BMW Advanced Diesel with BluePerformance Product Information

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Technical Training ­Product Information.
Advanced Diesel with BluePerformance.
BMW Service
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The information contained in the Product Information and the Workbook form an integral part of the training literature of BMW Technical Training.
Refer to the latest relevant BMW Service information for any changes/supplements to the Technical Data.
Information status: June 2008
Contact: conceptinfo@bmw.de
© 2008 BMW AG München, Germany Reprints of this publication or its parts require the written approval of BMW AG, München VH-23, International Technical Training
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Product Information.
Advanced Diesel.
Diesel engine for North America
Selective Catalytic Reduction (SCR)
Low pressure exhaust gas recirculation (LP EGR)
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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 important safety information as well as information that is
necessary to ensure smooth system operation and must be adhered to.
1 identifies the end of a note.
Information status and national variants
BMW vehicles conform to the highest safety and quality standards. Changes in terms of environmental protection, customer benefits and design render necessary continuous development of systems and components. Consequently, there may be discrepancies between this Product Information and the vehicles available in the training course.
This documentation describes left-hand drive vehicles. In right-hand drive vehicles, the arrangement of some controls or components may differ 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 topics can be found in the following:
- Owner's Handbook
- Integrated Service Technical Application.
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Contents.
Advanced Diesel.
Objectives
Product information and working reference for practical applications.
Models 3
Engine variants 3
Introduction 7
System components 23
Engine mechanical system 23 Air intake and exhaust system 25 Cooling system 38 Fuel preparation system 41 Overview of fuel supply system 43 Functions of the fuel supply system 47 Components of the fuel supply system 51 Overview of selective catalytic reduction 60 Functions of selective catalytic reduction system Components of the selective catalytic reduction system Engine electrical system 110 Automatic transmission 119
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Objectives.

Advanced Diesel.

Product information and working reference for practical applications.

This Product Information provides information on the design and function of the M57D30T2 US engine.
This Product Information is structured as a working reference and complements the subject material of the BMW Aftersales Training seminar. The Product Information is also suitable for self-study.
As a preparation for the technical training program, this Product Information provides an
insight into the diesel engine for the US market. 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 M57D30T2 US engine.
Technical and practical background knowledge of the current BMW diesel engines will simplify your understanding ofthesystems described here and their functions.
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Models.

Advanced Diesel.

Engine variants

Models with the M57D30T2 US engine at the time of market launch in Autumn 2008.
1 - BMW 335d 2 - BMW X5 xDrive35d
3
Model
335d E90 M57D30T2 2993 90/84
X5 xDrive35d E70 M57D30T2 2993 90/84
Model series
Engine
Cylinder capacity in cm
Bore/stroke
in mm
Power in
kW/bhp at rpm
200/265
4200
200/265
4200
Torque in
Nm at rpm
580
1750
580
1750
Market launch
11/08
11/08
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History of the M57 engine

The M57 engine is by far one of the most successful engines at BMW. It is fitted in numerous models right across the vehicle range. It plays the part of the extremely powerful top-of-the-range engine, for example in the 3 Series just as effectively as the well­balanced entry class engine in the 7 Series.
10 years have already passed since its introduction and many improvements have been made during this period. In particular the re-engineering that took place in 2002 and again in 2005 ensure that the M57 engine is still state-of-the-art.
The following table shows an overview of the individual models equipped with the M57 engine.
Engine
M57D30O0 530d E39 2926 135/184 390 DDE4.0 9/98 3/00 M57D30O0 730d E38 2926 135/184 410 DDE4.1 9/98 3/00 M57D30O0 330d E46 2926 135/184 390 DDE4.0 9/99 3/03 M57D25O0 525d E39 2497 120/163 350 DDE4.0 3/00 2/04 M57D30O0 530d E39 2926 142/193 390 DDE4.0 3/00 5/04 M57D30O0 730d E38 2926 142/193 430 DDE4.1 3/00 7/01 M57D30O0 X5 3.0d E53 2926 135/184 410 DDE4.0 4/01 9/03 M57D30O1 730d E65 2993 160/218 500 DDE506 9/02 3/05 M57D30O1 330d E46 2993 150/204 410 DDE506 3/03 9/06 M57D30O1 530d E60 2993 160/218 500 DDE508 3/03 4/04 M57D30O1 X3 3.0d E83 2993 150/204 410 DDE506 9/03 9/05 M57D30O1 X5 3.0d E53 2993 160/218 500 DDE506 9/03 9/06 M57D25O1 525d E60 2497 130/177 400 DDE509 4/04 3/07 M57D25O1 525d E61 2497 130/177 400 DDE509 4/04 3/07 M57D30O1 530d E60 2993 160/218 500 DDE509 4/04 9/05 M57D30O1 530d E61 2993 160/218 500 DDE509 4/04 9/05 M57D30T1 535d E90 2993 200/272 560 DDE606 9/04 3/07 M57D30T1 535d E61 2993 200/272 560 DDE606 9/04 3/07
Model
Model series
Cylinder capacity
in cm3Power output
in (kW/bhp)
Torque
in Nm
Engine
management
First used
Last used
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Engine
M57D30O2 730d E65 2993 170/231 520 DDE626 3/05 9/08 M57D30O2 330d E90 2993 170/231 500 DDE626 9/05 9/08 M57D30O2 330d E91 2993 170/231 500 DDE626 9/05 9/08 M57D30O2 530d E61 2993 170/231 500 DDE626 9/05 in production M57D30O2 530d E61 2993 170/231 500 DDE626 9/05 in production M57D30O2 730Ld E66 2993 170/231 520 DDE626 9/05 9/08 M57D30O2 X3 3.0d E53 2993 160/218 500 DDE626 9/05 in production M57D30U2 325d E90 2497 145/197 400 DDE606 9/06 in production M57D30U2 325d E91 2497 145/197 400 DDE606 9/06 in production M57D30O2 330d E92 2993 170/231 500 DDE626 9/06 in production M57D30T2 335d E90 2993 210/286 580 DDE626 9/06 in production M57D30T2 335d E91 2993 210/286 580 DDE626 9/06 in production M57D30T2 335d E92 2993 210/286 580 DDE626 9/06 in production M57D30T2 X3 3.0sd E83 2993 210/286 580 DDE626 9/06 in production M57D30U2 325d E92 2497 145/197 400 DDE606 3/07 in production M57D30U2 525d E60 2497 145/197 400 DDE606 3/07 in production M57D30U2 525d E61 2497 145/197 400 DDE606 3/07 in production M57D30O2 330d E93 2993 170/231 500 DDE626 3/07 in production M57D30O2 X5 3.0d E70 2993 173/235 520 DDE626 3/07 in production M57D30T2 535d E60 2993 210/286 580 DDE626 3/07 in production M57D30T2 535d E61 2993 210/286 580 DDE626 3/07 in production M57D30U2 325d E93 2497 145/197 400 DDE606 9/07 in production M57D30T2 635d E63 2993 210/286 580 DDE626 9/07 in production M57D30T2 635d E64 2993 210/286 580 DDE626 9/07 in production M57D30T2 X5 3.0sd E70 2993 210/286 580 DDE626 9/07 in production M57D30O2 X6
M57D30T2 X6
Model
xDrive30d
xDrive35d
Model series
Cylinder capacity
in cm3Power output
E71 2993 173/235 520 DDE626 5/08 in production
E71 2993 210/286 580 DDE626 5/08 in production
in (kW/bhp)
Torque
in Nm
Engine
management
First used
Last used
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Introduction.

Advanced Diesel.

A diesel engine for North America

Impressive power and performance as well as exemplary efficiency have contributed to making BMW diesel engines an attractive as well as future-oriented drive technology. This technology is now being made available to drivers in North America.
BMW is introducing this diesel technology to the USA and Canada under the name "BMW Advanced Diesel". The introduction is an integral part of the EfficientDynamics

History

In 1892, Rudolf Diesel applied for a patent for his first self-igniting combustion engine. Initially, this large, slow-running engine was intended for stationary operation only. The intricate engine structure and complicated injection system meant production costs were high. The first simple diesel engines were not particularly comfortable and powerful-revving machines. It was not possible to mistake the distinctive sound of the harsh combustion process in the diesel engine when cold (diesel knock). Compared to thesparkignition engine, it offered a poorer power/weight ratio, acceleration characteristics and lower specific output.
"Miniaturization" could be realized only by improving materials and the manufacturing process during the course of commercial vehicle production. Although the first diesel vehicle was presented as early as 1936, it was not before the 1970s that the diesel engine became accepted as a viable drive source. The breakthrough came in the 1980s when the diesel engine was finally refined enough to be a real alternative to the spark ignition engine. At this time, in view of the improved dynamics and acoustics the decision was
development strategy, which has become a synonym for extremely low CO2 emissions ­not surprising when considering its extremely low fuel consumption. EfficientDynamics is not solely an instrument for reducing fuel consumption but rather it is designed as an intelligent entity with increased dynamics. Not without good reason theM57D30T2 engine is referred to as the world's most agile diesel engine.
made to introduce the diesel engine in series production vehicles at BMW.
1 - Rudolf Diesel and his engine
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1983
The M21D24 engine introduced for the first time in the E28 as the 524td featured an exhaust turbocharger and had a displacement of 2.4 litres. It was derived from the M20 6­cylinder petrol engine and developed 85 kW/ 115 bhp. Both engines could therefore be built on the same production facilities.
At that time, the performance with a top speed of 180 km/h and acceleration from 0 to 100 km/h in 13.5 seconds set new standards in the dynamics of diesel motor vehicles. The 524td was therefore given the nickname "Sport diesel".
This was thefirst diesel engine at BMWand, at the same time, the last for a long time in the US market.
2 - BMW 524td with M21 engine
1985
The M21 was also built as a naturally­aspirated diesel engine as from September 1985, making it possible to offer a cost­effective "entry-level engine". This engine made a name for itself in the 324d (E30) as the smoothest running auto-ignition engine on the market.
1987
As the world's first carmaker to do so, BMW introduced the electronic engine management system, the so-called Digital Diesel Electronics (DDE). Faster and more exact than a mechanical control system, the electronics effectively controls:
• Exhaust emission characteristics
• Fuel consumption characteristics
• Noise emission
• Engine running refinement.
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1991
1991 saw the debut of the newly developed M51D25 engine which, with intercooling and an output of 105 kW/143 bhp was the most powerful diesel engine in its class throughout the world. It replaced the M21 engine and was
3 - BMW 525tds with M51 engine
fitted with a crankcase based on a completely new design.
The engine was offered in the output variants 115 bhp and 143 bhp. Exhaust emission and full load smoke were reduced by a V-shaped main combustion chamber in the piston.
1994
The M41 engine was the first4-cylinder diesel engine to beused at BMW. It was derived from the M51D25 engine and shared 56 % of its components. New features included the
hollow-cast camshaft mounted in 5 bearings as well as a cylinder head cover the isolated structure-borne noise.
This engine was fitted in various models of the E36 series.
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1998
In 1998 BMW built the most powerful 4­cylinder diesel engine - the M47 with direct fuel injection.
4 - BMW 320d with M47 engine
Motor sport provided the best proof of the efficiency and reliability of the new diesel technology. BMW celebrated a historic success on the Nürburg Ring.
With 100 kW developed from 2 litre displacement, a performance level was achieved which up until then was the reserve only of petrol engines. This corresponds to a specific output of 50 kW or 68 bhp.
With the 320d, a diesel engine won a 24 hour race for the first time in motor sports history in
1998. This victory came not only due to the fact that it needed fewer pit stops for refuelling but also because the BMW drove the fastest lap times.
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5 - BMW 320d touring car with M47 engine
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1999
The first V8 diesel engine, the M67D40 engine, with 4 litre displacement was presented in the E38 which developed an output of 175 kW. BMW proved its technical authority with the, at that time, world's most powerful passenger vehicle diesel engine with
6 - BMW 740d with M67 engine
common rail fuel injection and 2 exhaust turbochargers.
The engine is fitted with a crankcase made from high-strength cast iron with vermicular graphite (GGV), an aluminium cylinder head and a two-piece oil sump.
2001
The M47TU with the second generation common rail injection system and DDE5 boosted the power output to 110 kW/150 bhp.
The M57D30 engine is a further development of the M51D25 engine. It has a cast iron casing fitted with a light alloy cylinder head with 4-valve technology. The M57 engine is the world's first 6-cylinder in-line diesel engine in a passenger vehicle that is equipped with
future-oriented common rail injection technology.
This new, highly complex electronically controlled fuel injection system perfectly satisfies the demands for high and constant injection pressure over the entire injection period. The engine offers substantially lower fuel consumption compared to swirl-chamber engines, superior performance and smooth engine operation under extreme conditions.
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7 - BMW 530d with M57 engine
2004
The M57TU TOP engine with 2-stage turbocharging is introduced as the most powerful diesel engine (E60 and E61). One small and one large turbocharger is usedin the 2-stage turbocharging system. The diesel engine in the 535d develops 40 kW/54 bhp more than at the same displacement (3.0 litres) in the 530d.
The power output is 200 kW/272 bhp. The maximum torque of 560 Nm is reached at 2000 rpm. With this extraordinary engine, Luc Alphand won not only the diesel classification of the Paris-Dakar Rally, but also came fourth in the overall rankings.
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8 - BMW X5 3.0d with M57TU TOP engine
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2005
The M57TU2 engine is fitted in the E65. In addition to the increase in output and torque, it boasts the following technical features:
• Reduced weight through aluminium crankcase
• 3rd generation common rail system with piezo-injector and a fuel rail pressure of 1600 bar
• Compliance with the exhaust emission regulation EURO 4 and diesel particulate filter as standard
• Optimized electric boost pressure actuator for the turbocharger with variable turbine geometry.
9 - BMW 730d with M57TU2 engine
2005
The M67 engine in the E65 was comprehensively reengineered in the same year. The aim was to achieve a distinct boost in dynamics by increasing power output and reducing weight. In the case of the M67 specifically this aim is reflected in an increase
in power output of 16 % while simultaneously reducing the engine weight by 14 % - and achieved without increasing fuel consumption.
This was mainly achieved through a new, lightweight aluminium crankcase and by increasing the displacement to 4.4 litres.
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10 - BMW 745d with M67TU engine
2006
In 2006, the M57TU TOP engine was re­engineered and equipped with the same technical details as the M57TU2, such as an aluminium crankcase and piezo-fuel injectors. This engine was given the designation M57D30T2. It was introduced simultaneously into the 3 Series as the 335d and in the X3 as
the 3.0sd. This re-engineering resulted in further-improved power characteristics, enhanced smooth operation and a significant reduction in fuel consumption. This engine forms the basis for re-introducing diesel technology into the USA after more than 20 years.
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11 - X3 3.0sd with M57TU2 TOP engine
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Legislation

Since the first exhaust emission legislation for petrol engines came into force in the mid­1960s in California, the permissible limits for a range of pollutants have been further and further reduced. In the meantime, all industrial nations have introduced exhaust emission legislation that defines the emission limits for petrol and diesel engines as well as the test methods.
Essentially, the following exhaust emission legislation applies:
• CARB legislation (California Air Resources Board), California
• EPA legislation (Environmental Protection Agency), USA
• EU legislation (European Union) and corresponding ECE regulations (UN Economic Commission for Europe), Europe
• Japan legislation.
This legislation has lead to the development of different requirements with regard to the
limitation of various components in the exhaust gas. Essentially, the following exhaust gas constituents are evaluated:
• Carbon monoxide (CO)
• Nitrogen oxides (NOx)
• Hydrocarbons (HC)
• Particulates (PM)
It can generally be said that traditionally more emphasis is placed on low nitrogen oxide emissions in US legislation while in Europe the focus tends to be more on carbon monoxide.
The following graphic compares the standard applicable to BMW diesel vehicles with the current standards in Europe. A direct comparison, however, is not possible as
• different measuring cycles are used and
• different values are measured for hydrocarbons.
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12 - Comparison of exhaust
emission legislation
Standard Valid from CO
[mg/km]
EURO 4 01.01.2005 500 250 300 - 25 EURO 5 01.09.2009 500 180 230 - 5 EURO 6 01.09.2014 500 80 170 - 5 LEV II MY 2005 2110 31 - 47 6 * In Europe, the sum of nitrogen oxide and hydrocarbons is evaluated, i.e. the higher the HC
emissions, the lower the NOx must be and vice versa.
** In the USA, only the methane-free hydrocarbons are evaluated, i.e. all hydrocarbons with no methane
Although the European and US standards cannot be compared 1:1 it is clear that requirements relating to nitrogen oxide emissions are considerably more demanding.
Diesel engines generally have higher nitrogen oxide emission levels than petrol engines as
NO
[mg/km]
HC + NOx*
x
diesel engines are normally operated with an air surplus.
For this reason, the challenge of achieving approval in all 50 states of the USA had to be met with a series of new technological developments.
[mg/km]
NMHC**
[mg/km]PM[mg/km]
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Overview of innovations, modifications and special features

The following table provides an overview of the special features of the M57D30T2 US engine. They are divided into various categories.
• New development signifies a technology that has not previously been used on BMW engines.
• Modification signifies a component that was specifically designed for the
M57D30T2 US engine but does not represent a technical innovation.
• Adopted describes a component that has already been used in other BMW engines.
This Product Information describes only the main modifications to the M57D30T2 engine compared to the Europe version as well as fundamental vehicle systemsspecificto diesel engines.
Component
Engine mechanical system 7 Very few modifications have been made to
Air intake and exhaust system
Cooling system 7 In principle, the cooling system corresponds
Fuel preparation system 7 The functional principle of the fuel
New development
Modification
7 The most extensive changes were made to
Remarks
Adopted
the basic engine. The modifications that have been made focus mainly on ensuring smooth engine operation.
A significant feature, however, is the OBD monitoring of the crankcase breather.
the air intake and exhaust system. For instance, low pressure exhaust gas recirculation (low pressure EGR) is used for the first time at BMW on the E70.
In addition to other minor adaptations, there are substantial differences in the sensor and actuator systems.
to that of the Europe versions, however, it has been adapted to hot climate requirements.
preparation system does not differ from that of the Europe version, however, individual components have been adapted to the different fuel specification.
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Component
Fuel supply system 7 The fuel supply system is vehicle-specific
SCR system (Selective Catalytic Reduction)
Engine electrical system 7 The engine is equipped with the new DDE7
Automatic transmission 7 The automatic transmission corresponds to
New development
Modification
7 The SCR system is used for the first time at
Remarks
Adopted
and corresponds to the Europe version. There are, however, significantdifferencesto petrol engine vehicles.
BMW. Nitrogen oxide emissions are drastically reduced by the use of a reducing agent that isinjected into the exhaustsystem upstream of a special SCR catalytic converter. Since the reducing agent is carried in the vehicle, a supply facility, made up of two reservoirs, is part of this system.
(digital diesel electronics)control unit that will be used in thenext generation diesel engines (N47, N57).
The preheater system also corresponds to the N47/N57 engines.
that in the ECE variant of the X5 xDrive35d. The gearbox itself has already been used in the US version of the X5 4.8i, however, a different torque converter is used for the diesel model.
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Technical data

The following table compares the M57D30T2 US engine with petrol engines that are offered for the same models.
Designation N52B30O1 N54B30O0 N62B48O1 M57D30T2
Type Straight 6 Straight 6 V8 Straight 6 Displacement [cm3] 2996 2979 4799 2993 Firing order 1-5-3-6-2-4 1-5-3-6-2-4 1-5-4-8-6-3-7-2 1-5-3-6-2-4 Stroke/bore [mm] 88.0/85 88.9/84 88.3/93 90.0/84 Output
at engine speed Torque
at engine speed Governed engine
speed limit Power output per
litre Compression ratio ε 10.7 10.2 10.5 16.5 Cylinder spacing [mm] 91 91 98 91 Valves/cylinder 4 4 4 4 Intake valve [mm] 34.2 31.4 35.0 27.4 Exhaust valve [mm] 29.0 28.0 29.0 25.9 Main bearing
journal on crankshaft
Big-end bearing journal on crankshaft
Fuel specification [RON] 98 98 98 Fuel [RON] 91-98 91-98 91-98 Diesel Engine
management Exhaust emission
standard US * SAE-hp
[kW/hp*]
[rpm]
[Nm/lbft]
[rpm]
[rpm] 7000 7000 6500 4800
[hp/l] 86.7 100 72.9 89.3
[mm] 56 56 70 60
[mm] 50 50 54 45
193/260
6600
305/225
2500
MSV80 MSD80 ME9.2.3 DDE7.3
ULEVII ULEVII
225/300
5800
407/300
1400
261/350
6250
475/350
3500
ULEVII
200/265
4200
580/428
1750
LEVII
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Full load diagrams

To get an idea of the performance of the M57D30T2 US engine, it is compared to
various petrol engines in the following full load diagrams.
By comparing these two 3 litre engines it can be clearly seen that, despite virtually identical
13 - M57D30T2 US engine
compared to N52B30O1 engine
power output, the maximum torque of the diesel is almost double as high.
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This enormous difference in maximum torque is also apparent when comparing the
14 - M57D30T2 US engine
compared to N54B30O0 engine
turbocharged 3 litre petrol engine that has a considerably higher nominal power output.
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Even the 4.8 litre V8 engine cannot achieve the maximum torque of the 3 litre diesel engine.
However, the decisive factor is the low engine speeds at which the diesel engine develops
15 - M57D30T2 US engine
compared to N62B48O1 engine
this high torque. This means that more power is available in this range. In terms of power output, the diesel engine is superior to any of these petrol engines up to an engine speed of 4000 rpm.
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System components.

Advanced Diesel.

Engine mechanical system

Only slight modifications have been made to the engine mechanical system compared to the Europe version.

Crankshaft and big-end bearings

Only lead-free crankcase and big-end bearings are used in the M57D30T2 US engine. This conforms to requirements

Crankcase

In contrast to the Europe version, the M57D30T2 US engine has a larger reinforcement panel on the underside of the crankcase.
The reinforcement panel now covers four of the main bearing blocks for the crankshaft.

Pistons

The piston pin has a greater offset than in the Europe version. The offset of the piston pin means that the piston pin is slightly off centre. This provides acoustic advantages during
The modifications include:
• Crankcase
• Crankshaft and big-end bearings
• Pistons
• Crankcase breather.
relating to environmental protection and the disposal of end-of-life vehicles.
In principle, the reinforcement panel serves to enhance the stability of the crankcase. However, the enlargement was realized solely for acoustic reasons.
3 Never drive the vehicle without the
reinforcement panel. 1
changes in piston contact. The acoustic advantages of increasing the offset are further developed particularly at idle speed.
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Crankcase breather

The crankcase breather in the US version is generally heated. In addition, operation of the crankcase breather is OBD monitored (On Board Diagnosis). This is because a leaking system would produce emissions.
The only probable reason for a leak in the system would be that the blow-by pipe is not connected to the cylinder head cover. To facilitate protection of this situation by the OBD, the heating line isrouted via a connector to the cylinder head cover (2). Essentially, this connector serves only as a bridge so that actuation of the heating system is looped through. The plug connection is designed in such a way that correct contact is made only when the blow-by pipe has been connected correctly to the cylinder head cover, i.e. the contact for the heating system is not closed if the blow-by pipe is not connected to the cylinder head cover. OBD recognizes this situation as a fault.
1 - Blow-by pipe
Index Explanation
1 Cylinder head cover 2 Blow-by heater connector for OBD
monitoring
3 Blow-by heater connector at wiring
harness 4 Filtered air pipe 5 Intake air from intake silencer 6 Blow-by heater connector at blow-
by pipe 7 Intake air to exhaust turbocharger 8 Blow-by pipe
3 If the blow-by pipe is not connected to the
cylinder head correctly, the OBD will activate the MIL (Malfunction Indicator Lamp). 1
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Air intake and exhaust system

The M57D30T2 US engine exhibits the following special features in the air intake and exhaust system:
• Electric swirl flaps
• Electric exhaust gas recirculation valve (EGR valve)
• Low pressure EGR
• Turbo assembly adapted for low pressure EGR.
2 - Air intake and exhaust system - M57D30T2 US engine
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Index Explanation Index Explanation
1 M57D30T2 US engine 18 Oxidation catalytic converter and
2 Intake silencer 19 Exhaust gas temperature sensor
3 Hot-film air mass meter (HFM) 20 Oxygen sensor 4 Compressor bypass valve 21 Wastegate 5 Exhaust turbocharger, low pressure
stage
6 Exhaust turbocharger, high pressure
stage
7 Bypass valve for high pressure EGR
cooler 8 High pressure EGR cooler 25 Boost pressure sensor 9 Temperature sensor, high pressure
EGR 10 High pressure EGR valve 27 NOx sensor before SCR catalytic
11 Throttle valve 28 Temperature sensor after diesel
12 Charge air temperature sensor 29 Metering module (for SCR) 13 Intercooler 30 Mixer (for SCR) 14 Low pressure EGR valve with
positional feedback 15 Temperature sensor,
low pressure EGR 16 Low pressure EGR cooler 33 Digital Diesel Electronics (DDE) 17 Exhaust gas temperature sensor
after oxidation catalytic converter
22 Turbine control valve
23 Exhaust pressure sensor after
24 Swirl flap regulator
26 Exhaust differential pressure sensor
31 SCR catalytic converter
32 NOx sensor after SCR catalytic
34 Rear silencer
diesel particulate filter
before oxidation catalytic converter
exhaust manifold
converter
particulate filter
converter
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Air intake system

Intake air system
The intake air system differs on the E70 and E90. Both vehicles draw in unfiltered air behind the BMW kidney grille.
3 - Air intake system E70 and E90
Index Explanation Index Explanation
A Air intake system E70 3 Intake silencer (air cleaner housing) B Air intake system E90 4 Hot-film air mass meter (HFM) 1 Intake 5 Filtered air pipe 2 Unfiltered air pipe 6 Blow-by pipe
On the E90, the intake silencer is located at the front right oftheengine compartment fixed
to the vehicle. On the E70, the intake silencer is fixed over the engine.
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Swirl flaps
The engine is equipped with the familiar swirl flaps in thetangential port. A special feature on
the US engine is the electric actuating system with positional feedback.
4 - Intake manifold with electric swirl flaps
Index Explanation Index Explanation
1 Linkage for operating the swirl flaps 5 Swirl port 2 Connection to throttle valve 6 Tangential port 3 Intake manifold 7 Swirl flaps 4 Electric motor
This system provides advantages in terms of control, however, it is also a prerequisite for meeting OBD requirements.
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Exhaust system

9
5 - E70 and E90 exhaust systems
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Index Explanation Index Explanation
A Exhaust system E70 6 SCR catalytic converter B Exhaust system E90 7 NOx sensor after SCR catalytic
1 Oxygen sensor and concealed
exhaust temperature sensor before
oxidation catalytic converter 2 Exhaust gas temperature sensor
after oxidation catalytic converter 3 Differential pressure sensor 10 Metering module 4NO
5 Mixer
sensor before SCR catalytic
x
converter
8 Rear silencer
9 Exhaust gas temperature sensor
11 Diesel particulate filter
converter
after diesel particulate filter
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Exhaust gas recirculation (EGR)

Exhaust gas recirculation is one of the available options for reducing NOx emissions. Adding exhaust gas to the intake air reduces the oxygen in the combustion chamber, thus resulting in a lower combustion temperature.
The EGR systems in the E70 and E90 differ. Both vehicles are equipped with the familiar EGR system. Due to its higher weight, the E70 additionally features low pressure EGR, used for the first time at BMW.
Low pressure EGR
6 - Low pressure EGR
The known EGR system has been expanded by the low pressure EGR on the E70. This system offers advantages particularly at high loads and engine speeds. This is why it is used
in the heavier E70 as it is often driven in the higher load ranges.
The advantage is based on the fact that a higher total mass of exhaust gas can be recirculated. This is made possible for two reasons:
• Lower exhaust gas temperature
The exhaust gas for the low pressure EGR is tapped off at a point where a lower temperature prevails than in the high pressure EGR. Consequently, the exhaust gas has a higher density thus enabling a higher mass.
In addition, the exhaust gas is added to the fresh intake air before the exhaust turbocharger, i.e. before the intercooler, where it is further cooled. The lower temperature of the total gas enables a higher EGR rate without raising the temperature in the combustion chamber.
• Recirculation before the exhaust turbocharger
Unlike in the high pressure EGR where the exhaust gas is fed to the charge air already compressed, in this system the exhaustgas is added to the intake air before the exhaust turbocharger. A lower pressure prevails in this area under all operating conditions. This makes it possible to recirculate a large volume of exhaust gas even at higher engine speed and load whereas this is limited by the boost pressure in the high pressure EGR.
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The following graphic shows the control of the EGR system with low pressure EGR:
7 - Control of EGR system
Index Explanation Index Explanation
1 No exhaust gas recirculation 3 High and low pressure EGR are
active
2 Only high pressure EGR is active
As already mentioned, the low pressure EGR has the greatest advantageat higher loads and is therefore activated, as a function of the characteristic map, only in this operating mode. The low pressure EGR, however, is never active on its own but rather always operates together with thehighpressure EGR.
Added to this, it is only activated at a coolant temperature of more than 55 °C. The low pressure EGR valve is closed as from a certain load level so that only the high pressure EGR valve is active again. This means the EGR rate is continuously reduced.
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8 - Installation position LP EGR
Index Explanation Index Explanation
1 Diesel particulate filter 4 Low pressure EGR 2 Turbo assembly 5 Exhaust system 3 Exhaust turbocharger, low pressure
stage
The low pressure EGR system is located on the right-hand side on the engine directly next to the diesel particulate filter and the low pressure stage of the turbo assembly. The
exhaust gas is branched off directly after the diesel particulate filter and fed to the intake air before the compressor for the low pressure stage.
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34
9 - Low pressure EGR intake
Index Explanation Index Explanation
1 Low pressure EGR valve 3 Low pressure EGR port 2 Compressor, low pressure stage 4 Unfiltered air intake
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The following graphic shows the components of the low pressure EGR:
10 - LP EGR components
Index Explanation Index Explanation
1 Temperature sensor,
low pressure EGR 2 Low pressure EGR valve 6 Coolant return 3 Connection for positional feedback 7 Low pressure EGR cooler 4 Vacuum unit for
low pressure EGR valve
There is a fine meshed metal screen filter located at the exhaust gas inlet from the diesel particulate filter to the low pressure EGR system. The purpose of this filter is to ensure that no particles of the coating particularly in a new diesel particulate filter can enter the low pressure EGR system. Such particles would
5 Coolant infeed
8 Sheet metal gasket with filter
adversely affect the compressor blades of the exhaust turbocharger.
3 The metal screen filter must be installed
when fitting the low pressure EGR cooler to the diesel particulate filter otherwise there is a risk of the turbocharger being damaged. 1
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High pressure EGR The exhaust gas recirculation known to date is
referred to here as the high pressure EGR in order to differentiate it from the low pressure EGR.
Compared to the Europe version, the high pressure EGR is equipped with the following special features:
• Electric EGR valve with positional feedback
• Temperature sensor before high pressure EGR valve
11 - High pressure EGR
• EGR cooler with bypass.
36
12 - High pressure EGR system
Index Explanation Index Explanation
1 Coolant infeed 5 High pressure EGR cooler 2 High pressure EGR valve 6 Vacuum unit of bypass valve for high
pressure EGR cooler 3 Throttle valve 7 Coolant return 4 Temperature sensor, high pressure
EGR
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The electric actuating system of the EGR valve enables exact metering of the recirculated exhaust gas quantity. In addition, this quantity is no longer calculated based solely on the signals from the hot-film air mass meter and oxygen sensor but the following signals are also used:
• Travel of high pressure EGR valve
• Temperature before high pressure EGR valve
• Pressure difference between exhaust gas pressure in the exhaust manifold and boost pressure in the intake manifold.

Exhaust turbocharger

The US engine is equipped with the same variable twin turbo as the Europe version, however, the turbo assembly is modified due to the low pressure EGR.
This enables even more exact control of the EGR rate.
The EGR cooler serves the purpose of increasing the efficiency of the EGR system. However, reaching the operating temperature as fast as possible has priority at low engine temperatures. In this case, the EGR cooler can be bypassed in order to heat up the combustion chamber faster. For this purpose, a bypass that diverts the coolant is integrated in the EGR cooler. This bypass is actuated by a flap which, in turn, is operated by a vacuum unit. The bypass is either only in the "Open" or "Closed" position.
On the one hand, the inlet for the low pressure EGR is located on the compressor housing for the low pressure stage. On the other hand, the compressor wheels are nickel-coated to protect them from the exhaust gas.
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Cooling system

The cooling system,is in part, vehicle-specific. In principle, there are scarcely any differences between the cooling systems on petrol and diesel engines.
The two basic differences compared to petrol engines are:
• No characteristic map thermostat
• EGR cooler.
The E70 andE90 differ with regard tothe EGR cooler. Since the E70 is equipped with a low pressure EGR system, it has a second EGR cooler, the low pressure EGR cooler.
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13 - X5 xDrive35d cooling system
Index Explanation Index Explanation
1 Radiator
Coolant-to-air heat exchanger
2 Gearbox cooler
Coolant-to-air heat exchanger 3 Electric fan 12 Auxiliary coolant pump 4 Thermostat, gearbox oil cooler 13 Engine oil cooler
5 High pressure EGR cooler 14 Expansion tank 6 Thermostat 15 Gearbox oil cooler
7 Coolant pump 16 Ventilation line 8 Low pressure EGR cooler 17 Additional radiator
9 Coolant temperature sensor
10 Heating heat exchanger
11 Duo-valve
Engine oil-to-coolant heat exchanger
Gearbox oil-to-coolant heat exchanger
Coolant-to-air heat exchanger
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14 - 335d cooling system
Index Explanation Index Explanation
1 Gearbox cooler
Coolant-to-air heat exchanger
2 Radiator
Coolant-to-air heat exchanger
3 Additional radiator
Coolant-to-air heat exchanger
4 Thermostat, gearbox oil cooler 12 Engine oil cooler
5 High pressure EGR cooler 13 Expansion tank 6 Thermostat 14 Gearbox oil cooler
7 Coolant pump 15 Ventilation line 8 Coolant temperature sensor 16 Electric fan
9 Heating heat exchanger
10 Duo-valve
11 Auxiliary coolant pump
Engine oil-to-coolant heat exchanger
Gearbox oil-to-coolant heat exchanger
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Fuel preparation system

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15 - Fuel preparation system, M57D30T2 US engine
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Index Explanation Index Explanation
A Fuel feed 6 Return line B Fuel return 7 Feed line C Fuel high pressure 8 Fuel temperature sensor 1 Fuel rail pressure sensor 9 High-pressure line 2 High-pressure line 10 Fuel rail 3 Leakage oil line 11 Restrictor 4 Piezo injector 12 High-pressure pump 5 Fuel rail pressure control valve 13 Volume control valve
The fuel preparation system differs neither in terms of design layout nor function from the Europe version. However, some components have been adapted to the different fuel specification.
These components are:
• High-pressure pump
• Fuel rail
• Fuel injectors.
These adaptations are restricted to different coatings and materials on the inside.
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Overview of fuel supply system

16 - E90 Diesel fuel supply system
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Index Explanation Index Explanation
1 Fuel filler neck 5 Right-hand service opening 2 Left-hand service opening 6 Filler vent 3 Fuel return line 7 Electric fuel pump controller 4 Fuel filter with heating system

Design

As for petrol engines, the fuel system is vehicle-specific. There are, however, several general and significant differences compared to petrol engine vehicles.
These are:
• The system includes a fuel return line
• The breather system is significantly simpler
• There is no carbon canister (AKF) and no fuel tank leakage diagnosis module (DMTL)
• There is no pressure regulator
• The fuel filter is not located in the fuel tank.
The design layout of the fuel supply systems in the E70 and E90 are described in the following.
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E70 with diesel engine
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17 - Fuel tank on E70 with diesel engine
Index Explanation Index Explanation
A Fuel filler cap 1 Initial fill valve B Pressure relief valve 2 Intake mesh filter C Non-return valve 3 Fuel pump D Surge chamber 4 Pressure relief valve E Fuel tank 5 Feed line F Service cap 6 Return line G Lever-type sensor 7 Leak prevention valve H Filler vent valve 8 Suction jet pump I Connection 9 Air inlet valve J Maximum fill level 10 Suction jet pump K Non-return valve 11 Pressure relief valve L Filter
In addition to delivering the fuel to the engine, the fuel supply system also filters the fuel. The fuel tank contains an additional venting system.
The fuel tank is divided into two chambers because of the space available in the vehicle. The fuel supply system has two delivery units
that are accommodated in the right and left fuel tank halves.
The fuel pump (3) with intake filter (2) is a part of the right-hand delivery unit. The surge chamber including a suction jet pump (10) with pressure relief valve (11) and initial fill valve (1) as well as a lever-type sensor (G) complete this delivery unit.
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The suction jet pump (8), lever-type sensor (G), leak prevention valve (7) and air inlet valve (9) belong to the left-hand delivery unit.
E90 with diesel engine
A line leads from the filler vent valve (H) to the filter (L). The fuel fillerpipe is connected to this line via the non-return valve (K).
18 - Fuel tank on E90 with diesel engine
Index Explanation Index Explanation
A Fuel filler cap 1 Initial fill valve B Pressure relief valve 2 Intake mesh filter C Non-return valve 3 Fuel pump D Surge chamber 4 Pressure relief valve E Fuel tank 5 Feed line F Service cap 6 Return line G Lever-type sensor 7 Leak prevention valve H Filler vent valve 8 Suction jet pump I Connection 9 Non-return valve J Maximum fill level 10 Suction jet pump L Filter 11 Pressure relief valve
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Functions of the fuel supply system

Fuel tank

19 - Fuel tank for E70 with diesel engine
Index Explanation Index Explanation
A Fuel filler cap E Fuel tank B Pressure relief valve F Service cap C Non-return valve G Lever-type sensor D Surge chamber
A pressure relief valve (B) is integrated in the fuel filler cap (A) to protect the fuel tank (E) from excess pressure. A non-return flap (C) is located at the end of the fuel filler neck. The non-return flap prevents the fuel from sloshing back into the fuel filler neck.
The components in the fuel tank can be reached via the two service caps (F).
The fuel fill level can be determinedvia the two lever-type sensors (G).
The surge chamber (D) ensures that the fuel pump always has enough fuel available for delivery.
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Fuel supply system

20 - Fuel supply system for E70 with diesel engine
Index Explanation Index Explanation
1 Initial fill valve 7 Leak prevention valve 2 Intake mesh filter 8 Suction jet pump 3 Fuel pump 9 Air inlet valve 4 Pressure relief valve 10 Suction jet pump 5 Feed line 11 Pressure relief valve 6 Return line
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In the event of the surge chamber being completely empty, the initial filling valve (1) ensures that fuel enters the surge chamber while refuelling.
The fuel reaches the fuel pump (3) via the intake filter (2), then continues through the delivery line (5) to the fuel filter. The fuel pump is located in the surge chamber. A pressure relief valve (4) is integrated in the fuel pump to prevent pressure inthe delivery line from rising too high. As the engine switches off, the delivery line is depressurized but cannot run dry because, provided the system is not leaking, no air is able to enter it. In addition, after the fuel pump has switched off, the fuel pressure/temperature sensor is checked for plausibility.
Fuel that is required for lubrication and the function of high pressure generation flows back into the fuel tank via the return line (7). The fuel coming from the return line is divided into two lines downstream of the leak prevention valve (7). The non-return valve prevents the fuel tank from draining in the event of damage to lines on the engine or
underbody. It also prevents the return line from running dry while the engine is off.
One of the lines guides the fuel into the surge chamber via a suction jet pump (10). The suction jet pump transports the fuel from the fuel tank into the surge chamber. If the fuel delivery pressure in the return line increases too much, the pressure relief valve (11) opens and allows the fuel to flow directly into the surge chamber.
An air inlet valve is used in the E70. The air inlet valve (9) ensures that aircan enter the line when the engine is off, preventing fuel from flowing back from the right-hand half of the fuel tank to the left.
Instead of the air inlet valve (9) a non-return valve is used on the E90. The non-return valve ensures that, while the engine is off, fuel from the right-hand half of the fuel tank cannot flow back into the left-hand half. The return system remains completely filled with fuel.
A further line branches off into the left-hand half of the fuel tank after the non-return valve (7) and transports the fuel into the surge chamber via the suction jet pump (8).
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Air supply and extraction

21 - Tank ventilation system for E70 with diesel engine
Index Explanation Index Explanation
H Filler vent valve K Non-return valve I Connection L Filter J Maximum fill level
Fuel ventilation is ensured by means of the filler vent valve (H).
The filler vent valve is located in the fuel tank and uses the connection (I) to determine the maximum fill level (J). The filler vent valve contains afloat that buoys upwards on the fuel when the vehicle is refuelled and blocks the filler ventilation. The fuel rises in the fuel filler and the fuel nozzle switches off.
A roll-over valve is also integrated in the filler vent valve to block the ventilation line when a certain angle of incline is reached and prevents fuel from draining out if the vehicle were to roll over.
The non-return valve (K) prevents fuel from escaping via the ventilation when the vehicle is refuelled. During operation, air can flow into the fuel filler pipe and the fuel can flow from the fuel filler pipe into the tank.
The filter (L) prevents dirt or insects from entering the ventilation and blocking the line.
3 If the ventilation line does become
blocked, fuel consumption during operation would cause negative pressure and the fuel tank would be compressed and damaged. 1
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Components of the fuel supply system

Pressure relief valve in fuel filler cap

Index Explanation
1 Valve head 2 Excess pressure spring 3 Brace 4 Bottom section of housing 5 Pressure relief valve 6 Sealed housing
22 - Pressure relief valve
The pressure relief valve ensures that, if there is a problem with fuel tank ventilation, any excess pressure that may form can escape and the fuel tank is not damaged.
If excess pressure forms in the fuel tank, this causes the valve head (1) and with it the entire pressure relief valve (5) to be lifted off the sealed housing (6). The excess pressure can now escape into the atmosphere. The excess pressure spring (2) determines the opening pressure. The excess pressure spring uses a defined pressure to push the pressure relief valve onto the sealed housing and is supported by the brace (3).
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Protection against incorrect refuelling

Index Explanation Index Explanation
1 Housing 5 Torsion spring 2 Locking lever 6 Rivet 3 Tension spring 7 Hinged lever 4 Flap 8 Ground strap
23 - Protection against
incorrect refuelling
24 - Protection against
incorrect refuelling
52
Index Explanation Index Explanation
21 mm Petrol fuel nozzle 24 mm Diesel fuel nozzle
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The protection against incorrect refuelling feature ensures that the fuel tank cannot be filled with gasoline. As the previous graphic shows, only a fuel nozzle with a diameter of approximately 24 mm can fit. If the diameter is approximately 21 mm, the flap (4) does not open as the hinged lever (7) and the locking lever (2) cannot be pushed apart.
If a diesel fuel nozzle is inserted, this pushes the locking lever (2) and the hinged lever (7) at
the same time. The hinged lever is pushed outwards against the tension spring (3) and releases the flap (4). This is only possible, however, if the hinged lever cannot move freely and is also locked in position by the fuel nozzle.
3 To open the protection against incorrect
refuelling feature in the workshop, a special tool is required. 1
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Fuel pump

Today's diesel vehicles are fitted with electric fuel pumps only. The electric fuel pump is designed to deliver a sufficient amount of fuel to lubricate and cool the injectors and the high-pressure pump and to satisfy the maximum fuel consumption of the engine. It has to deliver the fuel at a defined pressure. That means that when the engine is idling or running at medium power, the fuel pump
delivers several times more than the amount of fuel required. The fuel pump delivers approximately three or four times the volume of maximum possible fuel consumption.
The electric fuel pump is located in the fuel tank. There it is well protected against corrosion and the pump noise is adequately soundproofed.
25 - Electric fuel pump
Index Explanation Index Explanation
1 Impeller 6 Electrical connection 2 Drive shaft 7 Sliding contacts 3 Electric motor 8 Pressure chamber 4 Pressure relief valve 9 Intake section 5 Pressure connection
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The fuel pump on BMW diesel engines may either be a gear pump, a roller-cell pump or a screw-spindle pump. The following fuel pumps are used on USA vehicles:
Vehicle Fuel pump
E70 Screw-spindle pump E90 Gear pump
The operating principle of each of these types of pump is described below. The pump itself is driven by the drive shaft (2) of the electric motor (3). The electric motor is controlled by the electrical connection (6) and sliding contacts (7).
Passing first through the intake filter and then the remainder of the intake section (9), the fuel enters the impeller (1). The fuel is pumped through pressure chamber (8) on the electric motor, past the pressure connection (5) and onwards to the fuel filter and engine.
If the fuel delivery pressure increases to an impermissible value, the pressure relief valve (4) opens and allows the fuel to flow into the surge chamber.
Control
In principle, there are three different types of fuel pump control:
• Unregulated: The fuel pump operates with "ignition ON". If the engine is not started, the fuel pump switches off again after a defined period. If the engine is running, the fuel pump
operates at maximum output and speed. The fuel is switched off with "engine OFF".
• Speed-regulated: The fuel pump operates with "ignition ON". If the engine is not started, the fuel pump switches off again after a defined period. The fuel pump is controlled by an interposed control unit (fuel pump controller) in response to a request signal from the DDE. The fuel pump controller monitors and regulates the pump speed. If the engine is switched off, so too is the fuel pump.
• Pressure-regulated: The fuel pump operates with "ignition ON". If the engine is not started, the fuel is switched off at a specific pressure. When the engine is running, the fuel pump is regulated on-demand by the interposed fuel pump controller in response to a load signal from the DDE in order to ensure a uniform fuel pressure at the inlet to the high-pressure pump.
Both speed regulation andpressureregulation have improved fuel economy, although it has been possible to improve fuel economy further still with pressure regulation. Other positive side effects include an increase in the fuel pump's service life, an unloading of the vehicle electrical system and a reduction in fuel pump noise.
Vehicle Control
E70 Pressure control E90 Speed control
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Gear pump
The type of gear pump used is a rotor pump.
The rotor pump comprises an outer rotor (1) with teeth on the inside, and an inner rotor (4) with teeth on the outside. The inner rotor is driven by the drive shaft (5) of the electric motor. The outer rotor is propelled by the teeth of the inner rotor and thus turns inside the pump housing.
The inner rotor has one tooth fewer than the outer rotor, which means that, with each revolution, fuel is carried into the next tooth gap of the outer rotor.
During the rotary motion, the spaces on the intake side enlarge, while those on the pressure side become proportionately smaller.
The fuel isfed into the rotorpump through two grooves in the housing, one on the intake side and one on the pressure side. Together with the tooth gaps, these grooves form the intake section (6) and pressure section (3).
26 - Gear pump/rotor pump
Index Explanation
1 Outer rotor 2 Fuel delivery to the engine 3 Pressure section 4 Inner rotor 5 Drive shaft 6 Intake section 7 Fuel from the fuel tank
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Screw-spindle pump
With the screw-spindle pump, two screw spindles intermesh in such a way that the flanks form a seal with each other and the housing. In the displacement chambers between the housing and the spindles, the fuel is pushed towards the pressure side with practically no pulsation.
In this way, the screw spindles pump fuel away from the fuel tank (5). The fuel is then fed to the engine (3) through the pump housing and the fuel delivery line.
27 - Screw-spindle pump
Index Explanation
1 Drive shaft screw spindle 2 Gearwheel 3 Fuel delivery to the engine 4 Screw spindle 5 Fuel from the fuel tank
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Fuel filter

The fuel filter with heater illustrated here was used in vehicle models with diesel engine and distributor injection pump. Later models with diesel engine and common rail system are equipped with the following fuel filters.
28 - Fuel filter with heater (later vehicle models)
3 BMW recommends the use of parts and
accessories for the vehicle that have been approved by BMW for this purpose. These parts and accessories have been tested by BMW for their functional safety and compatibility in BMW vehicles. BMW accepts product responsibility for them. However, BMW cannot accept any liability for non­approved parts or accessories. 1
The job of the fuel filter is to protect the fuel system against dirt contamination. The high­pressure pump and injectors in particular are very sensitive and can be damaged by even the tiniest amounts of dirt. The fuel delivered to the engine is always fed through the fuel filter. Contaminants are trapped by a paper­like material. The fuel filter is subject to a replacement interval.
Index Explanation
1 Fuel filter heater connection 2 Inlet into the fuel filter heating 3 Locking clamp 4 Fuel filter 5 Connection between fuel line and
high-pressure pump
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Fuel filter heater

The fuel filter heater is attached to the fuel filter housing and fixed with a locking clamp. The fuel flows through the fuel filter heating into the fuel filter.
Since winter-grade diesel fuel remains thin even at low temperatures, the fuel filter heater is not normally active when winter-grade diesel fuel is used. In order to save energy, the fuel filter heater is only switched on when the diesel actually becomes viscous due to low temperatures.
There are two different control systems depending on whether the fuel supply system is speed-controlled or pressure-controlled.
Speed-controlled system
The fuel filter heater is not controlled by the DDE. A pressure switch and a temperature sensor are located in the fuel filter housing.
The fuel filter heater is switched on when both of the following conditions are fulfilled:
• Temperature drops below a defined value
• A defined fuel delivery pressure is exceeded due to cold, viscous fuel.
If the filter is clogged, a corresponding signal is sent via a diagnosis line to the DDE. This is the case when, despite a sufficiently high temperature, the fuel pressure upstream of the filter does not drop.
Pressure-controlled system
The fuel filter heater is actuated by the DDE. A combined fuel pressure and temperature sensor upstream of the high pressure pump is used.
The fuel filter heater is switched on when both of the following conditions are fulfilled:
• Temperature drops below a defined value
• The required fuel pressure is not reached despite increased power intake of the electric fuel pump.
The DDE recognizes a clogged filter when the target pressure upstream of the high pressure pump is not reached despite asufficiently high fuel temperature and high power intake of the electric fuel pump.
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Overview of selective catalytic reduction

Selective catalytic reduction is a system for reducing nitrogen oxides (NOx) in the exhaust gas. For this purpose, a reducing agent (urea­water solution) is injected into exhaust gas downstream of the diesel particulate filter.
The nitrogen oxide reduction reaction then takes place in the SCR catalytic converter.
The urea-water solution is carried in two reservoirs in the vehicle. The quantity is measured out such that it is sufficient for one oil change interval.
The following graphic shows a simplified representation of the system:
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29 - Simplified representation of SCR system
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Index Explanation Index Explanation
1 Passive reservoir 10 Pump 2 Level sensors 11 Filter 3 Filler pipe, passive reservoir 12 Transfer line 4 Metering line 13 Metering module 5 Metering line heater 14 Level sensor 6 Pump 15 Filler pipe, active reservoir 7 Function unit 16 Exhaust system 8 Heater in active reservoir 17 SCR catalytic converter 9 Active reservoir
The reason for using two reservoirs is that the urea-water solution freezes at a temperature of -11 °C. Forthis reason, the smaller reservoir is heated but the larger reservoir not. In this way, the entire volume of the urea-water solution need not be heated, thus saving energy. The amount is sufficient, however, to cover large distances.
The small, heated reservoir is referred to as the active reservoir. A pump conveys the urea­water solution from this reservoir to the metering module. This line is also heated.
The larger, unheated reservoir is the passive reservoir. A pump regularly transfers the urea­water solution from the passive reservoir to the active reservoir.
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Installation locations in the E70

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30 - Installations locations, E70 SCR system
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Index Explanation Index Explanation
1 Active reservoir 8 Passive reservoir 2 Delivery module 9 Metering module 3 Filler for active reservoir 10 Exhaust gas temperature sensor
after diesel particulate filter
4 Transfer unit 11 NOx sensor before SCR catalytic
converter 5 Filter 12 Filler for passive reservoir 6 SCR catalytic converter 13 Oxidation catalytic converter and
diesel particulate filter 7 NOx sensor after SCR catalytic
converter
On the E70, the active reservoir, including the delivery unit, is located on the right-hand side directly behind the front bumper panel. The passive reservoir is located on the left in the
underbody, approximately under the driver's seat. The transfer unit is installed on the right in theunderbody. Both fillers are located in the engine compartment.
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Installation locations in the E90

64
31 - Installations locations, E90 SCR system
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Index Explanation Index Explanation
1 Active reservoir 8 Passive reservoir 2 Delivery module 9 Metering module 3 Filler for active reservoir 10 Exhaust gas temperature sensor
after diesel particulate filter 4 Transfer unit 11 NOx sensor before SCR catalytic
converter 5 Filter 12 Filler for passive reservoir 6 SCR catalytic converter 13 Oxidation catalytic converter and
diesel particulate filter 7 NOx sensor after SCR catalytic
converter
On the E90,both the active reservoir aswell as the passive reservoir are located under the luggage compartment floor with the active reservoir being the lowermost of both. The fillers are located on the left-hand side behind the rear wheel where they are accessible
through an opening in the bumper panel. The fillers are arranged in the same way as the reservoirs, i.e. the lowermost is the filler for the active reservoir. The transfer unit and the filter are located behind the filler.
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Detailed system overview

66
32 - SCR system overview
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Index Explanation Index Explanation
1 Operating vent 19 Filter 2 Passive reservoir 20 Metering line heater 3 Level sensors 21 Metering line 4 Filler vent 22 Operating vent 5 Filler pipe 23 Temperature sensor 6 Transfer line 24 Level sensor 7 Delivery module 25 Intake line heater 8 Delivery module heater 26 Filter 9 Delivery pump 27 Active reservoir 10 Reversing valve 28 Heating element in function unit 11 Filter 29 Function unit 12 Pressure sensor 30 Filler pipe 13 Filter 31 Metering module 14 Restrictor 32 NOx sensor before SCR catalytic
converter 15 Extractor connections 33 Exhaust gas temperature sensor
after diesel particulate filter 16 Filler vent 34 SCR catalytic converter 17 Non-return valve 35 NOx sensor after SCR catalytic
converter 18 Transfer pump
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E70 System circuit diagram

68
33 - E70 SCR system circuit diagram
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Index Explanation Index Explanation
1 Heater module 10 Exhaust gas temperature sensor
after diesel particulate filter 2 Delivery module with delivery pump,
reversing valve, pressure sensor and heater
3 Function unit with level sensor in
active reservoir, temperature sensor
and heater 4 Active reservoir 13 Passive reservoir 5 Metering line heater 14 Level sensors in passive reservoir 6 Digital Diesel Electronics (DDE) 15 Evaluator, level sensors in passive
7 NOx sensor after SCR catalytic
converter 8NO
9 Metering module 18 Evaluator, level sensor in active
sensor before SCR catalytic
x
converter
11 Transfer pump
12 Power distributor, battery
reservoir
16 DDE main relay
17 Power distributor, junction box
reservoir
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E90 System circuit diagram

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34 - E90 SCR system circuit diagram
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Index Explanation Index Explanation
1 DDE main relay 11 Transfer pump 2 Digital Diesel Electronics (DDE) 12 Evaluator, level sensor in active
reservoir
3 SCR relay 13 Function unit with level sensor in
active reservoir, temperature sensor
and heater 4 Power distributor, junction box 14 Active reservoir 5 Exhaust gas temperature sensor
after diesel particulate filter
6 Metering module 16 Heater module 7 Power distributor, battery 17 NOx sensor after SCR catalytic
8 Passive reservoir 18 NOx sensor before SCR catalytic
9 Level sensors in passive reservoir 19 SCR load relay 10 Evaluator, level sensors in passive
reservoir
15 Delivery module with delivery pump,
reversing valve, pressure sensor and
heater
converter
converter
20 Metering line heater
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Functions of selective catalytic reduction system

Selective catalytic reduction is currently the most effective system for reducing nitrogen oxides (NOx). During operation, it achieves an efficiency of almost 100 % and approx. 90 % over the entire vehicle operating range. The difference is attributed to the time the system
35 - SCR functions
Index Explanation Index Explanation
1 NOx sensor before SCR catalytic
converter
2 Metering module 4 Temperature sensor after diesel
requires until it is fully operative after a cold start.
This system carries a reducing agent, urea­water solution, in the vehicle.
3 NOx sensor after SCR catalytic
converter
particulate filter
The urea-water solution is injected into the exhaust pipe by the metering module upstream of the SCR catalytic converter. The DDE calculates the quantity that needs to be injected. The nitrogen oxide content in the exhaust gas is determined by the NOxsensor before the SCR catalytic converter. Corresponding to this value, the exact quantity of the urea-water solution required to fully reduce the nitrogen oxides is injected.
The urea-water solution converts to ammonia in the exhaust pipe. In the SCR catalytic converter, the ammonia reacts with the
nitrogen oxides to produce nitrogen (N2) and water (H2O).
A further NOx sensor that monitors this function is located downstream of the SCR catalytic converter.
A temperaturesensor in the exhaust pipe after the diesel particulate filter (i.e. before the SCR catalytic converter) and the metering module also influences this function. This is because injection of the urea-water solution only begins at a minimum temperature of 200 °C.
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Chemical reaction

The task of the SCR system is to substantially reduce the nitrogen oxides (NOx) in the exhaust gas. Nitrogen oxides occur in two different forms:
• Nitrogen monoxide (NO)
• Nitrogen dioxide (NO2).
36 - Nitrogen oxides
Ammonia (NH3) is used for the purpose of reducing the nitrogen oxides in a special catalytic converter.
38 - Urea-water solution
The urea-water solution is injected by the metering system into the exhaust system downstream of the diesel particulate filter. The required quantity must be metered exactly as otherwise nitrogen oxides or ammonia would emerge at the end. The following description of the chemical processes explains why this is the case.
37 - Ammonia
The ammonia is supplied in the form of a urea­water solution.
The conversion of urea into ammonia takes place in two stages.
Conversion of the urea-water solution
The uniform distribution of the urea-water solution in the exhaust gas and the conversion to ammonia take place in the exhaust pipe upstream of the SCR catalytic converter.
Initially, the urea ((NH2)2CO) dissolved in the urea-water solution is released.
39 - Release of urea from the
urea-water solution
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Thermolysis
Explanation: During thermolysis, the urea-water solution is split into two products
as the result of heating. Initial product: Urea ((NH2)2CO) Result: Ammonia (NH3)
Isocyanic acid (HNCO) Chemical formula: (NH2)2CO NH3 + HNCO
40 - Thermolysis: Urea converts to ammonia and isocyanic acid
This means, only a part of the urea-water solution is converted into ammonia during thermolysis. The remainder, which is in the
Hydrolysis
Explanation: The isocyanic acid that was produced during thermolysis is converted
into ammonia and carbon dioxide (CO2) by the addition of water in the
hydrolysis process. Initial products: Isocyanic acid (HNCO)
Water (H2O) Result: Ammonia (NH3)
Carbon dioxide (CO2) Chemical formula: HNCO + H2O NH3 + CO
41 - Hydrolysis: Isocyanic acid reacts with water to form ammonia and carbon dioxide
form of isocyanic acid, is converted in a second step.
2
74
The water required for this purpose is also provided by the urea-water solution.
Therefore, following hydrolysis, all the urea is converted into ammonia and carbon dioxide.
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NOx reduction
Nitrogen oxides are converted into harmless nitrogen and water in the SCR catalytic converter.
42 - Nitrogen and water
Reduction
Explanation: The catalytic converter serves as a "docking" mechanism for the
ammonia molecules. The nitrogen oxide molecules meet the ammonia molecules and the reaction starts and energy is released. This applies to NO in the same way as to NO2.
Initial products: Ammonia (NH3)
Nitrogen monoxide (NO)
Nitrogen dioxide (NO2)
Oxygen (O2)
Result: Nitrogen (N2)
Water (H2O)
Chemical formulae: NO + NO2 + 2NH3→ 2N2 + 3H2O
4NO + O2 + 4NH3→ 4N2 + 6H2O
6NO2 + 8NH3→ 7N2 + 12H2O
43 - NOx reduction: Nitrogen oxides react with ammonia to form nitrogen and water
It can be seen that each individual atom has found its place again at the end of the process, i.e. exactly the same elements are on the left as on the right. This takes place only when the ratio of the urea-water solution to nitrogen oxides is correct. Nitrogen oxides would
emerge if too little urea-water solution were injected. By the same token, ammonia would emerge if too much urea-water solution were injected, resulting in unpleasant odour and possible damage to the environment.
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SCR control

The SCR control is integrated in the digital diesel electronics (DDE). The SCR control is
divided into the metering system control and the metering strategy.
44 -
Index Explanation Index Explanation
1 Digital diesel electronics DDE7 10 Pressure sensor 2 SCR control 11 Temperature sensor in active
reservoir 3 Metering system control 12 Outside temperature sensor 4 Metering strategy 13 Level sensor in active reservoir 5 Injection pump 14 Level sensor in passive reservoir 6 Transfer pump 15 NOx sensor before SCR catalytic
converter 7 Metering module 16 NOx sensor after SCR catalytic
converter 8 Heater 17 Exhaust temperature sensor 9 Reversing valve
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Metering strategy
The metering strategy is an integral part of the SCR control that calculates how much area­water solution is to be injected at what time.
During normal operation, the signal from the NOx sensor before the SCR catalytic converter is used for the purpose of calculating the quantity. This sensor determines the quantity of nitrogen oxide in the exhaust gas and sends the corresponding value to the DDE.
However, the NOx sensor must reach its operating temperature before it can start measuring. Depending on the temperature, this can take up to 15 minutes. Until then the DDE uses a substitute value to determine the amount of nitrogen oxide in the exhaust gas.
A second NOx sensor is installed after the SCR catalytic converter for the purpose of monitoring the system. It measures whether there are still nitrogen oxides in the exhaust gas. If so the injected quantity of the urea­water solution is correspondingly adapted. The NOxsensor, however, measures not only nitrogen oxides but also ammonia but cannot distinguish between them.
If too much urea-water solution is injected, although the nitrogen oxides are completely reduced so-called "ammonia slip" occurs, i.e. ammonia emerges from the SCR catalytic converter. This in turn causes a rise in the value measured by the NOx sensor. The aim,
therefore, is to achieve a minimum of the sensor value.
45 - Nitrogen and ammonia emission diagram
Index Explanation
A Value output by NOx sensor B Injected quantity of urea-water
solution
1 Too little urea-water solution
injected
2 Correct quantity of little urea-water
solution injected
3 Too much urea-water solution
injected
This, however, is a long-term adaptation and not a short-term control process as the SCR catalytic converter performs a storage function for ammonia.
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Metering system control
The metering system control could be considered as the executing part. It carries out the requirements setby the metering strategy. This includes both the metering, i.e. injection as well as the supply of the urea-water solution.
The tasks of the metering system control during normal operation are listed in the following:
Metering of the urea-water solution:
• Implementation of the required target quantity of urea-water solution
• Feedback of the implemented actual
Supplying urea-water solution:
• Preparation of meteringprocess(filling lines
• Emptying lines during afterrunning
• Heater actuation.
In addition, the metering system control recognizes faults, implausible conditions or critical situations and initiates corresponding measures.

Metering of the urea-water solution

The metering strategy determines the quantity of urea-water solution to be injected. The metering system control executes this request. A part of the function is metering actuation that determines the actual opening of the metering valve.
Depending on the engine load, the metering valve injects at a rate of 0.5 Hz to 3.3 Hz.
The metering actuation facility calculates the following factors in order to inject the correct quantity:
• The duty factor of the actuator of the metering valve in order to determine the injection duration
• Actuation delay to compensate for the sluggishness of the metering valve.
The signal from the pressure sensor in the metering line is taken into account to ensure an accurate calculation; the pressure, however, should remain at a constant 5 bar.
The metering system control also calculates the quantity actually metered and signals this value back to the metering strategy.
The metering quantity is also determined over a longer period of time. This long-term calculation is reset during refuelling or can be reset by the BMW diagnosis system.
quantity of urea-water solution.
and pressure built-up)undercorresponding ambient conditions (temperature)
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Supplying urea-water solution

A supply of a urea-water solution is required for the selective catalytic reduction process. It is necessary to store this medium in the vehicle and to make it available rapidly under all operating conditions. In this case 'making available' means that the urea-water solution is applied at a defined pressure at the metering valve.
Various functions that are described in the following are required to carry out this task.
Heater
The systemmust be heated as the urea-water solution freezes at a temperature of -11 °C.
The heating system performs following tasks:
• To monitor the temperature in the active reservoir and the ambient temperature
• To thaw a sufficient quantity of urea-water solution and the components required for metering the solution during system start­up
• To prevent the relevant components freezing during operation
• To monitor the components of the heating system.
The following components are heated:
• Surge chamber in active reservoir
• Intake line in active reservoir
• Delivery module (pump, filter, reversing valve)
• Metering line (from active reservoir to metering module).
The heating systems for the metering line and delivery module are controlled dependent on the ambient temperature.
The heater in the active reservoir is controlled as a function of the temperature in the active reservoir.
The heating control is additionallygovernedby the following conditions:
Temperature in active reservoir and ambient temperature are the same
Condition 1 Condition 2 Condition 3 Condition 4
Ambient temperature and temperature in active reservoir
Metering line heater Not active Not active Active Active Active reservoir heater Not active Active Active Active Metering standby Established Established Established Delayed
> -4 °C < -4 °C < -5 °C < -9 °C
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Metering standby is delayed at a temperature below -9 °C in the active reservoir, i.e. a defined waiting period is allowed to elapse until an attempt to build up pressure begins. This time is constant from -9 °Cto -16.5 °Cas it is not possible to determine to what extent the urea-water solution is frozen. At temperatures below -16.5 °C, the heating time is extended until an attempt to build up the pressure is made.
Heating the metering line generally takes place much faster.Therefore, the temperature
in the active reservoir is the decisive factor for the period of time until an attempt to build up the pressure is undertaken. However, it is possible that the heating time for the metering line is longer at ambient temperature considerably lower than the temperatureinthe active reservoir. In this case, the ambient temperature is taken for the delay in metering standby.
The following graphic shows the delay as a function of the temperature sensor signals.
46 - Diagram - metering
standby delay times
Index Explanation Index Explanation
A Delay as a function of temperature in
active reservoir
t [s] Delay time in seconds T [°C] Temperature in degrees Celsius
The graphic shows that, with the same temperature signals, the delay time relating to the temperature in the active reservoir is longer than the delay caused by the ambient temperature.
Only the times at temperatures below -9 °C are relevant as they are shorter than 3 minutes at temperatures above -9 °C. 3 minutes is the time that the entire system requires to establish metering standby (e.g. also taking
B Delay as a function of ambient
temperature
into account the temperature in the SCR catalytic converter). This is also the time that is approved by the EPA (Environmental Protection Agency) as the preliminary period under all operating conditions. This time is extended significantly at very low temperatures.
The following example shows how the delay time up to metering standby is derived at low temperatures.
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Example: Ambient temperature: -30 °C, temperature in active reservoir: -12 °C
The vehicle was driven for a longer period of time at very low ambient temperatures of ­30 °C. The heater in the active reservoir has thawed the urea-water solution. The vehicle is now parked for a short period of time (e.g. 30 minutes). When restarted, the temperature in the active reservoir is -12 °C.
The delay time that is initiated by the temperature in the active reservoir is approx. 18 minutes while the delay time initiated by the ambient temperature is 25 minutes. Since the delay time initiated by the ambient temperature is longer, this will give rise to a longer delay.
Now another condition comes into play. Only the end of the delay caused by the
temperature in the active reservoir can enable metering. This means:
• The delay time initiated by the temperature in the active reservoir will have elapsed after 18 minutes. No enable is yet provided by the second delay caused by the ambient temperature. A second cycle of 18 minutes now begins.
• The delay time initiated by the ambient temperature will elapse after 25 minutes and will send its enable signal. However, this delay cannot enable metering.
• The second cycle of the delay time caused by the temperature in the active reservoir will have elapsed after 36 minutes. Since the enable from the delay caused by the ambient temperature is now applied, metering will be enabled.
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Transfer pumping
So-called transfer pumping is required since two reservoirs are used for storing the urea­water solution. The term transfer pumping
47 - Transfer pumping
relates to pumping the urea-water solution from the passive reservoir into the active reservoir.
Index Explanation Index Explanation
1 Passive reservoir 6 Pump 2 Level sensors 7 Non-return valve 3 Extractor connections 8 Level sensor 4 Transfer line 9 Active reservoir 5 Filter
The following conditions must be met for transfer pumping:
• There is aurea-water solution in the passive reservoir
• The ambient temperature is above a minimum value of -5 °C for at least 10 minutes
• A defined quantity (300 ml) was used up in the active reservoir or the reserve level in the active reservoir was reached.
The solution is then pumped for a certain time in order to refill the active reservoir. The transfer pumping procedure is terminated if the "full" level is reached before the time has elapsed.
If the passive reservoir was refilled, transfer pumping will only take place after a quantity of approx. 3 l has been used up in the active reservoir. The entire quantity is then pumped over. The system then waits again until a quantity of approx. 3 l has been used up in the active reservoir before again pumping the entire quantity while simultaneously starting the incorrect refilling detection function. This function determines whether the system has been filled with the wrong medium as it is present in high concentration in the active reservoir.
Transfer pumping does not take place in the event of a fault in the level sensor system.
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Delivery
The urea-water solution is delivered from the active reservoir to the metering module. This task is performed by a pump that is integrated in the delivery unit. The delivery unit additionally contains:
• Heater
• Pressure sensor
• Filter
• Return throttle
• Reversing valve.
48 - Delivery
Index Explanation Index Explanation
1 Metering line 8 Filter 2 Delivery module 9 Level sensor 3 Pump 10 Filter 4 Reversing valve 11 SCR catalytic converter 5 Filter 12 Exhaust system 6 Restrictor 13 Metering module 7 Pressure sensor
The pump is actuated by a pulse-width modulated signal (PWM signal) from the DDE. The PWM signal provides a speed specification for the purpose of establishing the system pressure. The value for the speed specification is calculated by the DDE based on the signal from the pressure sensor.
When the system starts up, the pump is actuated with a defined PWM signal and the line to the metering module is filled. This is followed by pressure build-up. Only then does pressure control take place.
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When the metering line is filled, the opened metering valve allows a small quantity of the urea-water solution to be injected into the exhaust system.
During pressure control, i.e. during normal operation with metering, the pump is actuated in such a way that a pressure of 5 baris applied in the metering line. Only a small part of the urea-water solution delivered by the pump is actually injected. The majorityof the solution is transferred via a throttle back into the active reservoir. This means, the delivery pressure is determined by the pump speed together with the throttle cross section.
The solution is injected four times per second. The quantity is determined by the opening time and stroke of the metering valve. However, the quantity is so low that there is no noticeable drop in pressure in the metering line.
Evacuating
After turning off theengine, the reversing valve switches to reverse the delivery direction of the pump, thus evacuating the metering line and metering module.
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49 - Evacuating
Index Explanation Index Explanation
1 Metering line 8 Filter 2 Delivery module 9 Level sensor 3 Pump 10 Filter 4 Reversing valve 11 SCR catalytic converter 5 Filter 12 Exhaust system 6 Throttle 13 Metering module 7 Pressure sensor
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Evacuation also takes place if the system has to be shut down due to a fault or if the minimum temperature in the active reservoir can no longer be maintained.
This is necessary to ensure no urea-water solution remains in the metering line or metering module as it can freeze.
The metering valve is opened during evacuation.
Level measurement
There are level sensors both in the active as well as in the passive reservoir. However, these sensors are not continuous sensors as in the fuel system for example. They can determine only a specific point, to which a defined quantity of urea-water solution in the reservoir is assigned.
Two separate level sensors are fitted in the passive reservoir, one for "full" and one for "empty". The signals from the level sensors are not sent directly to the DDE but rather to an evaluator.
The active reservoir contains one level sensor that has various measuring points:
• Full
• Warning
• Empty.
Also in this case, there is an evaluator installed between the sensors and the DDE, which fulfils the same tasks as for the passive reservoir.
This evaluator sends a plausible level signal to the DDE. It recognizes changes in the fill level caused, for example, by driving uphill/downhill or sloshing of the liquid as opposed to an actual change in the liquid level in the reservoir. Low level isthereforesignalled when the corresponding sensor isnolonger covered by the urea-water solution for a defined period of time. Once the level drops below this value, it can no longer be reached during normal operation. This means, the liquid sloshing on the sensor or driving uphill/downhill is no longer interpreted as a higher liquid level.
50 - Example: Level signal OK
Index Explanation
1 Measuring point "Full" 2 Measuring point "Warning" 3 Measuring point "Empty" 4 Reference 5 Level
Level of urea-water solution Level signal
Level > Full Full Full > Level > Warning OK Warning > Level > Empty Warning Empty > Level Empty
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The level measurement system must also recognize when the active and passive reservoirs are refilled. This is achieved by comparing the current level with the value last stored.
The level sensor signal after refilling corresponds to the signal while driving uphill. To avoid possible confusion, the refilling recognition function is limited to a certain period of time after starting the engine and driving off - as it can be assumed that refilling will only take place while the vehicle is stationary.
A certain vehicle speed must be exceeded to ensure that sloshing occurs, thus providing a clear indication that the system has been refilled.
Refilling the system while the engine is running can also be detected but with modified logic. The signals sent by the sensors while the vehicle is stationary are also used for this purpose. The vehicle must be stationary for a defined minimum period in order to make the filling plausible.
When the urea-water solution is frozen, a level sensor will show the same value as when it is not wetted/covered by the solution. A frozen reservoir is therefore shown as empty. For this reason, the following sensor signals are used for measuring the level:
• Ambient temperature
• Temperature in active reservoir
• Heater enable.
Level calculation
This function calculates the quantity of urea­water solution remaining in the active
reservoir. The calculation is calibrated together with the level measurement.
Every time the level drops below a level sensor the corresponding amount of urea-water solution in the reservoir is stored. The amount of urea-water solution actually injected is then subtracted from this value while the pumped quantity is added.
This makes it possible to determine the level more precisely than that would be possible by simple measurement. In addition, thelevel can still be determined in the event of one of the level sensors failing.
Since it is possible that refilling is not recognized, the calculation is continued only until the level ought to drop below the next lower sensor.
Example:
Once the level drops below the "full" level sensor, for example, from now on the quantity of used and repumped urea-water solution is taken into account and the actual level below "full" calculated. Normally, the level thendrops below the next lower level sensor at the same time as determined by the level calculation. An adjustment takes place at this point and the calculation is restarted.
If, however, a quantity of urea-water solution is refilled without it being detected, the actual level will be higher than the calculated level. The level calculation is stopped if it calculates that the level ought to have dropped below the next level sensor but the level sensor is still wetted/covered.
By way of exception, a defective level sensor can cause the calculation to continue until the reservoir is empty.
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SCR system modes

When the ignition is switched on, the SCR control undergoes a logical sequence of modes in the DDE. There are conditions that initiate the change from one mode to the
other. The following graphic shows the sequence of modes which are subsequently described.
51 - Sequence of modes in SCR control
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INIT (SCR initialization)
The control unit is switched on (terminal 15 ON) and the SCR system is initialized.
STANDBY (SCR not active)
STANDBY mode is assumed either after initialization or in the case of fault.
AFTERRUN mode is assumed if terminal 15 is switched off in this state or a fault occurs.
NOPRESSURECONTROL (waiting for enable for pressure control)
NOPRESSURECONTROL mode is assumed when no faults occur in the system. In this mode, the system is waiting for the pressure control enable that is provided by the following sensor signals:
• Temperature in catalytic converter
• Temperature in active reservoir
• Ambient temperature
• Engine status (engine running).
The system also remains in NOPRESSURECONTROL mode for a minimum period of time so that a plausibility check of the pressure sensor can be performed.
PRESSURECONTROL mode is assumed once the enable is finally given.
STANDBY mode is assumed if terminal 15 is switched off or a fault occurs in NOPRESSURECONTROL mode.
PRESSURECONTROL (SCR system running)
PRESSURECONTROL mode is the normal operating status of the SCR system and has four submodes.
PRESSURECONTROL mode is maintained until terminal 15 is switched off. A change to PRESSUREREDUCTION mode then takes place.
A change to PRESSUREREDUCTION mode also takes place if a fault occurs in the system.
The four submodes of PRESSURECONTROL are described in the following:
REFILL
The delivery module, metering line and the metering module are filled when REFILL mode is assumed. The pump is actuated and the metering valve opened by a defined value. The fill level is calculated.
The mode changes to PRESSUREBUILDUP when the required fill level is reached or a defined pressure increase is detected.
PRESSUREREDUCTION mode is assumed if terminal 15 is switched off or a fault occurs in the system.
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PRESSUREBUILDUP
In this mode, the pressure is built up to a certain value. For this purpose, the pump is actuated while the metering valve is closed.
If the pressure is built up within a certain time, the system switches to the next mode of METERINGCONTROL. If the required pressure built-up is not achieved after the defined period of time has elapsed, a status loop is initiated,andVENTILATION mode is assumed.
If the pressure cannot be built up after a defined number of attempts, the system signals a fault and assumes PRESSUREREDUCTION mode.
PRESSUREREDUCTION mode is also assumed when terminal 15 is switched off or another fault occurs in the system.
VENTILATION
If the pressure could not be increased beyond a certain value in PRESSUREBUILDUP mode, it is assumed that there is still air in the pressure line.
The metering valve is opened for a defined period of time to allow this air to escape. This status is exited after this time has elapsed and the system returns to PRESSUREBUILDUP mode. The loop
between PRESSUREBUILDUP and VENTILATION varies corresponding to the condition of thereducing agent. The reason for this is that a different level is established after REFILL depending on the ambient conditions. Repeating the ventilation function will ensure that the pressure line is completely filled with reducing agent.
PRESSUREREDUCTION mode is assumed if terminal 15 is switched off or a fault occurs in the system.
METERINGCONTROL
The system can enable metering in METERINGCONTROL mode. This is the actual status during normal operation. The urea-water solution is injected in this mode.
In this mode, the pump is actuated in such a way thata defined pressure is established. This pressure is monitored. If the pressure progression overshoots or undershoots defined parameters, a fault is detected and the system assumes PRESSUREREDUCTION mode. These faults are reset on return to METERINGCONTROL mode.
PRESSUREREDUCTION mode is also assumed if terminal 15 is switched off or another fault occurs in the system.
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PRESSUREREDUCTION
Metering enable is cancelled on entering PRESSUREREDUCTION mode.
This status reduces the pressure in the delivery module, metering line and the metering module after PRESSURECONTROL mode. For this purpose, the reversingvalve is opened andthe pump actuated at a certain value, the metering valve is closed.
PRESSUREREDUCTION mode ends when the pressure drops below a certain value. The system assumes NOPRESSURECONTROL mode if the pressure threshold is reached (undershot) within a defined time.
The system signals a fault if the pressure does not drop below the threshold after a defined time has elapsed. In this case or also in the case of another fault, the system assumes NOPRESSURECONTROL mode.
NOPRESSURECONTROL mode is also assumed when terminal 15 is switched on.
AFTERRUN
The system is shut down in AFTERRUN mode.
If terminal 15 is switched on again before afterrun has been completed, afterrun is cancelled and STANDBY mode is assumed. If this is not the case the system goes through the submodes of AFTERRUN.
TEMPWAIT (catalytic converter
cooling phase)
In AFTERRUN mode, TEMPWAIT submode is initially assumed if the system is filled. This is intended to prevent excessively hot exhaust gasses being drawn into the SCR system.
The duration of the cooling phase is determined by the exhaust gas temperature. EMPTYING submode is assumed after this time, in which the exhaust system cools down, has elapsed.
EMPTYING submode is also assumed if a fault occurs in the system.
If terminal 15 is switched on in this status, STANDBY mode is assumed.
EMPTYING
The system assumes AFTERRUN_EMPTYING submode after the cooling phase. The pressure line and the delivery module are emptied in this submode. Theurea-water solution is drawn back into the active reservoir by opening the reversing valve, actuating the pump and opening the metering valve. This is intended to prevent the urea-water solution freezing inthe metering lineor the metering module.
The level inthe metering line is calculated in this mode.
PRESSURECOMPENSATION mode is assumed if the metering line is empty. PRESSURECOMPENSATION mode is also assumed if a fault occurs in the system. If terminal 15 is switched on, STANDBY mode is assumed.
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PRESSURECOMPENSATION (intake line - ambient pressure)
After the system has been completely emptied, PRESSURECOMPENSATION submode is assumed. In this status the pump is switched off, the reversing valve is then closed followed by the metering valve after a delay. The time interval between switching off the pump and closing the valve prevents a vacuum forming in the intake line; pressure compensation between the intake line and ambient pressure takes place.

Warning and shut-down scenario

The SCR system is relevant to the vehicle complying with the exhaust emission regulations - it is a prerequisite for approval/ homologation! If the system fails, the approval will be invalidated and the vehicle must no longer be operated. A very plausible case leading to the system failure is that the urea­water solution runs out.
After executing the steps correctly the system assumes WAITING_FOR_SHUTOFF submode.
WAITING_FOR_SHUTOFF is also assumed if a fault occurs in the system.
If terminal 15 is switched on, STANDBY mode is assumed.
WAITING_FOR_SHUTOFF (shutting
down SCR)
The control unit is shut down and switched off.
Vehicle operation is no longer permitted without the urea-water solution, therefore, the engine will no longer start.
To ensure the driver is not caught out, a warning and shut-down scenario is provided that begins at a sufficiently long time before the vehicle actually shuts down so that the driver can either conveniently top up the urea­water solution himself or have it topped up.
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Warning scenario
The warning scenario begins when the level drops below the "Warning" level sensor in the active reservoir. At this point, the active reservoir is still approximately 50 % full with urea-water solution. The level is then determined as a defined volume (depending on type of vehicle).
From this point on, the actual consumption of the urea-water solution is subtracted from this value. The mileage is recorded when the amount of 2500 ml is reached.
A countdown from 1000 mls now takes place
- irrespective of the actual consumption of the urea-water solution. The driver receives a priority 2 (yellow) check control message showing the remaining range.
53 - CC message in CID, range < 1000 mls
The driver receives a priority 1 (red) check control message as from 200 mls.
52 - CC message in instrument
cluster, range < 1000 mls
If the vehicle is equipped with an on-board computer (CID - Central Information Display), instruction will also be displayed.
54 - CC message in instrument
cluster, range < 200 mls
In this case the following message is shown in the CID:
55 - CC message in CID, range < 200 mls
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Shut-down scenario
If the range reaches 0 mls, similar as to in the fuel gauge, three dashes are shown instead of the range.
56 - CC message in instrument
cluster, range = 0 mls
The check control message in the CID changes and shows that the engine can no longer be started.
Exhaust fluid incorrect
If the systemis filled with anincorrect medium, this will become apparent after several hundred miles (kilometres) later by elevated nitrogen oxide values in the exhaust gas despite adequate injection of the supposed urea-water solution. The system recognizes an incorrect medium when certain limits are exceeded. From this point on, a warning and shut-down scenario is also initiated that allows a remaining range of 200 mls.
58 - CC message in instrument
cluster in the case of incorrect exhaust fluid
The exclamation mark in the symbol identifies the fault in the system.
In this case, the message in the CID informs the driver to go to the nearest workshop.
57 - CC message in CID, range = 0 mls
In this case, it will no longer be possible to start the engine if it has been shut down for longer than three minutes. This is intended to allow the driver to move out of a hazardous situation if necessary.
If the system is refilled only after engine start has been disabled, the logic of the refill recognition system is changed in this special case, enabling faster refill.
59 - CC message in CID in the case of incorrect exhaust fluid
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Refilling

The active and passive reservoirs can be refilled with urea-water solution either by the service workshop or by the customer himself.
The system can be refilled without any problems with thevehicle on an inclineof up to 5° in any direction. In this case, 90 % of the maximum possible fill is still achieved.
The volume of the urea-water solution reservoir is designed such that the range is large enough to cover one oil change interval. This means the "normal" refill takes place as part of the servicing work in the workshop. If, however, the supply of urea-water solution should run low prematurely due to extraordinary driving profile, itis possible to top up a smaller quantity.
Refilling in service workshop
Refilling in the service workshop refers to the routine refill as part of the oil change procedure. This takes place at the latest after:
• 13000 mls on the E90,
• 11000 mls on the E70 or
• one year.
In this case, the system must be emptied first in order to remove older urea-water solution. This takes place via the extractor connections in the transfer line. Although a small residual quantity always remains in the reservoirs, it is negligible.
Topping up
Any required quantity can be topped up if the urea-water solution reserve does not last up to the next oil change. Ideally, this quantity should only be as much as is required to reach the next oil change, as the system is then emptied.
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