • Throttle valve • Inlet for exhaust gas recirculation • Intake air manifold • Boost pressure sensor • Swirl flaps • Swirl flap actuator In the meantime, the intake system is made from aluminium or plastic. The plastic material is heat resistant up to a temperature of 140 °C and, compared to aluminium, provides a further weight saving of up to one third. On the inside, the intake system should exhibit smooth surfaces and no steps. The first section of the air system and the transition to the air cleaner also require particular meticulous design. The average flow rate in the intake pipe is approx. 50-200 m/s.

8

• Exhaust turbocharger • Sensors – Exhaust temperature sensor – Oxygen sensor – Exhaust backpressure sensor • Oxidation catalytic converter • Diesel particulate filter • Primary silencer • Intermediate silencer • Rear silencer – Tail pipe – Exhaust flap

System overview. Air Intake and Exhaust System - Diesel.

Overview Air intake system In addition to reducing the intake noise, the air intake system ensures an optimum supply of fresh air to the combustion chamber. A wave of negative pressure acting against the direction of flow of the fresh air intake is created by the movement of the piston after opening the intake valve. The resulting pressure fluctuations are radiated in the form of sound via the mouth of the intake system. In addition, the pulsation that occurs inside the air intake system causes the walls of the components to vibrate, thus also radiating noise. The air intake system is therefore optimized in such a way that no disturbing or annoying vibration can occur thus conforming to the noise emission limits applicable worldwide.

The intake system can be divided intotwosection. Theintake snorkel, intercoolerand, with exceptions,the intake silencer are specifically assigned to the vehicle and differ even in connection with the same type of engine due to the different characteristics of the vehicle models. The exhaust turbocharger and the intake system with swirl flaps, throttle valve and various sensors are assigned to the engine. Apartfrom theexhaust turbocharger and exhaust manifold, the exhaust system is designed vehicle-specific anddiffersdepending onthe type of vehicle and specification.

9

N47D20T0 Engine

1 - Air intake system, N47D20T0 engine

10

Index

Explanation

Index

Explanation

A

Unfiltered air

7

Charge-air pipe

B

Filtered air

8

Intercooler

C

Heated charge air

9

Charge air pipe

D

Cooled charge air

10

Charge air temperature sensor

1

Unfiltered air pipe

11

Throttle valve

2

Intake silencer

12

Inlet for exhaust gas recirculation

3

Hot-film air mass meter

13

Boost pressure sensor

4

Filtered air pipe

14

Intake air manifold

5

Blow-by gas connection

15

Swirl flap actuator

6

Exhaust turbocharger

The unfiltered air (A) that is drawn in reaches intake silencer (2) through the intake snorkel (not shown) and unfiltered air pipe (1). In the intake silencer, the unfiltered air is filtered to become filtered air (B). The filtered air flows via hot-film air mass meter (3) and filtered air pipe (4) to exhaust turbocharger (6). At the same time, blow-by gases are fed into the filtered air pipe through blow-by gas connection (5). In the exhaust turbocharger, the filtered air is compressed and thereby heated. The compressed, heated charge air (C) is conveyed in charge air pipe (7) to intercooler (8).

From the intercooler, the now cooled charge air (D) flows via charge air pipe (9) past charge air temperature sensor (10) to throttle valve (11). Depending on the position of the throttle valve more or less cooled charge air (D) flows into intake manifold (14). The inlet for the recirculated exhaust gas (12) also joins the intake manifold.

3 If the filtered air pipe downstream of the blow-by gas connection is heavily oiled, this could imply increased blow-by gas levels. The cause of this is usually a leak in the engine (e.g. crankshaft seal) or surplus air taken in through the vacuum lines. A consequential symptom would then be an oily exhaust turbocharger, which does not mean that there is a fault with the exhaust turbocharger itself. 1

11

M57D30T2 Engine

2 - Air intake system, M57D30T2 engine

12

Index

Explanation

Index

Explanation

A

Unfiltered air

5


B

Filtered air

6

Charge-air pipe

C

Heated charge air

7

Intercooler

D

Cooled charge air

8

Charge air pipe

1

Unfiltered air snorkel

9

Throttle valve

2

Intake silencer

10

Intake air manifold

3

Hot-film air mass meter

11

Valve cover with swirl ports

4

Filtered air pipe

Exhaust system

3 - E81/E87 Exhaust system, N47D20O0 engine

Index

Explanation

Index

Explanation

1

Rear silencer

7

EGR bypass actuator

2

Intermediate silencer

8


3

Exhaust backpressure sensor

9

VNT actuator

4

Exhaust manifold

10

Oxidation catalytic converter and diesel particulate filter (DPF)

5

EGR valve

11

Oxygen sensor

6

EGR cooler

12

Exhaust temperature sensor

13

The task of the exhaust system is to direct combustion gasses into the atmosphere with as little noise and as environmentally acceptable as possible. In order to fulfil these requirements, while also producing a defined sound, the individual components such as silencer, catalytic converter, diesel particulate filter, exhaust turbocharger, exhaust manifold and various sensors are mutually matched.

The notion that an engine with reduced noise damping has a greater power output is incorrect and proven by the previous information. The design layout of the exhaust system positively influences the flow of exhaust gasses. The pressure reduction at the point of valve intersection is specifically used for the purpose of initiating the induction stroke and increasing power output.

3 The exhaust system is designed such that

The power output can be influenced by the pipe length and position of the silencers (catalytic converter/diesel particulate filter).

the vibrations corresponding to the engine timing (intake and pressure waves) optimize the charge cycle and therefore the engine output. Consequently, in the event of a defect in the exhaust system, the vibrationcoordinated charge cycle is influenced negatively, thus consequently reducing engine output while increasing fuel consumption. 1

14

Current exhaust systems are equipped with one catalytic converter, one diesel particulate filter and two silencers.

System overviews of current engines Using the N47D20O0 engine, N47D20T2 engine, M57D30O2 engine, M57D30T1 engine, M57D30T2 engine and the M67D44O1 engine as examples, the following system overviews illustrate the air intake and exhaust systems. The graphics demonstrate the differences between the various types of engine (4-cylinder engine, 6-cylinder engine and 8-cylinder engine) together with their specific characteristics.

The air intake and exhaust systems differ depending on the type of engine and exhaust emission legislation. The system overviews provide an initial insight into the complexity and differences of the individual engine series.

15

N47D20O0 Engine

4 - Air intake and exhaust system, N47D20O0 engine

16

Index

Explanation

Index

Explanation

1

N47D20O0 Engine

11

Rear silencer

2

Intake silencer (air cleaner)

12

Digital diesel electronics (DDE)

3

Hot-film air mass meter (HFM)

13

EGR (exhaust gas recirculation) valve and position sensor

4

Exhaust turbocharger with VNT

14


5


15

Throttle valve

6

Oxygen sensor

16

EGR bypass valve

7


17

EGR cooler

8

Oxidation catalytic converter

18

Intercooler

9

Diesel particulate filter (DPF)

19


10


17

N47D20T0 Engine

5 - Air intake and exhaust system, N47D20T0 engine

18

Index

Explanation

Index

Explanation

1


12

Oxidation catalytic converter and diesel particulate filter (DPF)

2

Intercooler

13

Wastegate

3

Intake silencer

14

Exhaust turbocharger, low pressure stage

4


15

Turbine control valve

5

Compressor bypass valve

16

Exhaust turbocharger, high pressure stage

6

EGR cooler with bypass valve

17

N47D20T0 Engine

7


18


8

Oxygen sensor

19

EGR valve

9


20

Throttle valve

10

Primary silencer

21


11


19

M57D30O2 Engine


20

Index

Explanation

Index

Explanation

1

M57D30O2 Engine

10


2


11

Rear silencer

3


12


4


13

EGR valve

5


14


6

Oxygen sensor

15

Throttle valve

7


16

EGR cooler

8


17

Intercooler

9


18


21

M57D30T1/M57D30T2 Engine

7 - Air intake and exhaust system, M57D30T1/M57D30T2 engine

22

Index

Explanation

Index

Explanation

1

M57D30T1/M57D30T2 Engine

12


2


13


3


14


4


15

Rear silencer

5

Small exhaust turbocharger

16


6

Large exhaust turbocharger

17

Throttle valve

7


18

EGR valve

8

Wastegate

19


9


20

EGR cooler

10

Oxygen sensor

21

Intercooler

11


22

Intake air temperature sensor

23

M67D44O1 Engine


24

Index

Explanation

Index

Explanation

1


11

Diesel particulate filter

2

Intercooler

12


3

Throttle valve

13

Oxygen sensor

4

EGR cooler

14


5

EGR valve

15


6


16

Digital diesel electronics (DDE) master

7


17


8


18

Rear silencer

9

Swirl flaps

19

DDE Slave

10


25

26

System components. Air Intake and Exhaust System - Diesel.

Unfiltered air duct The unfiltered air duct consists of the unfiltered air snorkel, pipe and the unfiltered air area of the intake silencer. The unfiltered air snorkel and pipe are designed with the crash

safety of pedestrians in mind. This entails the use of especially soft materials and yielding connections.

M57D30T2 Engine The M57D30T2 engine draws in the unfiltered air laterally behind the bumper ahead of the cooling module. The unfiltered air is routed via coarse-mesh screen (1) via unfiltered air snorkel (2) and unfiltered air pipe (3) into the unfiltered air area of intake silencer (4). The coarse-mesh screen prevents large particles such as leaves from being drawn in.

Theunfilteredfreshair is directedvia theunfiltered airduct intothe intake system of the respective engine.

The unfiltered air snorkel in the N47 engine is designed as an unfiltered air intake shroud. This has a large surface area, but is exceptionally flat. The air is drawn in by the cooling module.

1 - Unfiltered air duct, M57D30T2 engine

Index

Explanation

1

Coarse-mesh screen

2

Unfiltered air snorkel

3

Unfiltered air pipe

4

Unfiltered air area of intake silencer

5

Filter element

6

Filtered air area of intake silencer

27

Intake silencer The intake silencer houses the filter element and is designed such that the filter element has as long a service life as possible. The larger the filter element, the longer the service life and also the greater the space The intake silencer reduces the intake noise and houses the filter element.

requirement. The housing of the intake silencer is also designed to deform in the event of impact from above (pedestrian collision). This means that it compresses by several centimetres.

M57D30O2 Engine Index

Explanation

1

Filter element

2

Housing

In order to optimally utilize the available space and not to have to develop a new intake silencer for each type of vehicle, the intake silencer is mounted on the engine and part of the cylinder head cover.

2 - Intake silencer with filter element, M57D30O2 engine

M57TU2 TOP engine Since the combustion chamber is required for both turbochargers on twin turbo engines, the intake silencer is not fitted directly on the engine. In this case, the intake silencer is positioned laterally on the wheel well.

3 - Intake silencer, M57TU2 TOP engine

28

Index

Explanation

1

Filter element

2

Housing cover

3

Bottom section of housing

Exhaust turbocharger Exhaust turbocharger In 1925 Alfred Büchi produced the first exhaust turbocharging system with a 40 % increase in power output. This development heralded the step-by-step introduction of exhaust turbocharging. In exhaust turbocharging a part of the exhaust energy is used to drive a turbine. The exhaust energy would simply be wasted without exhaust turbocharging. Mounted on the turbine shaft, an impeller (pump wheel) draws in the air and directs it compressed to the engine. Compared to a naturally aspirated engine of the same size, the engine supercharged with an exhaust turbocharger has lower fuel consumption as a part of the exhaust energy that would otherwise not be utilized is used to increase the engine output. The torque progression of an engine charged with an exhaust turbocharger can be laid out more favourably. Due to the sharp rise in torque at low engine speed, almost the full power output is made available below the rated engine speed (speed at which the engine reaches its maximum power output). This means it is not necessary to shift so often when driving uphill.

Design An exhaust turbocharger consists of a turbine and a compressor that are connected by a common shaft. Driven by the exhaust gasses, the turbine provides the drive energy for the compressor. The compressors used in BMW engines are radial-flow compressors. A compressor consists of the impeller and the turbine housing. The speed of the turbine and therefore of the impeller draws in air axially which is accelerated to high speeds in the impeller. The air leaves the impeller in radial direction. The speed of the air is reduced virtually without loss in the diffuser, resulting in an increase in pressure and air temperature. The diffuser consists of the sealing plate and a part of the compressor housing. The air is collected in the compressor housing and the speed is further reduced up to the outlet to the intercooler.

The exhaust turbocharger uses a part of the exhaust energy to compress the intake air, thus increasing the efficiency of the engine. A swirl element is used to optimize the effect on the fresh air side.

Operation of the exhaust turbocharger is documented under .

Compared to naturally aspirated engines, the turbocharged engine looses virtually no power even at great altitude. The turbocharged engine can be operated with a larger air surplus. This is the basis for low consumption operation of current diesel engines. The exhaust turbocharger compresses the intake air. In this way, significantly more oxygen can be delivered to the combustion chamber. The operation of the exhaust turbocharger is described in the Exhaust system section.

29

4 - Exhaust turbocharger

30

Index Explanation

Index

Explanation

1

Turbine housing

11

Vacuum unit

2

Turbine wheel

12

Impeller

3

Heat shield

13

Piston ring seal

4

Bearing housing

14

Main bearing

5

Outlet to intercooler

15

Bearing bush

6

Oil inlet

16

Oil return

7

Safety plate

17

Inlet from exhaust manifold

8

Sealing plate

18

Wastegate

9

Compressor housing

19

Outlet to catalytic converter

10

Inlet from intake silencer

Functional principle

Index

Explanation

The functional principle of an exhaust turbocharger is described based on its characteristic map. It shows the pressure conditions as a function of volumetric flow.

1

Surge line

2

Turbine speed 60,000 rpm

3


The effective characteristic map range of the exhaust turbocharger is limited by

4


5


• Surge line

6


• Choke line

7


• Maximum permissible turbine speed

8


9

Vη = 0.75

10

Vη = 0.70

11

Vη = 0.68

12

Vη = 0.65

13

Vη = 0.60

Vη = Compressor efficiency, limit on the right-hand side corresponds to the choke line The graphic shows an example of the limits for different design layouts of the exhaust turbocharger. For instance, the exhaust turbocharger reaches the surge limit (1) at a compressor efficiency of 0.60. At the same compressor efficiency of 0.60, the choke line forms the right marking of the limitation Vη = 0.60 (13).

5 - Compressor characteristic map

31

Surge line

Choke line

The flow detaches from the compressor blades (3) at too low a volumetric flow and too high a pressure, thus interrupting the delivery. Due to the vacuum on the intake side, the air flows backwards through the compressor (2) until stable pressure conditions are reestablished and the air flows in forward direction again.

The maximum volumetric flow (2) of the exhaust turbocharger is limited by the cross section at the compressor inlet. No matter how much the speed is raised, the throughput cannot be increased beyond a certain value. This value is reached when the air in the wheel inlet reaches the speed of sound (3).

7 - Choke line 6 - Surge line

Index

Explanation

Index

Explanation

1

Impeller

1

Impeller

2

Volumetric flow

2

Air flow

3

Flow at the speed of sound

3

Flow stall

The pressure builds up again and the procedure is repeated in rapid sequence. The term "search" is derived from the resulting noise.

32

Swirler The swirler improves the flow at the compressor blades. The swirler shifts the surge line thus improving pressure build-up. The angle at which the air flow hits the impeller is changed so that the flow adapts more effectively to the compressor blades. This means flow stall (surge line) occurs later.

The graphic shows that the air flow (2) hits the compressor blade (1) at angle of incidence (3). Flow stall (4) can occur under certain conditions. The following graphic shows the effect of the swirler under the same operating conditions. The swirler changes the angle of incidence (3) causing the flow (5) to pass close against the turbine blade.

8 - Exhaust turbocharger without swirler 9 - Exhaust turbocharger with swirler

Index

Explanation

1

Compressor blade

Index

Explanation

2

Air flow

1

Compressor blade

3

Flow angle of incidence

2

Air flow

4

Flow stall

3

Flow angle of incidence

5

Flow

The swirler is based on a flexible design so that this function is achieved under various operating conditions. The following graphics show the swirler in operation in the range close to idle speed and under full load.

33

10 - Swirler at idle speed

11 - Swirler at full load

The swirler increases efficiency and reduces flow noise. The reason for this is that the swirler rotates the intake air into the impeller thus reducing the resistance of the intake air. This gives rise to the advantage of the turbocharging responding earlier from idle speed. The air resistance through the swirler would increase substantially at higher speeds, however, this is avoided by the flexible deformation of the swirler.

34

Intercooler Overview The temperature of the air increases as the air is compressed in the exhaust turbocharger. This causes the air to expand. This effect undermines the benefits of the exhaust turbocharger because less oxygen can be delivered to the combustion chamber. The intercooler cools the compressed air, the air's density increases and thus more oxygen can be delivered to the combustion chamber.

density of the compressed air, i.e. so too the oxygen content per volume. As a result, a larger volume of fuel-air mixture can be combusted and converted into mechanical energy.

The intercooler is responsible for reduced intake air temperatures compared to a vehicle with no intercooler. This means the power outputcan be additionallyincreased as a larger mass of air can be conveyed into the combustion chamber.

On BMW diesel engines, charge air is cooled exclusively by fresh air with an air-to-air heat exchanger. The charge air cooling rate greatly depends on the vehicle speed, temperature of the incoming fresh air and the design of the intercooler. The main purpose of turbocharging in a diesel engine is to boost output. Since more air is delivered to the combustion chamber as a consequence of "forced aspiration", it is also possible to have more fuel injected, which leads to high output yields.

12 - Intercooler

However, the air density and therefore the mass of oxygen that can be delivered to the combustion chamber is reduced because the air heats up, and thus expands, as it is compressed.

Index

Explanation

1

Heated charge air

2

Cooled charge air

3

Cool fresh air

The intercooler counteracts this effect because the cooling process increases the

4

Heated fresh air

35

Examples Using two examples of the M57D30T2 engine, the following table shows the extent

the air is cooled under defined operating conditions.

Mass air flow

Charge air temperature before intercooler

Cooling air temperature

Charge air temperature after intercooler

0.17 kg/s

130 °C

25 °C

68 °C

0.18 kg/s

155 °C

35 °C

66 °C

Taking the N47D20O0 engine as an example, the following table shows the cooling capacity

at various operating points.

Operating point

Mass cooling air flow

Charge air volume

Cooling capacity

Driving uphill

4 kg/m2s

300 kg/h

approx. 5.8 kW

Vmax

8 kg/m2s

700 kg/h

approx. 11.9 kW

The intercooler is located in the cooling module underneath the coolant radiator. Compressed air flows parallel through the intercooler in several plates, around which cooling air is circulated.

turbocharging process is directed through the intercooler. The intercooler transfers the thermal energy of the charge air to the ambient air thus cooling the charge air.

Intercooler, N47D20O0 engine

36

The entire volume of fresh air that is delivered to the engine and heated as part of the Index Explanation

Index

Explanation

A

Unfiltered air

6


B

Filtered air

7

Throttle valve

C

Heated charge air

8


D

Cooled charge air

9

EGR in-feed line

1

Intake silencer

10

Charge-air pipe

2

Blow-by gas connection

11

Intercooler

3


12

Charge-air pipe

4

Swirl flap actuator

13

Unfiltered air pipe

5

Intake air manifold

13 - Intake system, N47D20O0 engine

37

Sensors - air intake system Hot-film air mass meter Index

Explanation

1

HFM

2

Measurement tube housing

The hot-film air mass meter is located directly downstream of the intake silencer. It is secured to its housing. The digital HFM 6 is used on the current engines. The HFM signal is used as a basis for fuel apportioning and for determining the EGR rate. Various sensors are used in the air intake system. These include the hot-film air mass meter, charge air temperature sensor and the boost pressure sensor. Thesesensors are required for the purpose of calculatingthe EGRrate,fuel volume apportioning and for controlling the boost pressure.

14 - Hot-film air mass meter

15 - Sectional view of hot-film air mass meter

Index

Explanation

Index

Explanation

1

Electric connections

5

Partial flow for measurement, exhaust

2

Measurement tube housing

6

Labyrinth

3

Electronic evaluator

7

Sensor measuring cell

4

Mass air flow

8

Sensor housing

A labyrinth (6) makes sure that only the actual air mass is recorded. Thanks to the labyrinth, backflow and pulsation are not registered. In this way, the HFM determines the actual air mass irrespective of the air pressure and backflow. An electrically heated sensor measuring cell (7) protrudes into the air flow (4). The sensor measuring cell is always kept at a constant temperature. The air flow absorbs air from the measuring cell. The greater the mass air flow, 38

the more energy is required to keep the temperature of the measuring cell constant.

The evaluator electronics (3) digitizes the sensor signals. This digitized sensor signal is then transferred frequency-modulated to the DDE. In order to be able to compensate for

temperature influences, the air mass signal is referred to the variable temperature signal. The HFM is supplied with on-board voltage and connected to earth by the DDE.

16 - HFG signal progression

Index

Explanation

A

Air mass signal

B

Air mass

C

Temperature signal

1

Air mass signal (A) as a function of air mass (B) and temperature signal (C)

2

The period duration of the air mass signal (A) decreases as the air mass (B) increases

3

The period duration of the air mass signal (A) is extended as the air mass (B) reduces

4

When the temperature increases (C) and air mass (B) remains constant, the period duration of the air mass signal (A) is extended in order to compensate for temperature influences

5

When air mass (B) increases, the period duration of the air mass signal decreases while taking the temperature signal (C) into account

39

Charge air temperature sensor The charge-air temperature sensor records the temperature of the compressed fresh air. It is located in the boost-pressure pipe, directly upstream of the throttle valve.

The DDE connects the intake temperature sensor to earth. A further connection is connected to a voltage divider circuit in the DDE.

The charge-air temperature is used as a substitute value for calculating the air mass. This is used to check the plausibility of the value of the HFM. If the HFM fails, the substitute value is used to calculate the fuel flow measurement and the EGR rate.

The intake temperature sensor contains a temperature-dependent resistor that protrudes into the flow of intake air and assumes the temperature of the intake air.

17 - Charge air temperature sensor

The resistor has a negative temperature coefficient (NTC). This means that the resistance decreases as temperature increases. The resistor is part of a voltage divider circuit that receives a 5 V voltage from the DDE. The electrical voltage at the resistor is dependent on the air temperature. There is a table stored in the DDE that specifies the corresponding temperature for each voltage value; the table is therefore a solution to compensate for the non-linear relationship between voltage and temperature. The resistance changes in relation to temperature from approx. 75 kΩ to 87 Ω, corresponding to a temperature of -40 °C to 120 °C.

Boost pressure sensor information is sent to the DDE on a signal line. The evaluation signal fluctuates depending on the pressure. On the M57D30T2 engine, the measuring range from approx. 0.1 - 0.74 V corresponds to an absolute pressure from 50 kPa (0.5 bar) to 330 kPa (3.3 bar).

18 - Boost pressure sensor

The boost pressure sensor is required for boost pressure control. The boost pressure sensor monitors and controls the boost pressure in accordance with a characteristic map resident in the DDE. The boost pressure is also used for calculating the volume of fuel. The sensor is supplied with a 5 V voltage and connected to earth by the DDE. The 40

Throttle valve Overview A throttle valve is required in all diesel engines equipped with a diesel particulate filter. By throttling the intake air, the throttle valve ensures that the elevated exhaust gas temperatures required for diesel particulate filter regeneration are achieved.

When no power is applied to the drive unit, the throttle valve is set, spring-loaded, to an emergency operation position.

The throttle valve is closed when the engine is shut down to avoid engine judder. After the engine has stopped, the throttle valve is reopened. The throttle valves also serves the additional function of effectively preventing overrevving of the engine. If the DDE detects overrevving without an increase in the injection volume, the throttle valve will close in order to limit the engine speed. This situation can occur as the result of combustible substances entering the combustion chamber. Substances may be engine oil from an exhaust turbocharger with bearing damage. This function can effectively prevent major damage to the engine. The throttle valve is located directly upstream of the intake manifold. The DDE calculates the position of the throttle valve from the position of theaccelerator pedal and from the torque requirement of other control units. The DDE controls actuation of the throttle valve by means of a PWM signal with a pulse duty factor of 5 to 95 %.

The throttle valve is required for regenerating the diesel particulate filterin orderto increasethe exhaust temperature by intervening in the air-fuel mixture. In addition, the throttle valve is closed when the engine is shut down in order to reduce shut-down judder. The throttle valve also effectively prevents overrevving of the engine.

19 - Throttle valve, M57TU2 engine

Index

Explanation

1

Housing

2

Vacuum unit

3

Electric motor with electronics

4

Intake air

5

Connection from intercooler

6

EGR connection

To achieve optimum control of the throttle valve, its exact position must be recorded on a continual basis. The throttle valve position is monitored contactlessly in the throttle valve actuator by 2 Hall sensors. The sensor is supplied with a 5 V voltage and connected to earth by the DDE. Two data lines guarantee redundant feedback of the throttle valve position to the DDE. The second signal is output as the inverse of the first. The DDE evaluates the plausibility of the signal through subtraction. The actuator motor for operating the throttle valve is designed as a DC motor. It is driven by the DDE on demand. An H-bridge is used for activation which makes it possible to drive the motor in the opposite direction. The H-bridge in the DDE is monitored by the diagnostics system.

41

Intake air manifold Design The intake manifold distributes the filtered air coming from the intake silencer to the individual cylinders. The filtered air per cylinder is additionally divided in a swirl and tangential port in order to more effectively mix the injected fuel with the fresh air located in the combustion chamber. Additional swirl flaps are fitted in each tangential port for this purpose.

In most cases, the intake manifold is made of plastic. Inside it, the air is branched off the individual cylinders. In addition, the ports to each individual cylinder branch off further into swirl ports and tangential ports. In the N47 engines, both ports are routed along the side of the cylinder head.

ensures optimum cylinder charge, which is why the tangential port is also referred to as a charge port. The swirl flaps are located in the tangential ports. The swirl port is identifiable by its almost rectangular cross section, while the tangential port is round.

The swirl port ensures reliable swirl in the combustion chamber, and the tangential port

20 - Intake manifold, M67TU engine

42

Index Explanation

Index

Explanation

1

Intake manifold

5

Actuator motor for swirl flaps

2

EGR port

6

Linkage for swirl flaps

3

Swirl port

7

Swirl flaps

4

Tangential port

Swirl flaps The DDE activates the electric motor by means of a pulse width modulated signal. Pulse width modulation enables infinitely variable adjustment of the swirl flaps. The position of the swirl flaps is defined by a characteristic map. The position is based on the driver's load choice, engine speed and the coolant temperature.

21 - Intake and exhaust ports

Index

Explanation

1

Exhaust port

2

Swirl port

3

Tangential port

4

Swirl flap

Swirl flap (4) closes tangential port (3) to achieve greater turbulence of the air via swirl port (2) in the combustion chamber at low engine speeds. With increasing engine speed, it opens to facilitate charging through the tangential ports. The following table shows the type of activation used for the different engines. Engine

Electrical

Pneumatic

M67D44O1

X

-

M57D30T2

-

X

M57TU2

-

X

N47D20T0

X

-

N47

X

-

M47TU2

-

X

22 - Swirl flap, M57D30T2 engine

Index

Explanation

A

Swirl flap, opened

B

Swirl flap, closed

1

Linkage

2

Swirl flap

3

Vacuum unit

4

Swirl port

5

Tangential port

The swirl flaps are varied by a linkage (1) that is operatedby a DCmotor ora vacuum unit(3).

To increase the swirl effect, swirl flaps that close tight are used on the M57TU engines. Electrical actuation makes it possible to assume intermediate positions, thus further optimizing internal mixture formation.

43

Exhaust manifold

On current diesel engines, the exhaust manifold is made from spherical graphite cast iron. An air gap insulated exhaust manifold is used on the M57TU engines.

The exhaust manifold conjoins the exhaust openings in the cylinder head into one or several ports and transfers the exhaust gasses. The design layout of the exhaust

manifold has an influence on the output yield. Current exhaust manifolds are made of cast iron and sheet steel.

Cast exhaust manifold The spheroidal graphite cast iron exhaust manifold (GGG) bundles the exhaust gasses coming from the cylinder head and transfers them to the exhaust turbocharger. As the exhaust gasses can reach extremely high temperatures, it is important that the exhaust manifold is designed correspondingly temperature-resistant. The exhaust turbocharger is mounted at the outlet of the exhaust manifold. An important advantage of

the cast exhaust manifold is its cost-effective production and high stability as a support for the exhaust turbocharger.

23 - Cast exhaust manifold, M67D44O0 engine

Air gap insulated exhaust manifold An air gap insulated exhaust manifold is used on the M57TU engines. Advantages: • Lower weight • Lower heat absorption and therefore quicker response of underfloor catalytic converter • Favourable exhaust gas flow • Lower heat input in engine compartment The air gap insulated exhaust manifold is made up of individual parts (see graphic). The inner exhaust pipes carry the exhaust gasses. The outer sleeve (second shell) shields heat radiation by means of an air gap between the shells. Due to the thin material used for the inner exhaust pipes, the heat absorption capacity is very low. Consequently, the hot exhaust gas reaches the catalytic converter and the diesel particulate filter more quickly. However, a cast exhaust manifold was again used on the successor engine as it was possible to eliminate the disadvantage of the slower response of the catalytic converter by arranging it directly downstream of the exhaust turbocharger.

44

24 - Air gap insulated exhaust manifold, M57TU engine

Index

Explanation

A

Assembly

B

Exploded view

Exhaust gas recirculation Overview The diesel engine normally operates without throttling the intake air. The load is controlled by the injected quantity of fuel. Only a slight fuel surplus is available at full load, ensuring relatively "clean" combustion. There is an oxygen surplus when the full power output is not required. Nitrogen oxides (NOx) are produced in the combustion process at an increased rate in connection with a surplus of oxygen. Exhaust gas recirculation is used to reduce these nitrogen oxides.

• A reduction in the maximum combustion temperature of up to 500 °C. This effect is increased still further if the recirculated exhaust gases are cooled.

M57TU2 Engines Exhaust gas recirculation is used to reduce NOx emissions. The oxygen content inthe cylinder is reduced by mixing exhaust gas with the intake air.Adding exhaust gas meansthere is less oxygen available for combustion thus reducing the combustion temperature.

The average combustion temperature is reduced by adding exhaust gas to the intake air and therefore to the combustion chamber. This has a positive effect on pollutant emissions. The following pollutant emissions increase as the result of air deficiency in connection with a large volume of recirculated exhaust gas: • Soot • Carbon monoxide • Hydrocarbon To substantially reduce the nitrogen oxide emissions by means of exhaust gas recirculation, exact adaptation of the fuel quantity to the available air mass is required also in the partial load range. The recirculated quantity of exhaust gas must be limited such that a sufficient quantity of oxygen is available to ensure effective combustion of the injected fuel. Nitrogen oxides are produced in large amounts if combustion takes place with an air surplus and at very high temperatures. Oxygen combines with the nitrogen in the combustion air to form nitrogen monoxide (NO) and nitrogen dioxide (NO2).

25 - EGR system, M57D30O2 engine

Index

Explanation

1

Exhaust manifold

2

EGR cooler

3

EGR valve

The exhaust gas recirculation is occasionally required at idling speed but always in the partial load range because this is where the engine works with a particularly high air surplus. The recirculated exhaust gas, which is mixed with the fresh air and acts as an inert gas, serves to achieve the following: • A lower oxygen and nitrogen content in the cylinder,

45

M67D44O1 Engine

26 - EGR system, M67D44O2 engine

Index

Explanation

Index

Explanation

1

Cylinder head

4

Coolant connection

2

EGR valve

5

EGR port

3

EGR cooler

The EGR system of the M67D44O2 engine features EGRports cast into the cylinder head. From a flange cast on the exhaust manifold, the exhaust gas is routed via a port integrated in the cylinder head to the EGR valve. From the EGR valve, the exhaust gas is directed through a further port integrated in the cylinder head to the EGR cooler and from here via a port integrated in the cylinder head and a connecting pipe into the intake system. The EGR cooler is located in the V-space of the engine. The EGR valves are mounted on the cylinder head and the valve seats are integrated in the cylinder head.

46

N47D20O0 engine and N47D20T0 engine

EGR valve, which controls the volume of recirculated exhaust gas.

On the N47 engines, the exhaust gas recirculation system begins at the exhaust manifold. There is a connection at the front end for this purpose. Connected here is the

Located downstream of the EGR valve is the EGR cooler. Its design differs depending on the power class and equipment. The EGR valve and the EGR cooler are contained in the EGR module.

27 - EGR module, N47D20O0 engine

Index

Explanation

Index

Explanation

1

EGR cooler

5

EGR bypass actuator

2

EGR path sensor

6

Coolant supply

3

EGR valve

7

Coolant return

4

Hot exhaust gas

8

Cooled exhaust gas

The EGR port from the EGR cooler to the intake manifold is cast into the cylinder head. At the intake manifold, the exhaust gas is ultimately mixed with the fresh air.

47

EGR valve The required quantity of exhaust gas is directed via the EGR valve to the intake system. The EGR valve is operated either pneumatically or electrically.

M57 Engines The EGR valve opens by applying vacuum at vacuum connection (9). The vacuum presses diaphragm (1) against spring (10) and the EGR valve head is lifted from blade-type sleeve (4). Exhaust gas (5) can now flow past the EGR

valve head into the intake port. The exhaust gas now mixes with the intake air from throttle valve (2) and is directed in the form of a fresh air-exhaust gas-air mixture (6) to the engine. The blade-type sleeve has the advantage that, when the EGR valve is closed, any deposits formed on the sleeve are removed by the blade shape, ensuring the EGR valve always closes reliably. In this way, a coking ring is prevented from forming on the surface of the valve seat.

28 - EGR valve, M57 engine

48

Index

Explanation

Index

Explanation

1

Diaphragm

6

Fresh air-exhaust gas-air mixture

2

Intake air from throttle valve

7

Guide sleeve

3

EGR valve head

8

EGR housing

4

Blade-type sleeve

9

Vacuum connection

5

Exhaust gas

10

Spring

M67D44O1 Engine

The following graphic shows the design of the EGR valve. Cam disc (2) is moved by electric motor shaft (10). A spring pushes the cam disc back into its initial position. A roller (1) rests against the cam disc. The roller transfers the movement of the cam disc to stem (8), thus lifting valve (7) from valve seat (6). The valve is therefore opened and exhaust gas can flow past the valve into the port to the EGR cooler. Plain bearing (4) provides an adequate seal to the electric motor and ensures the necessary smooth movement under various operating conditions. The electric motor is connected to the DDE via plug connection (9).

29 - EGR valve, M67D44O1 engine

The EGR valve of the M67D44O1 engine is operated by an electric motor. Electric actuation enables extremely precise metering of the exhaust gas recirculation rate. Since the electronics cannot withstand the same high temperatures as the vacuum-controlled EGR valves, the EGR valves of the M67D44O1 engine are cooled.

31 - EGR valve, M67TU engine

Index

Explanation

1

Roller

2

Cam disc

3

Cooling channel

4

Plain bearing

5

Exhaust port

30 - EGR valve, M67TU engine

6

Valve seat

Index

Explanation

7

Valve

1

Socket

8

Stem

2

Cooling channel

9

Plug connection

3

Stem

10

Electric motor shaft

4

Ball

Coolant enters cooling channel (2) of the EGR valve via socket (1). Ball (4) closes off the hole necessary to produce the cooling channel. Stem (3) is moved by the electric motor. 49

component itself is not cooled. This is not essential because it is controlled by a vacuum unit. The EGR valve is opened in response to negative pressure. An electropneumatic pressure converter (EPDW) is controlled by the DDE by means of a pulse-widthmodulated signal (PWM signal). The EPDW then places a corresponding negative pressure on the vacuum unit of the EGR valve. This causes the EGR valve to open against the force of a spring. The PWM signal determines the negative pressure, and the negative pressure determines the opening dimension of the valve. In this way, it is possible to have a defined volume of exhaust gas recirculated. With a pulse width of 10 %, the EGR valve is fully closed and, at 90 %, it is fully open. 32 - EGR valve, M67TU engine

Index

Explanation

2

Cam disc

7

Valve

N47 Engines The EGR valve controls the return of exhaust gas to the air intake system. It is located upstream of the EGR cooler and therefore subjected to high thermal loads. However, the

If there is no pressure present, the EGR valve is closed due to the force of the spring. As a consequence, no exhaust gas can be recirculated in the event of an electrical or pneumatic system failure. A new feature is the sensor on the EGR valve that records the opening dimension. This sensor is a potentiometer. Recording the opening dimension makes it possible to regulate the EGR rate much more accurately.

33 - EGR valve, N47 engines

50

Index

Explanation

Index

Explanation

1

Exhaust gas from exhaust manifold

6

Vacuum connection

2

Valve holder

7

Diaphragm

3

Guide

8

Exhaust gas to EGR cooler

4

Valve housing

9

Valve head

5

EGR position sensor

Exhaust gas recirculation cooler The use of an EGR cooler increases the efficiency of exhaust gas recirculation. The cooled exhaust gas is able to draw off more thermal energy from the combustion and thus reduce the maximum combustion temperature. The EGR cooler in the N47 engines is located downstream of the EGR valve. The engine's coolant flows through it. The exhaust gas is fed through this coolant flow in several flat

pipes (almost rectangular cross section). In the process, its thermal energy is transferred to the coolant. Different EGR coolers are used for the upper and lower power class. In addition, different EGR coolers are available to the upper power class depending on whether the vehicle concerned has a manual or automatic transmission.

34 - EGR cooler with bypass

Index

Explanation

Index

Explanation

1

Feed from exhaust manifold

4

Bypass

2

Cooling jacket

5

Bypass valve

3

EGR pipe

6

EGR valve

51

EGR Bypass valve The EGR cooler for vehicles with manual transmission offers a new feature. It is equipped with a bypass valve, which allows the exhaust gas to bypass the EGR cooler when required. This is useful in the engine warm-up phase for bringing the catalytic converter up to its operating temperature more rapidly. The bypass valve is adjusted by a vacuum unit. There are two states only: open and closed.

The vacuum canister is controlled by an electric changeover valve, which in turn is controlled by the DDE. With no negative pressure, the bypass valve is closed, i.e. the exhaust gas flows through the EGR cooler. If no negative pressure is present, the bypass valve opens the bypass (located inside the housing of the EGR cooler) and at the same time closes the supply to the EGR cooler.

35 - Bypass valve closed and open

Index

Explanation

Index

Explanation

A

Bypass valve closed

B

Bypass valve open

M57D30O2 in X3 The X3 has an exhaust valve (flap) upstream of the EGR cooler. This flap is closed when the engine is cold to avoid particles clogging the EGR cooler.

52

Exhaust turbocharger The turbocharger is driven by the engine's exhaust gases. The hot, pressurized exhaust gases are directed through the turbine of the exhaust turbocharger, thus producing the drive force for the compressor. The intake air is precompressed so that a higher air mass enters the combustion chamber in the engine. In this way, it is possible to inject and combust a greater quantity of fuel, which increases the engine's power output and torque.

The speeds of the turbine are between 100,000 rpm and 200,000 rpm. The exhaust inlet temperature may be up to approx. 900 °C. The performance of a turbocharged engine can reach the levels achieved by a naturally aspirated engine with significantly more capacity. However, the boost effect can also be used in a small engine to achieve a certain output with comparatively reduced consumption.

Exhaust turbocharger with wastegate

The exhaust turbocharger consists of a turbine and compressor mounted on a common shaft. It develops speeds of up to 200,000 rpm and operates at exhaust temperatures of approx. 900 °C.Up to 3 different basic designs of exhaust turbocharger are used. Theseare the exhaust turbocharger with wastegate, exhaust turbocharger with VNT and twin turbocharging with two turbochargers connected in series.

Wastegate The simplest form of controlling the boost pressure is the bypass on the turbine side which is also known as the wastegate. The turbine is selected small enough to meet the requirements in terms of torque at low engine speeds. Smooth engine operation is the prerequisite for this system. In this set-up, more exhaust gas than is required for developing the boost pressure is fed to the turbine just before reaching the maximum torque. The wastegate allows exhaust gas to flow past the exhaust turbocharger thus limiting the boost pressure. The wastegate is operated by a diaphragm unit. On the first exhaust turbochargers, this diaphragm unit was connected to the intake manifold. The wastegate was opened on exceeding the boost pressure set at the control rod and the boost air was correspondingly limited.

53

regulate the boost pressure and adapt it to respective operating conditions over a larger engine speed range. Compared to pure pneumatic control that only limited the boost pressure at full load, flexible boost pressure control also makes it possible to set the optimum boost pressure in the partial load range. The boost pressure is optimally set as a function of various parameters such as the charge air temperature and start of injection. The wastegate is operated by a diaphragm unit. Modulated vacuum is applied to this diaphragm unit, ensuring infinitely variable control of the wastegate. The vacuum is modulated by the electropneumatic pressure converter (EPDW). The electropneumatic pressure converter is actuated by the DDE.

3 Theoretically, varying the control rod in 36 - Engine operation line in compressor characteristic map

Index

Explanation

A

Engine operation line

1

Surge line

2


3


4


5


6


7


8


9

Vη = 0.75

10

Vη = 0.70

11

Vη = 0.68

12

Vη = 0.65

13

Vη = 0.60

14

Exhaust turbocharger operation line

Vη = Throughput/efficiency rate yield limit on the right-hand side corresponds to thechoke line Since its introduction, the digital diesel electronics DDE has been responsible for monitoring and controlling the boost pressure. The layout of the exhaust turbochargers has now been redesigned such that the maximum boost pressure is already reached at lower engine speeds. This now makes it possible to 54

"wastegate opens later" direction would increase the boost pressure. However, since the boost pressure is monitored by the DDE with the aid of a boost pressure sensor, this change is detected. A characteristic map stored in the DDE permits deviations in a defined range in order to compensate for changes in operation. If this range is exceeded as the result of manual intervention, a fault will be detected as the result of evaluating the received sensor signals in the DDE. This status is indicated by the emission warning lamp in the instrument cluster. This will result in a reduction in the boost pressure and therefore in the engine output. 1

VNT Variable nozzle turbine (VNT) In contrast to boost pressure control with the wastegate where the exhaust gas bypasses the turbine, with the variable nozzle turbine system, the entire flow of exhaust gas is always directed through the turbine. This is made possible by the variable geometry of the nozzle turbine, which allows the flow cross section to be adapted to the turbine depending on the engine operating point. This variable configuration enables effective utilization of the entire exhaust energy, thus improving the efficiency of the exhaust turbocharger and therefore of the engine compared to the wastegate control system. The position of the guide vanes is varied by theboost pressure actuator (diaphragm unit or electric actuator). The adjustment of the vanes reduces the flow cross section ("s", see following graphic). The flow rate of the exhaust gas and thus the exhaust gas pressure acting on the turbine wheel increases. The exhaust gas now additionally acts on the end of the turbine blades thus additionally boosting the efficiency by increasing the leverage.

37 - VNT vane mechanism, "closed"

The transfer of power (efficiency improvement) to the turbine wheel and compressor is therefore increased, particularly at low engine speeds. The boost pressure increases and a higher injection rate can be authorized by the DDE. As the engine speed increases, the vanes are gradually opened so that the power transfer always remains in equilibrium at the desired charger speed and required boost pressure level. The boost pressure actuator is controlled by the DDE by means of a pulse width modulated signal. Control rod (1) turns shaft (2) and therefore displacement ring (3) which in turn moves guide vanes (4). The position of the vanes affects the size of the flow cross section to the turbine wheel.

38 - Vane adjustment mechanism

Index

Explanation

1

Control rod

2

Shaft

3

Displacement ring

4

Guide vane

55

40 - Vane adjustment mechanism

39 - VNT vane mechanism, "open"

The guide vanes are wide open when a large volume of exhaust gas now flows through the turbine at high engine speed. The leverage at which the exhaust gas hits the turbines is reduced.

56

This means that there is an additional degree of freedom in the optimization of thermodynamic behaviour by comparison with a conventional exhaust turbocharger (ATL), which has a permanently constant flow cross section. Furthermore, the exhaust turbocharger with VNT does not need a wastegate valve.

Twin turbocharging Due to the operating principle as previously mentioned, the design of a turbocharger always involves a conflict of objectives. A small exhaust turbocharger responds quickly and provides ample torque at low engine speeds. However, its power output is limited as it quickly reaches the surge and choke line. Although it can generate high pressures, the volumetric flow is limited due to its size.

41 - Advantages of two-stage exhaust turbocharging

A large exhaust turbocharger is capable of producing high power output levels at high engine speeds. However, it responds sluggishly and is not capable of generating a high boost pressure at low engine speeds.

Index

Explanation

P

Engine output

t

Response characteristic

One solution to elevate this conflict of objectives is the use of variable nozzle turbine technology as implemented in the majority of BMW diesel engines. The flow cross section is adapted to the engine operating point by adjusting the vanes of the turbine wheel. Nevertheless, the effect of this system is limited so that the entire operating range of the engine cannot be optimally covered.

Engine

The ideal solution would be to have two exhaust turbochargers. One small turbocharger for quick response and one large turbocharger for maximum output yield. Precisely this configuration has now been developed for BMW twin turbo diesel engines. Two series-connected exhaust turbochargers are used. A small turbocharger for the high pressure stage and a larger turbocharger for the low pressure stage. The two turbochargers do not have variable vanes.

Boost pressure (absolute) [bar]

N47D20T0

3.0

N47

2.6

M57D30T1

2.85

M57D30T2

2.95

The two turbochargers can be variably combined providing an optimum for the entire operating range. This interplay is made possible by various flaps and valves. These are: • Turbine control valve (exhaust side) • Compressor bypass valve (air side) • Wastegate (exhaust side)

57

Design in 3D animation

58

To aid understanding, the design and the flap position are replicated by means of the following animation.

The buttons underneath the graphic can be used to control the flap position as a function of the engine speed range.

The animation is started by clicking on the graphic with your mouse.

The animation is supported by Adobe Reader version 7.08 or more recent versions.

Index

Explanation

Index

Explanation

1

High-pressure stage

5


2

Low-pressure stage

6

Vacuum canister for the compressor bypass valve

3


7

Wastegate valve

4

Vacuum canister for the turbine control valve

8

Vacuum canister for the wastegate valve

High pressure stage


42 - High pressure stage, N47D20T0 engine

The high pressure stage is the smaller of the two exhaust turbochargers. This is designed as a so-called "integral manifold" as the housing for the exhaust turbocharger and the exhaust manifold are one single cast unit. The high pressure stage is not connected by a valve. The oil inlet and outlet provides the necessary lubrication of the bearing.

Low pressure stage

44 - Turbine control valve, N47D20T0 engine

The turbine control valve opens a bypass channel on the exhaust side to the low pressure stage (past the high pressure stage). It is operated pneumatically by a vacuum unit and can be variably adjusted. An electropneumatic pressure converter (EPDW) applies vacuum to the vacuum unit. In development, the turbine control valve is referred to as the main control valve.

43 - Low pressure stage, N47D20T0 engine

The large exhaust turbocharger houses the turbine control valve and wastegate. It is mounted on the exhaust manifold and is additionally supported against the crankcase. The low pressure stage also has a separate oil supply for the bearing.

59


45 - Compressor bypass valve, N47D20T0 engine

The compressor bypass valve controls the bypass of the high pressure stage on the air intake side. It is operated pneumatically by a vacuum unit. The compressor bypass valve is either fully opened or completely closed. An electric changeover valve (EUV) applies vacuum to the vacuum unit.

60

Wastegate

46 - Wastegate, N47D20T0 engine

On reaching the nominal engine output, the wastegate opens to avoid high boost and turbine pressures. A part of the exhaust gas flows via the tailgate past the turbine of the low pressure stage. It is operated pneumatically by a vacuum unit. The wastegate can be variable adjusted. An electropneumatic pressure converter (EPDW) applies vacuum to the vacuum unit.

Sensors - exhaust system Exhaust temperature sensor TheDDE requires theexhaust temperature for controlling regeneration of the diesel particulate filter. The exhaust temperature sensor is designed as an NTC resistor sensor (the resistance decreases as temperature increases).

Version with 2 exhaust temperature sensors (EURO3 + EURO4)

Temperatur Resistance e

Voltage

-40 °C

approx. 96 kΩ

approx.4.95 V

±0 °C

approx. 30 kΩ

approx.4.84 V

+100 °C

approx. 2.79 kΩ approx.3.68 V

An exhaust temperature in excess of 240 °C is required for regenerating the filter. Initiating the filter generation procedure at temperatures below 240 °C would produce white smoke caused by excess hydrocarbon (HC). The exhaust temperature sensor upstream of the oxidation catalytic converter ensures the regeneration procedure is only enabled at temperatures above 240 °C.

+800 °C

approx. 31.7 kΩ approx.0.15 V

3 The electrical supply line must not be subjected to a pulling force of more than 80 N. Sensors that have been dropped must not be used again. 1

One exhaust temperature sensor is located upstream of the oxidation catalytic converter and the other upstream of the diesel particulate filter.

Three different types of sensor are used in the exhaust system. These sensors detect the exhaust temperature, exhaust backpressure and exhaust composition (oxygen sensor). The location and numberof exhaust temperature sensors vary depending on the type of vehicle.

The exhaust temperature upstream of the diesel particulate filter is registered in order to control post-injection and therefore the exhaust temperature itself ahead of the diesel particulate filter. Depending on the type of vehicle, the exhaust temperature sensor upstream of the diesel particulate filter sets a temperature between 580 °C - 610 °C based on the post-injection volume.

61

47 - E60 Exhaust system with M57D30O1 engine

Index

Explanation

Index

Explanation

1


5


2

Oxygen sensor

6


3

Connecting pipe, exhaust backpressure sensor

7


4


48 - Catalytic converter and DPF with sensors, M67D44O1 engine

62

Index

Explanation

1

Exhaust backpressure connection

2

Oxygen sensor

3


4


5


6


Exhaust system with one exhaust temperature sensor (EURO4) In line with the introduction of the oxidation catalytic converter and the diesel particulate filter in one housing, only one exhaust temperature sensor upstream of the oxidation catalytic converter was used. The sensor

upstream of the diesel particulate filter is replaced by a characteristic map in the DDE. Currently, however, a second exhaust temperature sensor is again used upstream of the diesel particulate filter as the characteristic map cannot provide the required degree of accuracy.

Oxygen sensor More stringent exhaust emission limits have rendered necessary more accurate control of the exhaust gasses. The mean quantity adaptation (MMA) makes it possible to comply with the specified limits with a corresponding safety margin. This is necessary as the emission limits must still be maintained despite component tolerances and operating influences. With mean quantity value adaptation the fuelair ration (lambda) is adjusted by corresponding adaptation of the exhaust gas recirculation. This feature compensates for any inaccuracies relating to manufacturing tolerances of the hot-film air mass meter or of the fuel injectors. This function was used for the first time on the E83 with the M57TU engine. An injection volume averaged across all cylinders is calculated from the fuel-air ration measured by the oxygen sensor and the air mass measured by the HFM. This value is compared with the injection volume specified by the DDE. If a discrepancy is detected, the fresh air mass is adapted to match the actual

injection volume by correspondingly adjusting the EGR valve, thus establishing the correct fuel-air ratio. The MMA is not an "instantaneous" regulation but an adaptive learning process. In other words, the injection volume error is taught into an adaptive characteristic map that is permanently stored in the control unit.

3 The MMA characteristic map must be reset with the aid of the BMW diagnosis system after replacing one of the following components: • Hot-film air mass meter • Fuel injector(s) • Rail-pressure sensor 1 For optimum combustion, a diesel engine is operated with a fuel-air ratio of λ > 1, i.e. richin oxygen. λ = 1 signifies a mixture of 1 kg fuel with 14.5 kg air. The oxygen sensor is located at the inlet to the shared housing of the diesel particulate filter (DPF) and oxidation catalytic converter.

63

Control sensor with rising characteristic

49 - Control sensor with rising characteristic

The control sensor with rising characteristic is a type LSU 4.9 broadband oxygen sensor supplied by Bosch. This broadband oxygen sensor is installed upstream of the catalytic converter close to the engine. The oxygen concentration in the exhaust gas can be determined over a large range with the broadband oxygen sensor. This makes it possible to determine the fuel-air ratio in the combustion chamber. The broadband oxygen sensor is capable of providing accurate measurements not only at λ = 1 but also at λ < 1 (rich) and λ > 1 (lean). The broadband oxygen sensor supplies a distinct, steady-state electrical signal from λ = 0.7 to λ = ∞ (λ ∞ = air). The oxygen sensor is connected by 5 lines to the connector housing. The following connections lead into the housing: • Pump current, positive • Pump current and Nernst voltage, negative • Heating, negative • Heating, positive • Nernst voltage, positive

3 A compensating resistor that compensates for production tolerances is integrated in the oxygen sensor connector. This resistor is connected to a free contact. 1

The measuring cell of the broadband oxygen sensor is a zirconium dioxide ceramic material ZrO2. It is designed as the combination of a Nernst concentration cell (sensor cell with the function of an oxygen sensor with erratic characteristic) and an oxygen pump cell that transports oxygen ions.

64

The oxygen pump cell (items 7, 11 and 12) and the Nernst concentration cell (items 4, 5 and 6) are arranged such that there is a diffusion gap (8) of about 10 to 50 µm between them. The diffusion gap is connected via an exhaust inlet hole (9) to the exhaust gas. On the one side, the Nernst concentration cell is connected via a reference air channel (3) and opening to the surrounding atmosphere. On the other side, it is exposed to the exhaust gas over a diffusion gap (8). The exhaust gas passes through the gas inlet hole and enters the diffusion gap of the Nernst concentration cell. Initially, the same oxygen concentration as in the exhaust gas is established in the diffusion gap. In order to achieve λ = 1 in the diffusion gap, the Nernst concentration cell compares the exhaust gas in the diffusion gap with the ambient air in the reference air channel.

3 It is extremely important to ensure that the cable connection to the oxygen sensor is free of soiling so that the ambient air can enter the reference air channel. It is therefore necessary to protect the plug connection from soiling, washing agents, preservatives etc. 1

50 - Design of broadband oxygen sensor

Index

Explanation

Index

Explanation

1

Insulation layer

8

Diffusion gap

2

Heating element

9

Porous diffusion barrier

3

Reference air channel

10

Exhaust inlet hole

4

Inner electrode, reference cell

11

Ceramic layer made of ZrO2

5

Ceramic layer made of ZrO2

12

Outer electrode, oxygen pump cell

6

Outer electrode reference cell

13

Protective layer

7

Inner electrode, oxygen pump cell

65

51 - Broadband oxygen sensor with lean mixture

Index

Explanation

Index

Explanation

1

Exhaust pipe

7

Connection, oxygen sensor heater, negative

2

Connection, outer electrode of oxygen pump cell, positive

8

Pump current in mA (red = positive)

3

Connection, inner electrode of oxygen pump cell, negative

9

Evaluator circuit

4

Connection, outer electrode of reference cell, negative

10

Reference voltage in V (< 450 mV = blue)

5

Connection, inner electrode of reference cell, positive

11

Oxygen ion flow initiated by pump current

6

Connection, oxygen sensor heater, positive

O2

Oxygen ions

By applying a pump voltage to the outer electrode (2) and inner electrode (3) of the oxygen pump cell, oxygen can be pumped in or out from the exhaust gas through the porous diffusion barrier into the diffusion gap. An evaluator circuit (9) in the DDE controls this voltage applied at the pump cell with the aid of the Nernst concentration cell such that the composition of the gas in the diffusion gap is always at a constant λ = 1. In the case of exhaust gas from lean combustion, the oxygen pump cell pumps the oxygen ions out of the 66

diffusion gap. Conversely, in the case of exhaust gas from rich combustion, the oxygen ions, resulting from catalytic decomposition of CO2 and H2O at the outer electrode of the pump cell, are pumped out of the surrounding exhaust gas into the diffusion gap. No oxygen ions need to be transported at λ = 1. The pump current is zero. The pump current is proportional to theoxygen ionconcentration in the exhaust air and therefore a measure for the fuel-air ratio λ .

52 - Broadband oxygen sensor with rich mixture

Index

Explanation

Index

Explanation

1

Exhaust pipe

7


2


8

Pump current in mA (blue = negative)

3

Connection, outer electrode of oxygen pump cell, negative

9

Evaluator circuit

4


10

Reference voltage in V (> 450 mV = red)

5


11


6


O2

Oxygen ions

67

53 - Broadband oxygen sensor, λ = 1

Index

Explanation

Index

Explanation

1

Exhaust pipe

7


2


8

Pump current in mA (grey = zero)

3

Connection, outer electrode of oxygen pump cell, negative

9

Evaluator circuit

4


10

Reference voltage in V ( 450 mV = green)

5


11


6


O2

Oxygen ions

The following diagram shows the correlation between pump current and fuel-air ratio λ .

68

Index

Explanation

A

Characteristic curve

1

Fuel-air ratio λ

2

Pump current

54 - Pump current/fuel-air ratio diagram

Exhaust backpressure sensor The DDE requires the exhaust backpressure sensor for controlling regeneration of the diesel particulate filter.

Absolute pressure Voltage 0.6 bar

approx. 1.9 V

The exhaust backpressure sensor is connected by means of a hose to the exhaust system after the oxidation catalytic converter and before the diesel particulate filter. The reason for the distance from the exhaust system is the high temperatures radiated by the exhaust system and impurities that could otherwise affect the sensor element. The hose connection must face downward. The sensor is mounted on the engine.

1.0 bar

approx. 2.65 V

2.0 bar

approx. 4.5 V

3 If the sensor fails, the DDE initiates filter regeneration every 500 km and a fault code entry is stored in the DDE. 1

The exhaust back pressure sensor measures the pressure ahead of the diesel particulate filter. The DDE will initiate regeneration of the diesel particulate filter if the pressure rises above a permissible value. The exhaust backpressure is applied to the diaphragm with the sensor element (piezoelement). Ambient pressure acts on the other side of the diaphragm. The deflection of the diaphragm is converted by the sensor element into an electrical signal. The evaluator circuit processes the signal and sends an analogue voltage signal to the DDE. The voltage signal is applied in linear form as the exhaust backpressure increases.

69

Oxidation catalytic converter Design and function The oxidation catalytic converter is accommodated in a stainless steel housing and is firmly embedded in a damping mat. The oxidation catalytic converter reduces hydrocarbons and carbon monoxide under all operating conditions. An important characteristic is its rapid response. Its location varies depending on the type of vehicle and version.

A monolith (ceramic body) or metal substrate serves as the carrier.

Ceramic substrate The walls of the monolith are extremely thin to minimize resistance to flow. The walls are only approx. 0.3 mm thick.

An important factor is to ensure as large a surface as possible so that large quantities of exhaust gas can be processed. The substrate is made up of thousands of channels (pores) through which the exhaust gas flows. The channels are approx. 1 mm wide.

56 - Ceramic substrate

The advantages of the ceramic substrate are the improved recovery of the precious metals, the cost-effective manufacture and the more constant operating temperature. The ceramic substrate is made of magnesium aluminium silicate with low thermal expansion and high heat resistance. The melting point is above 1400 °C.

55 - Catalytic converter and DPF with sensors, M67D44O1 engine

70

Index

Explanation

1

Exhaust backpressure connection

2

Oxygen sensor

3


4


5


6


Metal substrate The risk of mechanical damage or burnthrough is lower with the metal substrate and the wall thickness can be reduced to approx. 0.05 mm. The metal substrate is made from extremely thin steel foil.

substrate (1) to increase the available surface. This intermediate layer increases the effective surface of the monolith by a factor of 700. The oxygen storage capability is also increased. The promoters boost the catalytic effect of the active noble metal layer. This noble metal layer (3) is vaporized microscopically thin onto the intermediate layer. The noble metal used for this purpose in oxidation catalytic converters for diesel engines is platinum and possibly palladium which enhance the oxidation processes.

Exhaust composition

57 - Metal substrate

The advantages of the metal substrate can be found in its impact resistance, heat resistance, short heating-up phase and the lower backpressure. 59 - Exhaust gas composition of a diesel engine before exhaust treatment

Design

The following deals with treatment of the exhaust components illustrated in the above graphic. To simplify the representation, the illustration only shows the constituents that generally undergo a change in the catalytic converter or diesel particulate filter.

58 - Structure of the oxidation catalytic converter

Index

Explanation

1

Ceramic substrate or metal substrate

2

Intermediate layer

3

Noble metal layer

An intermediate layer (2), consisting of aluminium oxide (Al2O3) with promoters, is applied on the ceramic substrate (1) or metal 71

Function

60 - Function Function of the oxidation oxidation catalytic catalytic converter converter

Exhaust constituents before the oxidation catalytic converter

Exhaust constituents after the oxidation catalytic converter

61 - Exhaust Exhaust constituents constituents after the oxidation oxidation catalytic converter converter

72

Index

Explanation

O2

Oxygen

HC

Hydrocarbon

CO

Carbon monoxide

SO2

Sulphur dioxide

NO

Nitrogen monoxide

H2O

Water

C

Carbon

CO2

Carbon dioxide

SO3

Sulphur trioxide

NO2

Nitrogen dioxide

62 - Exhaust constituen constituents ts before the oxidation oxidation catalytic catalytic converter

The exhaust constituents remain in the cataly catalytic tic conve converte rterr for severa severall hundre hundredth dthss of a second second.. For For thegas mol molecu eculesthis lesthis is suffic sufficien ientt time to reach the surface of the catalyst as a resu result lt of the the high high diff diffus usio ion n pres pressu sure re and and reac reactt with the surface. Owing to their size, the particles contained in the exhaust gas have a lower diffusion rate that is approximately 100 to 1000 times lower than that of molecules. This This means means separa separatio tion n or reacti reaction on takes takes place place only to a limited extent.

The high propensity of the oxidation catalytic converter to convert gaseous substances results in the formation of SO3 from SO2 and therefore in a substantial increase in the total particulate mass depending on the composition of the fuel. In addition, the oxidatio oxidation n catalytic catalytic converte converterr converts converts NO to an increasing extent to NO2. NO2 is required for the downstream diesel particulate filter or particulate trap catalytic converter. The near engine oxidation catalytic converter ensures the conversion of the following exhaust gas constituents across the entire operating range:

• (2SO2 + O2 => 2SO3) depending on the sulphur content in the fuel! Soot particles flow through the oxidation catalytic converter unimpeded. Due to the high oxygen content of the exhaust gas, the oxidation catalytic converter starts to work at approximately 170 ° 170 °C. C. Above around 350 ° 350 °C, C, the partic particle le emissi emissions ons begin begin to increa increase se again. again. Sulphates form due to the sulphur content of the fuel (sulphur-oxygen compounds). Lowering the sulphur content in the fuel contri contribut butes es to reduci reducing ng partic particle le format formatio ion n and therefore to reducing the particle mass.

• 2NO + O2 => 2NO2 • 2CO + O2 => 2CO2 • CxHy + (x+y/4)O2 => xCO2 + y/2 H2O

Application examples Catalytic converter coating on EU4 vehicles:

e m u l o v r e t l i l n F i

) t f / g ( 3 g m n i d t / a g o n C i

) t P g ( n i m u t n h i g t a i e l P w

) d P ( g m n i u t i d h a g l l i a e P w

o i t a r m u i d a l l a p : m u n i t a l P

3

l e d o M

e n i g n E

n o i s s i m s n a r T

E60/E61

M57D30O2

Manual

1.127

7.06 (200)

5.31

2,65

2:1

E60/E61

M57D30O2

Automatic

1.127

5.30 (150)

3.98

1.99

2:1

E90/E91

M57D30O2

Manual

1.127

7.06 (200)

5.31

2.65

2:1

E90/E91

M57D30O2

Automatic

1.127

5.30 (150)

3.98

1.99

2:1

E70

M57D30O2

Automatic

1.127

5.30 (150)

3.98

1.99

2:1

The oxidation catalytic converter is coated in zones. This means that the coating at the catalytic converter inlet is greater than at the outlet. The reason for this is that the exhaust gasses at the inlet to the catalytic converter are hotter and the effect is greater with a thicker coating at the inlet.

73

Diesel particulate filter Design and function Thediesel particulatefilter particulatefilter filters filters the carbon substances out of the exhaust gas, buffers them and initiates conversion from carbon to CO2. Othersolid particles particles contained contained in the exhaust gas are permanently stored. It also supplements the oxidation catalytic converter while converting CO to CO 2.

Design

Function

The diesel particulate filter is accommodated in a stainless steel housing and is firmly embedded in a damping mat.

The diesel particulate filter ensures the conversion of the following exhaust gas constituents:

The design of the diesel particulate filter is very similar to that of the oxidation catalytic converter. A monolith (ceramic body) serves as the carrier.

• C + 2NO2 => CO2 + 2NO

In the same way as the oxidation catalytic converter, the diesel particulate filter is made up of thousands of channels (pores) through whic which h the the exha exhaus ustt gas gas flow flows. s. The The diff differ eren ence ce is that the walls a porous, enabling the gaseous substances to flow through them.

The coati coating ng helps helps to achie achieve ve a reduct reductio ion n in the soot ignition temperature and thus to guarantee good regeneration characteristics of the diesel particulate filter.

As on the oxidation catalytic converter, the surface is coated with the noble metals platinum and palladium.

• C + O2 => CO2 • 2CO + O2 => 2CO2

The exhaust gases flow out of the oxidation catalytic converter and into the inlet ducts of the diesel diesel partic particula ulate te filter filter.. These These are closed closed at their ends. Each inlet duct is surrounded by four exhaust ducts. The soot particles deposit on the coating of the the inle inlett duct ductss and and rema remain in ther there e unti untill they they are are combusted as a result of an increase in the exhaust temperature. The cleaned exhaust gas gas flow flowss out out of the the exha exhaus ustt duct ductss thro throug ugh h the the coated, porous filter walls.

63 - E60 Diesel Diesel particulate particulate filter with M57TU2 M57TU2 TOP engine engine

64 - Cross Cross section of the diesel diesel particulat particulate e filter

74

In the the long long term term,, the the soot soot part partic icle less that that coll collec ectt on the filter walls would clog up the diesel particulate filter. It is therefore necessary to burn off these soot particles. This happens when when the exhaus exhaustt temper temperatu ature re rises rises above above the soot ignition temperature. This process is known as filter regeneration. The carbon particles are converted to gaseous carbon dioxide (CO2).

Soot particles have a relatively high ignition temperature. These temperatures are achievable during permanent full load operation. It complements the natural regeneration supported by the upstream oxidation catalytic converter through the formation of NO2.

It is necessary to periodically change the filter as the deposited ash gradually blocks the pores thus increasing the backpressure. The higher backpressure results in shorter regeneration intervals. The DDE calculates the remaining time from the fuel consumption and the measured exhaust backpressure.

The exhaust temperature required is not usually achieved if a diesel engine runs permanently in the partial load range. The particles retained in the diesel particulate filter increase the exhaust backpressure.

3 If the sulphur content in the diesel fuel is > 50 - 100 ppm, there is a possibility of heavy white smoke development and a sulphur odour from the exhaust tailpipe. 1

A pressure sensor records the increase in pressure upstream of the diesel particulate filter, a regeneration can be initiated. To this end, the intake air is throttled by the throttle valve so that less cool air flows into the cylinder, which would otherwise draw heat away from theexhaust gas. A delayed injection start and a secondary injection also increase the exhaust temperature. The conversion of nitrogen monoxide to nitrogen dioxide in the oxidation catalytic converter brings about a reduction in the ignition temperature of the soot particles, thereby promoting the regeneration of soot particles in the diesel particulate filter.

3 The diesel particulate filter retains all particles. These include non-regenerative particles, such as oil ash, swarf and additive residues. The non-regenerative particles gradually lead to a blockage of the diesel particulate filter over time. Over a distance of 1000 km, approx. 0.6 grams of powder ash are deposited in the rear third of the diesel particulate filter. The diesel particulate filter is therefore subject to a replacement interval. The replacement interval can be anywhere between 160,000 km and 220,000 km. 1

75

65 - Diesel particulate filter M57TU engines

76

Index

Explanation

Index

Explanation

1

Exhaust gas from oxidation catalytic converter

5

Inlet channel

2


6

Outlet channel

3


7

Particle-free exhaust to silencer

4

Filter element locking device

66 - Function of diesel particulate filter

Exhaust constituents before the diesel particulate filter:

Exhaust constituents after the oxidation catalytic converter

68 - Exhaust constituents after the diesel particulate filter

67 - Exhaust constituents before the diesel particulate filter

Index

Explanation

O2

Oxygen

SO2

Sulphur dioxide

H2O

Water

C

Carbon

CO2

Carbon dioxide

SO3

Sulphur trioxide

NO2

Nitrogen dioxide

NO

Nitrogen monoxide

77

TheDDE determines thesoot accumulation in thediesel particulate filter based on theengine operating point. Regeneration can take place continuously or cyclically. • Continuous regeneration: In a slow oxidation process, the soot particles are converted directly to carbon monoxide (CO) carbon dioxide (CO2) in operating ranges where the exhaust temperature is above the ignition temperature of the soot (> 350 °C). The nitrogen oxide (NO2) in the exhaust gas is used as the oxidizing agent. If the exhaust temperature is not sufficiently high for this process, the soot particles are initially collected in the diesel particulate filter and then burnt off the next time the exhaust temperature is elevated. • Cyclic regeneration: Targeted regeneration is initiated if operating conditions do not allow for continuous regeneration of the diesel particulate filter (e.g. prolonged partial load operation in urban traffic at low exhaust temperatures). This procedure is initiated based on the signals from the exhaust backpressure

sensor and the exhaust temperature sensor(s).Cyclic regeneration takes placein the same way as continuous regeneration without any noticeable effects on vehicle handling. Depending on the load point, this regeneration procedure is carried out by specifically throttling the intake air combined with 1 or 2 post-injection cycles. The energy made available by the fuel is converted into heat, raising the exhaust temperature to approx. 620 °C. The soot is now burned off by the residual oxygen (O2) contained in the exhaust gas. The regeneration process can take up to several minutes. The regeneration intervals greatly depend on the load collective of the vehicle in the last 500 km. Depending on the driving profile, a filter regeneration cycle is additionally initiated every 700 - 2500 kilometres. The diesel particulate filter is regenerated every 500 km in the event of the pressure sensor or temperature sensors failing.

Application examples Diesel particulate filter coating on EURO4 vehicles: o i t a r

l ) n 2 i e e n o m Z u l + o v 1 r e e n t l i o F Z (

) 2 3 e t n f / o ( g Z g : 3 n 1 m i t e d a n / o o g n C Z i

) t P ( g n i m u t n h i g t i a e l P w

) d P ( g m n u i i t d h a g l l i a e P w

m u i d a l l a p : m u n i t a l P

l e d o M

e n i g n E

n o i s s i m s n a r T

E60/E61

M57D30O2

Manual

3.94

3.18 (90) : 0.71 (20)

5.31

2.65

2:1

E60/E61

M57D30O2

Automatic

3.94

2.47 (70) : 0.71 (20)

3.98

1.99

2:1

E90/E91

M57D30O2

Manual

3.94

3.18 (90) : 0.71 (20)

5.31

2.65

2:1

E90/E91

M57D30O2

Automatic

3.94

2.47 (70) : 0.71 (20)

3.98

1.99

2:1

E70

M57D30O2

Automatic

3.94

2.47 (70) : 0.71 (20)

3.98

1.99

2:1

The diesel particulate filter is coated in zones. The diesel particulate filter is divided into two zones each of 50 %. The coating in zone 1 is thicker than that in zone 2. The reason for this is that the exhaust gasses at the inlet to the diesel particulate filter are hotter and the effect is greater with a thicker coating at the inlet.

78

Particulate trap catalytic converter Design and function The particulate trap catalytic converter was used for the first time on the E87 with automatic transmission. The reason was that an automatic transmission vehicle has a higher mechanical loss and the engine therefore operates under higher load. This has a negative effect on soot formation and therefore on particle emissions.

• It is not a filter but rather a catalytic converter with soot particle separator.

For this reason, particulate trap catalytic converters were used for E87 and E90 vehicles with M47TU2 engine and automatic transmission.

The particulate trap catalytic converter is housed near-engine in a stainless steel housing together with the oxidation catalytic converter. The particle separator is made of metal. Layers of corrugated metal alternate with a metal fibre mesh.

In contrast to the diesel particulate filter, the particulate trap catalytic converter is designed as a simple separator system with no sensors. The particulate trap catalytic converter is required in order to comply with EURO4 emission legislation with a safety margin in all operating ranges.

• The maximum filtration efficiency is 50 % compared to a diesel particulate filter. • Its operation requires no sensors.

The particulate trap catalytic converter makes it possible to reduceparticleemissionby upto 50 % by simplemeans. Theparticula te trap catalytic converter is a simple separator system with no sensors.

Design

69 - Particulate trap catalytic converter, M47TU2 engines

Index

Explanation

1

Particulate trap catalytic converter

2


3

Particle separator

The particulate trap catalytic converter differs from the diesel particulate filter by following features: 79

70 - Metal substrate of soot particle separator

Index

Explanation

Index

Explanation

1

Metal fibre mesh

2

Corrugated layer

The particle separator has many openings in the corrugated layers (2). These openings are designed as baffles. The openings create crossconnections to the channels. In this way, a proportion of the exhaust flow and therefore approx. 50 % of the particles are diverted over the baffles through the metal fibre mesh (1). The particles contained in the exhaust gas retained by the metal fibre mesh. The soot particles are converted when the exhaust temperature increased to above 350 °C. Through oxidation (oxygen), the soot (carbon) is converted to carbon dioxide (CO 2). The nitrogen oxide(NO2) produced in the oxidation catalytic converter is used as the oxidizing agent.

80

Silencer Silencing Various silencing options are available. Silencing can be achieved by absorption, reflection or interference.

Using the E90 rear silencer as an example, the following describes the function of different types of silencing systems.

The design layout of the silencer is adapted to the respective model and package space.

The silencer system contributes to optimum vehicle performance. A further task is to accommodate the corresponding systems forreducing pollutant and noise emissions.

71 - E90 Rear silencer

Index

Explanation

Index

Explanation

1

Long exhaust route through two chambers

3

Medium exhaust route through one chamber

2

Direct exhaust route 81

Absorption

Reflection

The higher (particularly annoying) frequencies are absorbed by sound-insulating materials (basalt fibres, steel wool) or the sound energy is converted into frictional heat.

Targeted design layout cancels out noise energy by way of echo effects.

72 - Absorption

Index

Explanation

A

Sound-insulating material

B

Outlet pipe

C

Inlet pipe

Index

Explanation

1

Incoming sound

A

Silencer chamber

2

Noise reduction

B

Inlet pipe

3

Outgoing sound

C

Outlet pipe

1

Incoming sound

2

Echo

3

Result

4

Higher frequency sound

5

Lower frequency sound

The incoming sound (1) that occurs at a certain frequency and amplitude is directed through the sound insulation material (A). The noise level (2) is reduced in the sound insulation material. The outgoing sound (3) exits the silencer via the outlet pipe.

73 - Reflection

The silencer chamber (A) in the reflection system is designed such that the sound is reflected phase-offset. The sound (1) coming from the inlet pipe (B) which has a certain frequency hits the opposite side and is reflected phase-offset by 180°. An echo (2) is created. The incoming sound and echo mutually cancel each other out. The result (3) is that the corresponding frequency is eliminated. Higher frequency sound (4) or lower frequency sound (5) can barely be influenced.

82

Interference

(inflections) of different length. The paths of different length are achieved by corresponding design of the silencers.

A part of the sound energy is cancelled out when coinciding after passing through turns

74 - Interference

Index

Explanation

Index

Explanation

A

Inlet pipe, silencer

I

Chamber 2

B

Outlet pipe, silencer

J

Chamber 3

C

Inlet pipe, chamber 3

1

Incoming sound

D

Outlet pipe, chamber 3

2

Sound transfer

E

Inlet pipe, chamber 1

3

Incoming sound, chamber 3

F

Outlet pipe, chamber 1

4

Incoming sound, chamber 1

G

Outlet pipe, silencer

5

Outgoing sound, chamber 1

H

Chamber 3

6

Result

In the interference system, the incoming sound (1) via chamber 3 (H) passes through chamber 1 (J) as outgoing sound chamber 1 (5) and in chamber 2 (I) comes up against the sound from the sound transfer point (2). Due to the different length of the path, the sound is eliminated in a similar way as in the reflection system. The frequency range is now substantially reduced as the sound result (6).

83

Examples E87 with M47D20O2 engine

75 - E87 exhaust system with M47D20O2 engine

84

Index

Explanation

Index

Explanation

A

Exhaust system, M47D20O2 engine with manual transmission

2

Decoupling element

B

Exhaust system, M47D20O2 engine with automatic transmission

3


1

Oxidation catalytic converter with 4 diesel particulate filter or particulate trap catalytic converter

Rear silencer

E87 with N47 engines

76 - E81/E87 Exhaust system, N47 engines

Index

Explanation

Index

Explanation

1

Rear silencer

7

EGR bypass actuator

2


8


3


9

VNT actuator

4

Exhaust manifold

10

Oxidation catalytic converter and diesel particulate filter

5

EGR valve

11

Oxygen sensor

6

EGR cooler

12


85

E60 with M57TU2 engines

77 - E60 Exhaust system, M57TU2 engines

86

Index

Explanation

Index

Explanation

1


6


2

Connecting pipe

7

Decoupling element

3

Oxygen sensor

8


4


9


5


10

Rear silencer

Decoupling element The decoupling element makes it possible to compensate for relative movements of the engine with respect to the vehicle body in all directions. The freedom of movement is ensured by the fact that the inner sleeveis secured only at one end and the other end can be displaced. The gaiter at both ends provides a gas-tight seal.

The lowfrequency noise emission drops by up to 10 decibels. The perceivable volume is halved. The frequency and tone increase at higher engine speeds. There is then no longer any point in damping the low frequency noise emission. The rolling and driving noise is then prevalent and the low frequency noise emission retreats to the background. The most important factor at high engine speeds is to reduce theexhaust backpressure. This is made possible by opening the exhaust flap and the engine can reach its full power output. The exhaust flap is controlled by a vacuum unit (1) mounted on the tailpipe. The vacuum required for activation is supplied by the engine vacuum system via a hose line up to the electrical changeover valve. The electrical changeover valve is controlled by the DDE and applies the vacuum to the vacuum unit as required. The exhaust flap is closed.

78 - Decoupling element, N47 engines

Index

Explanation

1

Braided sleeve

2

Gaiter

3

Inner sleeve

Tailpipe The shape and length of the tailpipe are adapted to the exhaust system. The length of the tailpipe also contributes to noise reduction.

79 - Exhaust flap

Index

Explanation

1

Vacuum unit

Exhaust flap A low frequency noise emission prevails at low engine speeds and in coasting mode. Approximately two thirds of the low frequency noise emission is swallowed up when a tailpipe is closed off at low engine speeds.

87

Activation of the exhaust flap depends on the respective operating conditions. The following

graphic shows the positions of the exhaust flap as a function of the operating conditions.

80 - Exhaust flap operating ranges

88

Index

Explanation

Index

Explanation

A

Normal engine operation

2

Exhaust flap closed

B

Regeneration of diesel particulate filter

3

Exhaust flap open

1

Load

4

Engine speed

Vacuum system System overview N47D20T0 Engine

The vacuum system is required for the purpose of actuating various flapsand valves.The maintaskis to provide power assistance for the braking system. In addition, vacuum is supplied to various components on the engine.

81 - Vacuum system, N47D20T0 engine

Index

Explanation

Index

Explanation

1

Electric changeover valve (EUV)

9

Electric changeover valve

2

Vacuum unit for EGR bypass valve

10

Vacuum unit for compressor bypass valve

3

Electropneumatic pressure converter (EPDW)

11

Electropneumatic pressure converter

4

Vacuum unit for EGR valve

12

Vacuum unit for wastegate

5

Brake booster

13

Vacuum reservoir

6

Non-return valve

14

Non-return valve

7


15

Vacuum pump

8

Vacuum unit for turbine control valve

To simplify assignment, thevacuum lines from several valves to the vacuum units are marked in colour. This colour code is also used for the actual components.

Component

Colour


Blue


Red

Wastegate

Black

EGR bypass valve

Red

EGR valve

Blue

89

M57D30T1 Engine

82 - Vacuum system, M57D30T1 engine

90

Index

Explanation

Index

Explanation

1


11


2

Vacuum unit for compressor bypass 12 valve


3


Engine mount

4

Vacuum unit for turbine control valve 14


5

Vacuum reservoir

15

Vacuum unit for swirl flaps

6


16


7


17

Vacuum unit for exhaust flap

8

Non-return valve

18

Brake booster

9

Vacuum pump

19

Non-return valve

10


13

M57D30T2 Engine

83 - Vacuum system, M57D30T2 engine

91

Index

Explanation

Index

Explanation

1

Brake booster

17

Vacuum line, EPDW wastegate

2

Non-return valve

18


3

EUV swirl flaps

19

Vacuum line, EUV engine mount

4


20

Engine mount

5

Vacuum line, EUV engine mount

21

Vacuum reservoir

6

Vacuum line, engine mount

22

Vacuum unit, EPDW turbine control valve

7

Variable engine mount

23

Vacuum line, EPDW turbine control valve

8

Vacuum distributor

24

Vacuum line, EUV compressor bypass valve

9


25

EUV compressor bypass valve

10

Vacuum line, EPDW wastegate

26


11

Vacuum line, vacuum reservoir

27

EPDW wastegate

12

Vacuum line, brake booster

28

EPDW turbine control valve

13

Non-return valve

29

EPDW EGR valve

14

Vacuum pump

30

EUV engine mount

15


31

Vacuum line, swirl flaps

16


To simplify assignment, the vacuum lines from several valves to the vacuum units are marked in colour. Component

92

Colour

Wastegate

Blue


Red


Black

EGR valve

Blue

Engine mount

Black

Swirl flaps

White

Vacuum line, EUV swirl flaps

84 - Vacuum system, M57TU2 TOP engine

Index

Explanation

Index

Explanation

1


10


2



3



4

Vacuum unit for turbine control valve 13

Engine mount

5

Vacuum reservoir

14


6


15


7


16

Brake booster

8

Non-return valve

17

Non-return valve

9

Vacuum pump

12

93

Vacuum pump Vacuum pump on engine

Index

Explanation

3

Rotor

4

Housing cover

5

Vacuum connection

6

Housing

7

Non-return valve

The vacuum pump is driven by the exhaust camshaft that is connected to rotor (3) by means of a jaw clutch. While the engine is running, sliding blocks (1) run against housing cover (4). The engine oil lubrication system provides a seal to the two different chambers on both sides of slide valve (2). The air is drawn in via vacuum connection (5) on the right-hand side and delivered to the engine via non-return valve (7) on the left-hand side. 85 - Vacuum pump, M57TU2 TOP engine

94

Index

Explanation

1

Sliding block

2

Slide valve

The vacuum pump has a volume of 0.15 litres. Evacuation of the vacuum system to a vacuum (negative pressure) of 500 mbar (absolute) (depending on type of engine) takes place in less than 5 seconds at an engine speed of approx. 720 rpm. The volume to be evacuated amounts to approx. 4.2 litres.

Vacuum pump in oil pan The vacuum pump of the N47 engines is fitted inside the sump and forms a single unit

together with the oil pump and the reinforcement shell.

86 - Oil/vacuum pump with intake pipe in the N47 engines

Index

Explanation

Index

Explanation

1

Oil pump

4

Vacuum pump

2

Intake pipe

5

Oil/vacuum pump sprocket

3

Reinforcement shell

The reason for the unusual installation location is to reduce the engine height dimension. It was designed in this manner with passive pedestrian safety in mind. The pump is a vane-type pump with aluminium housing (AlSi9Cu3) with a steel rotor and a plastic vane. It is chain-driven together with the oil pump by the crankshaft.

The vacuum pump evacuates down to a negative pressure of 500 mbar (absolute) in fewer than 5 s. The negative pressure duct passes through the oil pump housing and the crankcase. At the outletof the crankcases, the main negative pressure line is connected to the brake force amplifier and the other loads. A non-return valve is located at this connection.

95

Non-return valve Non-return valve, vacuum pump

Non-return valve, brake booster

The non-return valve is mounted directly on the vacuum pump or at the vacuum connection on the crankcase on N47 engines.

The non-return valve prevents vacuum escaping from the brake booster when the engine is not running.

The non-return valve prevents vacuum escaping via the vacuum pump when the engine is not running.

From the vacuum connection to vacuum pump (2), the air is drawn out of the brake booster via valve plate (1) above the brake booster vacuum connection. To prevent incorrect installation, direction arrows (3) indicate the direction of flow (4).

87 - Non-return valve, vacuum pump

Index

Explanation

1

Retaining ring

2

Opening

Index

Explanation

3

Hole

1

Valve plate

4

Housing

2

5

Seal

Vacuum connection to vacuum pump

6

Spring

3

Direction arrow

4

Direction of flow

5

Vacuum connection, brake booster

Retaining ring (1) supports spring (6). The other end of the spring presses seal (5) against hole (3). The vacuum built up in the hole and in the vacuum system firmly sucks the seal onto the hole, ensuring no vacuum can escape via the vacuum pump. The seal is forced against the spring while the vacuum pump is in operation thus releasing the hole. Air can now be drawn in via the hole and openings (2) in the seal.

96

88 - Non-return valve, brake booster

Vacuum distributor The task of the vacuum distributor is to distribute the vacuum via lines to various system. Different sized throttles are built into the connections of the vacuum distributor. This makes sure that the majority of the vacuum is always available for power assisted braking. Unused connections are closed off with a rubber cap.

M57D30T2 Engine A distributor with five connections is used on the M57D30T2 engine. Connection

Throttle

Wastegate

∅ 0.8 mm

Compressor bypass valve Turbine control valve

∅ 0.8 mm

EGR valve

∅ 0.8 mm

Engine mount

∅ 0.5 mm

Swirl flaps

∅ 0.5 mm

89 - Vacuum distributor, M57D30T2 engine

N47D20T0 Engine A distributor with four connections is used on the N47D20T0 engine. Connection

Throttle

Turbine control valve Compressor bypass valve

∅ 0.8 mm

Wastegate

∅ 0.8 mm

EGR bypass valve EGR valve

∅ 0.8 mm

Not used

∅ 0.5 mm

97

Electropneumatic pressure converter The electropneumatic pressure converter is used for components that are activated infinitely variable with vacuum. The electropneumatic pressure converter is able to mix the incoming vacuum with ambient air and set any required negative pressure (mixed pressure) between these two negative pressure levels. The resulting negative pressure is then used as the control variable for actuating pneumatic components. These components include: • Vacuum unit for EGR valve • Vacuum unit for turbine control valve • Vacuum unit for wastegate The vacuum (negative pressure) is applied at vacuum connection (1). The ambient pressure passes through filter element (3) into the valve. Vacuum connection outlet (2) may be marked in colour (here blue) to prevent confusion with several components of the same type. The mixed pressure is made available via the vacuum outlet. The mixed pressure is used to set infinitely variable any position between "open" and "closed". The DDE actuates the electropneumatic pressure converter pulse width modulated at approx. 250 Hz. The negative pressure at the vacuum outlet is infinitely variable depending on the pulse duty factor. The pulse duty factor may be between 0 and 100 %. The electropneumatic pressure converter is closed at a pulse duty factor of 6 % and ambient pressure is applied. The electropneumatic pressure converter is fully open at a pulse duty factor of 98 % and the maximum vacuum of the vacuum system is applied.

98

90 - Electropneumatic pressure converter

Index

Explanation

1

Vacuum connection

2

Vacuum outlet

3

Filter element

4

Electric plug connection

Circuit symbol 91 - Circuit symbol Electropneumatic pressure converter

Electric changeover valve The electric changeover valve is used for components that switch in two positions. The electric changeover valve makes it possible to switch either no vacuum or the maximum available vacuum from the vacuum connection (1) to vacuum outlet (2). In contrast to the electropneumatic pressure converter, here no mixed pressure is set but rather the vacuum in the system is switched through to the vacuum unit. On the M57D30T2 and N47D20T0 engines this electric changeover valve is used for the variable engine mounts and the compressor bypass valve. The electric changeover valve is actuated by the DDE.

92 - Electric changeover valve

Index

Explanation

1

Vacuum connection

2

Vacuum outlet

3

Electric plug connection

Circuit symbol 93 - Circuit symbol Electric changeover valve

Vacuum reservoir The vacuum reservoir retains a defined vacuum for the purpose of making available vacuum to meet temporary increases in vacuum requirements. For instance, on twin turbo engines this makes it possible to still control the turbine control valve and the compressor bypass valve in the event of the vacuum failing in the system. If this would not be possible, an immediate drop in engine output would be noticeable.

maximum. However, the capacity of such a pump would be fully utilized only very rarely. A vacuum reservoir therefore represents the most efficient option of covering maximum vacuum requirements.

A situation in which such a failure in the vacuum system may occur is when the brake booster requires large quantities of vacuum. For this purpose, the vacuum reservoir is equipped with a non-return valve that prevents the vacuum escaping in the direction of the brake booster. If it were not for this vacuum reservoir, the vacuum pump would have to be built much larger so as to make available sufficient vacuum to control the turbocharger assembly while the brake booster is operating at 99

100

Service Information. Air Intake and Exhaust System - Diesel.

System overview Overview Air intake system

Exhaust system

3 If the filtered air pipe downstream of the

exhaustt sys system tem is design designed ed such such that that 3 The exhaus

blow-by gas connection is heavily oiled, this could could imp imply ly increa increased sed blow-b blow-byy gas levels levels.. The caus cause e of this this is usua usuallllyy a leak leak in the the engi engine ne (e.g. (e.g. cran cranks ksha haft ft seal seal)) or surp surplu luss air air take taken n in thro throug ugh h the vacuum lines. A consequential symptom would then be an oily exhaust turbocharger, whic which h does does not not mean mean that that ther there e is a faul faultt with with the exhaust turbocharger itself. 1

the vibrations corresponding to the engine timing (intake and pressure waves) optimize the charge cycle and therefore the engine outp output ut.. Cons Conseq eque uent ntly ly,, in the the even eventt of a defe defect ct in the exhaust system, the vibrationcoordinated charge cycle is influenced negatively, thus consequently reducing engine output while increasing fuel consumption. 1

Youwill find find thisservice thisservice informa informatio tion n under System Overview.

101

System components Exhaust turbocharger Exhaust turbocharger with wastegate

3 Theoretically, varying the control rod in Youwill find find this this servic service e inform informati ation on under System Components.

"wastegate opens later" direction would increase the boost pressure. However, since the boost pressure is monitored by the DDE with the aid of a boost pressure sensor, this change is detected. A characteristic map stored in the DDE permits deviations in a defined range in order to compensate for

change changess in operat operatio ion. n. If this this range range is exceed exceeded ed as the the resu result lt of manu manual al inte interv rven enti tion on,, a faul faultt will will be detected as the result of evaluating the received sensor signals in the DDE. This status is indicated by the emission warning lamp in the instrument cluster. This will result in a reduction in the boost pressure and therefore in the engine output. 1

Sensors Exhaust temperature sensor

3 A compensating resistor that

3 The electrical supply line must not be

compensates for production tolerances is integrated in the oxygen sensor connector. This resistor is connected to a free contact.

subjected to a pulling force of more than >80 N. Sensors that have been dropped must not be used again. 1

Oxygen sensor

3 The MMA characteristic map must be reset with the aid of the BMW diagnosis system after replacing one of the following components:

1

3 It is extrem extremely ely imp import ortant ant to ensure ensure that that the cabl cable e conn connec ecti tion on to the the oxyg oxygen en sens sensor or is free free of soil soilin ing g so that that the the ambi ambien entt air air can can ente enterr the the refere reference nce air channe channel.l. It is theref therefore ore neces necessar saryy to protect the plug connection from soiling, washing agents, preservatives etc. 1

• Hot-f Hot-film ilm air mass mass mete meterr


• Fuel Fuel inje inject ctor or(s (s))

3 If the sensor fails, the DDE initiates filter

• Rail Rail-p -pre ress ssur ure e sensor sensor 1

regeneration every 500 km and a fault code entry is stored in the DDE. 1

Diesel particulate filter Design and function

3 The diesel particulate filter retains all particles. These include non-regenerative non-regenerative particles, such as oil ash, swarf and additive residues. The non-regenerative particles gradually lead to a blockage of the diesel particulate filter over time. Over a distance of 1000 1000 km km,, appr approx ox.. 0.6 0.6 gram gramss of powd powder er ash ash are are deposited in the rear third of the diesel particulate filter. The diesel diesel partic particula ulate te filter filter is theref therefore ore subjec subjectt to a replacement interval. The replacement interval can be anywhere between 160,000 km and 220,000 km. 1

3 If the sulphur content in the diesel fuel is > 50 - 100 ppm, ppm, the there is a poss possib ibiility ity of heav eavy 102

white smoke development and a sulphur odour from the exhaust tailpipe. 1

Summary Air Intake and Exhaust System - Diesel.

Points to remember The table below summarizes the most important information on the subject of air intake and exhaust system, diesel

This list outlines the main points in concise form and provides the opportunity of rechecking the most important facts provided in this Product Information.

Introduction It is necessary to implement appropriate design measures on the air intake and exhaust system in order to be able to meet the emission limits specified throughout the world. The design of the air intake and exhaust system differs for different types of engine.

Points to remember for everyday theoretical and practical applications.

Overview The intake system can be divided into two sections. The intake snorkel, intercooler and, with exceptions, the intake silencer are specifically assigned to the vehicle and differ even in connection with the same type of engine due to the different characteristics of the vehicle models. The exhaust turbocharger and the intake system with swirl flaps, throttle valve and various sensors are assigned to the engine. Apart from the exhaust turbocharger and exhaust manifold, the exhaust system is designed vehicle-specific and differs depending on the type of vehicle and specification.

103

System overviews of current engines The air intake and exhaust systems differ depending on the type of engine and exhaust emission legislation. The system overviews provide an initial insight into the complexity and differences of the individual engine series.

Unfiltered air duct The unfiltered fresh air is directed via the unfiltered air duct into the intake system of the respective engine.

Intake silencer The intake silencer reduces the intake noise and houses the filter element.

104

Exhaust turbocharger The exhaust turbocharger uses a part of the exhaust energy to compress the intake air, thus increasing the efficiency of the engine. A swirler is used to optimize the effect on the fresh air side.

Intercooler The intercooler is responsible for reduced intake air temperatures compared to a vehicle with no intercooler. This means the power output can be additionally increased as a larger mass of air can be conveyed into the combustion chamber.

Sensors - air intake system Various sensors are used in the air intake system. These include the hot-film air mass meter, charge air temperature sensor and the boost pressure sensor. These sensors are required for the purpose of calculating the EGR rate, fuel volume apportioning and for controlling the boost pressure.

105

Throttle valve The throttle valve is required for regenerating the diesel particulate filter in order to increase the exhaust temperature by intervening in the air-fuel mixture. In addition, the throttle valve is closed when the engine is shut down in order to reduce shut-down judder. The throttle valve also effectively prevents inadvertent overrevving of the engine.

Intake manifold The intake manifold distributes the filtered air coming from the intake silencer to the individual cylinders. The filtered air per cylinder is additionally divided in a swirl and tangential port in order to more effectively mix the injected fuel with the fresh air located in the combustion chamber. Additional swirl flaps are fitted in each tangential port for this purpose. Exhaust manifold On current diesel engines, the exhaust manifold is made from spherical graphite cast iron. An air gap insulated exhaust manifold is used on the M57TU engines.

106

Exhaust gas recirculation Exhaust gas recirculation is used to reduce NOx emissions. The oxygen content in the cylinder is reduced by mixing exhaust gas with the intake air. Adding exhaust gas means there is less oxygen available for combustion thus reducing the combustion temperature.

Exhaust turbocharger The exhaust turbocharger consists of a turbine and compressor mounted on a common shaft. It develops speeds of up to 200,000 rpm and operates at exhaust temperatures of approx. 900 °C. Up to 3 different basic designs of exhaust turbocharger are used. These are the exhaust turbocharger with wastegate, exhaust turbocharger with VNT and twin turbocharging with two turbochargers connected in series.

Sensors Three different types of sensors are used in the exhaust system. These sensors detect the exhaust temperature, exhaust backpressure and exhaust composition (oxygen sensor). The location and number of exhaust temperature sensors vary depending on the type of vehicle.

Oxidation catalytic converter The oxidation catalytic converter reduces hydrocarbons and carbon monoxide under all operating conditions. An important characteristic is its rapid response. Its location varies depending on the type of vehicle and version.

107

Diesel particulate filter The diesel particulate filter filters the carbon substances out of the exhaust gas, buffers them and initiates conversion from carbon to CO2. Other solid particles contained in the exhaust gas are permanently stored. It also supplements the oxidation catalytic converter while converting CO to CO 2.

Particulate trap catalytic converter The particulate trap catalytic converter makes it possible to reduce particle emission by up to 50 % by simple means. The particulate trap catalytic converter is a simple separator system with no sensors.

Exhaust silencer The silencer system contributes to optimum vehicle performance. A further task is to accommodate the corresponding systems for reducing pollutant and noise emissions.

Vacuum system The vacuum system is required for the purpose of actuating various flaps and valves. The main task is to provide power assistance for the braking system. In addition, vacuum is supplied to various components on the engine.

108

Test questions. Air Intake and Exhaust System - Diesel.

Questions In this this sect sectio ion n you you have have the the oppo opport rtun unit ityy to test test the knowledge you have acquired. It contains questions about the air intake and

exhaust system - diesel described in this Product Information.

1. Which exhaust exhaust constituent constituents s in a diesel engine can be found found directly directly after combustion? 4

N2

4

H2O

4

CO2

4

Cl

4

S

Consolidate and recheck what you have learned.

2. What are are the tasks tasks of of the intake intake system? system? 4

To dampen noise

4

To filter air

4

To generate boost pressure

3. Does the engine engine power output output increase if the silencing silencing system system is defective defective (loud)? 4

Yes

4

No

4. Which of of the followin following g statements statements are correct? correct? 4

In exhaust turbocharging a part of the exhaust energy is used to generate the boost pressure.

4

The power output of an exhaust turbocharged engine is greatly reduced at high altitude.

4

The swirler improves the flow at the compressor blades.

4

The The chok choke e line line of the the exha exhaus ustt turb turboc ocha harg rger er is reac reache hed d when when the the air air in the the comp compre ress ssor or inle inlett reaches the speed of sound.

4

The surge line can be displaced with the swirler to delay flow stall.

5. What is the task of the the intercoole intercooler? r? 4

The interc intercoo ooler ler reduce reducess the charge charge air temper temperatu ature re depend depending ing on the outsid outside e temper temperatu ature re and driving speed.

4

The intercooler reduces the charge air temperature by 50 ° 50 °C. C.

4

The intercooler reduces the intake air temperature before the exhaust turbocharger in order to cool it.

109

6. Why is a hot-film hot-film air air mass meter (HFM) (HFM) used? used? 4

The HFM is used in the regeneration of the diesel particulate filter for the purpose of controlling the correct exhaust composition.

4

The HFM is used for the purpose of determining the exhaust recirculation rate.

4

The HFM is used for the purpose of apportioning the fuel.

7. What are the the functions functions of the charge charge air temperature temperature sensor sensor and of the the boost pressure sensor? 4

The charge air temperature sensor is used to drive the electric fan.

4

The charge air temperature sensor is used for calculating a substitute value for air mass.

4

The boost pressure sensor is used for calculating the injection volume.

4

The boost pressure sensor is required for boost pressure control.

8. What is is the task task of the throttl throttle e valve? valve? 4

The throttle valve is used to control power output.

4

The throttle valve is required for regeneration of the diesel particulate filter.

4

The throttle valve reduces engine judder during shut-down.

4

The throttle valve can prevent overrevving of the engine.

9. What is the task of the the swirl flaps? flaps? 4

The swirl flaps close the tangential ports so that, at low engine speeds, a more powerful swirl of air is generated in the combustion chamber.

4

The The swir swirll flap flapss clos close e the the swir swirll port portss so that that,, at low low engi engine ne spee speeds ds,, a mo more re powe powerf rful ul swir swirll of air is generated in the combustion chamber.

10. Which exhaust exhaust manifolds manifolds for diesel engines engines are you familiar with?

110

4

Cast exhaust manifold

4

Air gap insulated exhaust manifold

4

Aluminium exhaust manifold

11. What is the task task of exhaust exhaust gas recircula recirculation? tion? 4

Exhaust gas recirculation is required only under full load.

4

Exhaust gas recirculation reduces the mean combustion temperature and therefore the formation of pollutants.

4

Exhaus Exhaustt gas recirc recircula ulatio tion n reduce reducess the maximu maximum m combus combustio tion n temper temperatu ature re by up to 500 500 °C.

12. What is the special feature of the exhaust gas recirculation system for the N47 engines? 4

The exhaust gas recirculation valve is equipped with an angle sensor.

4

A bypass valve is used for manual transmission or upper performance stage vehicles.

4

An exha exhaus ustt gas gas reci recirc rcul ulat atio ion n valv valve e with with an elec electr tric ic mo moto torr is used used on the the N47D N47D20 20O0 O0 engi engine ne..

13. Which basic basic types of exhaust turbocharg turbocharger er are used on diesel engines? engines? 4

Turbocharger with wastegate

4

VNT

4

Twin turbocharger

4

Twin scroll turbocharger

14. Which sensors sensors are used in in the exhaust system? system? 4


4

Oxygen sensor with rising characteristic

4

Oxygen sensor with erratic characteristic

4


4

Exhaust differential pressure sensor

15. Which pollutants are reduced by the diesel particulate filter? 4

CO2

4

C

4

CO

16. Which types types of silencing silencing are used in the exhaust exhaust system? 4

Absorption

4

Adaptation

4

Reflection

4

Subtraction

4

Interference

111

17. What is the task of the exhaust flap? 4

The exhaust flap reduces low frequency noise emission by up to 10 decibels at low engine speeds.

4

The exhaust flap supports regeneration of the diesel particulate filter.

4

The exhaust flap increases power output in the lower engine speed range.

18. Which component ensures the vacuum in the vacuum system does not drop while the engine is not in operation?

_________.

112

Answers to questions 1. Which exhaust constituents in a diesel engine can be found directly after combustion? 5

N2

5

H2O

5

CO2

4

Cl

4

S

Check it!

2. What are the tasks of the intake system? 5

To dampen noise

5

To filter air

5

To generate boost pressure

3. Does the engine power output increase if the silencing system is defective (loud)? 4

Yes

5

No

4. Which of the following statements is correct? 5

In exhaust turbocharging a part of the exhaust energy is used to generate the boost pressure.

4

The power output of an exhaust turbocharged engine is greatly reduced at high altitude.

5

The swirler improves the flow at the compressor blades.

5

The choke line of the exhaust turbocharger is reached when the air in the compressor inlet reaches the speed of sound.

5

The surge line can be displaced with the swirler to delay flow stall.

5. What is the task of the intercooler? 5

The intercooler reduces the charge air temperature depending on the outside temperature and driving speed.

4

The intercooler reduces the charge air temperature by 50 °C.

4

The intercooler reduces the intake air temperature before the exhaust turbocharger in order to cool it.

113

6. Why is a hot-film air mass meter (HFM) used? 4

The HFM is used in the regeneration of the diesel particulate filter for the purpose of controlling the correct exhaust composition.

5

The HFM is used for the purpose of determining the exhaust recirculation rate.

5

The HFM is used for the purpose of apportioning the fuel.

7. What are the functions of the charge air temperature sensor and of the boost pressure sensor? 4

The charge air temperature sensor is used to drive the electric fan.

5

The charge air temperature sensor is used for calculating a substitute value for air mass.

4

The boost pressure sensor is used for calculating the injection volume.

5

The boost pressure sensor is required for boost pressure control.

8. What is the task of the throttle valve? 4

The throttle valve is used to control power output.

5

The throttle valve is required for regeneration of the diesel particulate filter.

5

The throttle valve reduces engine judder during shut-down.

5

The throttle valve can prevent overrevving of the engine.

9. What is the task of the swirl flaps? 5

The swirl flaps close the tangential ports so that, at low engine speeds, a more powerful swirl of air is generated in the combustion chamber.

4

The swirl flaps close the swirl ports so that, at low engine speeds, a more powerful swirl of air is generated in the combustion chamber.

10. Which exhaust manifolds for diesel engines are you familiar with?

114

5

Cast exhaust manifold

5

Air gap insulated exhaust manifold

4

Aluminium exhaust manifold

11. What is the task of exhaust gas recirculation? 4

Exhaust gas recirculation is required only under full load.

5

Exhaust gas recirculation reduces the mean combustion temperature and therefore the formation of pollutants.

5

Exhaust gas recirculation reduces the maximum combustion temperature by up to 500 °C.

12. What is the special feature of the exhaust gas recirculation system for the N47 engines? 5

The exhaust gas recirculation valve is equipped with an angle sensor.

5

A bypass valve is used for manual transmission or upper performance stage vehicles.

4

An exhaust gas recirculation valve with an electric motor is used on the N47D20O0 engine.

13. Which basic types of exhaust turbocharger are used on diesel engines? 5

Turbocharger with wastegate

5

VNT

5

Twin turbocharger

4

Twin scroll turbocharger

14. Which sensors are used in the exhaust system? 5


5

Oxygen sensor with rising characteristic

4

Oxygen sensor with erratic characteristic

5


4

Exhaust differential pressure sensor

15. Which pollutants are reduced by the diesel particulate filter? 4

CO2

5

C

5

CO

16. Which types of silencing are used in the exhaust system? 5

Absorption

4

Adaptation

5

Reflection

4

Subtraction

5

Interference

115

17. What is the task of the exhaust flap? 5

The exhaust flap reduces low frequency noise emission by up to 10 decibels at low engine speeds.

5

The exhaust flap supports regeneration of the diesel particulate filter.

4

The exhaust flap increases power output in the lower engine speed range.

18. Which component ensures the vacuum in the vacuum system does not drop while the engine is not in operation?

_____8____.

116

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Diesel Air Intake and Exhaust System

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