Technicaltraining. [608134]

Technical￿training.
Product￿information.
BMW￿ServiceN20￿Engine

General￿information
Symbols￿used
The￿following￿symbol￿/￿sign￿is￿used￿in￿this￿document￿to￿facilitate￿better￿comprehension￿and￿to￿draw
attention￿to￿particularly￿important￿information:
Contains￿important￿safety￿guidance￿and￿information￿that￿is￿necessary￿for￿proper￿system￿functioning
and￿which￿it￿is￿imperative￿to￿follow.
Information￿status￿and￿national-market￿versions
The￿BMW￿Group￿produces￿vehicles￿to￿meet￿the￿very￿highest￿standards￿of￿safety￿and￿quality.￿Changes
in￿terms￿of￿environmental￿protection,￿customer￿benefits￿and￿design￿make￿it￿necessary￿to￿develop
systems￿and￿components￿on￿a￿continuous￿basis.￿Consequently,￿this￿may￿result￿in￿differences￿between
the￿content￿of￿this￿document￿and￿the￿vehicles￿available￿in￿the￿training￿course.
As￿a￿general￿principle,￿this￿document￿describes￿left-hand￿drive￿vehicles￿in￿the￿European￿version.￿Some
controls￿or￿components￿are￿arranged￿differently￿in￿right-hand￿drive￿vehicles￿than￿those￿shown￿on￿the
graphics￿in￿this￿document.￿Further￿discrepancies￿may￿arise￿from￿market‐specific￿or￿country-specific
equipment￿specifications.
Additional￿sources￿of￿information
Further￿information￿on￿the￿individual￿topics￿can￿be￿found￿in￿the￿following:
• Owner's￿Handbook
• Integrated￿Service￿Technical￿Application.
Contact:￿[anonimizat]
©2010￿BMW￿AG,￿Munich,￿Germany
Reprints￿of￿this￿publication￿or￿its￿parts￿require￿the￿written￿approval￿of￿BMW￿AG,￿Munich
The￿information￿in￿the￿document￿is￿part￿of￿the￿BMW￿Group￿technical￿training￿course￿and￿is￿intended
for￿its￿trainers￿and￿participants.￿Refer￿to￿the￿latest￿relevant￿BMW￿Group￿information￿systems￿for￿any
changes/supplements￿to￿the￿technical￿data.
Contacts
Gernot￿Nehmeyer/Udo￿Metz
Telephone￿+49￿(0)￿89￿382￿34059/+49￿(0)￿89￿382￿58506
[anonimizat]/[anonimizat]
Information￿status:￿ November￿2010
BV-72/Technical￿Training

N20￿Engine
Contents
1. Introduction …………………………………………………………………………………………………………………………………………………………………………………………………………………1
1.1. History. ………………………………………………………………………………………………………………………………………………………………………………………………………….1
1.1.1. Historic￿BMW￿AG￿engines …………………………………………………………………………………………………………………….1
1.1.2. Historic￿BMW￿M￿engines ……………………………………………………………………………………………………………………….3
1.2. Technical￿data. ……………………………………………………………………………………………………………………………………………………………………………………3
1.2.1. Comparison￿ ……………………………………………………………………………………………………………………………………………………………4
1.3. New￿features/changes ………………………………………………………………………………………………………………………………………………………………6
1.3.1. Overview. ……………………………………………………………………………………………………………………………………………………………………..6
1.4. Engine￿identification …………………………………………………………………………………………………………………………………………………………………..7
1.4.1. Engine￿designation …………………………………………………………………………………………………………………………………………7
1.4.2. Engine￿identification ……………………………………………………………………………………………………………………………………..8
2. Engine￿Components …………………………………………………………………………………………………………………………………………………………………………………..11
2.1. Engine￿housing ……………………………………………………………………………………………………………………………………………………………………………..11
2.1.1. Engine￿block. ………………………………………………………………………………………………………………………………………………………12
2.1.2. Cylinder￿head￿gasket ……………………………………………………………………………………………………………………………….16
2.1.3. Cylinder￿head …………………………………………………………………………………………………………………………………………………….17
2.1.4. Cylinder￿head￿cover. ………………………………………………………………………………………………………………………………….18
2.1.5. Oil￿sump. ………………………………………………………………………………………………………………………………………………………………….24
2.2. Crankshaft￿drive ……………………………………………………………………………………………………………………………………………………………………………27
2.2.1. Crankshaft￿with￿bearings.. …………………………………………………………………………………………………………………..27
2.2.2. Connecting￿rod￿ ……………………………………………………………………………………………………………………………………………..42
2.2.3. Piston￿with￿piston￿rings. ……………………………………………………………………………………………………………………….43
2.3. Camshaft￿drive. ………………………………………………………………………………………………………………………………………………………………………………45
2.4. Counterbalance￿shafts. ………………………………………………………………………………………………………………………………………………………..46
2.5. Valve￿gear ……………………………………………………………………………………………………………………………………………………………………………………………..50
2.5.1. Design. ………………………………………………………………………………………………………………………………………………………………………..50
2.5.2. Valvetronic. …………………………………………………………………………………………………………………………………………………………….55
2.6. Belt￿drive ……………………………………………………………………………………………………………………………………………………………………………………………….63
3. Oil￿Supply …………………………………………………………………………………………………………………………………………………………………………………………………………………..65
3.1. Overview ………………………………………………………………………………………………………………………………………………………………………………………………..65
3.1.1. Hydraulic￿circuit￿diagram. ……………………………………………………………………………………………………………………66
3.1.2. Oil￿passages ………………………………………………………………………………………………………………………………………………………..68
3.2. Oil￿pump￿and￿pressure￿control. …………………………………………………………………………………………………………………………………73
3.2.1. Oil￿pump.. …………………………………………………………………………………………………………………………………………………………………73
3.2.2. Control ………………………………………………………………………………………………………………………………………………………………………..75
3.2.3. Pressure-limiting￿valve.. …………………………………………………………………………………………………………………………83
3.3. Oil￿filtering￿and￿cooling. ………………………………………………………………………………………………………………………………………………………84
3.3.1. Oil￿cooling. ……………………………………………………………………………………………………………………………………………………………..84
3.3.2. Oil￿filtering ……………………………………………………………………………………………………………………………………………………………..85

N20￿Engine
Contents
3.4. Oil￿monitoring. …………………………………………………………………………………………………………………………………………………………………………………86
3.4.1. Oil￿pressure￿and￿temperature￿sensor ………………………………………………………………………………….86
3.4.2. Oil￿level￿monitoring.. …………………………………………………………………………………………………………………………………..87
3.5. Oil￿spray￿nozzles.. ………………………………………………………………………………………………………………………………………………………………………..87
3.5.1. Piston￿crown￿cooling.. ………………………………………………………………………………………………………………………………87
3.5.2. Chain￿drive. ……………………………………………………………………………………………………………………………………………………………88
3.5.3. Camshaft ………………………………………………………………………………………………………………………………………………………………….89
3.5.4. Gearing,￿Valvetronic￿servomotor. ……………………………………………………………………………………………….91
4. Cooling ……………………………………………………………………………………………………………………………………………………………………………………………………………………………93
4.1. Overview ………………………………………………………………………………………………………………………………………………………………………………………………..93
4.2. Heat￿management …………………………………………………………………………………………………………………………………………………………………….96
4.2.1. Coolant￿pump ……………………………………………………………………………………………………………………………………………………96
4.2.2. Map￿thermostat ………………………………………………………………………………………………………………………………………………97
4.2.3. Heat￿management￿function.. ……………………………………………………………………………………………………………97
4.3. Internal￿engine￿cooling.. ………………………………………………………………………………………………………………………………………………………98
5. Air￿Intake/Exhaust￿Emission￿Systems. ……………………………………………………………………………………………………………………………99
5.1. Overview ………………………………………………………………………………………………………………………………………………………………………………………………..99
5.2. Intake￿air￿system.. ……………………………………………………………………………………………………………………………………………………………………101
5.2.1. Hot-film￿air￿mass￿meter. ……………………………………………………………………………………………………………………102
5.2.2. Intake￿manifold …………………………………………………………………………………………………………………………………………….102
5.3. Exhaust￿turbocharger ………………………………………………………………………………………………………………………………………………………..103
5.3.1. Function￿of￿TwinScroll￿exhaust￿turbocharger. ……………………………………………………….105
5.4. Exhaust￿emission￿system. ……………………………………………………………………………………………………………………………………………108
5.4.1. Exhaust￿manifold ……………………………………………………………………………………………………………………………………….108
5.4.2. Catalytic￿converter …………………………………………………………………………………………………………………………………..108
6. Vacuum￿System …………………………………………………………………………………………………………………………………………………………………………………………….110
7. Fuel￿Preparation …………………………………………………………………………………………………………………………………………………………………………………………..112
7.1. Overview …………………………………………………………………………………………………………………………………………………………………………………………….112
7.2. Fuel￿pump￿control.. ………………………………………………………………………………………………………………………………………………………………..113
7.3. High-pressure￿pump …………………………………………………………………………………………………………………………………………………………..113
7.4. Injectors ………………………………………………………………………………………………………………………………………………………………………………………………114
8. Fuel￿Supply ………………………………………………………………………………………………………………………………………………………………………………………………………….117
8.1. Tank￿ventilation.. ………………………………………………………………………………………………………………………………………………………………………..117
8.1.1. Two-stage￿tank￿ventilation… ………………………………………………………………………………………………………….117
8.1.2. Two-stage￿tank￿ventilation￿with￿shutoff￿valve ………………………………………………………..119
9. Engine￿Electrical￿System.. ……………………………………………………………………………………………………………………………………………………………..122

N20￿Engine
Contents
9.1. Overview …………………………………………………………………………………………………………………………………………………………………………………………….122
9.2. Engine￿control￿unit ……………………………………………………………………………………………………………………………………………………………….124
9.2.1. Overall￿function ……………………………………………………………………………………………………………………………………………126

N20￿Engine
1.￿Introduction
1BMW￿has￿decided￿to￿bring￿back￿the￿4–cylinder￿engine￿to￿the￿US￿market.￿The￿last￿BMW￿4–cylinder
engine￿in￿the￿US￿was￿the￿M44,￿this￿lasted￿until￿1999￿and￿was￿installed￿in￿the￿E36￿318is/318ti/Z3.
Since￿then￿BMW￿in￿the￿US￿has￿not￿had￿a￿4–cylinder￿engine.￿The￿N20￿engine￿represents￿the￿new
generation￿of￿BMW￿4-cylinder￿gasoline￿engines.￿It￿will￿gradually￿be￿phased￿in￿on￿a￿number￿of￿BMW
models￿starting￿in￿September￿2011.￿The￿N20￿will￿replace￿the￿N52￿6-cylinder￿naturally￿aspirated
engines.￿The￿N20￿engine￿is￿equipped￿with￿the￿latest￿technology,￿such￿as￿TVDI￿(Turbocharged
Valvetronic￿Direct￿Injection)￿in￿conjunction￿with￿a￿TwinScroll￿exhaust￿turbocharger.￿As￿a￿whole,￿it￿is
closely￿related￿to￿the￿N55￿engine,￿this￿is￿why￿constant￿reference￿is￿made￿to￿the￿N55￿engine￿in￿this
document.
1.1.￿History
The￿history￿of￿BMW￿4-cylinder￿engines￿began￿back￿in￿1927￿with￿the￿BMW￿3/15.￿From￿that￿point￿on,
apart￿from￿an￿interruption￿stretching￿from￿1936￿to￿1962,￿the￿4-cylinder￿gasoline￿engines￿have￿again
and￿again￿been￿the￿precursors￿to￿new￿technologies￿and￿have￿often￿also￿been￿forerunners.￿Thus,
the￿M31￿engine￿(predecessor￿of￿the￿M10￿engine)￿was￿the￿world's￿first￿4-cylinder￿production￿engine
to￿feature￿a￿TwinScroll￿exhaust￿turbocharger￿and￿back￿in￿1973￿already￿achieving￿a￿power￿output￿of
125￿kW￿/￿167￿bhp￿from￿a￿displacement￿of￿2￿liters.￿In￿motorsport￿the￿crankcase￿of￿the￿M10￿with￿a
displacement￿of￿1.5￿liters￿produced￿the￿first￿Formula￿1￿world￿champion￿with￿a￿turbocharged￿engine.￿In
the￿world￿of￿motor￿racing￿performance￿figures￿of￿up￿to￿1350￿bhp￿from￿a￿displacement￿of￿1.5￿liters￿were
achieved,￿figures￿which￿to￿date￿have￿only￿been￿achieved￿by￿BMW.
1.1.1.￿Historic￿BMW￿AG￿engines
Designation Power
output￿in
bhp/rpmDisplacement
in￿[cm³]Year￿of
launchModel Series
DA￿1,￿2,￿4* 15/3000 748 1927BMW￿3/15 3/15
DA￿3* 18/3500 748 1930Wartburg 3/15
M68* 20/3500 782 1932BMW￿3/20 3/20
M68* 22/4000 845 1934BMW￿309 309
M115** 75/5700 1499 1961BMW￿1500 115
M115**
Available￿in
the￿US80/5500 1499 1962BMW￿1500 115
M116**
Available￿in
the￿US83/5500 1573 1964BMW￿1600 116
M116** 85/5700 1573 1966 BMW
1600-2114C
M116** 105/6000 1573 1967BMW￿1600ti 116
M116** 75/5800 1573 1975BMW￿1502 114
M118** 90/5250 1773 1963BMW￿1800 118
M118** 110/5800 1773 1964BMW￿1800ti 118

N20￿Engine
1.￿Introduction
2Designation Power
output￿in
bhp/rpmDisplacement
in￿[cm³]Year￿of
launchModel Series
M118**
Available￿in
the￿US130/6100 1773 1965 BMW
1800ti￿SA118
M118**
short-stroke90/5250 1766 1968BMW￿1800 118
M118**
short-stroke90/5500 1766 1974BMW￿518 E12/4
M05**
Available￿in
the￿US100/5500 19901965–1972 BMW
2000/2002121
M05** 120/5500 1990 1965BMW￿2000ti 121
M15**
Available￿in
the￿US130/5800 1990 1968 BMW
2000tii/2002tii121
M17** 115/5800 1990 1972BMW￿520 E12/4
M31** 170/5800 1990 1974 BMW
2002￿turboE20
M41** 90/6000 1573 1975BMW￿316 E21
M42** 98/5800 1766 1975BMW￿318 E12
M42** 90/5500 1766 1976BMW￿518 E12
M43/1** 109/5800 1990 1975BMW￿320 E21
M64** 125/5700 1990 1975BMW￿320i E21
M10￿(M92**) 105/5800 1766 1980BMW￿318i E30
M10￿(M99**) 90/5500 1766 1980 BMW
316/518E30/E28
M98** 75/5800 1573 1981BMW￿315 E21
M10
Available￿in
the￿US102/5800 1766 1984 BMW
318i￿CatE30
M40B16 102/5500 1596 1988BMW￿316i E30
M40B16 99/5500 1596 1988 BMW
316i￿CatE30
M40B18 116/5500 1796 1987BMW￿318i E30
M40B18 113/5500 1796 1987 BMW
318i￿Cat
BMW
518i￿CatE28/
E30/E34
M42B18O0
Available￿in
the￿US140/6000 1796 1989318is/318ti E36

N20￿Engine
1.￿Introduction
3Designation Power
output￿in
bhp/rpmDisplacement
in￿[cm³]Year￿of
launchModel Series
M43B16O0 102/5500 1596 1993 316iE36
M43B16O0 87/5500 1596 1996 316g E36
M43B18O0 116/5500 1796 1993318i/518i/
Z3￿1.8E34/E36
M43B19U1 105/5300 1895 2000 316iE46
M43B19O1 118/5500 1895 1998318i/Z3￿1.8 E36/E46
M44B19O0
Available￿in
the￿US149/6000 1895 1995318is/318ti/
Z3￿1.9E36
*￿denotes￿engines￿up￿to￿1933,￿**￿denotes￿engines￿from￿1957–1980,￿Cat￿=￿catalytic￿converter￿from
M42/1989￿data￿with￿and￿without￿catalytic￿converter.
Note:￿Not￿all￿engines￿in￿the￿chart￿above￿were￿available￿in￿the￿US￿market.￿The￿M44B19O0￿was
the￿last￿4￿cylinder￿engine￿available￿in￿the￿US￿up￿to￿the￿introduction￿of￿the￿N20￿in￿9/2011.
1.1.2.￿Historic￿BMW￿M￿engines
Designation Power
output￿in
bhp/rpmDisplacement
in￿[cm³]Year￿of
launchModel Series
S14B23 197/6750 2302 1986BMW￿M3 E30
1.2.￿Technical￿data
Model￿designation Engine￿designation Series￿introduction
Various￿BMW￿models N20B20O0 2012￿Model￿year

N20￿Engine
1.￿Introduction
41.2.1.￿Comparison
N20B20O0￿engine￿compared￿with￿N52B30O1￿engine
Full-load￿diagram,￿N20B20O0￿engine￿compared￿with￿N52B30O1￿engine

N20￿Engine
1.￿Introduction
5Unit N52B30O1 N20B20O0
Design Inline￿6 Inline￿4
Displacement [cm³] 2996 1997
Bore/stroke [mm] 85/88 84/90.091
Power￿output
at￿engine￿speedkW/bhp
[rpm]190/254
6600180/240
5000￿-￿6500
Power￿output￿per￿liter [kW/l] 63.4 90.14
Torque
at￿engine￿speedNm/ft-lbs
[rpm]310/228
2600￿-￿3000350/255
1250￿-￿4800
Compression￿ratio [ε] 10.7 10.0￿:￿1
Valves￿per￿cylinder 4 4
Fuel￿consumption l/100 km 9.9 7,9
CO2￿emissions [g/km] 230 183
Digital￿Engine￿Electronics MSV80 MEVD17.2.4
Exhaust￿emissions￿legislation ULEV￿II ULEV￿II

N20￿Engine
1.￿Introduction
61.3.￿New￿features/changes
1.3.1.￿Overview
System Comment
Engine￿mechanical
components• Aluminium￿crankcase￿with￿coated￿cylinder￿bore
• Optimized￿cooling￿jackets
• Use￿of￿the￿TVDI￿technology
• TwinScroll￿exhaust￿turbocharger
• 3rd￿generation￿Valvetronic￿with￿new￿intermediate￿levers
• New￿generation￿VANOS￿with￿central￿valves
• Assembled￿camshafts
• Two￿mode￿crankcase￿ventilation
• Forged￿crankshaft
• Positive￿crankshaft￿offset
• Piston￿with￿negative￿pin￿offset
• Chain￿drive￿for￿counterbalance￿shafts￿with￿chain￿tensioner
• Counterbalance￿shafts￿arranged￿on￿top￿of￿one￿another.
Oil￿supply • Map-controlled￿oil￿pump
• New￿pendulum-slide￿oil￿pump￿design
• Unfiltered￿oil￿cooling
• New￿combined￿oil￿pressure￿and￿temperature￿sensor.
Cooling • Electric￿coolant￿pump
• Map￿controlled￿thermostat.
Air￿intake￿and￿exhaust
emission￿systems• TwinScroll￿exhaust￿turbocharger
• Hot-film￿air￿mass￿meter
• Enhanced￿crankcase￿ventilation.

N20￿Engine
1.￿Introduction
7System Comment
Vacuum￿system • Two-stage￿vacuum￿pump
• Vacuum￿reservoir￿for￿the￿wastegate￿valve￿is￿built￿into￿the
engine￿cover.
Fuel￿preparation • High-pressure￿injection￿(as￿N55)
• Solenoid￿valve￿injectors
• Bosch￿high-pressure￿pump
• High-pressure￿lines￿to￿the￿injectors￿are￿soldered￿to￿the￿rail
• No￿fuel￿low-pressure￿sensor.
Engine￿electrical￿system • Bosch￿MEVD17.2.4￿engine￿control￿unit.
1.4.￿Engine￿identification
1.4.1.￿Engine￿designation
The￿N20 engine￿is￿described￿in￿the￿following￿version:￿N20B20O0.
The￿technical￿documentation￿also￿features￿the￿short￿form￿of￿the￿engine￿designation￿N20,￿which￿only
allows￿assignment￿of￿the￿engine￿type.
Item Meaning Index￿/￿explanation
1 Engine￿developer M,￿N￿=￿BMW￿Group
P￿=￿BMW￿Motorsport
S￿=￿BMW￿M￿GmbH
W￿=￿non-BMW￿engines
2 Engine￿type 1￿=￿Inline￿4￿(e.g.￿N12)
2￿=￿Inline￿4￿(e.g.￿N20)
4￿=￿Inline￿4￿(e.g.￿N43)
5￿=￿Inline￿6￿(e.g.￿N53)
6￿=￿V8￿(e.g.￿N63)
7￿=￿V12￿(e.g.￿N73)
8￿=￿V102￿(e.g.￿S85)
3 Change￿to￿the￿basic￿engine
concept0￿=￿basic￿engine
1￿to￿9￿=￿changes,￿e.g.
combustion￿process
4 Working￿method￿or￿fuel￿type
and￿possibly￿installation
positionB￿=￿gasoline,￿longitudinal
installation
D￿=￿diesel,￿longitudinal
installation
H￿=￿hydrogen
5 Displacement￿in￿liters 1￿=￿1￿liter￿+

N20￿Engine
1.￿Introduction
8Item Meaning Index￿/￿explanation
6 Displacement￿in￿1/10￿liter 8￿=￿0.8￿liters￿=￿1.8￿liters
7 Performance￿class K￿=￿Smallest
U￿=￿Lower
M￿=￿Middle
O￿=￿Upper￿(standard)
T￿=￿Top
S￿=￿Super
8 Revision￿relevant￿to￿approval 0￿=￿New￿development
1￿–￿9￿=￿Revision
Breakdown￿of￿N20￿engine￿designation
Index Explanation
N BMW￿Group￿Development
2 4-cylinder￿in-line￿engine
0 Engine￿with￿exhaust￿turbocharger,￿Valvetronic
and￿direct￿fuel￿injection￿(TVDI)
B Gasoline￿engine,￿longitudinally￿installed
20 2.0￿liters￿displacement
O Upper￿performance￿class
0 New￿development
1.4.2.￿Engine￿identification
The￿engines￿have￿an￿identification￿mark￿on￿the￿crankcase￿to￿ensure￿proper￿identification￿and
classification.
With￿the￿N55￿engine,￿this￿identification￿was￿subject￿to￿a￿further￿development,￿with￿the￿previous￿eight
positions￿being￿reduced￿to￿seven.￿The￿engine￿number￿can￿be￿found￿on￿the￿engine￿below￿the￿engine
identification.￿This￿consecutive￿number,￿in￿conjunction￿with￿the￿engine￿identification,￿allows￿proper
identification￿of￿each￿individual￿engine.

N20￿Engine
1.￿Introduction
9Item Meaning Index￿/￿explanation
1 Engine￿developer M,￿N￿=￿BMW￿Group
P￿=￿BMW￿Motorsport
S￿=￿BMW￿M￿GmbH
W￿=￿non-BMW￿engines
2 Engine￿type 1￿=￿Inline￿4￿(e.g.￿N12)
2￿=￿Inline￿4￿(e.g.￿N20)
4￿=￿Inline￿4￿(e.g.￿N43)
5￿=￿Inline￿6￿(e.g.￿N53)
6￿=￿V8￿(e.g.￿N63)
7￿=￿V12￿(e.g.￿N73)
8￿=￿V102￿(e.g.￿S85)
3 Change￿to￿the￿basic￿engine
concept0￿=￿basic￿engine
1￿to￿9￿=￿changes,￿e.g.
combustion￿process
4 Working￿method￿or￿fuel￿type
and￿possibly￿installation
positionB￿=￿gasoline,￿longitudinal
installation
D￿=￿diesel,￿longitudinal
installation
H￿=￿hydrogen
5 Displacement￿in￿liters 1￿=￿1￿liter￿+
6 Displacement￿in￿1/10￿liter 8￿=￿0.8￿liters￿=￿1.8￿liters
7 Type￿test￿concerns￿(changes
that￿require￿a￿new￿type￿test)A￿=￿Standard
B￿-￿Z￿=￿depending￿on
requirement,￿e.g. RON 87

N20￿Engine
1.￿Introduction
10
N20￿engine￿number,￿engine￿identification￿and￿engine￿number
Index Explanation
00034772 Individual￿consecutive￿engine￿number
N Engine￿developer,￿BMW￿Group
2 Engine￿type,￿Inline￿4
0 Change￿to￿the￿basic￿engine￿concept,￿Turbocharged￿Valvetronic￿Direct￿Injection
B Operating￿principle￿or￿fuel￿type￿and￿installation￿position,￿gasoline￿longitudinal
installation
20 Displacement￿in￿1/10￿liter,￿2￿liters
A Type￿test￿concerns,￿standard

N20￿Engine
2.￿Engine￿Components
112.1.￿Engine￿housing
The￿engine￿housing￿comprises￿the￿engine￿block￿(crankcase￿and￿bedplate),￿the￿cylinder￿head,￿the
cylinder￿head￿cover,￿the￿oil￿sump￿and￿the￿gaskets.
N20￿engine,￿structure￿of￿engine￿housing
Index Explanation
1 Cylinder￿head￿cover
2 Cylinder￿head￿cover￿gasket
3 Cylinder￿head
4 Cylinder￿head￿gasket
5 Crankcase

N20￿Engine
2.￿Engine￿Components
12Index Explanation
6 Sealant
7 Bedplate
8 Oil￿sump￿gasket
9 Oil￿sump
2.1.1.￿Engine￿block
The￿engine￿block￿is￿made￿from￿diecast￿aluminium￿AlSi9Cu3￿along￿with￿the￿crankcase￿and￿the
bedplate.￿A￿new￿coating￿for￿the￿cylinder￿wall￿is￿being￿used￿for￿the￿first￿time￿by￿BMW.￿Its￿referred￿to￿as
electric￿arc￿wire￿spraying.
The￿cooling￿jacket￿has￿also￿been￿optimized￿to￿improve￿cooling￿between￿the￿cylinders,￿this￿is￿due￿to
the￿requirements￿of￿a￿turbocharged￿engine.
Oil￿passages
The￿graphic￿below￿shows￿the￿oil￿passages￿in￿the￿engine￿block.
N20￿engine,￿oil￿passages

N20￿Engine
2.￿Engine￿Components
13Index Explanation
1 Oil￿return￿duct
2 Blow-by￿duct
3 Clean￿oil￿passages
4 Unfiltered￿oil￿passages
Coolant￿ducts
The￿graphic￿below￿shows￿the￿coolant￿passages￿in￿the￿engine￿block.
N20￿engine,￿cooling￿jacket￿and￿coolant￿passages
Index Explanation
1 Cooling￿jacket,￿exhaust￿side
2 Cooling￿jacket,￿intake￿side
3￿+￿4 Coolant￿passages￿between￿the￿cylinders
Compensation￿openings
The￿crankcase￿features￿large￿milled￿longitudinal￿ventilation￿holes.￿These￿ventilation￿holes￿improve
the￿pressure￿compensation￿of￿the￿oscillating￿air￿columns￿created￿by￿the￿up￿and￿down￿strokes￿of￿the
pistons.
Additional￿openings￿on￿the￿intake￿side￿on￿the￿bearing￿seat￿between￿the￿cylinders￿also￿improve
crankcase￿pressure.

N20￿Engine
2.￿Engine￿Components
14
N20￿engine,￿compensation￿openings￿in￿the￿bearing￿seat
Index Explanation
1￿+￿2￿+￿3 Openings
4￿+￿5 Ventilation￿holes
Cylinder
An￿iron￿wire￿is￿used￿in￿the￿electric￿arc￿wire￿spraying￿process￿(arc￿spray￿process)￿to￿coat￿the￿aluminium
cylinder￿bores.￿High￿voltage￿is￿used￿to￿ignite￿an￿electric￿arc￿at￿both￿ends￿of￿the￿wire.￿The￿temperatures
generated￿in￿the￿process￿are￿in￿the￿region￿of￿3000￿°C￿/￿5432￿°F.￿The￿high￿temperatures￿melt￿the￿wire,
which￿is￿continually￿fed￿by￿the￿wire￿feed￿unit.￿The￿molten￿iron￿is￿blasted￿onto￿the￿cylinder￿wall￿surface
at￿pressure￿via￿the￿central￿and￿secondary￿compressed-air￿supplies.
The￿liquid￿iron￿adheres￿to￿the￿aluminium￿surface￿through:
• Mechanical￿bonding:
Molten￿particles￿penetrate￿as￿a￿result￿of￿high￿kinetic￿energy￿and￿capillary￿action￿into
depressions￿and￿undercuts,￿where￿they￿solidify￿to￿create￿a￿very￿strong￿coating.

N20￿Engine
2.￿Engine￿Components
15
Electric￿arc￿spraying
Index Explanation
1 Direction￿of￿movement
2 Coated￿cylinder￿surface
3 EAS￿unit
4 Spray￿jet
5 Nozzle
6 Secondary￿compressed-air￿supply
7 Spray￿wire
8 Power￿supply

N20￿Engine
2.￿Engine￿Components
16Index Explanation
9 Central￿compressed-air￿supply
10 Contact￿tube
11 Wire￿feed￿unit
12 Electric￿arc
Advantages:
• Spray￿particles￿adhere￿with￿the￿base￿metal
• Ideal￿for￿thick￿coatings￿or￿large￿surfaces
• Greatest￿application￿rate￿per￿hour￿of￿all￿the￿thermal￿spraying￿processes
• The￿arc￿spray￿coating￿can￿barely￿be￿distinguished￿in￿terms￿of￿color￿from￿the￿base￿metal
• The￿low-oxide￿spray￿coating￿can￿be￿processed￿during￿manufacturing￿like￿a￿solid￿material
• High￿tensile￿strength￿and￿lower￿contraction￿strain
• Micro-porous￿surface￿reduces￿friction
• Coating￿properties￿such￿as￿coating￿hardness￿or￿surface￿quality￿can￿be￿determined
• All￿materials￿can￿be￿added￿as￿coatings,￿such￿as￿for￿example￿ferrous/nonferrous￿alloy￿on￿cast
iron
• Low￿thermal￿stress￿thanks￿to￿optimized￿heat￿transfer.
The￿low￿coating￿thickness￿of￿about￿1mm￿produces￿optimum￿heat￿transfer￿but￿does￿not￿allow
reworking￿of￿the￿cylinder￿bore￿surface￿in￿service.
If￿a￿cylinder￿is￿determined￿out￿of￿specification￿the￿entire￿engine￿block￿must￿be￿replaced.
2.1.2.￿Cylinder￿head￿gasket
A￿three-layer￿spring￿steel￿gasket￿is￿used￿for￿the￿cylinder￿head￿gasket.￿A￿stopper￿plate￿(2)￿is￿welded￿on
in￿the￿area￿of￿the￿cylinder￿bores￿in￿order￿to￿achieve￿sufficient￿contact￿pressure￿for￿sealing.￿All￿the￿layers
of￿the￿gasket￿are￿coated,￿the￿cylinder￿head￿and￿the￿engine￿block￿contact￿surfaces￿are￿coated￿with￿a
partial￿fluorocaoutchouc￿(elastomer)￿with￿non-stick￿coating.
N20￿engine,￿cylinder￿head￿gasket

N20￿Engine
2.￿Engine￿Components
17Index Explanation
1 Top￿spring￿steel￿layer￿with￿non-stick￿coating
2 Welded-on￿stopper￿plate
3 Middle￿spring￿steel￿layer￿with￿coating
4 Bottom￿spring￿steel￿layer￿with￿non-stick￿coating
2.1.3.￿Cylinder￿head
The￿cylinder￿head￿in￿the￿N20￿engine￿is￿similar￿to￿the￿cylinder￿head￿in￿the￿N55.￿The￿3rd￿generation
Valvetronic￿system￿introduced￿in￿the￿N55￿is￿also￿used￿in￿the￿N20￿engine.
The￿classic￿VANOS￿with￿separate￿solenoid￿valve￿in￿the￿N55￿engine￿has￿been￿replaced￿in￿the￿N20
engine￿by￿a￿central￿VANOS￿with￿integrated￿solenoid￿valve.￿The￿benefit￿of￿this￿system￿is￿a￿reduced
number￿of￿oil￿passages￿in￿the￿cylinder￿head.
As￿in￿the￿N55￿engine￿the￿N20￿also￿uses￿TVDI￿technology.
The￿combination￿of￿exhaust￿turbocharger,￿Valvetronic￿and￿direct￿fuel￿injection￿is￿known￿as￿Turbo
Valvetronic￿ Direct￿Injection￿(TVDI).
N20￿engine,￿cylinder￿head

N20￿Engine
2.￿Engine￿Components
18Index Explanation
1 VANOS￿solenoid￿actuator,￿intake
2 VANOS￿solenoid￿actuator,￿exhaust
3 Roller￿tappet,￿high-pressure￿pump
4 Valvetronic￿servomotor
5 Spring
6 Guide￿block
7 Intermediate￿lever
8 Eccentric￿shaft
2.1.4.￿Cylinder￿head￿cover
Design
The￿cylinder￿head￿cover￿is￿a￿new￿development.￿All￿the￿components￿for￿crankcase￿ventilation￿and￿the
blow-by￿ducts￿are￿integrated￿into￿the￿cover.￿A￿pressure￿control￿valve￿prevents￿an￿excessive￿vacuum
from￿being￿generated￿in￿the￿crankcase.￿Ventilation￿is￿performed￿via￿different￿ducts￿depending￿on
whether￿the￿engine￿is￿running￿in￿turbocharged￿(Boost)￿or￿normally￿aspirated￿(NA)￿mode.
In￿NA￿mode,￿ventilation￿is￿performed￿via￿the￿pressure￿control￿valve￿at￿about￿38 mbar.

N20￿Engine
2.￿Engine￿Components
19
N20￿engine,￿cylinder￿head￿cover￿with￿crankcase￿ventilation
Index Explanation
A Section￿A
B Section￿B
C Section￿C
1 Connection￿to￿clean￿air￿pipe￿ahead￿of￿exhaust￿turbocharger

N20￿Engine
2.￿Engine￿Components
20Index Explanation
2 Non-return￿valve
3 Pressure￿control￿valve
4 Spring￿tab￿separator
5 Oil￿separator
6 Settling￿chamber
7 Non-return￿valve
8 Non-return￿valve
9 Blow-by￿duct￿to￿the￿intake￿ports￿in￿the￿cylinder￿head
The￿blow-by￿gases￿pass￿through￿the￿opening￿in￿the￿intake￿side￿area￿of￿cylinder￿one￿to￿the￿three￿spring
tab￿separators.￿The￿oil￿in￿the￿blow-by￿gas￿is￿separated￿by￿the￿spring￿tab￿separators,￿and￿flows￿along
the￿walls￿down￿through￿a￿non-return￿valve￿and￿back￿into￿the￿cylinder￿head.￿The￿blow-by￿gas￿separated
from￿the￿oil￿now￿passes￿into￿the￿air￿intake￿system￿ports￿or￿fresh￿air￿pipe￿(depending￿on￿the￿operating
mode).
Function
In￿naturally￿aspirated￿mode,￿the￿non-return￿valve￿in￿the￿blow-by￿duct￿of￿the￿cylinder￿head￿cover￿is
opened￿by￿the￿vacuum￿pressure￿in￿the￿air￿intake￿system￿and￿the￿blow-by￿gases￿are￿drawn￿off￿via￿the
pressure￿control￿valve.￿The￿vacuum￿pressure￿simultaneously￿closes￿the￿second￿non-return￿valve￿in￿the
duct￿to￿charge-air￿suction/fresh￿air￿line.
The￿blow-by￿gases￿are￿routed￿directly￿into￿the￿cylinder￿head￿intake￿ports￿via￿the￿passages￿integrated
in￿the￿cylinder￿head￿cover￿.
A￿purge￿air￿line,￿which￿is￿connected￿to￿the￿fresh￿air￿pipe￿ahead￿of￿the￿turbocharger￿and￿to￿the
crankcase,￿routes￿fresh￿air￿via￿a￿non-return￿valve￿directly￿into￿the￿crankcase.￿The￿greater￿the￿vacuum
in￿the￿crankcase,￿the￿higher￿the￿air￿mass￿introduced.￿This￿purging￿prevents￿the￿pressure￿control￿valve
from￿icing￿up￿by￿reducing￿moisture￿in￿the￿system.

N20￿Engine
2.￿Engine￿Components
21
N20￿engine,￿crankcase￿ventilation,￿naturally￿aspirated￿mode
Index Explanation
B Ambient￿pressure
C Vacuum
D Exhaust￿gas
E Oil
F Blow-by￿gas
1 Air￿filter
2 Intake￿plenum

N20￿Engine
2.￿Engine￿Components
22Index Explanation
3 Perforated￿plates
4 Passages￿in￿cylinder￿head￿and￿cylinder￿head￿cover
5 Blow-by￿gas￿duct
6 Purge￿air￿line
7 Non-return￿valve
8 Crankcase
9 Oil￿sump
10 Oil￿return￿passage
11 Turbocharger
12 Non-return￿valve,￿oil￿return
13 Charge-air￿suction￿line/fresh￿air￿pipe
14 Connection￿to￿charge-air￿suction￿line
15 Non-return￿valve￿with￿restrictor
16 Throttle￿valve
17 Pressure￿control￿valve
18 Non-return￿valve￿with￿restrictor
Once￿in￿boost￿mode￿the￿pressure￿in￿the￿intake￿plenum￿rises￿thus￿it￿is￿no￿longer￿possible￿for￿the
blow-by￿gases￿to￿be￿introduced￿via￿this￿route.￿A￿non-return￿valve￿in￿the￿blow-by￿duct￿of￿the￿cylinder
head￿cover￿closes￿the￿duct￿to￿the￿intake￿plenum￿and￿thereby￿protects￿the￿crankcase￿against￿excess
pressure.
The￿now￿greater￿fresh-air￿demand￿generates￿a￿vacuum￿in￿the￿fresh￿air￿pipe￿between￿the￿turbocharger
and￿the￿intake￿silencer.￿This￿vacuum￿is￿sufficient￿to￿open￿the￿non-return￿valve￿in￿the￿cylinder￿head
cover￿and￿draw￿off￿the￿blow-by￿gases￿directly￿without￿regulation.￿The￿pressure￿control￿valve￿(17)￿is
bypassed￿in￿this￿mode,￿since￿only￿a￿low￿vacuum￿is￿generated￿which￿does￿not￿have￿to￿be￿limited.

N20￿Engine
2.￿Engine￿Components
23
N20￿engine,￿crankcase￿ventilation,￿boost￿mode
Index Explanation
A Charging￿pressure
C Vacuum
D Exhaust￿gas
E Oil
F Blow-by￿gas
1 Air￿filter
2 Intake￿plenum

N20￿Engine
2.￿Engine￿Components
24Index Explanation
3 Perforated￿plates
4 Passages￿in￿cylinder￿head￿and￿cylinder￿head￿cover
5 Blow-by￿gas￿duct
6 Purge￿air￿line
7 Non-return￿valve
8 Crank￿chamber
9 Oil￿sump
10 Oil￿return￿passage
11 Turbocharger
12 Non-return￿valve,￿oil￿return
13 Charge-air￿suction￿line/clean￿air￿pipe
14 Connection￿to￿charge-air￿suction￿line
15 Non-return￿valve￿with￿restrictor
16 Throttle￿valve
17 Pressure￿control￿valve
18 Non-return￿valve￿with￿restrictor
2.1.5.￿Oil￿sump
The￿oil￿sump￿is￿made￿from￿plastic￿for￿rear￿wheel￿drive￿vehicles￿and￿cast￿aluminium￿for￿xDrive￿models.
For￿xDrive￿vehicles￿the￿oil￿sump￿has￿been￿modified￿due￿to￿the￿input￿shafts￿and￿attachment￿points￿for
the￿axle￿drive.
The￿oil￿pump￿with￿the￿counterbalance￿shafts￿covers￿the￿entire￿oil￿sump￿and￿thereby￿protects￿the
crankshaft￿against￿“oil￿splashing”￿by￿doubling￿as￿a￿windage￿tray.￿The￿oil￿flowing￿back￿through￿the￿oil
return￿passages￿is￿routed￿directly￿into￿the￿oil￿sump￿and￿therefore￿cannot￿come￿into￿contact￿with￿the
crankshaft.

N20￿Engine
2.￿Engine￿Components
25
N20￿engine,￿oil￿pump￿with￿counterbalance￿shafts
Index Explanation
1 Chain￿drive
2 Counterbalance￿shaft
3 Oil￿return￿ducts,￿intake￿side
4 Oil￿pump
5 Oil￿return￿ducts,￿exhaust￿side

N20￿Engine
2.￿Engine￿Components
26
N20￿engine,￿oil￿sump￿with￿oil￿pump￿and￿counterbalance￿shafts
Index Explanation
1 Chain￿drive
2 Housing,￿counterbalance￿shafts
3 Oil￿sump
4 Oil￿pump

N20￿Engine
2.￿Engine￿Components
272.2.￿Crankshaft￿drive
2.2.1.￿Crankshaft￿with￿bearings
Crankshaft
The￿crankshaft￿of￿the￿N20￿engine￿has￿a￿stroke￿of￿89.6￿mm￿and￿is￿made￿of￿the￿material￿C38modBY.￿It￿is
a￿forged￿crankshaft￿with￿four￿balance￿weights￿and￿weighs￿13.9 kg/30.6￿lbs.
N20￿engine,￿crankshaft
Crankshaft￿bearings￿and￿rod￿bearings
The￿crankshaft￿is￿supported￿by￿five￿(lead-free￿two￿component)￿bearings.￿The￿thrust￿bearing￿is￿located
in￿the￿middle￿at￿the￿third￿bearing￿position.￿The￿thrust￿bearing￿is￿only￿designed￿for￿180°￿and￿is￿located
in￿the￿bearing￿seat.￿The￿bearing￿in￿the￿bearing￿cap￿does￿not￿provide￿any￿axial￿guidance.

N20￿Engine
2.￿Engine￿Components
28
N20￿engine,￿crankshaft￿bearings
Index Explanation
1 Upper￿bearing￿shell￿with￿groove￿and￿oil￿hole
2 Thrust￿bearing￿with￿groove￿and￿oil￿hole
3 Lower￿bearing￿shell￿without￿groove
The￿N20￿uses￿the￿same￿procedure￿as￿with￿N55￿for￿calculating￿the￿correct￿bearing￿size￿by￿using￿the
crankcase￿and￿crankshaft￿codes.
The￿identification￿markings￿for￿the￿upper￿bearings￿are￿found￿stamped￿on￿the￿crankcase￿and￿for￿the
lower￿bearings￿on￿the￿crankshaft.￿If￿the￿crankshaft￿is￿to￿be￿fitted￿with￿new￿bearings￿ refer￿to￿the￿repair
instructions￿for￿more￿information￿on￿the￿procedure￿to￿determine￿the￿correct￿bearing￿size/color.

N20￿Engine
2.￿Engine￿Components
29
N20￿engine,￿bearing￿identification,￿crankshaft￿code
Index Explanation
1 Code￿digits￿for￿crankshaft￿bearings￿(21211)
2 Code￿letters￿for￿connecting￿rod￿bearings￿(rrrr)
Two￿bearing￿categories￿are￿used.￿These￿bearing￿categories￿are￿“r”￿and￿“b”.
The￿following￿applies￿to￿the￿bearing￿position￿and￿bearing￿allocation:
Bearing￿category￿or￿code
letterInstallation￿location Bearing￿color
Rod￿end Violet b
Bearing￿cap￿end Blue
Rod￿end Yellow r
Bearing￿cap￿end Red
The￿bearing￿shells￿are￿identical￿parts￿to￿those￿used￿in￿the￿N54￿and￿N55￿engines.￿A￿locating￿groove
prevents￿the￿wrong￿bearing￿shell￿from￿being￿installed.

N20￿Engine
2.￿Engine￿Components
30
N20￿engine,￿bearing￿identification,￿crankcase
Index Explanation
1 “K”￿stands￿for￿clutch￿end
2 Bearing￿5
3 Bearing￿4
4 Bearing￿3
5 Bearing￿2
6 Bearing￿1
The￿“K”￿designation￿in￿position￿(1)￿stands￿for￿clutch￿end￿(German:￿Kupplungsseite).￿Thus￿the￿first
code￿digit￿(2)￿is￿the￿ID￿code￿for￿bearing￿5￿in￿the￿crankcase.￿The￿second￿code￿digit￿(3)￿stands￿for
bearing￿4,￿etc.
The￿following￿is￿an￿example￿of￿how￿to￿calculate￿the￿correct￿crankshaft￿main￿and￿rod￿bearings￿using￿the
stamping￿codes.

N20￿Engine
2.￿Engine￿Components
31
Example￿of￿the￿crankshaft￿bearing￿selection￿procedure.
Example￿of￿the￿connecting￿rod￿bearing￿selection￿procedure.

N20￿Engine
2.￿Engine￿Components
32
Note:￿This￿training￿material￿is￿intended￿for￿classroom￿instruction￿only.￿It￿is￿not￿meant￿to
replace￿currently￿available￿repair￿instructions.￿Always￿refer￿to￿the￿most￿current￿version￿of
repair￿instructions,￿technical￿data￿and￿torque￿specifications.￿Refer￿to￿the￿latest￿version￿of
ISTA.
Pin￿offset
Pistons￿always￿require￿a￿running￿clearance.￿The￿running￿clearance￿means￿that￿there￿is￿always￿a￿certain
degree￿of￿lateral￿movement￿(piston￿slap)￿as￿the￿piston￿changes￿direction￿from￿up-stroke￿to￿down-
stroke.￿The￿greater￿the￿force￿acting￿on￿the￿piston￿and￿the￿greater￿the￿running￿clearance,￿the￿greater
the￿piston￿slap.
Pin￿offset￿involves￿advancing￿the￿time￿when￿the￿piston￿changes￿between￿the￿compression￿and￿power
stroke￿to￿the￿lower￿pressure￿range￿before￿top￿dead￿center.￿This￿results￿in￿a￿reduction￿of￿noise￿and
friction.
Pin￿offset￿refers￿to￿the￿displacement￿of￿the￿wrist￿pin￿axis￿from￿the￿cylinder￿center￿line￿of￿the￿piston.￿A
positive￿offset￿indicates￿offset￿to￿the￿major￿thrust￿face,￿a￿negative￿offset￿denotes￿offset￿to￿the￿minor
thrust￿face.￿The￿major￿thrust￿face￿refers￿to￿that￿side￿of￿the￿piston￿on￿which￿the￿piston￿rests￿in￿the
combustion￿stroke￿on￿its￿way￿to￿bottom￿dead￿center￿(see￿arrow￿of￿III).￿Minor￿thrust￿is￿the￿piston's
thrust￿against￿the￿opposite￿cylinder￿wall￿during￿the￿compression￿stroke￿(see￿arrow￿of￿I).
The￿following￿graphic￿shows￿a￿conventional￿crankshaft￿drive￿without￿pin￿and￿crankshaft￿offset.

N20￿Engine
2.￿Engine￿Components
33
Conventional￿crankshaft￿drive
Index Explanation
I Piston￿position￿and￿crankshaft￿position￿shortly￿before￿top￿dead￿center￿(TDC)
II Piston￿position￿and￿crankshaft￿position￿at￿top￿dead￿center
III Piston￿position￿and￿crankshaft￿position￿after￿top￿dead￿center
A Major￿thrust￿face
B Minor￿thrust￿face
C Direction￿of￿engine￿rotation
1 Wrist￿pin
2 Center￿of￿crankshaft￿rotation
3 Thrust￿force
As￿the￿graphic￿shows,￿in￿a￿conventional￿crankshaft￿drive￿assembly￿the￿wrist￿pin￿boss,￿the￿connecting
rod￿and￿the￿center￿of￿crankshaft￿rotation￿are￿in￿line￿at￿top￿dead￿center￿(TDC).￿Because￿of￿this
arrangement,￿the￿piston￿is￿forced￿against￿the￿minor￿thrust￿face￿(B)￿during￿the￿up-stroke.￿At￿TDC￿the
forces￿are￿compensated￿because￿the￿pressure￿on￿the￿minor￿thrust￿face￿decreases￿as￿the￿crankshaft
rotates￿away￿from￿TDC￿and￿the￿piston￿tilts￿towards￿the￿major￿thrust￿face￿(A).￿Because￿there￿is￿already
high￿pressure￿at￿TDC,￿this￿abrupt￿change￿of￿face￿causes￿a￿noise￿which￿is￿referred￿to￿as￿piston￿slap.
Pin￿offset￿can￿be￿effected￿towards￿the￿major￿thrust￿face￿(positive)￿and￿also￿towards￿the￿minor￿thrust
side￿(negative).￿Major-thrust-face￿pin￿offset￿is￿also￿referred￿to￿as￿noise￿offset.

N20￿Engine
2.￿Engine￿Components
34Minor-thrust-face￿pin￿offset￿is￿also￿referred￿to￿as￿thermal￿offset.￿In￿this￿position￿the￿sealing￿effect￿of
the￿piston￿rings￿is￿improved.
Pin￿offset
Index Explanation
A Major-thrust-face￿pin￿offset￿(positive)
B Minor-thrust￿face￿pin￿offset￿(negative)
OT Top￿dead￿center
UT Bottom￿dead￿center
Because￿the￿noise￿can￿be￿heard￿during￿the￿change￿of￿faces,￿technical￿measures￿are￿used￿to￿shift￿this
change￿of￿faces￿as￿far￿as￿possible￿to￿a￿range￿(piston￿position)￿in￿which￿the￿acting￿forces￿are￿lower.￿This
is￿done￿in￿current￿BMW￿engines￿by￿offsetting￿the￿wrist￿pin￿towards￿the￿major￿thrust￿face.
The￿offset￿is￿about.￿0.3￿-￿0.8￿mm￿in￿conventional￿engines￿and￿is￿therefore￿virtually￿imperceptible￿to￿the
eye.￿This￿is￿also￿the￿reason￿why￿the￿pistons￿have￿a￿directional￿marking￿at￿the￿top.￿Incorrect￿installation
may￿result￿in￿extreme￿noise￿similar￿to￿that￿generated￿by￿piston￿damage.

N20￿Engine
2.￿Engine￿Components
35
Piston￿rocking￿in￿an￿engine￿with￿pin￿offset
Index Explanation
I Piston￿position￿and￿crankshaft￿position￿before￿top￿dead￿center
II Piston￿position￿and￿crankshaft￿position￿shortly￿before￿top￿dead￿center,￿with
perpendicular￿connecting￿rod
III Piston￿position￿and￿crankshaft￿position￿at￿top￿dead￿center
A Major￿thrust￿face
B Minor￿thrust￿face
C Direction￿of￿engine￿rotation
1 Wrist￿pin
2 Center￿of￿crankshaft￿rotation
3 Thrust￿force
The￿piston￿rests￿against￿the￿minor￿thrust￿face￿during￿the￿up-stroke.￿A￿neutral￿piston￿position￿is￿already
achieved￿before￿TDC￿by￿offsetting￿the￿wrist￿pin.￿This￿is￿the￿case￿when￿the￿center￿lines￿of￿the￿cylinder
and￿of￿the￿big￿and￿small￿connecting￿rod￿eyes￿are￿parallel￿to￿each￿other.￿Already￿before￿TDC￿the￿piston
changes￿from￿the￿minor￿thrust￿face￿to￿the￿major￿thrust￿face.￿In￿this￿phase￿the￿force￿on￿the￿piston￿is
still￿low.￿Due￿to￿the￿off-center￿support￿of￿the￿piston,￿the￿force￿acting￿on￿the￿piston￿from￿above￿has￿a
higher￿lever￿arm￿on￿the￿one￿face￿than￿on￿the￿other.￿In￿this￿way,￿the￿piston￿is￿already￿tilted￿during￿the￿up-

N20￿Engine
2.￿Engine￿Components
36stroke,￿resulting￿in￿contact￿with￿the￿major￿thrust￿face￿at￿the￿upper￿edge.￿In￿its￿subsequent￿movement
the￿piston￿again￿travels￿straight￿ahead,￿so￿that￿the￿piston￿rests￿completely￿on￿the￿major￿thrust￿face.
The￿change￿of￿faces￿is￿much￿quieter￿than￿in￿a￿conventional￿crankshaft￿drive.
The￿downside￿of￿pin￿offset￿is￿that￿there￿is￿a￿slight￿increase￿in￿friction￿on￿the￿major￿thrust￿face.￿This
minor￿downside,￿however,￿is￿made￿up￿for￿by￿the￿reduced￿noise.
Crankshaft￿offset
A￿crankcase￿with￿crankshaft￿offset￿is￿used￿for￿the￿first￿time￿by￿BMW.
Crankshaft￿offset￿denotes￿the￿offset￿of￿the￿crankshaft￿axis￿from￿the￿cylinder￿center￿line.￿This￿offset￿can
effect￿on￿both￿the￿major￿thrust￿face￿and￿the￿minor￿thrust￿face.￿A￿positive￿offset￿denotes￿offset￿to￿the
major￿thrust￿face,￿a￿negative￿offset￿denotes￿offset￿to￿the￿minor￿thrust￿face.
Crankshaft￿offset￿can￿basically￿be￿effected￿in￿both￿directions,￿but￿up￿to￿now￿only￿the￿variation￿in￿the
positive￿direction￿(A)￿has￿been￿used.
Crankshaft￿offset
Index Explanation
A Positive￿offset
B Negative￿offset
OT Top￿dead￿center
UT Bottom￿dead￿center

N20￿Engine
2.￿Engine￿Components
37The￿following￿graphic￿clearly￿shows￿that￿positive￿crankshaft￿offset,￿when￿compared￿with￿positive￿pin
offset,￿has￿an￿opposed￿effect￿on￿piston￿rocking.￿Thus￿piston￿rocking￿occurs￿much￿later￿and￿in￿the
range￿of￿a￿high￿cylinder￿pressure.
Piston￿rocking￿in￿an￿engine￿with￿crankshaft￿offset
Index Explanation
I Piston￿position￿and￿crankshaft￿position￿shortly￿after￿top￿dead￿center
II Piston￿position￿and￿crankshaft￿position￿with￿perpendicular￿connecting￿rod
III Piston￿position￿and￿crankshaft￿position￿after￿piston￿rocking
A Major￿thrust￿face
B Minor￿thrust￿face
C Direction￿of￿engine￿rotation
1 Wrist￿pin
2 Crankshaft
OT Top￿dead￿center
UT Bottom￿dead￿center

N20￿Engine
2.￿Engine￿Components
38The￿top￿and￿bottom￿dead￿centers￿are￿also￿shifted￿by￿the￿crankshaft￿offset.￿The￿top￿and￿bottom￿dead
centers￿are￿achieved￿in￿the￿extended￿and￿overlap￿positions￿respectively.￿The￿connecting￿rod￿and￿the
crankshaft￿point￿geometrically￿in￿the￿same￿direction.
TDC￿position￿in￿an￿engine￿with￿crankshaft￿offset
Index Explanation
OT Top￿dead￿center
UT Bottom￿dead￿center
l Connecting￿rod￿length
r Crank￿throw
y Crankshaft￿offset
sOT Distance￿TDC
h Piston￿stroke
1 Angle￿in￿TDC￿position￿αTDC
Bottom￿dead￿center￿likewise￿changes￿its￿position￿and￿runs￿to￿a￿crank￿angle￿of￿over￿180°.

N20￿Engine
2.￿Engine￿Components
39
BDC￿position￿in￿an￿engine￿with￿crankshaft￿offset
Index Explanation
OT Top￿dead￿center
UT Bottom￿dead￿center
l Connecting￿rod￿length
r Crank￿throw
y Crankshaft￿offset
sUT Distance￿BDC
h Piston￿stroke
2 Angle￿in￿BDC￿position￿α￿BDC
A￿combination￿of￿positive￿crankshaft￿offset￿and￿negative￿pin￿offset￿is￿used￿in￿the￿N20￿engine .
Both￿negative￿and￿positive￿pin￿offset￿affect￿the￿piston￿rocking￿behavior.￿In￿response￿to￿the￿distribution
of￿forces￿during￿piston￿rocking,￿this￿occurs￿later￿and￿more￿quietly.

N20￿Engine
2.￿Engine￿Components
40
Combination￿of￿crankshaft￿and￿pin￿offset
Index Explanation
OT Top￿dead￿center
UT Bottom￿dead￿center
l Connecting￿rod￿length
r Crank￿throw
y Crankshaft￿offset
sD Pin￿offset
sOT Distance￿TDC
h Piston￿stroke
The￿N20￿engine￿features￿connecting￿rods￿144.35￿mm￿long,￿with￿a￿crank￿throw￿of￿44.8￿mm.￿Crankshaft
offset￿is￿+14￿mm,￿offset￿of￿the￿wrist￿pin￿is￿-0.3￿mm.

N20￿Engine
2.￿Engine￿Components
41Data Value
Stroke 90.09￿mm
TDC +￿4.336°
BDC +￿188.259°
Induction￿cycle￿angle￿and￿power￿cycle￿angle 183.923°
Compression￿cycle￿angle￿and￿exhaust￿cycle
angle176.077°
Advantages
In￿an￿engine￿with￿crankshaft￿offset,￿the￿connecting￿rod￿in￿the￿power￿stroke￿is￿in￿a￿roughly
perpendicular￿position￿(see￿the￿graphic￿on￿the￿right)￿in￿contrast￿to￿an￿engine￿without￿crankshaft￿offset
(see￿the￿graphic￿on￿the￿left).￿This￿design￿significantly￿reduces￿the￿thrust￿force￿(5)￿and￿the￿friction￿of￿the
piston￿on￿the￿cylinder￿wall￿which￿result￿is￿increased￿efficiency.￿The￿crankshaft￿offset￿in￿the￿N20￿engine
is￿thus￿considered￿one￿more￿BMW￿EfficientDynamics￿measure.
System￿diagram￿of￿acting￿forces,￿left:￿normal￿engine,￿right:￿engine￿with￿crankshaft￿offset

N20￿Engine
2.￿Engine￿Components
42Index Explanation
1 Pressure￿force￿from￿combustion
2 Normal￿piston￿force
3 Opposite￿piston￿force
4 Lateral￿piston￿force
5 Thrust￿force
6 Resulting￿force
7 Crankshaft￿offset
2.2.2.￿Connecting￿rod
Connecting￿rod
The￿connecting￿rod￿of￿the￿N20￿engine￿has￿an￿inside￿diameter￿of￿144.35 mm.￿As￿with￿the￿N55￿the￿N20
uses￿a￿specially￿formed￿hole￿in￿the￿small￿end￿of￿the￿connecting￿rod.￿This￿formed￿hole￿is￿machined
wider￿on￿the￿lower￿edges￿of￿the￿wrist￿pin￿bushing/bore.￿This￿design￿evenly￿distributes￿the￿force￿acting
on￿the￿wrist￿pin￿over￿the￿entire￿surface￿of￿the￿rod￿bushing￿and￿reduces￿the￿load￿at￿the￿edges,￿as￿the
piston￿is￿forced￿downward￿on￿the￿power￿stroke.

N20￿Engine
2.￿Engine￿Components
43
N20￿engine,￿connecting￿rod
2.2.3.￿Piston￿with￿piston￿rings
A￿full￿slipper￿skirt￿piston￿manufactured￿by￿the￿company￿FM￿is￿used.￿The￿piston￿diameter￿is￿84 mm.
The￿first￿piston￿ring￿is￿a￿steel-nitrided￿plain￿compression￿ring.￿The￿second￿piston￿ring￿is￿a￿stepped
compression￿ring.￿The￿oil￿scraper￿ring￿is￿a￿steel￿band￿ring￿with￿a￿spring,￿which￿is￿also￿known￿as￿an￿MF
system￿ring.
As￿previously￿discussed￿the￿wrist￿pin￿axis￿has￿a￿negative￿offset￿to￿the￿minor￿thrust￿face.
An￿installation￿position￿arrow￿is￿stamped￿on￿the￿piston.￿This￿arrow￿always￿points￿to￿the￿installation￿of
the￿piston￿in￿a￿longitudinal￿direction￿facing￿the￿timing￿chain.￿It￿is￿necessary￿to￿install￿the￿piston￿in￿the
correct￿position,￿since￿the￿asymmetric￿valve￿reliefs￿on￿the￿intake￿and￿exhaust￿sides￿will￿result￿in￿valve
and￿cylinder￿wall￿damage.

N20￿Engine
2.￿Engine￿Components
44
N20￿engine,￿piston
N20￿engine,￿piston￿rings

N20￿Engine
2.￿Engine￿Components
45Index Explanation
1 Plain￿compression￿ring
2 Stepped￿compression￿ring
3 MF￿system￿ring
4 Piston
2.3.￿Camshaft￿drive
The￿camshaft￿drive￿design￿is￿similar￿to￿previous￿engines.￿The￿oil￿pump￿is￿gear￿driven￿via￿the
counterbalance￿shafts.￿To￿ensure￿that￿the￿counterbalance￿shafts￿are￿correctly￿positioned￿in￿relation
to￿the￿crankshaft,￿a￿secondary￿chain￿drive￿is￿used￿which￿is￿also￿equipped￿with￿a￿chain￿tensioner.￿Both
chains￿have￿tooth-type￿design.
N20￿engine,￿camshaft￿drive

N20￿Engine
2.￿Engine￿Components
46Index Explanation
1 Exhaust￿VANOS
2 Intake￿VANOS
3 Chain￿tensioner
4 Primary￿chain
5 Tensioning￿rail
6 Sprocket,￿driven￿by￿crankshaft
7 Secondary￿chain￿(tooth-type￿chain)
8 Chain￿tensioner
9 Sprocket￿for￿counterbalance￿shaft￿and￿oil￿pump￿drive
2.4.￿Counterbalance￿shafts
The￿purpose￿of￿the￿counterbalance￿shafts￿is￿to￿improve￿the￿engine's￿smooth￿running￿and￿acoustic
performance.￿This￿is￿achieved￿using￿two￿counter-rotating￿shafts￿which￿are￿fitted￿with￿balance￿weights.
The￿counterbalance￿shafts￿are￿driven￿by￿the￿crankshaft￿via￿a￿tooth-type￿chain.￿The￿tooth-type￿chain
requires￿the￿use￿of￿special￿gears￿on￿the￿crankshaft￿and￿the￿counterbalance￿shafts.￿The￿tooth-type
chain￿optimizes￿the￿rolling￿of￿the￿drive￿chain￿on￿the￿sprockets,￿thereby￿reducing￿noise.
N20￿engine,￿counterbalance￿shaft￿and￿oil￿pump￿drive

N20￿Engine
2.￿Engine￿Components
47Index Explanation
1 Crankshaft￿sprocket
2 Tooth-type￿chain
3 Chain￿tensioner
4 Counterbalance￿shaft￿sprocket
N20￿engine,￿counterbalance￿shafts
Index Explanation
1 Sprocket￿on￿crankshaft
2 Upper￿counterbalance￿shaft
3 Lower￿counterbalance￿shaft
4 Gear,￿upper￿counterbalance￿shaft
5 Gear,￿oil￿pump
6 Oil￿pump
7 Tooth-type￿chain,￿counterbalance￿shaft￿and￿oil￿pump￿drive
8 Counterbalance￿shaft￿sprocket

N20￿Engine
2.￿Engine￿Components
48Before￿removing￿and￿installing￿the￿counterbalance￿drive￿sprocket￿the￿lower￿counterbalance￿shaft
must￿be￿secured￿with￿a￿4.5 mm￿thick￿alignment￿pin￿(special￿tool￿#￿2￿212￿825)￿to￿securely￿position￿the
counterbalance￿shafts￿with￿the￿crankshaft.
Counterbalance￿shaft￿alignment￿pin￿tool￿2￿212￿825
A￿seal￿plug￿which￿is￿inserted￿in￿the￿locating￿hole￿must￿be￿removed￿for￿this￿purpose.￿This￿seal￿plug
prevents￿oil￿from￿flowing￿into￿the￿counterbalance￿shaft￿chamber￿during￿operation,￿a￿situation￿which
would￿cause￿oil￿foaming.￿It￿is￿thus￿imperative￿that￿this￿seal￿plug￿be￿reinstalled￿during￿final￿assembly.
The￿excess￿oil￿in￿the￿chamber￿is￿carried￿along￿by￿the￿rotation￿of￿the￿balance￿weights￿and￿returned￿via￿a
discharge￿opening￿to￿the￿oil￿sump.
Counterbalance￿shaft￿seal￿plug
Positioning￿of￿the￿counterbalance￿shafts￿in￿alignment￿is￿necessary￿to￿ensure￿smooth,￿fault-
free￿engine￿operation.￿Please￿refer￿to￿the￿repair￿instructions￿for￿more￿information .

N20￿Engine
2.￿Engine￿Components
49
N20￿engine,￿cutaway￿view￿of￿counterbalance￿shafts
Index Explanation
1 Discharge￿opening
2 Upper￿counterbalance￿shaft
3 Lower￿counterbalance￿shaft
4 Alignment￿pin,￿lower￿counterbalance￿shaft
5 Seal￿plug

N20￿Engine
2.￿Engine￿Components
502.5.￿Valve￿gear
2.5.1.￿Design
N20￿engine,￿valve￿gear
Index Explanation
1 Intake￿camshaft
2 Roller￿cam￿follower
3 Intermediate￿lever
4 Guide￿block
5 Torsion￿spring
6 Eccentric￿shaft
7 Valvetronic￿servomotor
8 Exhaust￿camshaft

N20￿Engine
2.￿Engine￿Components
51
N20￿engine,￿valve￿gear
Index Explanation
1 Torsion￿spring
2 Intermediate￿lever
3 Eccentric￿shaft
4 VANOS￿unit,￿intake
5 Intake￿camshaft
6 HVCC￿element,￿intake
7 Roller￿cam￿follower,￿intake
8 Valve￿spring,￿intake￿valve

N20￿Engine
2.￿Engine￿Components
52Index Explanation
9 Intake￿valve
10 Valvetronic￿servomotor
11 Exhaust￿valve
12 Valve￿spring,￿exhaust￿valve
13 Roller￿cam￿follower,￿exhaust
14 HVCC￿element,￿exhaust
15 Exhaust￿camshaft
16 VANOS￿unit,￿exhaust
The￿roller￿cam￿followers￿on￿the￿intake￿side￿are￿made￿from￿sheet￿metal￿and￿subdivided￿into￿five
classes,￿Class￿“1”￿to￿Class￿“5”.￿The￿intermediate￿levers￿are￿now￿also￿made￿from￿sheet￿metal￿and￿are
subdivided￿into￿six￿classes,￿Class￿“00”￿to￿Class￿“05”.
Camshafts
The￿N20￿engine￿is￿fitted￿with￿the￿assembled￿camshafts￿already￿known￿from￿the￿M73￿engine.￿All￿the
components￿are￿shrink-fitted￿onto￿the￿shaft.￿The￿timing￿of￿the￿camshafts￿requires￿new￿special￿tool,￿#
2￿212￿831.￿Please￿refer￿to￿the￿repair￿instructions￿for￿proper￿timing￿procedures.
N20￿engine,￿assembled￿camshafts
Index Explanation
1 Exhaust￿camshaft
2 Intake￿camshaft

N20￿Engine
2.￿Engine￿Components
53
N20￿engine,￿assembled￿camshafts
Index Explanation
1 Flange￿for￿VANOS￿unit,￿exhaust
2 Cam
3 Cam￿for￿high-pressure￿pump
4 Sealing￿cap
5 Pipe
6 Hexagon￿head
7 Flange￿for￿VANOS￿unit,￿intake
8 Cam

N20￿Engine
2.￿Engine￿Components
54Index Explanation
9 Sealing￿cap
10 Pipe
11 Hexagon￿head
12 Vacuum￿pump￿drive
Valve￿timing
N20￿engine,￿valve￿timing￿diagram
N55B30M0 N20B20O0
Intake￿valve￿dia./stem￿dia. [mm] 32/5 32/5
Exhaust￿valve￿dia./stem￿dia. [mm] 28/6 28/6
Maximum￿valve￿lift,￿intake/exhaust￿valve [mm] 9.9/9.7 9.9/9.3
VANOS￿adjustment￿range,￿intake [°CA] 70 70
VANOS￿adjustment￿range,￿exhaust [°CA] 55 55
Spread,￿intake￿camshaft [°CA] 120￿–￿50 120￿–￿50
Spread,￿exhaust￿camshaft [°CA] 115￿–￿60 115￿–￿60
Opening￿period,￿intake￿camshaft [°CA] 258 258
Opening￿period,￿exhaust￿camshaft [°CA] 261 252

N20￿Engine
2.￿Engine￿Components
55Intake￿and￿exhaust￿valves
The￿intake￿and￿exhaust￿valves￿are￿carryover￿parts￿from￿the￿N55￿engine.￿The￿intake￿valve￿has￿a￿stem
diameter￿of￿5 mm.￿The￿exhaust￿valve￿has￿a￿stem￿diameter￿of￿6 mm,￿because￿it￿is￿hollow￿and￿sodium
filled.￿The￿exhaust￿valve￿seats￿are￿made￿from￿hardened￿material￿and￿the￿intake￿valve￿seats￿are
induction-hardened.
Valve￿springs
The￿valve￿springs￿used￿for￿the￿intake￿and￿exhaust￿valves￿are￿different.￿The￿intake￿valve￿springs￿have
already￿been￿used￿in￿the￿N52,￿N52TU￿and￿N55￿engines.￿The￿exhaust￿valve￿springs￿are￿familiar￿from
the￿N51,￿N52,￿N52TU,￿N54￿and￿N55￿engines.
2.5.2.￿Valvetronic
The￿Valvetronic￿comprises￿fully￿variable￿valve￿lift￿control￿and￿variable￿camshaft￿control￿(double
VANOS),￿which￿makes￿the￿closing￿time￿of￿the￿intake￿valve￿freely￿adjustable.
Valve￿lift￿control￿is￿performed￿on￿the￿intake￿side,￿while￿camshaft￿control￿is￿performed￿on￿both￿the
intake￿and￿exhaust￿sides.
Throttle-free￿load￿control￿is￿only￿possible￿if:
• the￿lift￿of￿the￿intake￿valve
• and￿camshaft￿adjustment￿of￿the￿intake￿and￿exhaust￿camshafts￿are￿variably￿controllable.
Result:
The￿opening￿and￿closing￿times￿and￿thus￿the￿opening￿period￿and￿the￿lift￿of￿the￿intake￿valve￿are￿freely
adjustable.
VANOS
The￿VANOS￿system￿has￿been￿modified.￿This￿modification￿now￿provides￿for￿even￿faster￿VANOS￿unit
setting￿speeds.￿The￿modification￿has￿also￿further￿reduced￿system￿failure.￿The￿following￿comparison￿of
the￿VANOS￿systems￿of￿N55￿and￿N20￿engines￿shows￿that￿fewer￿oil￿passages￿are￿necessary.

N20￿Engine
2.￿Engine￿Components
56
N55￿engine,￿VANOS￿with￿oil￿supply
Index Explanation
1 Main￿oil￿passage
2 VANOS￿solenoid￿valve,￿intake￿side
3 VANOS￿solenoid￿valve,￿exhaust￿side
4 Chain￿tensioner
5 VANOS￿unit,￿exhaust￿side
6 VANOS￿unit,￿intake￿side

N20￿Engine
2.￿Engine￿Components
57
N20￿engine,￿VANOS￿with￿oil￿supply
Index Explanation
1 Oil￿passage￿to￿VANOS￿unit,￿intake￿side
2 VANOS￿unit,￿intake￿side
3 Camshaft￿sensor￿wheel,￿intake￿camshaft
4 VANOS￿solenoid￿actuator,￿intake￿side
5 Main￿oil￿passage
6 Oil￿passage￿for￿intake￿camshaft￿and￿HVCC￿elements
7 Camshaft￿sensor￿wheel,￿exhaust￿camshaft
8 VANOS￿solenoid￿actuator,￿exhaust￿side
9 VANOS￿unit,￿exhaust￿side
10 Oil￿passage￿to￿VANOS￿unit,￿intake￿side
11 Oil￿passage￿for￿exhaust￿camshaft￿and￿HVCC￿elements
12 Chain￿tensioner

N20￿Engine
2.￿Engine￿Components
58The￿following￿graphic￿shows￿the￿oil￿passages￿in￿the￿VANOS￿unit.￿The￿intake￿camshaft￿can￿be
“advanced”￿with￿the￿passages￿shaded￿light￿yellow;￿the￿VANOS￿unit￿can￿be￿“retarded”￿with￿the
passages￿shaded￿dark￿yellow.
The￿cam￿shaft￿sensor￿wheels￿require￿a￿new￿special￿tool￿for￿proper￿positioning,￿tool￿#￿2￿212￿830.
Please￿refer￿to￿the￿repair￿instructions￿for￿more￿information.
N20￿engine,￿VANOS￿unit,￿intake￿camshaft
Index Explanation
1 Rotor
2 Oil￿passage￿for￿advancing￿the￿timing
3 Oil￿passage￿for￿retarding￿the￿timing
4 Oil￿passage￿for￿advancing￿the￿timing
5 Oil￿passage￿for￿retarding￿the￿timing
The￿locking￿pin￿ensures￿that￿the￿VANOS￿unit￿is￿locked￿in￿a￿set￿position￿when￿in￿the￿depressurized
state.￿The￿spiral￿or￿torsion￿spring￿(not￿shown￿here)￿is￿designed￿to￿compensate￿the￿middle￿camshaft
friction,￿because￿without￿the￿spring￿the￿VANOS￿adjusts￿much￿faster￿to￿“retarded”￿(with￿friction)￿than
to￿“advanced”￿(against￿friction).￿The￿locking￿effect￿is￿provided￿by￿the￿oil￿pressure,￿which￿when￿the

N20￿Engine
2.￿Engine￿Components
59actuator￿is￿nonregistered￿always￿forces￿the￿VANOS￿unit￿into￿the￿locking￿position￿(where￿the￿locking
pin￿engages￿and￿blocks￿the￿VANOS￿unit).￿The￿timing￿can￿be￿adjusted￿in￿this￿way.￿This￿is￿important
when￿the￿engine￿is￿started￿to￿ensure￿exact￿timing.￿The￿locking￿pin￿is￿simultaneously￿supplied￿with
the￿oil￿pressure￿available￿for￿timing￿advance￿via￿oil￿passages￿in￿the￿VANOS￿unit.￿If￿the￿camshaft￿is￿to
be￿“advanced”,￿the￿locking￿pin￿is￿then￿forced￿by￿the￿applied￿oil￿pressure￿against￿the￿locking￿spring
towards￿the￿cartridge￿and￿the￿locking￿cover￿is￿released￿for￿VANOS￿adjustment.
N20￿engine,￿locking￿pin
Index Explanation
1 Locking￿cover
2 Locking￿pin
3 Locking￿spring
4 Cartridge

N20￿Engine
2.￿Engine￿Components
60Index Explanation
5 Oil￿passage
6 Locking￿cover
7 Oil￿passage
8 VANOS￿central￿valve
The￿VANOS￿unit￿is￿secured￿to￿the￿camshaft￿by￿the￿VANOS￿central￿valve.￿The￿oil￿flow￿into￿the￿VANOS
unit￿is￿simultaneously￿controlled￿by￿this￿VANOS￿central￿valve.￿The￿system￿is￿actuated￿by￿a￿solenoid
actuator￿(which￿presses￿against￿the￿plunger￿(4)￿of￿the￿VANOS￿central￿valve)￿thereby￿switching￿this
valve￿from￿advance￿to￿the￿retard￿position.
The￿plunger￿in￿the￿central￿valve￿controls￿the￿oil￿flow.￿In￿the￿illustration￿below￿the￿plunger￿is￿shown
extended.￿The￿large￿graphic￿shows￿the￿flow￿of￿oil￿from￿the￿main￿oil￿passage￿into￿the￿VANOS￿unit,￿while
the￿small￿graphic￿shows￿the￿flow￿of￿oil￿from￿the￿VANOS￿unit￿into￿the￿cylinder￿head.

N20￿Engine
2.￿Engine￿Components
61
N20￿engine,￿VANOS￿central￿valve,￿intake￿camshaft
Index Explanation
1 Filter
2 Ball
3 Spring
4 Plunger
5 Sleeve
6 Housing

N20￿Engine
2.￿Engine￿Components
62Index Explanation
7 Opening￿in￿plunger
8 Oil￿supply￿from￿main￿oil￿passage
9 Bore￿to￿oil￿passage￿in￿VANOS￿(timing￿advance)
10 Bore￿to￿oil￿passage￿in￿VANOS￿(timing￿retard)
N20￿engine,￿VANOS￿central￿valve,￿intake￿camshaft
Valve￿lift￿control
As￿can￿been￿seen￿from￿the￿following￿graphic,￿valve￿lift￿control￿with￿the￿Valvetronic￿servomotor￿is
identical￿in￿terms￿of￿design￿to￿that￿of￿the￿N55￿engine.￿The￿eccentric￿shaft￿sensor￿is￿integrated￿in￿the
Valvetronic￿servomotor.
The￿system￿uses￿Valvetronic￿III,￿which￿is￿already￿used￿in￿the￿N55￿engine.

N20￿Engine
2.￿Engine￿Components
63
N20￿engine,￿cylinder￿head
Index Explanation
1 VANOS￿solenoid￿actuator,￿intake
2 VANOS￿solenoid￿actuator,￿exhaust
3 Roller￿tappet,￿high-pressure￿pump
4 Valvetronic￿servomotor
5 Spring
6 Guide￿block
7 Intermediate￿lever
8 Eccentric￿shaft
2.6.￿Belt￿drive
The￿belt￿drive￿consists￿of￿a￿main￿belt￿drive￿with￿alternator￿and￿A/C￿compressor￿and￿an￿auxiliary￿belt
drive￿with￿the￿power￿steering￿pump.￿The￿main￿belt￿drive￿is￿equipped￿with￿a￿belt￿tensioner,￿the￿auxiliary
belt￿drive￿is￿an￿elasto-belt￿tensioning￿system.

N20￿Engine
2.￿Engine￿Components
64
N20￿engine,￿belt￿drive
Index Explanation
1 Belt￿pulley,￿power￿steering￿pump
2 Belt,￿power￿steering￿pump
3 Belt￿pulleys,￿crankshaft
4 Belt￿tensioner
5 Belt￿pulley,￿alternator
6 Belt￿pulley,￿A/C￿compressor
7 Belt

N20￿Engine
3.￿Oil￿Supply
65The￿oil￿supply￿in￿the￿N20￿engine￿is￿very￿similar￿to￿that￿in￿the￿N55￿engine.￿There￿are￿a￿few￿changes
to￿the￿design￿with￿some￿slight￿differences￿in￿operation.￿Due￿to￿the￿complexity￿of￿this￿system,￿it￿is
discussed￿again￿in￿greater￿detail￿in￿this￿training￿material.
The￿special￿features￿of￿the￿oil￿supply￿in￿the￿N20￿engine￿are:
• Map-controlled￿oil￿pump
• New￿pendulum-slide￿oil￿pump￿design
• New￿VANOS￿valves
• Chain￿tensioner￿for￿counterbalance￿shaft/oil￿pump￿drive
• Unfiltered￿oil￿cooling
• New￿combined￿oil￿pressure￿and￿temperature￿sensor.
3.1.￿Overview
The￿following￿hydraulic￿circuit￿diagram￿and￿graphics￿provide￿an￿overview￿of￿the￿N20￿oil￿supply￿and￿a
better￿understanding￿of￿the￿actual￿layout￿of￿the￿oil￿passages￿in￿the￿engine.

N20￿Engine
3.￿Oil￿Supply
663.1.1.￿Hydraulic￿circuit￿diagram
N20￿engine,￿hydraulic￿circuit￿diagram
Index Explanation
A Oil￿sump
B Crankcase
C Cylinder￿head
D Oil￿filter￿module

N20￿Engine
3.￿Oil￿Supply
67Index Explanation
E VANOS￿central￿valve,￿intake￿camshaft￿(also￿oil￿supply,￿lubrication￿point,
camshaft￿thrust￿bearing)
F VANOS￿central￿valve,￿exhaust￿camshaft￿(also￿oil￿supply,￿lubrication￿point,
camshaft￿thrust￿bearing)
1 Oil￿pump
2 Pressure-limiting￿valve
3 Chain￿tensioner,￿counterbalance￿shaft￿and￿oil￿pump￿drive
4 Engine￿oil-to-coolant￿heat￿exchanger
5 Permanent￿bypass
6 Non-return￿valve
7 Oil￿filter
8 Filter￿bypass￿valve
9 Lubrication￿points,￿intake￿camshaft￿bearings￿(via￿4th￿bearing,￿supply￿of
vacuum￿pump)
10 Oil￿spray￿nozzle,￿gearing,￿Valvetronic￿servomotor
11 Oil￿spray￿nozzles,￿cams,￿intake￿camshaft
12 Hydraulic￿valve￿clearance￿compensation￿(HVCC),￿intake￿side
13 Lubrication￿points,￿bearings,￿exhaust￿camshaft
14 Hydraulic￿valve￿clearance￿compensation￿(HVCC),￿exhaust￿side
15 Non-return￿valve
16 Filter
17 4/3-way￿valve
18 VANOS￿unit,￿intake￿camshaft
19 VANOS￿unit,￿exhaust￿camshaft
20 Oil￿spray￿nozzles,￿cams,￿exhaust￿camshaft
21 Chain￿tensioner,￿timing￿chain
22 Oil￿spray￿nozzles￿for￿piston￿crown￿cooling
23 Combined￿oil￿pressure￿and￿temperature￿sensor
24 Lubrication￿points,￿crankshaft￿main￿bearings
25 Map￿control￿valve
26 Emergency￿valve/pressure￿limiting￿blow￿off￿valve
27 Lubrication￿points,￿bearings,￿counterbalance￿shafts

N20￿Engine
3.￿Oil￿Supply
683.1.2.￿Oil￿passages
N20￿engine,￿oil￿passages￿(phantom￿rear￿left￿view)
Index Explanation
1 Oil￿filter
2 Lubrication￿points￿in￿cylinder￿head￿(details,￿see￿below)
3 Oil￿spray￿nozzles￿for￿piston￿crown￿cooling
4 Main￿oil￿passage
5 Lubrication￿points,￿connecting￿rod￿bearings
6 Lubrication￿points,￿crankshaft￿main￿bearings

N20￿Engine
3.￿Oil￿Supply
69Index Explanation
7 Oil￿pump
8 Emergency￿valve/pressure￿limiting￿blow￿off￿valve
9 Map￿control￿valve
10 Unfiltered￿oil￿passage
N20￿engine,￿oil￿passages￿(phantom￿right￿front￿view)

N20￿Engine
3.￿Oil￿Supply
70Index Explanation
1 Lubrication￿points￿in￿cylinder￿head￿(details,￿see￿below)
2 VANOS￿actuator￿unit,￿exhaust￿camshaft
3 VANOS￿actuator￿unit,￿intake￿camshaft
4 Unfiltered￿oil￿passage
5 Engine￿oil-to-coolant￿heat￿exchanger
6 Chain￿tensioner,￿counterbalance￿shaft￿and￿oil￿pump￿drive
7 Oil￿suction￿pipe
8 Lubrication￿points,￿counterbalance￿shaft￿bearings
9 Lubrication￿points,￿crankshaft￿main￿bearings
10 Lubrication￿points,￿connecting￿rod￿bearings
11 Oil￿spray￿nozzles￿for￿piston￿crown￿cooling
12 Chain￿tensioner,￿timing￿chain
N20￿engine,￿oil￿passages￿in￿cylinder￿head￿(phantom￿left￿view)

N20￿Engine
3.￿Oil￿Supply
71Index Explanation
1 Lubrication￿points,￿intake￿camshaft￿bearings
2 Oil￿spray￿nozzles￿in￿Guide￿block￿for￿intermediate￿levers￿and￿intake￿cams
3 Oil￿spray￿nozzle,￿gearing,￿Valvetronic￿servomotor
4 HVCC￿elements,￿intake￿valves
5 VANOS￿actuator￿unit,￿intake￿camshaft
6 VANOS￿actuator￿unit,￿exhaust￿camshaft
7 Chain￿tensioner,￿timing￿chain
8 Oil￿pipe￿for￿oil￿spray￿nozzles,￿exhaust￿cams
9 HVCC￿elements,￿exhaust￿valves
10 Lubrication￿points,￿exhaust￿camshaft￿bearings

N20￿Engine
3.￿Oil￿Supply
72
N20￿engine,￿oil￿return￿passages￿(phantom￿left￿rear￿view)
Index Explanation
1 Ventilation￿passages￿in￿cylinder￿head
2 Ventilation￿passages￿in￿crankcase
3 Ventilation￿passages￿in￿bedplate
4 Oil￿return￿passages￿in￿bedplate
5 Oil￿return￿passages￿in￿crankcase
6 Oil￿return￿passages￿in￿cylinder￿head

N20￿Engine
3.￿Oil￿Supply
733.2.￿Oil￿pump￿and￿pressure￿control
A￿variable-volumetric-flow￿slide￿oil￿pump￿is￿used￿in￿the￿N20￿engine.￿Despite￿its￿shape￿being￿modified,
its￿function￿is￿familiar￿to￿that￿of￿the￿N63￿and￿N55￿engines.￿Although￿these￿two￿engines￿share￿a￿similar
oil￿pump,￿they￿differ￿in￿how￿they￿are￿controlled.￿While￿the￿oil￿pump￿in￿the￿N63￿engine￿is￿volumetric-
flow-controlled,￿in￿the￿N55￿and￿N20￿engines￿its￿map-controlled.
3.2.1.￿Oil￿pump
The￿oil￿pump￿is￿connected￿to￿the￿counterbalance￿shaft￿housing.￿The￿oil￿pump￿is￿located￿at￿the
flywheel￿side￿of￿the￿engine,￿but￿is￿driven￿at￿the￿front￿of￿the￿engine￿by￿the￿crankshaft￿via￿a￿chain.
The￿chain￿sprocket￿connects￿to￿the￿oil￿pump￿via￿a￿long￿shaft.￿This￿shaft￿forms￿part￿of￿the￿first
counterbalance￿shaft￿which￿rotates￿in￿the￿same￿direction￿as￿the￿crankshaft.￿The￿rotational￿speed￿is
stepped￿down￿from￿the￿counterbalance￿shaft￿for￿the￿oil￿pump￿via￿a￿pair￿of￿gears.
N20￿engine,￿oil￿pump￿with￿counterbalance￿shafts
Index Explanation
1 Sprocket￿on￿crankshaft
2 Upper￿counterbalance￿shaft
3 Lower￿counterbalance￿shaft
4 Gear,￿upper￿counterbalance￿shaft
5 Gear,￿oil￿pump
6 Oil￿pump
7 Tooth-type￿chain,￿counterbalance￿shaft￿and￿oil￿pump￿drive
8 Counterbalance￿shaft￿sprocket

N20￿Engine
3.￿Oil￿Supply
74As￿already￿mentioned,￿the￿function￿of￿the￿slide￿oil￿pump￿has￿not￿changed.￿The￿main￿difference￿is￿that
the￿slide￿mechanism￿no￿longer￿pivots￿on￿an￿axis￿during￿adjustment,￿but￿instead￿is￿moved￿in￿parallel.
N20￿engine,￿inner￿workings￿of￿oil￿pump
Index Explanation
1 Pressure￿side
2 sliding￿block
3 Outer￿rotor
4 Pendulum
5 Inner￿rotor
6 Control￿oil￿chamber
7 Suction￿side
8 Housing
9 Main￿spring
As￿in￿all￿newer￿generation￿slide￿oil￿pumps￿the￿oil￿acts￿directly￿on￿the￿slide￿mechanism.￿The￿higher￿the
pressure￿here,￿the￿more￿the￿sliding￿block￿is￿forced￿against￿the￿spring￿in￿the￿direction￿of￿the￿center￿of
the￿pump,￿which￿reduces￿the￿volumetric￿displacement.￿This￿reduces￿the￿pump￿delivery￿rate￿and￿limits

N20￿Engine
3.￿Oil￿Supply
75the￿pressure￿in￿the￿system.￿In￿this￿way,￿it￿is￿possible￿to￿achieve￿purely￿hydraulic/mechanical￿control￿of
the￿volumetric￿flow,￿allowing￿sufficient￿operating￿pressure￿to￿be￿set.￿This￿pressure￿is￿determined￿by
the￿strength￿of￿the￿main￿spring￿in￿the￿oil￿pump￿which￿acts￿on￿the￿sliding￿block.
As￿with￿the￿N55￿the￿N20￿engine￿features￿a￿map￿control￿valve￿which￿the￿DME￿activates￿to￿influence￿the
pump￿delivery￿rate.
The￿oil￿pump￿cannot￿be￿replaced￿separately.￿The￿entire￿unit￿including￿the￿counterbalance￿shafts￿must
be￿replaced￿if￿the￿oil￿pump￿fails.
3.2.2.￿Control
Controlling￿the￿delivery￿rate￿of￿the￿oil￿supply￿pump￿is￿crucial￿component￿of￿the￿BMW
EfficientDynamics￿strategy.￿Essentially,￿engineers￿attempt￿to￿design￿a￿pump￿with￿regard￿to￿its￿power
input￿as￿small￿as￿possible￿in￿order￿to￿keep￿engine￿losses￿as￿low￿as￿possible.￿On￿the￿other￿hand,￿the
pump￿must￿also￿be￿designed￿in￿such￿a￿way￿as￿to￿deliver￿sufficient￿volume￿and￿pressure￿under￿all
operating￿conditions.￿A￿conventional,￿non-variable￿pump￿would￿therefore￿have￿to￿be￿designed￿in
accordance￿with￿the￿second￿standpoint,￿i.e.￿large￿enough￿to￿be￿able￿to￿deliver￿sufficient￿amounts￿of￿oil
at￿all￿times.￿However,￿this￿means￿that￿the￿pump￿may￿deliver￿far￿too￿much￿oil￿volume￿and￿pressure￿over
a￿large￿portion￿of￿its￿service￿life￿and￿thereby￿draw￿more￿energy￿than￿necessary￿from￿the￿powertrain.
For￿this￿reason,￿more￿and￿more￿pumps￿are￿now￿variable￿in￿design￿and￿their￿control￿is￿becoming
increasingly￿more￿fine-tuned.￿Thus￿the￿conventional￿pump￿was￿followed￿by￿volumetric￿flow￿control,
which￿was￿subsequently￿extended￿to￿included￿map￿control.
Volumetric￿flow￿control
The￿N20￿uses￿a￿vane￿type￿oil￿pump.￿The￿core￿of￿this￿variable-volumetric-flow￿oil￿pump￿is￿the￿sliding
mechanism.￿It￿can￿be￿displaced￿with￿respect￿to￿the￿pump￿shaft￿to￿vary￿the￿pump's￿delivery￿rate.
N20￿engine,￿oil￿pump￿(left￿at￿maximum￿delivery,￿right￿at￿minimum￿delivery)

N20￿Engine
3.￿Oil￿Supply
76Index Explanation
1 Control￿oil￿chamber
2 Pressure￿side
3 Sliding￿block
4 Main￿spring
5 Suction￿side
In￿the￿maximum￿delivery￿setting￿the￿sliding￿block￿is￿positioned￿off-center￿with￿respect￿to￿the￿pump
shaft.￿In￿this￿way,￿an￿increase￿in￿volume￿occurs￿on￿the￿suction￿side￿and￿correspondingly￿a￿decrease￿in
volume￿occurs￿on￿the￿pressure￿side.￿This￿generates￿high￿pump￿capacity.
When￿the￿sliding￿block￿is￿displaced￿towards￿the￿pump￿shaft,￿the￿pump￿volume￿is￿reduced.￿Therefore,
the￿pump￿capacity￿is￿reduced￿until￿finally￿the￿minimum￿delivery￿is￿reached.
The￿position￿of￿the￿sliding￿block￿is￿dependent￿on￿the￿oil￿pressure￿in￿the￿pump's￿control￿oil￿chamber.
This￿pressure￿pushes￿on￿the￿sliding￿block￿against￿the￿force￿of￿a￿spring.￿When￿the￿pressure￿is￿low￿in￿the
control￿chamber,￿the￿sliding￿block￿is￿moved￿off-center￿by￿the￿force￿of￿the￿spring￿and￿the￿delivery￿rate
is￿high.￿When￿the￿pressure￿is￿high￿in￿the￿control￿chamber,￿the￿sliding￿block￿is￿displaced￿towards￿the
center￿of￿the￿pump￿as￿the￿spring￿is￿compressed￿and￿the￿delivery￿rate￿decreases.
With￿pure￿volumetric￿flow￿control,￿the￿pressure￿in￿the￿control￿oil￿chamber￿corresponds￿to￿that￿in￿the
main￿oil￿passage.￿In￿this￿way,￿it￿is￿possible￿to￿maintain￿a￿relatively￿uniform￿pressure￿irrespective￿of￿the
necessary￿volumetric￿flow.￿One￿reason￿for￿large￿differences￿in￿the￿necessary￿volumetric￿flow￿in￿the
oil￿circuit￿is￿the￿VANOS￿variable￿camshaft￿timing￿control￿system.￿In￿the￿VANOS￿units￿the￿oil￿is￿used
not￿only￿for￿lubrication￿purposes￿but￿also￿for￿hydraulic￿actuation￿of￿the￿cam￿timing.￿A￿large￿oil￿volume
is￿thus￿necessary￿during￿the￿adjustment￿phase,￿which￿causes￿the￿pressure￿in￿the￿system￿to￿drop.
The￿falling￿pressure￿causes￿the￿sliding￿block￿in￿the￿oil￿pump￿to￿be￿displaced￿in￿the￿direction￿of￿higher
delivery.￿In￿this￿way,￿a￿higher￿volumetric￿flow￿is￿made￿available￿and￿the￿pressure￿drop￿is￿compensated
for.
As￿already￿mentioned,￿the￿pressure￿that￿is￿set￿in￿the￿oil￿system￿is￿dependent￿on￿the￿force￿of￿the￿spring
which￿counteracts￿the￿pressure￿in￿the￿control￿oil￿chamber.￿With￿a￿softer￿spring,￿the￿sliding￿block￿can
be￿displaced￿more￿easily,￿i.e.￿with￿a￿lower￿pressure,￿towards￿the￿center.￿With￿a￿harder￿spring,￿more
pressure￿is￿required￿to￿reduce￿the￿volumetric￿displacement￿of￿the￿pump.￿Thus￿the￿appropriate￿spring
was￿calculated￿and￿selected￿to￿properly￿operate￿the￿N20￿oil￿system.
Map￿control￿represents￿a￿further￿fine-tuning￿of￿volumetric￿flow￿control.
Map￿control
Map￿control￿is￿used￿to￿influence￿the￿pressure￿in￿the￿control￿oil￿chamber￿of￿the￿pump.￿Two￿valves￿are
involved￿in￿this￿process,￿a￿solenoid￿valve￿called￿the￿map￿control￿valve￿and￿a￿hydraulic￿valve￿which￿also
acts￿as￿a￿fail-safe.￿This￿“fail￿safe”￿valve￿is￿also￿referred￿to￿as￿an￿emergency￿valve￿or￿a￿second-level
mode￿control￿valve.
The￿map￿control￿valve￿is￿located￿on￿the￿left￿side￿of￿the￿engine￿(bolted￿to￿bedplate)￿and￿channels￿the
oil￿pressure￿from￿the￿main￿oil￿passage￿to￿the￿control￿oil￿chamber￿within￿the￿pump.￿Its￿purpose￿is￿to
influence￿pump￿volume￿output￿by￿gradually￿and￿smoothly￿reducing￿the￿oil￿pressure￿in￿the￿control￿oil
chamber.

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Map￿control￿valve
The￿further￿it￿reduces￿the￿pressure,￿the￿more￿volume￿is￿delivered￿by￿the￿oil￿pump￿as￿the￿sliding￿block
moves￿further￿off￿center.￿However,￿this￿mode￿does￿not￿produce￿a￿positive￿effect￿on￿energy￿saving.
Therefore￿the￿main￿spring￿in￿the￿oil￿pump￿which￿acts￿on￿the￿sliding￿block￿is￿softer￿than￿the￿one￿used
in￿a￿purely￿volumetric-flow-controlled￿system.￿In￿other￿words,￿the￿sliding￿block￿can￿be￿moved￿to￿a
centred￿position￿very￿easily,￿as￿the￿pump￿switches￿to￿minimum￿delivery.￿In￿this￿way,￿there￿are￿lower
pressure￿conditions￿in￿the￿oil￿system,￿which￿in￿turn￿translates￿into￿less￿energy￿spent￿to￿drive￿the￿oil
pump.￿Where￿necessary,￿the￿pressure￿in￿the￿control￿oil￿chamber￿can￿now￿be￿reduced￿by￿the￿map
control￿valve￿which￿also￿reduces￿the￿delivery￿rate.
The￿second￿stage￿of￿map￿control￿is￿a￿hydraulic/emergency￿valve￿which￿is￿located￿in￿the￿oil￿pump
housing.

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N20￿engine,￿oil￿pump￿with￿hydraulic￿emergency￿valve
Index Explanation
1 Connection￿from￿main￿oil￿passage
2 Connection￿from￿map￿control￿valve
3 Hydraulic/Emergency￿valve
4 Channel￿to￿control￿oil￿chamber
5 Connection￿to￿counterbalance￿shafts
6 Control￿oil￿chamber
This￿is￿3/2-way￿valve￿is￿used￿to￿channel￿the￿main￿oil￿pressure￿into￿the￿oil￿pump's￿control￿oil￿chamber.
The￿oil￿from￿the￿main￿oil￿passage￿forces￿a￿plunger￿against￿a￿spring￿until￿the￿passage￿to￿the￿oil￿pump
control￿chamber￿is￿opened.￿The￿oil￿pressure￿from￿the￿map￿control￿valve￿acts￿on￿the￿other￿end￿of￿the
plunger.￿The￿pressure￿in￿the￿map￿control￿valve￿port￿counter￿acts￿the￿main￿oil￿passage￿pressure￿to￿fine
tune￿the￿oil￿pressure￿within￿the￿oil￿pump's￿volume￿control￿chamber￿which￿in￿turn￿varies￿the￿oil￿delivery
rate￿of￿the￿pump.

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N20￿engine,￿emergency￿valve
Index Explanation
1 Oil￿pump￿housing
2 Emergency￿spring
3 Plunger
4 From￿main￿oil￿passage
5 To￿control￿oil￿chamber￿in￿oil￿pump
6 From￿map￿control￿valve
The￿hydraulic￿valve￿is￿located￿between￿the￿map￿control￿valve￿and￿the￿control￿oil￿chamber￿in￿the￿oil
pump.￿The￿following￿graphic￿shows￿this￿in￿a￿simplified￿oil￿circuit.
N20￿engine,￿simplified￿map￿control￿oil￿circuit

N20￿Engine
3.￿Oil￿Supply
80Index Explanation
1 Oil￿pump
2 Main￿oil￿passage
3 Map￿control￿valve
4 Emergency￿valve
In￿map￿control￿mode￿oil￿pressure￿acts￿on￿both￿ends￿of￿the￿plunger.￿The￿oil￿pressure￿directly￿from￿the
main￿oil￿passage￿acts￿against￿the￿emergency￿valve￿spring.￿At￿the￿same￿time￿the￿oil￿pressure￿released
by￿the￿map￿control￿valve￿acts￿on￿the￿other￿end,￿i.e.￿along￿with￿the￿emergency￿valve￿spring.
N20￿engine,￿hydraulic￿3/2-way￿valve￿with￿map￿control
The￿plunger￿remains￿constantly￿in￿its￿end￿position￿during￿map￿control.￿To￿displace￿the￿plunger,￿there
would￿have￿to￿be￿a￿pressure￿of￿5.5 bar￿in￿the￿main￿oil￿port￿to￿counter￿act￿the￿spring.￿This￿never￿arises
in￿map￿control￿mode,￿since￿the￿maximum￿set￿pressure￿in￿the￿system￿is￿4.5 bar￿in￿the￿circuit.￿In￿this
setting￿the￿emergency￿valve￿forms￿a￿connection￿between￿the￿map￿control￿valve￿and￿the￿oil￿pump's
control￿oil￿chamber￿(the￿valve￿is￿ closed￿to￿the￿main￿oil￿duct).
N20￿engine,￿simplified￿oil￿circuit￿with￿map￿control
The￿pump￿delivery￿rate￿is￿controlled￿by￿the￿pressure￿in￿the￿pump's￿control￿oil￿chamber￿which￿in￿turn￿is
determined￿directly￿by￿the￿DME￿via￿the￿map￿control￿valve.
Map￿control￿is￿the￿oil￿system's￿standard￿operating￿mode.￿It￿is￿always￿engaged￿when￿there￿are￿no￿faults
in￿the￿system￿and￿the￿operating￿conditions￿do￿not￿exceed￿or￿drop￿below￿certain￿values￿(see￿below).
Up￿to￿now￿map￿control￿system￿would￿manage￿without￿the￿emergency￿valve.￿This￿is￿however￿a￿second
stage￿of￿map￿control￿–￿a￿kind￿of￿fail￿safe￿mode.

N20￿Engine
3.￿Oil￿Supply
81If￿the￿map￿control￿valve￿is￿deactivated,￿the￿chamber￿at￿the￿end￿of￿the￿spring￿in￿the￿emergency￿valve
is￿depressurized.￿Because￿the￿plunger￿is￿now￿only￿being￿held￿by￿the￿spring￿the￿main￿oil￿pressure
displaces￿it￿and￿makes￿its￿way￿into￿the￿pump's￿control￿chamber.￿A￿pressure￿difference￿of￿5.5 bar￿is
required￿to￿switch￿the￿emergency￿valve￿into￿this￿position.
N20￿engine,￿emergency￿valve￿with￿“second-level￿control”
In￿this￿mode￿the￿pressure￿is￿channelled￿from￿the￿main￿oil￿passage￿directly￿into￿the￿oil￿pump's￿control
oil￿chamber.
N20￿engine,￿simplified￿oil￿circuit￿in￿emergency￿mode
There￿is￿no￿map￿control￿in￿emergency￿mode￿because￿the￿oil￿pressure￿is￿set￿to￿5.5 bar￿max.￿and￿there
is￿no￿oil￿admitted￿into￿the￿oil￿pump's￿control￿oil￿chamber￿below￿this￿level.
The￿map￿control￿valve￿is￿closed￿at￿zero￿current.￿Therefore,￿should￿the￿map￿control￿valve￿fail,￿the
system￿is￿automatically￿in￿emergency￿mode,￿guaranteeing￿pressure￿limitation￿to￿5.5 bar.￿As￿already
mentioned,￿map￿control￿mode￿is￿the￿normal￿mode￿of￿operation.￿There￿are,￿however,￿several￿reasons
why￿the￿DME￿will￿switch￿to￿emergency￿mode.
Emergency￿mode￿is￿applied￿in￿the￿following￿conditions:
• Map￿control￿valve￿faulty
• Oil￿pressure￿sensor￿faulty
• Outside￿temperature￿less￿than￿- 20 °C/-￿4￿°F
• High￿engine￿oil￿or￿coolant￿temperature
• Driving￿profile￿(e.g.￿high￿engine￿revs￿for￿a￿long￿time)

N20￿Engine
3.￿Oil￿Supply
82The￿oil￿pressure￿sensor￿signal￿allows￿the￿DME￿to￿identify￿whether￿the￿emergency￿valve￿is￿stuck.￿If￿this
is￿the￿case,￿the￿DME￿attempts￿to￿free￿the￿emergency￿valve￿by￿applying￿a￿varying￿pressure￿buildup.
If￿the￿emergency￿valve￿is￿stuck￿in￿the￿“closed”￿position,￿it￿is￿possible￿to￿continue￿map￿control.￿If,
however,￿the￿emergency￿valve￿is￿stuck￿in￿the￿“open”￿position￿sufficient￿pressure￿buildup￿is￿no￿longer
possible.￿The￿oil￿pressure￿indicator￿light￿is￿activated￿and￿the￿engine￿must￿be￿shut￿down￿immediately.
Summary
By￿applying￿oil￿pump￿map￿control,￿it￿is￿possible￿to￿deliver￿an￿oil￿supply￿to￿match￿demand￿and￿to
reduce￿the￿average￿pressure￿level￿in￿the￿oil￿circuit.￿This￿ensures￿that￿the￿oil￿pump￿has￿a￿lower￿energy
requirement.
The￿map￿control￿valve￿controls￿the￿pressure￿in￿the￿system￿and￿in￿turn￿allows￿the￿delivery￿rate￿to￿be
controlled￿by￿the￿DME.
The￿following￿diagram￿shows￿(in￿simplified￿form)￿the￿pressure￿curves￿plotted￿against￿engine￿speed￿for
different￿oil￿pumps.
Simplified￿pressure￿curves￿for￿different￿oil￿pumps

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3.￿Oil￿Supply
83Index Explanation
A Oil￿pressure
B Engine￿speed
1 Non-controlled￿oil￿pump
2 Volumetric-flow-controlled￿oil￿pump
3 Map-controlled￿oil￿pump￿at￿full￿load
4 Map-controlled￿oil￿pump￿at￿partial￿load
The￿diagram￿illustrates￿the￿advantage￿of￿controlled￿oil￿pumps.￿When￿a￿sufficient￿oil￿pressure￿is
reached,￿the￿delivery￿rate￿of￿the￿oil￿pump￿can￿be￿reduced.￿Lower￿pressure￿is￿synonymous￿with
fuel￿saving.￿Thus￿the￿map-controlled￿oil￿pump￿offers￿the￿greatest￿advantage￿here,￿since￿it￿can￿be
controlled￿regardless￿of￿engine￿speed.￿At￿partial￿load,￿for￿example,￿only￿lower￿pressures￿are￿required,
because￿the￿crankshaft￿main￿bearings￿have￿to￿bear￿less￿load.￿Accordingly,￿a￿lower￿oil￿pressure￿can
be￿set￿in￿the￿partial￿load￿range,￿which￿illustrates￿even￿more￿clearly￿the￿advantage￿over￿the￿volumetric-
flow-controlled￿oil￿pump.
The￿oil￿pressure￿in￿map￿mode￿ranges￿between￿1.5￿and￿4.5 bar.
The￿emergency￿valve￿has￿been￿integrated￿in￿the￿system￿as￿a￿fail￿safe￿and￿to￿facilitate￿a￿higher￿pressure
in￿certain￿conditions.￿For￿example￿if￿the￿map￿control￿valve￿fails,￿it￿ensures￿the￿necessary￿pressure￿is
built￿up￿and￿the￿oil￿pump￿pressure￿control￿of￿5.5 bar.
3.2.3.￿Pressure-limiting￿valve
Additionally￿available￿to￿control￿the￿oil￿pump￿is￿a￿pressure-limiting￿valve,￿which￿is￿often￿also￿known￿as￿a
cold-start￿valve.
N20￿engine,￿pressure-limiting￿valve￿in￿oil￿pump
Index Explanation
1 Oil￿pump￿housing
2 Oil￿pump￿cover
3 Pressure-limiting￿valve

N20￿Engine
3.￿Oil￿Supply
84The￿pressure-limiting￿valve￿is￿located￿in￿the￿oil￿pump￿housing￿and￿in￿the￿oil￿circuit￿as￿the￿first
component￿after￿the￿pump.￿It￿opens￿at￿a￿pressure￿of￿roughly￿12￿to￿13 bar￿and￿discharges￿the￿oil
directly￿into￿the￿oil￿sump.￿It￿is￿necessary￿at￿low￿temperatures￿and￿when￿the￿oil￿has￿a￿higher￿viscosity.
In￿these￿situations￿the￿pressure-limiting￿valve￿prevents￿damage￿to￿components,￿in￿particular￿to￿the￿oil
filter￿module￿and￿its￿seals.￿This￿is￿relevant￿at￿temperatures￿of￿below￿-20 °C￿/￿-4 °F,￿since￿map￿control￿is
already￿active￿above￿this￿temperature.
3.3.￿Oil￿filtering￿and￿cooling
The￿N20￿engine￿has￿a￿similar￿plastic￿oil￿filter￿housing￿as￿the￿N55￿engine,￿to￿which￿the￿engine￿oil-to-
coolant￿heat￿exchanger￿is￿also￿directly￿mounted.￿This￿entire￿unit￿is￿known￿as￿the￿oil￿filter￿module.
N20￿engine,￿oil￿filter￿module
Index Explanation
1 Oil￿filter
2 Engine￿oil-to-coolant￿heat￿exchanger
3.3.1.￿Oil￿cooling
In￿the￿N20￿engine￿the￿engine￿oil-to-coolant￿heat￿exchanger￿is￿located￿in￿the￿oil￿circuit￿ahead￿of￿the￿oil
filter.￿This￿is￿known￿as￿raw/unfiltered￿oil￿cooling,￿in￿contrast￿to￿clean￿oil￿cooling.￿This￿is￿due￿to￿the￿lead-
free￿crankshaft￿and￿connecting￿rod￿bearings.￿Because￿these￿components￿are￿extremely￿sensitive￿to
dirt￿particles,￿this￿arrangement￿brings￿the￿oil￿filter￿even￿closer￿to￿just￿before￿the￿bearing￿positions.￿The
importance￿is￿even￿greater￿should￿auxiliary￿engine￿oil￿coolers￿be￿used￿in￿later￿models,￿as￿here￿there￿is
always￿the￿risk￿of￿dirt￿getting￿into￿the￿oil￿circuit￿after￿an￿accident.
Permanent￿bypass
The￿N20￿engine￿does￿not￿have￿a￿heat￿exchanger￿bypass￿valve.￿Instead,￿as￿the￿N55,￿it￿has￿a￿permanent
bypass.￿This￿is￿a￿permanently￿open￿bypass￿around￿the￿engine￿oil-to-coolant￿heat￿exchanger.￿The
bypass￿incorporates￿a￿flow￿restrictor￿to￿ensure￿that￿the￿majority￿of￿the￿oil￿flows￿through￿the￿engine￿oil-
to-coolant￿heat￿exchanger.

N20￿Engine
3.￿Oil￿Supply
853.3.2.￿Oil￿filtering
The￿full-flow￿oil￿filter￿used￿in￿the￿N20￿engine.￿Instead￿of￿a￿non-return￿valve,￿a￿non-return￿diaphragm￿is
mounted￿directly￿on￿the￿filter￿element.￿The￿function￿of￿this￿diaphragm￿is￿to￿prevent￿the￿oil￿filter￿from
draining￿after￿the￿engine￿is￿shut￿down.
N20￿engine,￿oil￿filter
Index Explanation
1 Oil￿filter
2 Non-return￿diaphragm
The￿non-return￿diaphragm￿is￿made￿of￿rubber￿and￿is￿raised￿by￿the￿oil￿pressure￿to￿admit￿oil￿into￿the￿filter.
When￿the￿engine￿is￿shut￿down￿and￿the￿oil￿pressure￿drops,￿the￿non-return￿diaphragm￿uses￿its￿shape
and￿elasticity￿to￿seal￿off￿the￿oil￿duct.￿The￿engine￿oil￿is￿unable￿to￿flow￿out￿of￿the￿filter.￿The￿non-return
diaphragm￿is￿part￿of￿the￿oil￿filter￿and￿is￿therefore￿automatically￿replaced￿each￿time￿the￿filter￿is￿changed.
The￿N20￿engine￿has￿a￿filter￿bypass￿valve￿which￿can￿open￿a￿bypass￿around￿the￿filter￿if,￿for￿example,￿the
engine￿oil￿is￿cold￿and￿has￿a￿higher￿viscosity.￿This￿occurs￿if￿the￿pressure￿difference￿between￿before￿and
after￿the￿filter￿exceeds￿about.￿2.5￿bar.￿The￿allowable￿pressure￿difference￿has￿been￿increased￿from￿2.0
to￿2.5 bar￿in￿order￿to￿protect￿the￿lead-free￿crankshaft￿and￿connecting￿rod￿bearings.￿This￿ensures￿that
the￿filter￿is￿bypassed￿much￿less￿frequently￿and￿any￿dirt￿particles￿are￿reliably￿filtered￿out.

N20￿Engine
3.￿Oil￿Supply
863.4.￿Oil￿monitoring
3.4.1.￿Oil￿pressure￿and￿temperature￿sensor
N20￿engine,￿oil￿pressure￿and￿temperature￿sensor
A￿new￿combined￿oil￿pressure￿and￿temperature￿sensor￿is￿used.￿The￿pressure￿signal￿is￿required￿for￿oil
pump￿map￿control,￿the￿temperature￿signal￿for￿engine￿heat￿management.
The￿sensor￿is￿exposed￿in￿the￿main￿oil￿passage￿to￿the￿oil￿pressure￿prevailing￿there￿and￿the￿oil
temperature.￿Thus,￿what￿is￿measured￿is￿no￿longer￿the￿oil￿temperature￿in￿the￿oil￿sump,￿but￿instead￿the
actual￿oil￿temperature￿in￿the￿engine.
Combined￿pressure￿and￿temperature￿sensors￿usually￿have￿four￿connections￿(power￿supply,￿ground,
temperature￿signal,￿pressure￿signal).￿The￿oil￿pressure￿and￿temperature￿sensor￿has￿only￿three
connections.￿The￿temperature￿and￿pressure￿signals￿are￿not￿transmitted￿on￿separate￿wires.￿Instead,
the￿sensor￿outputs￿a￿pulse-width-modulated￿(PWM)￿signal.￿This￿PWM￿signal￿is￿split￿into￿three￿fixed
cycles.￿The￿first￿cycle￿is￿for￿synchronization￿and￿diagnosis,￿the￿second￿transmits￿the￿temperature,￿and
the￿third￿the￿pressure.￿The￿duration￿of￿the￿“high￿level”￿of￿a￿respective￿cycle￿determines￿the￿value.
Cycle Function Duration￿of￿cycle Duration￿of￿high
level
1 Synchronization￿and
diagnosis1024 μs 256￿–￿640 μs
2 Temperature 4096 μs 128￿–￿3968 μs
3 Pressure 4096 μs 128￿–￿3968 μs
The￿length￿of￿the￿high￿level￿is￿for￿the￿diagnostic￿signal￿always￿a￿multiple￿of￿128 μs￿(microsecond￿=
0.000001￿seconds),￿as￿is￿shown￿in￿the￿table￿below:
Duration￿of￿high￿signal Pulse￿width Meaning
256￿μs 25 % Diagnosis￿OK
384￿μs 37.5 % Pressure￿measurement￿failed
512￿μs 50 % Temperature￿measurement
failed
640￿μs 62.5 % Hardware￿fault
For￿this￿purpose￿the￿sensor￿is￿capable￿of￿self-diagnosis￿and￿can￿identify￿sensor-internal￿mechanical
and￿electrical￿faults.

N20￿Engine
3.￿Oil￿Supply
87For￿the￿temperature￿signal:
• 128 μs￿(3.125 %￿pulse￿width)￿=￿-40 °C/-40 °F
• 3968￿μs￿(96.875 %￿pulse￿width)￿=￿160 °C/320￿°F
For￿the￿pressure￿signal:
• 128￿μs￿(3.125 %￿pulse￿width)￿=￿0.5￿bar￿(absolute)
• 3968￿μs￿(96.875 %￿pulse￿width)￿=￿10.5 bar￿(absolute)
The￿times￿indicated￿are￿nominal￿values.￿Actually￿the￿durations￿of￿each￿cycle￿and￿of￿the￿respective￿high
level￿are￿measure￿and￿compared￿with￿each￿other.￿The￿resulting￿pulse￿width￿produces￿the￿respective
measured￿value.
The￿actual￿oil￿pressure￿can￿be￿measured￿by￿installing￿special￿tool￿#￿2￿212￿823.￿Please￿refer￿to
the￿repair￿instructions.
3.4.2.￿Oil￿level￿monitoring
The￿established￿thermal￿oil￿level￿sensor￿is￿used￿to￿monitor￿the￿oil￿level￿and￿the￿oil￿temperature.
3.5.￿Oil￿spray￿nozzles
As￿with￿previous￿BMW￿engines￿those￿components￿which￿cannot￿be￿reached￿directly￿by￿an￿oil￿passage
are￿lubricated￿and/or￿cooled￿by￿oil￿spray￿nozzles.
3.5.1.￿Piston￿crown￿cooling
The￿oil￿spray￿nozzles￿for￿piston￿crown￿cooling￿are￿used￿in￿the￿N20￿engine.￿They￿incorporate￿a￿non-
return￿valve￿to￿enable￿them￿to￿open￿and￿close￿only￿from￿a￿specific￿oil￿pressure.
As￿well￿as￿cooling￿the￿piston￿crowns,￿they￿are￿also￿responsible￿for￿lubricating￿the￿wrist￿pins,￿which￿is
why￿it￿is￿very￿important￿for￿them￿to￿be￿precisely￿aligned.
N20￿engine,￿oil￿spray￿nozzles￿for￿piston￿crown￿cooling
Opening￿pressure 2.5￿–￿2.9 bar
Closing￿pressure 2.1 bar

N20￿Engine
3.￿Oil￿Supply
88
The￿oil￿spray￿nozzles￿for￿piston￿crown￿cooling￿in￿the￿N20￿engine￿must￿be￿correctly￿positioned￿using￿a
special￿tool￿#￿2￿212￿829￿after￿being￿installed.￿Refer￿to￿the￿repair￿instructions.
There￿are￿two￿different￿variants￿of￿oil￿spray￿nozzle￿for￿piston￿crown￿cooling￿for￿the￿N20￿engine,
depending￿on￿their￿arrangement￿in￿the￿engine.￿One￿variant￿for￿cylinders￿1￿and￿3￿and￿one￿variant￿for
cylinders￿2￿and￿4.
3.5.2.￿Chain￿drive
The￿chain￿drive￿in￿the￿N20￿engine￿is￿divided￿into￿an￿upper￿section￿(the￿camshaft￿drive)￿and￿a￿lower
section￿(the￿oil￿pump￿drive).
Camshaft￿drive
The￿timing￿chain￿is￿lubricated￿by￿an￿oil￿spray￿nozzle￿located￿in￿the￿chain￿tensioner.￿There￿is￿an￿opening
in￿the￿tensioning￿rail￿through￿which￿the￿oil￿can￿be￿sprayed￿for￿this￿purpose.
N20￿engine,￿chain￿tensioner￿with￿oil￿spray￿nozzle￿for￿timing￿chain

N20￿Engine
3.￿Oil￿Supply
89Counterbalance￿shaft￿and￿oil￿pump￿drive
N20￿engine,￿counterbalance￿shaft￿and￿oil￿pump￿drive
Index Explanation
1 Crankshaft￿sprocket
2 Chain
3 Chain￿tensioner
4 Counterbalance￿shaft￿sprocket
Oil￿is￿sprayed￿onto￿the￿chain￿through￿the￿chain￿tensioner￿for￿the￿counterbalance￿shaft￿and￿oil￿pump
drive.￿This￿is￿however￿not￿necessary￿for￿lubrication,￿since￿the￿chain￿is￿immersed￿in￿the￿oil￿sump.￿In￿this
case,￿this￿helps￿the￿oil￿to￿drain￿from￿the￿chain￿tensioner.
3.5.3.￿Camshaft
The￿lobes￿on￿the￿camshaft￿are￿also￿lubricated￿via￿oil￿spray￿nozzles.￿For￿the￿intake￿camshaft￿there￿are
fine￿grooves￿in￿the￿gates￿which￿are￿supplied￿with￿oil￿from￿the￿screw￿hole.

N20￿Engine
3.￿Oil￿Supply
90
N20￿engine,￿guide￿block￿with￿oil￿spray￿nozzles￿for￿intake￿cams
Index Explanation
1 Screw￿connection,￿gates
2 Oil￿spray￿nozzles￿for￿intake￿cams
3 Oil￿supply￿for￿oil￿spray￿nozzles
When￿fitting￿the￿guide￿block￿it￿is￿essential￿to￿work￿in￿absolutely￿clean￿conditions,￿as￿any￿soiling￿could
block￿the￿oil￿spray￿nozzles.￿Lubrication￿of￿the￿cam￿lobes￿would￿no￿longer￿be￿guaranteed￿and￿could
result￿in￿damage￿to￿the￿valvetrain.
For￿the￿exhaust￿camshaft,￿the￿cylinder￿head￿features￿an￿oil￿pipe￿which￿sprays￿oil￿through￿small￿holes
directly￿onto￿the￿cam￿lobes.￿Accordingly,￿there￿are￿eight￿holes￿for￿lubricating￿the￿exhaust￿valve￿lobes
and￿an￿extra￿hole￿for￿lubricating￿the￿triple￿cam￿which￿drives￿the￿high-pressure￿fuel￿pump.
N20￿engine,￿oil￿pipe￿with￿oil￿spray￿nozzles￿for￿exhaust￿cam￿lobes

N20￿Engine
3.￿Oil￿Supply
91Index Explanation
1 Oil￿pipe
2 Hole
3.5.4.￿Gearing,￿Valvetronic￿servomotor
N20￿engine,￿oil￿spray￿nozzle￿for￿Valvetronic￿servomotor
The￿N20￿engine￿features￿the￿same￿Valvetronic￿servomotor￿as￿the￿N55￿engine￿including￿the￿same
installation￿position.￿The￿worm￿gear￿for￿adjusting￿the￿eccentric￿shaft￿is￿also￿lubricated￿by￿an￿oil￿spray
nozzle.￿This￿nozzle￿must￿be￿correctly￿aligned￿when￿fitted.￿However,￿this￿does￿not￿require￿the￿use￿of￿a
special￿tool.￿Instead￿the￿nozzle￿has￿to￿be￿carefully￿and￿noticeably￿engaged￿in￿the￿designated￿guide￿on
the￿Valvetronic￿servomotor.

N20￿Engine
3.￿Oil￿Supply
92
N20￿engine,￿engaged￿oil￿spray￿nozzle￿for￿Valvetronic￿servomotor￿gearing
Index Explanation
1 Oil￿spray￿nozzle￿for￿Valvetronic￿servomotor￿gearing
2 Valvetronic￿servomotor
3 Correctly￿engaged￿oil￿spray￿nozzle
Due￿to￿the￿size￿of￿the￿oil￿spray￿nozzle￿and￿the￿fact￿that￿the￿motor￿can￿be￿assembled￿without￿the￿oil
spray￿nozzle,￿there￿is￿the￿danger￿of￿it￿being￿forgotten￿during￿fitting.
Make￿sure￿when￿fitting￿the￿oil￿spray￿nozzle￿that￿it￿is￿correctly￿positioned￿and￿engaged.￿An￿incorrectly
engaged￿oil￿spray￿nozzle￿will￿be￿subjected￿to￿vibrations￿and￿may￿break.￿Refer￿to￿the￿repair￿instructions.

N20￿Engine
4.￿Cooling
93The￿cooling￿system￿is￿very￿similar￿to￿the￿N55￿engine.￿In￿the￿N20￿engine￿an￿engine￿oil-to-coolant￿heat
exchanger￿is￿used￿to￿cool￿the￿engine￿oil.￿The￿cooling￿system￿is￿controlled￿(e.g.￿electric￿coolant￿pump,
map￿thermostat￿and￿electric￿fan)￿by￿the￿heat￿management￿coordinator￿in￿the￿DME.
4.1.￿Overview
N20￿engine,￿cooling￿circuit
Index Explanation
1 Radiator
2 Electric￿fan
3 Map￿thermostat
4 Heater￿for￿map￿thermostat
5 Fill￿level￿sensor￿in￿expansion￿tank
6 Expansion￿tank
7 Exhaust￿turbocharger

N20￿Engine
4.￿Cooling
94Index Explanation
8 Heater￿core
9 Engine￿oil-to-coolant￿heat￿exchanger
10 Coolant￿temperature￿sensor
11 Electric￿coolant￿pump
The￿cooling￿module￿itself￿only￿comes￿in￿one￿variant.￿An￿auxiliary￿radiator￿(in￿the￿right￿wheel￿arch)￿is
used￿in￿vehicles￿used￿in￿hot￿climates￿markets￿and￿in￿combination￿with￿the￿maximum￿speed￿optional
equipment.
The￿electric￿fan￿has￿a￿nominal￿power￿of￿600 W.
The￿following￿graphics￿show￿the￿installation￿locations￿and￿layouts￿of￿the￿components.
N20￿engine,￿cooling￿system￿components￿from￿rear

N20￿Engine
4.￿Cooling
95Index Explanation
1 Engine￿oil-to-coolant￿heat￿exchanger
2 Engine￿return,￿bypass￿circuit
3 Map￿thermostat
4 Radiator
5 Ventilation￿line
6 Expansion￿tank
7 Engine￿feed
8 Electric￿coolant￿pump
9 Auxiliary￿radiator￿(not￿installed￿in￿all￿models)
10 Feed,￿heater￿core
11 Return,￿heater￿core
N20￿engine,￿cooling￿system￿components￿on￿engine￿front￿view

N20￿Engine
4.￿Cooling
96Index Explanation
1 Expansion￿tank
2 Map￿thermostat
3 Engine￿return,￿bypass￿circuit
4 Engine￿oil-to-coolant￿heat￿exchanger
5 Connection,￿feed,￿heater￿core
6 Feed,￿radiator
7 Return,￿heater￿core
8 Electric￿coolant￿pump
9 Return,￿radiator
4.2.￿Heat￿management
The￿N20￿engine￿has￿the￿same￿heat￿management￿functions￿in￿the￿DME￿as￿the￿N55.￿This￿allows
independent￿control￿of￿the￿electric￿cooling￿components￿of￿electric￿fan,￿map￿thermostat￿and￿coolant
pump.
4.2.1.￿Coolant￿pump
The￿N20￿engine￿has￿an￿electric￿coolant￿pump,￿as￿is￿the￿case￿with￿many￿BMW￿engines.￿Its￿nominal
power￿consumption￿is￿400 W.
N20￿engine,￿coolant￿pump
If￿the￿coolant￿pump￿is￿removed￿but￿is￿to￿be￿reused,￿it￿is￿important￿to￿ensure￿that￿it￿is￿set￿down￿still￿filled
with￿coolant.￿Drying￿out￿may￿cause￿the￿bearings￿to￿stick.￿Not￿following￿this￿procedure￿can￿possibly
cause￿the￿coolant￿pump￿not￿start,￿which￿in￿turn￿may￿result￿in￿damage￿to￿the￿engine.
Before￿installing,￿turn￿the￿pump￿impeller￿manually￿to￿ensure￿that￿it￿moves￿freely.

N20￿Engine
4.￿Cooling
974.2.2.￿Map￿thermostat
The￿N20￿engine￿is￿fitted￿with￿a￿conventional￿map￿thermostat￿which￿has￿the￿following￿technical￿data￿in
non-electrically￿controlled￿mode:
Setting￿of￿map￿thermostat Coolant￿temperature
Starts￿to￿open 97 ±2 °C￿/￿206￿±2 °F
Fully￿open 109 °C￿/￿228￿±2 °F
In￿addition,￿an￿electric￿heater￿in￿the￿map￿thermostat￿can￿be￿used￿to￿make￿the￿thermostat￿open￿at￿a
lower￿coolant￿temperature.
4.2.3.￿Heat￿management￿function
The￿heat￿management￿determines￿the￿current￿cooling￿requirement￿and￿controls￿the￿cooling￿system
accordingly.￿Under￿certain￿circumstances￿the￿coolant￿pump￿can￿even￿be￿shut￿down￿entirely,￿for
example￿in￿order￿to￿heat￿the￿coolant￿more￿quickly￿in￿the￿warm-up￿phase.￿The￿coolant￿pump￿continues
to￿deliver￿when￿the￿engine￿is￿stopped￿and￿very￿hot￿to￿cool￿the￿exhaust￿turbochargers.￿The￿cooling
output￿can￿therefore￿be￿requested￿independently￿of￿the￿engine￿speed.￿In￿addition￿to￿the￿map
thermostat￿the￿heat￿management￿is￿able￿to￿activate￿the￿coolant￿pump￿using￿different￿program￿maps.
The￿engine￿management￿is￿thus￿able￿to￿adapt￿the￿coolant￿temperature￿to￿the￿driving￿situation.
The￿following￿temperature￿ranges￿are￿adjusted￿by￿the￿engine￿management:
• 109 °C￿/￿228￿±2 °F=￿Economy￿operation
• 106 °C￿/￿222￿±2 °F=￿Normal￿operation
• 95 °C￿/￿203￿±2 °F=￿High￿operation
• 80 °C￿/￿176￿±2 °F=￿High￿operation￿and￿current￿supply￿to￿the￿map￿thermostat.
If￿the￿engine￿control￿unit￿identifies￿the￿”Economy”￿operating￿range￿on￿the￿basis￿of￿running
performance,￿the￿engine￿management￿adjusts￿to￿a￿higher￿temperature￿(109￿°C￿/￿228￿°F).￿In￿this
temperature￿range￿the￿engine￿is￿to￿be￿operated￿with￿a￿relatively￿low￿fuel￿requirement.￿Internal￿engine
friction￿is￿reduced￿at￿higher￿temperature.￿The￿temperature￿increase￿therefore￿favors￿the￿lower￿fuel
consumption￿in￿the￿low￿load￿range.￿In￿”High￿operation￿and￿current￿supply￿to￿the￿map￿thermostat”
mode￿the￿driver￿would￿like￿to￿utilize￿the￿engine's￿optimum￿power￿development.￿Thus￿the￿temperature
in￿the￿cylinder￿head￿is￿reduced￿to￿80￿°C￿/￿176￿°F￿for￿this￿purpose.￿This￿reduction￿improves￿volumetric
efficiency,￿which￿results￿in￿an￿engine￿torque￿increase.￿The￿engine￿control￿unit￿can￿now￿(adapted￿to
the￿relevant￿driving￿situation)￿adjust￿a￿specific￿operating￿range.￿It￿is￿therefore￿possible￿to￿influence
consumption￿and￿power￿output￿via￿the￿cooling￿system.
System￿protection
If￿the￿coolant￿or￿engine￿oil￿is￿subject￿to￿excessive￿temperatures￿during￿engine￿operation,￿certain
functions￿in￿the￿vehicle￿are￿influenced￿in￿such￿a￿way￿that￿more￿energy￿is￿made￿available￿for￿engine
cooling.
The￿measures￿are￿split￿into￿two￿operating￿modes:
• Component￿protection

N20￿Engine
4.￿Cooling
98- Coolant￿temperature￿from￿117￿°C/￿242￿°F
– Engine￿oil￿temperature￿from￿143￿°C￿/￿289￿°F￿at￿the￿oil￿pressure￿and￿temperature￿sensor￿in
the￿main￿oil￿passage
– Measure:￿e.g.￿power￿reduction￿of￿climate￿control￿and￿of￿engine
• Emergency
– Coolant￿temperature￿from￿122￿°C￿/￿251￿°F
– Engine￿oil￿temperature￿from￿151￿°C￿/￿303￿°F￿at￿the￿oil￿pressure￿and￿temperature￿sensor￿in
the￿main￿oil￿passage
– Measure:￿e.g.￿power￿reduction￿of￿engine￿(up￿to￿about.￿90￿%)
4.3.￿Internal￿engine￿cooling
As￿in￿the￿N55￿engine,￿the￿coolant￿passages￿in￿the￿cylinder￿head￿also￿surround￿the￿injectors,￿which￿are
cooled￿in￿this￿way.
Unlike￿the￿N55￿engine,￿the￿N20￿engine￿has￿no￿grooves￿on￿the￿block￿deck￿between￿the￿cylinders.
Instead,￿the￿N20￿engine￿has￿bore￿holes￿between￿the￿cylinders,￿two￿on￿each￿side,￿which￿meet￿in￿the
middle.
N20￿engine,￿cooling￿jacket￿and￿coolant￿passages
Index Explanation
1 Cooling￿jacket,￿exhaust￿side
2 Cooling￿jacket,￿intake￿side
3￿+￿4 Coolant￿passages￿in￿the￿lands

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
99The￿air￿intake￿and￿exhaust￿emission￿systems￿are￿in￿principle￿similar￿to￿the￿N55.￿The￿list￿below￿itemizes
the￿most￿important￿features￿of￿the￿air￿intake￿and￿exhaust￿emission￿systems:
• Permanently￿attached￿intake￿silencer
• Hot-film￿air￿mass￿meter
• TwinScroll￿exhaust￿turbocharger￿with￿integrated￿wastegate￿and￿blowoff￿valves
• Three￿connections￿for￿crankcase￿ventilation
5.1.￿Overview
N20￿engine,￿air￿intake￿and￿exhaust￿emission￿systems
Index Explanation
1 Charge￿air￿cooler
2 Blowoff￿valve
3 Intake￿silencer
4 Hot-film￿air￿mass￿meter
5 Exhaust￿turbocharger

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
100Index Explanation
6 Wastegate￿valve
7 Oxygen￿sensor￿before￿catalytic￿converter
8 Catalytic￿converter
9 Oxygen￿sensor￿after￿catalytic￿converter
10 Digital￿Engine￿Electronics￿(DME)
11 Intake￿manifold￿pressure￿sensor
12 Throttle￿valve
13 Charge￿air￿temperature￿and￿pressure￿sensor

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
1015.2.￿Intake￿air￿system
N20￿engine,￿air￿intake￿system
Index Explanation
1 Intake￿manifold
2 Intake￿manifold￿pressure￿sensor
3 Throttle￿valve
4 Charge￿air￿temperature￿and￿pressure￿sensor
5 Hot-film￿air￿mass￿meter
6 Intake￿silencer

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
102Index Explanation
7 Unfiltered￿air￿intake
8 Charge￿air￿cooler
9 Connection,￿crankcase￿ventilation,￿turbocharged￿mode
10 Connection,￿purge￿air￿line,￿crankcase￿ventilation
11 Blowoff￿valve
12 Exhaust￿turbocharger
5.2.1.￿Hot-film￿air￿mass￿meter
The￿N20￿engine￿is￿equipped￿with￿a￿hot-film￿air￿mass￿meter￿,￿which￿is￿very￿similar￿to￿that￿in￿the￿N74
engine.
It￿can￿generally￿be￿said￿that￿the￿quality￿of￿air￿mass￿determination￿by￿measurement￿using￿a￿hot-film￿air
mass￿meter￿and￿by￿calculation￿of￿the￿substitute￿value￿(of￿intake￿air￿temperature,￿charging￿pressure,
engine￿speed,￿etc.)￿is￿to￿be￿considered￿as￿equal￿in￿the￿current￿state￿of￿development.￿The￿calculated
substitute￿value￿is￿nevertheless￿used￿for￿engine￿load￿control.￿This￿value￿is￿however￿regularly￿adjusted
with￿the￿value￿of￿the￿hot-film￿air￿mass￿meter￿in￿order￿to￿compensate￿for￿tolerances￿which￿arise￿on
account￿of￿the￿complex￿flow￿conditions￿in￿the￿air￿intake￿system.￿The￿more￿sophisticated￿the￿mixture
preparation￿method￿(Valvetronic,￿High￿Precision￿Injection￿(especially￿in￿conjunction￿with￿stratified
charge￿mode),￿TVDI),￿the￿more￿important￿it￿is￿to￿adjust￿the￿substitute￿value￿with￿the￿hot-film￿air￿mass
meter.￿TVDI￿is￿currently￿the￿most￿sophisticated￿mixture￿preparation￿method.￿For￿this￿reason,￿all￿TVDI
engines￿are￿also￿equipped￿with￿a￿hot-film￿air￿mass￿meter.
The￿use￿of￿a￿hot-film￿air￿mass￿meter￿also￿offers￿the￿opportunity￿of￿extended￿diagnostics,￿e.g.￿for￿tank
or￿crankcase￿ventilation,￿as￿these￿systems￿create￿a￿deviation￿in￿the￿air￿mass￿that￿can￿be￿interpreted
and￿used￿to￿diagnose￿running￿faults.
Failure￿or￿disconnection￿of￿the￿hot-film￿air￿mass￿meter￿does￿not￿immediately￿result￿in￿emergency
engine￿operation.￿However,￿impaired￿mixture￿preparation￿and￿therefore￿poorer￿emission￿values￿are
possible,￿which￿is￿why￿the￿emissions￿warning￿lamp￿(Check￿Engine￿Light)￿lights￿up.
5.2.2.￿Intake￿manifold
As￿in￿the￿N55￿engine,￿the￿Digital￿Engine￿Electronics￿(DME)￿is￿mounted￿on￿the￿intake￿manifold.
However,￿there￿are￿differences.￿First,￿the￿DME￿is￿located￿on￿the￿intake￿manifold￿and￿not￿under￿it.
Second,￿the￿intake￿manifold￿is￿not￿open￿after￿the￿DME￿is￿removed.￿Located￿between￿the￿intake
manifold￿and￿the￿DME￿is￿a￿metal￿plate￿(heat￿sink)￿which￿conducts￿heat￿away￿from￿the￿DME￿this￿plate￿is
cooled￿by￿the￿air￿flow￿of￿the￿intake￿manifold.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
103
N20￿engine,￿intake￿manifold￿with￿throttle￿valve
Index Explanation
1 Throttle￿valve
2 Intake￿manifold￿pressure￿sensor
3 Connection￿from￿tank￿vent￿valve
4 Metal￿plate￿for￿accommodating￿the￿DME
5 Intake￿manifold
Intake￿manifold￿pressure￿sensor
Located￿directly￿behind￿the￿throttle￿valve,￿at￿the￿entry￿to￿the￿intake￿manifold,￿is￿the￿intake￿manifold
pressure￿sensor.￿On￿closer￿inspection,￿it￿can￿be￿seen￿to￿be￿a￿combined￿pressure￿and￿temperature
sensor.￿The￿temperature￿signal￿is￿therefore￿not￿read￿out.￿The￿reason￿for￿using￿this￿sensor￿lies￿in￿the
concept￿of￿common￿parts.￿It￿is￿better￿to￿use￿the￿same￿sensor￿which￿is￿also￿used￿as￿the￿charge￿air
temperature￿and￿pressure￿sensor￿and￿simply￿not￿to￿read￿out￿the￿temperature￿signal￿than￿to￿introduce￿a
separate￿sensor.
5.3.￿Exhaust￿turbocharger
The￿N20￿engine￿features￿an￿exhaust￿turbocharger￿with￿TwinScroll￿technology.￿It￿includes￿at￿the
turbine￿inlet￿two￿separate￿ports￿in￿which￿the￿exhaust￿gas￿is￿routed￿from￿two￿cylinders￿to￿the￿turbine
vanes.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
104
N20￿engine,￿turbocharger
Index Explanation
A Exhaust￿port,￿cylinders￿2￿and￿3
B Exhaust￿port,￿cylinders￿1￿and￿4
C Outlet￿to￿catalytic￿converter
D Inlet￿from￿intake￿silencer
E Ring￿port
F Outlet￿to￿charge￿air￿cooler
1 Vacuum￿unit￿for￿wastegate￿valve
2 Oil￿supply
3 Wastegate￿valve
4 Turbine￿wheel

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
105Index Explanation
5 Cooling￿passage
6 Oil￿passage
7 Coolant￿return
8 Blowoff￿valve
The￿turbocharger￿has￿a￿familiar￿design￿with￿an￿electric￿blowoff￿valve￿and￿a￿vacuum-controlled
wastegate￿valve.
5.3.1.￿Function￿of￿TwinScroll￿exhaust￿turbocharger
The￿designation￿TwinScroll￿denotes￿an￿exhaust￿turbocharger￿with￿a￿twin-scroll￿turbine￿housing.￿The
exhaust￿gas￿from￿two￿cylinders￿in￿each￿case￿is￿routed￿separately￿to￿the￿turbine.￿In￿the￿N20￿engine￿(as
is￿usual￿in￿4-cylinder￿engines)￿cylinders￿1￿and￿4￿and￿cylinders￿2￿and￿3￿are￿brought￿together￿to￿form￿two
ports￿each￿feeding￿one￿scroll.￿This￿results￿in￿pulse￿charging￿which￿is￿used￿to￿greater￿effect.
Pressure￿and￿pulse￿charging
Two￿principles￿of￿forced￿induction￿are￿used￿in￿engines￿with￿exhaust￿turbochargers￿–￿pressure￿and
pulse￿charging.￿Pressure￿charging￿means￿that￿the￿pressure￿ahead￿of￿the￿turbine￿is￿approximately
constant.￿The￿energy￿which￿drives￿the￿exhaust￿turbocharger￿is￿obtained￿from￿the￿pressure￿difference
before￿and￿after￿the￿turbine.
In￿the￿case￿of￿pulse￿charging,￿the￿pressure￿before￿the￿turbine￿is￿high-speed￿and￿greatly￿fluctuating,￿or
pulsating￿by￿the￿discharge￿of￿the￿exhaust￿gas￿from￿the￿combustion￿chamber.￿The￿pressure￿increase
results￿in￿a￿pressure￿wave￿which￿strikes￿the￿turbine.￿In￿this￿case,￿the￿kinetic￿energy￿of￿the￿exhaust￿gas
is￿used,￿whereby￿the￿pressure￿waves￿drive￿the￿turbocharger.
Pulse￿charging￿provides￿for￿a￿fast￿response￿by￿the￿turbocharger,￿especially￿at￿low￿speeds,￿because
pulsation￿is￿at￿its￿strongest￿here,￿whereas￿in￿the￿case￿of￿pressure￿charging￿the￿pressure￿difference
between￿before￿and￿after￿the￿turbine￿is￿still￿low.
In￿actual￿fact,￿both￿principles￿are￿always￿used￿in￿exhaust￿turbochargers￿in￿passenger￿car￿engines.￿The
proportion￿of￿pulse￿charging￿is￿higher￿or￿lower,￿depending￿on￿the￿size￿factors,￿the￿exhaust￿port￿guides
and￿the￿number￿of￿cylinders.
Dependence￿on￿the￿number￿of￿cylinders
In￿a￿single-cylinder￿engine￿there￿is￿an￿exhaust￿cycle￿every￿two￿revolutions￿of￿the￿crankshaft.
Theoretically,￿exhaust￿gas￿is￿therefore￿discharged￿for￿180°￿every￿720°￿crank￿angle.￿The￿graphic￿below
shows￿in￿highly￿simplified￿form￿the￿pressure￿conditions￿before￿the￿exhaust￿turbocharger￿in￿a￿single-
cylinder￿engine.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
106
Pressure￿diagram￿in￿exhaust￿port￿before￿the￿turbocharger￿in￿a￿1-cylinder￿engine
Index Explanation
A Bottom￿dead￿center,￿exhaust￿valve￿opens
B Top￿dead￿center,￿exhaust￿valve￿closes,￿intake￿valve￿opens
C Bottom￿dead￿center,￿intake￿valve￿closes
D Top￿dead￿center,￿ignition
As￿can￿be￿seen￿here,￿every￿720°￿CA￿there￿is￿a￿pressure￿wave￿which￿strikes￿the￿turbine.￿This￿pulse
accelerates￿the￿turbine.
The￿next￿graphic￿shows￿the￿pressure￿conditions￿before￿the￿turbine￿in￿a￿4-cylinder￿engine.
Pressure￿diagram￿in￿exhaust￿port￿before￿exhaust￿turbocharger￿in￿a￿4-cylinder￿engine
Index Explanation
1 Exhaust￿valve,￿1st￿cylinder,￿opens
2 Exhaust￿valve,￿2nd￿cylinder,￿opens
3 Exhaust￿valve,￿3rd￿cylinder,￿opens
4 Exhaust￿valve,￿4th￿cylinder,￿opens
Because￿each￿cylinder￿had￿its￿exhaust￿cycle￿after￿two￿full￿crankshaft￿revolutions,￿there￿are￿four
pressure￿waves￿within￿the￿720°￿CA.￿Because￿of￿the￿firing￿interval,￿they￿are￿distributed￿evenly￿at￿an
interval￿of￿180°￿CA.￿The￿pressure￿waves￿are￿superimposed￿here.￿While￿the￿pressure￿of￿one￿cylinder
decreases,￿the￿pressure￿of￿the￿next￿cylinder￿is￿already￿increasing.
This￿produces￿a￿superimposed￿pressure￿before￿the￿turbine,￿as￿the￿next￿graphic￿shows.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
107
Pressure￿diagram￿in￿exhaust￿port￿before￿the￿turbocharger￿in￿a￿4-cylinder￿engine,￿superimposed
Because￿they￿are￿superimposed,￿the￿pressure￿difference￿from￿minimum￿to￿maximum￿is￿clearly￿lower.
In￿this￿way,￿the￿pulse￿by￿the￿pressure￿wave￿on￿the￿turbine￿also￿decreases.￿In￿this￿cases,￿the￿proportion
of￿pulse￿supercharging￿in￿the￿exhaust￿turbocharger￿is￿lower.
One￿way￿of￿preventing￿this￿in￿a￿4-cylinder￿engine￿is￿the￿TwinScroll￿exhaust￿turbocharger.￿By￿splitting
the￿four￿cylinders￿into￿two￿ports,￿the￿pressure￿conditions￿of￿a￿2-cylinder￿engine￿are￿depicted￿in￿the￿two
ports￿in￿each￿case,￿as￿the￿following￿graphic￿shows.
Pressure￿diagram￿in￿exhaust￿port￿before￿the￿turbocharger￿in￿a￿4-cylinder￿engine,￿individually￿and￿superimposed
Index Explanation
1 Exhaust￿valve,￿1st￿cylinder,￿opens
4 Exhaust￿valve,￿4th￿cylinder,￿opens
Here￿too￿the￿pressures￿of￿the￿two￿cylinders￿are￿superimposed.￿However,￿cylinders￿1￿and￿4￿and￿2￿and￿3
are￿combined￿in￿the￿two￿ports.￿Because￿of￿the￿firing￿order￿of￿a￿4-cylinder￿engine,￿there￿is￿in￿each￿case
an￿interval￿of￿360°￿CA￿between￿the￿exhaust￿cycles￿of￿a￿port.￿Thus￿there￿is￿a￿large￿pressure￿difference
and￿the￿kinetic￿energy￿of￿the￿exhaust￿gas￿can￿be￿better￿utilized.
A￿specially￿shaped￿exhaust￿manifold￿is￿used￿to￿combine￿the￿exhaust￿pipes￿from￿cylinders￿1￿and￿4￿and
2￿and￿3.
In￿the￿turbocharger￿these￿two￿ports￿run￿separately￿from￿each￿other￿up￿to￿the￿turbine.￿The￿TwinScroll
exhaust￿turbocharger￿differs￿from￿a￿conventional￿exhaust￿turbocharger￿in￿that￿the￿turbine￿housing
separates￿in￿two￿forming￿a￿ring￿channel￿around￿the￿turbine.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
1085.4.￿Exhaust￿emission￿system
5.4.1.￿Exhaust￿manifold
The￿exhaust￿manifold￿is￿identical￿in￿design￿to￿that￿of￿the￿N55￿engine.￿It￿is￿air-gap-insulated￿and
welded￿to￿the￿turbocharger.￿The￿exhaust￿manifold￿in￿the￿N20￿engine￿is￿a￿four-into-two￿type,￿which
is￿necessary￿for￿the￿special￿function￿of￿the￿TwinScroll￿turbocharger.￿Here￿the￿exhaust￿outlet￿pipes￿of
cylinders￿1￿and￿4￿and￿2￿and￿3￿are￿combined￿in￿each￿case￿into￿one￿port￿as￿previously￿discussed.
N20￿engine,￿exhaust￿manifold￿with￿exhaust￿turbocharger
Index Explanation
1 Exhaust￿ports,￿cylinders￿1￿and￿4
2 Exhaust￿ports,￿cylinders￿2￿and￿3
3 Exhaust￿turbocharger
5.4.2.￿Catalytic￿converter
The￿N20￿engine￿has￿an￿upstream￿catalytic￿converter￿with￿two￿ceramic￿monoliths.

N20￿Engine
5.￿Air￿Intake/Exhaust￿Emission￿Systems
109
Cutaway￿view￿of￿catalytic￿converter
Index Explanation
1 Connection￿to￿exhaust￿system
2 De-coupling￿element
3 Monitoring￿sensor
4 Control￿sensor
5 Connection￿to￿turbine
6 Ceramic￿monolith￿1
7 Ceramic￿monolith￿2
Volume Diameter Number￿of￿cells
Ceramic￿monolith￿1 0.75 118.4 600
Ceramic￿monolith￿2 0.99 125 400
Oxygen￿sensors
The￿Bosch￿oxygen￿sensors￿used￿are￿familiar￿from￿previous￿engines:
• Pre￿oxygen￿sensor:￿LSU￿ADV
• Post￿oxygen￿sensor:￿LSF4.2.
The￿pre￿oxygen￿sensor￿is￿located￿ahead￿of￿the￿primary￿catalytic￿converter,￿as￿close￿as￿possible￿to￿the
turbine￿outlet.￿Its￿position￿has￿been￿chosen￿so￿that￿all￿the￿cylinders￿can￿be￿recorded￿separately.￿The
post￿oxygen￿sensor￿is￿positioned￿between￿the￿first￿and￿second￿ceramic￿monoliths.

N20￿Engine
6.￿Vacuum￿System
110The￿vacuum￿system￿of￿the￿N20￿engine￿is￿comparable￿with￿that￿of￿the￿N55￿engine.￿As￿well￿as￿supplying
the￿brake￿servo,￿it￿is￿needed￿primarily￿to￿activate￿the￿wastegate￿valve￿on￿the￿turbocharger.￿In￿addition,
the￿exhaust￿flap￿is￿actuated￿by￿vacuum￿in￿the￿N20￿engine.
N20￿engine,￿vacuum￿system
Index Explanation
1 Connection,￿brake￿servo
2 Vacuum￿pump
3 Connection,￿exhaust￿flap
4 Vacuum￿reservoir
5 Electro-pneumatic￿pressure￿converter￿for￿wastegate￿valve
6 Vacuum￿unit,￿wastegate￿valve

N20￿Engine
6.￿Vacuum￿System
111The￿vacuum￿pump￿as￿usual￿is￿designed￿to￿have￿two￿stages￿so￿that￿the￿majority￿of￿the￿generated
vacuum￿is￿made￿available￿to￿the￿brake￿servo.￿A￿vacuum￿reservoir￿is￿used￿to￿provide￿sufficient￿vacuum
for￿actuating￿the￿wastegate￿valve.￿This￿reservoir￿is￿built￿into￿the￿engine￿cover.
Disconnect￿the￿vacuum￿line￿before￿removing￿the￿engine￿cover,￿as￿otherwise￿there￿is￿a￿risk￿of￿damage.

N20￿Engine
7.￿Fuel￿Preparation
112The￿N20￿engine￿uses￿high-pressure￿injection,￿which￿was￿introduced￿in￿the￿N55￿engine.￿It￿differs￿from
high-precision￿injection￿(HPI)￿in￿that￿it￿uses￿solenoid￿valve￿injectors￿with￿multi-hole￿nozzles￿instead￿of
the￿piezoelectric￿type.
7.1.￿Overview
The￿following￿overview￿shows￿the￿fuel￿preparation￿system￿of￿the￿N20￿engine.￿It￿essentially
corresponds￿to￿the￿systems￿with￿direct￿fuel￿injection￿familiar￿in￿BMW￿models.
N20￿engine,￿fuel￿preparation

N20￿Engine
7.￿Fuel￿Preparation
113Index Explanation
1 Connection,￿quantity￿control￿valve
2 High-pressure￿pump
3 Low-pressure￿line
4 High-pressure￿line,￿rail￿-￿injector
5 High-pressure￿line,￿high-pressure￿pump￿-￿rail
6 Rail
7 Solenoid￿valve￿injector
Bosch￿high-pressure￿fuel￿injectors￿with￿the￿designation￿HDEV5.2￿are￿used.￿The￿high￿pressure￿pump￿is
already￿known￿from￿the￿8￿and￿12￿cylinder￿engines.￿An￿innovation￿in￿the￿N20￿engine￿is￿the￿fact￿that￿the
high-pressure￿lines￿from￿rail￿to￿injector￿are￿now￿no￿longer￿screwed￿at￿the￿rail￿end,￿but￿welded.￿Another
feature￿when￿compared￿with￿established￿BMW￿fuel￿systems￿is￿the￿omission￿of￿the￿fuel￿low-pressure
sensor.
Work￿on￿the￿fuel￿system￿is￿only￿permitted￿after￿the￿engine￿has￿cooled￿down.￿The￿coolant
temperature￿must￿be￿below￿40￿°C￿/￿104°F,￿to￿avoid￿risk￿of￿injury￿due￿to￿spray￿back￿from
residual￿pressure￿in￿the￿high-pressure￿fuel￿system.
When￿working￿on￿the￿high-pressure￿fuel￿system,￿it￿is￿essential￿to￿adhere￿to￿conditions￿of
absolute￿cleanliness￿and￿to￿observe￿the￿work￿sequences￿described￿in￿the￿repair￿instructions.
Even￿the￿slightest￿contamination￿and￿damage￿to￿the￿threaded￿fittings￿of￿the￿high-pressure
lines￿can￿cause￿leaks.
When￿working￿on￿the￿fuel￿system￿of￿the￿N20￿engine,￿it￿is￿important￿to￿ensure￿that￿the￿ignition￿coils
are￿not￿wet￿with￿fuel.￿The￿resistance￿of￿the￿insulating￿silicone￿material￿is￿greatly￿reduced￿by￿sustained
contact￿with￿fuel.￿This￿may￿result￿in￿arcing￿on￿the￿spark￿plug￿connection￿and￿thus￿in￿misfires.
• Before￿making￿any￿modifications￿to￿the￿fuel￿system,￿remove￿the￿ignition￿coils￿and￿protect￿the
spark￿plugs￿by￿covering￿with￿a￿cloth
• Before￿reinstalling￿the￿solenoid￿valve￿injectors,￿remove￿the￿ignition￿coils￿and￿ensure￿that￿the
cleanest￿possible￿conditions￿are￿maintained.
• Ignition￿coils￿heavily￿saturated￿by￿fuel￿must￿be￿replaced.
7.2.￿Fuel￿pump￿control
As￿already￿mentioned,￿there￿is￿no￿fuel￿low-pressure￿sensor￿in￿the￿N20￿engine.￿The￿fuel￿pressure￿is
calculated￿by￿monitoring￿pump￿speed￿and￿load.
7.3.￿High-pressure￿pump
The￿Bosch￿high-pressure￿pump,￿familiar￿from￿the￿N63￿and￿N74￿is￿used.￿This￿is￿a￿single-plunger￿pump
which￿is￿driven￿from￿the￿exhaust￿camshaft￿via￿a￿triple￿lobe￿on￿the￿cam.

N20￿Engine
7.￿Fuel￿Preparation
114For￿further￿information￿on￿the￿high-pressure￿pump,￿please￿refer￿to￿the￿N63￿and￿N74￿engine￿training
information￿available￿on￿TIS￿and￿ICP.
7.4.￿Injectors
The￿Bosch￿HDEV5.2￿solenoid￿valve￿injector￿is￿an￿inward-opening￿multi-hole￿valve￿unlike￿the￿outward-
opening￿piezo￿injector￿used￿in￿HPI￿engines.￿The￿HDEV5.2￿is￿also￿characterized￿by￿high￿variability￿with
regard￿to￿spray￿angle￿and￿spray￿pattern,￿and￿is￿configured￿for￿a￿system￿pressure￿of￿up￿to￿200￿bar.
These￿injectors￿are￿already￿used￿in￿the￿N55￿engine.￿However,￿their￿operating￿principle￿is￿the￿same￿as
that￿of￿the￿injectors￿used￿in￿the￿N73￿engines.
Note:￿The￿N73￿HDEV￿control￿modules￿contain￿pulse￿width￿modulated￿final￿output￿stages
with￿high￿performance￿capacitors￿to￿transform￿the￿system￿voltage￿up￿to￿85￿to￿100￿volts.￿See
ST042￿E65￿Complete￿Vehicle￿/N73￿engine￿training￿material￿available￿on￿TIS￿and￿ICP.

N20￿Engine
7.￿Fuel￿Preparation
115
Index Explanation
1Fuel￿line￿connection
2Electrical￿connection
3Stem
4Compression￿spring
5Solenoid￿coil
6Armature
7Nozzle￿pintle
86-hole￿nozzle
A￿magnetic￿field￿is￿generated￿when￿the￿coil￿is￿energized.￿This￿magnetic￿field￿lifts￿the￿nozzle￿pintle
against￿spring￿pressure￿off￿the￿valve￿seat￿and￿opens￿the￿discharge￿holes￿of￿the￿injector￿nozzle.￿The
high￿pressure￿in￿the￿rail￿forces￿the￿fuel￿through￿discharge￿holes￿at￿high￿speed￿into￿the￿cylinder.￿To
terminate￿injection,￿current￿is￿shut￿off,￿the￿nozzle￿pintle￿is￿forced￿closed￿by￿spring￿force￿back￿onto￿the
valve￿seat.

N20￿Engine
7.￿Fuel￿Preparation
116The￿valve￿opens￿and￿closes￿at￿very￿high￿speed￿and￿ensures￿a￿constant￿opening￿cross-section￿during
the￿opening￿period.￿The￿injected￿fuel￿quantity￿is￿dependent￿on￿the￿rail￿pressure,￿the￿back￿pressure￿in
the￿combustion￿chamber￿and￿the￿opening￿period￿of￿the￿injector.
For￿further￿information￿on￿injector￿activation,￿refer￿to￿the￿section￿entitled￿Engine￿Electrical￿System￿of
this￿training￿material.
Unlike￿the￿injectors￿previously￿used,￿the￿solenoid￿valve￿injectors￿of￿the￿N55￿and￿N20￿engines￿have
long￿and￿relatively￿sensitive￿stems￿made￿necessary￿by￿the￿shape￿of￿the￿cylinder￿head.￿Each￿stem￿is
made￿of￿plastic￿on￿the￿outside￿but￿on￿the￿inside￿there￿is￿a￿metal￿tube￿serves￿as￿a￿fuel￿line.
The￿stems￿of￿the￿solenoid￿valve￿injectors￿can￿only￿withstand￿6Nm￿of￿torque￿which￿translates
to￿2000￿N￿of￿tensile￿force.￿It￿is￿essential￿when￿removing￿and￿installing￿the￿injectors￿to￿follow
the￿specific￿procedure￿set￿out￿in￿the￿repair￿instructions,￿along￿with￿the￿use￿of￿special￿tool￿#0
496￿885￿for￿injector￿removal.￿If￿this￿tool￿is￿not￿used￿the￿injectors￿will￿be￿damaged .

N20￿Engine
8.￿Fuel￿Supply
117The￿fuel￿supply￿is￿vehicle-specific.￿Hardly￿any￿changes￿have￿been￿made￿to￿the￿already￿existing
models.￿Therefore￿only￿the￿tank￿ventilation￿system￿on￿the￿engine￿will￿be￿described￿in￿greater￿detail
here.
8.1.￿Tank￿ventilation
Similar￿to￿the￿N55
8.1.1.￿Two-stage￿tank￿ventilation
The￿two-stage￿tank￿venting￿is￿used￿on￿the￿N20￿engine.￿This￿sophisticated￿system￿is￿made￿necessary
by￿the￿TVDI￿technology,￿because￿in￿this￿case￿sufficient￿vacuum￿in￿the￿intake￿manifold￿is￿much￿less
common.￿This￿was￿introduced￿with￿the￿N55￿engine.

N20￿Engine
8.￿Fuel￿Supply
118
N20￿engine,￿tank￿ventilation
Index Explanation
1 Intake￿silencer
2 Charge￿air￿pipe￿(from￿charge￿air￿cooler￿to￿throttle￿valve)
3 T-connector￿with￿suction￿jet￿pump
4 Clean￿air￿pipe￿(from￿intake￿silencer￿to￿exhaust￿turbocharger)
5 Connection￿of￿purge￿air￿line,￿crankcase￿ventilation

N20￿Engine
8.￿Fuel￿Supply
119Index Explanation
6 Connection￿of￿tank￿ventilation￿to￿clean￿air￿pipe
7 Intake￿manifold
8 Line￿from￿carbon￿canister￿of￿tank￿ventilation￿system
9 Tank￿vent￿valve￿with￿shut￿off￿valve
10 Throttle￿valve
11 Connection￿before￿throttle￿valve￿for￿driving￿suction￿jet￿pump
However,￿a￿suction￿jet￿pump￿is￿additionally￿used￿in￿view￿of￿the￿fact￿that￿sufficient￿vacuum￿cannot
always￿be￿guaranteed￿in￿the￿clean￿air￿pipe.￿In￿order￿to￿drive￿this￿pump,￿the￿line￿to￿the￿suction￿jet￿pump
is￿connected￿before￿the￿throttle￿valve.￿This￿creates￿a￿connection￿between￿the￿charge￿air￿pipe￿and￿the
clean￿air￿pipe.￿In￿turbocharged￿mode￿the￿pressure￿in￿the￿charge￿air￿pipe￿is￿always￿higher￿than￿in￿the
clean￿air￿pipe,￿which￿generates￿in￿this￿line￿a￿flow￿to￿the￿clean￿air￿pipe.
N20￿engine,￿T-connector￿with￿suction￿jet￿pump￿for￿tank￿ventilation
Index Explanation
1 Line￿to￿clean￿air￿pipe
2 Line￿from￿tank￿vent￿valve
3 T-connector￿with￿suction￿jet￿pump
4 Line￿from￿charge￿air￿pipe
The￿line￿from￿the￿tank￿vent￿valve￿is￿connected￿to￿this￿suction￿jet￿pump.￿The￿venturi￿effect￿ensures￿that
the￿carbon￿canister￿is￿safely￿purged.
Non-return￿valves￿on￿both￿lines￿from￿the￿tank￿vent￿valve￿ensure￿that￿there￿is￿no￿return￿flow￿into￿the
tank￿vent￿valve￿in￿the￿event￿of￿excess￿pressure￿in￿these￿lines.
8.1.2.￿Two-stage￿tank￿ventilation￿with￿shutoff￿valve
The￿two￿stage￿tank￿ventilation￿has￿a￿second￿electrical￿valve￿which￿is￿very￿similar￿in￿design￿to￿the￿tank
vent￿valve.￿This￿is￿known￿as￿a￿shutoff￿valve.

N20￿Engine
8.￿Fuel￿Supply
120The￿shutoff￿valve￿serves￿to￿diagnose￿the￿second￿point￿of￿admission￿and￿is￿designed￿to￿close￿off￿the
first￿admission￿into￿the￿intake￿manifold￿under￿certain￿conditions.
N20￿engine,￿tank￿vent￿valve
Index Explanation
1 Connection￿after￿throttle￿valve
2 Line￿for￿connection￿to￿clean￿air￿pipe
3 Tank￿vent￿valve
4 Connection￿from￿carbon￿canister
5 Shutoff￿valve
It￿is￿mounted￿directly￿below￿the￿tank￿vent￿valve￿and￿is￿able￿to￿seal￿off￿the￿line￿to￿the￿throttle￿valve.

N20￿Engine
8.￿Fuel￿Supply
121
N20￿engine,￿overview,￿two-stage￿version￿of￿tank￿ventilation￿with￿second￿valve
Index Explanation
1 Intake￿silencer
2 Exhaust￿turbocharger
3 T-connector￿with￿suction￿jet￿pump
4 Throttle￿valve
5 Non-return￿valve￿for￿connection￿to￿clean￿air￿pipe
6 Tank￿vent￿valve
7 Non-return￿valve￿for￿connection￿after￿throttle￿valve
8 Shutoff￿valve
The￿shutoff￿valve￿is￿powered￿closed￿and￿spring￿loaded￿open￿at￿zero￿current.

N20￿Engine
9.￿Engine￿Electrical￿System
1229.1.￿Overview
N20￿engine,￿system￿wiring￿diagram￿MEVD17.2.4

N20￿Engine
9.￿Engine￿Electrical￿System
123Index Explanation
1 Engine￿electronics￿Valvetronic￿direct￿fuel￿injection￿MEVD17.2.4
2 Ambient￿pressure￿sensor
3 Temperature￿sensor
4 A/C￿compressor
5 Junction￿box￿electronics
6 Refrigerant￿pressure￿sensor
7 Electronic￿fuel￿pump￿control
8 Electric￿fuel￿pump
9 Car￿Access￿System￿CAS
10 Brake￿light￿switch
11 Starter￿motor
12 DME￿main￿relay
13 Clutch￿module
14 Relay,￿Valvetronic
15 Relay,￿ignition￿and￿injectors
16 Relay,￿terminal￿30￿switched
17 Diagnosis￿module,￿tank￿ventilation
18 Relay￿for￿electric￿fan
19 Electric￿fan
20 Map￿thermostat
21 Blowoff￿valve
22 Tank￿vent￿valve
23 VANOS￿solenoid￿actuator,￿intake￿camshaft
24 VANOS￿solenoid￿actuator,￿exhaust￿camshaft
25 Switchable￿engine￿sound￿system
26 Map￿control￿valve
27 Electro-pneumatic￿pressure￿converter￿for￿wastegate￿valve
28 Quantity￿control￿valve
29￿–￿32 Injectors
33￿–￿36 Ignition￿coils
37 Engine￿ventilation￿heating
38 Ground￿connections
39 Oxygen￿sensor￿after￿catalytic￿converter￿(monitoring￿sensor)
40 Oxygen￿sensor￿before￿catalytic￿converter￿(control￿sensor)
41 Diagnostic￿socket

N20￿Engine
9.￿Engine￿Electrical￿System
124Index Explanation
42 Intake￿manifold￿pressure￿sensor
43 Rail￿pressure￿sensor
44 Charge￿air￿temperature￿and￿pressure￿sensor
45 Knock￿sensor￿1￿–￿2
46 Knock￿sensor￿3￿–￿4
47 Hot-film￿air￿mass￿meter
48 Camshaft￿sensor,￿intake￿camshaft
49 Camshaft￿sensor,￿exhaust￿camshaft
50 Crankshaft￿sensor
51 Accelerator￿pedal￿module
52 Throttle￿valve
53 Coolant￿temperature￿sensor
54 Oil￿pressure￿and￿temperature￿sensor
55 Thermal￿oil￿level￿sensor
56 Valvetronic￿servomotor
57 Dynamic￿Stability￿Control￿DSC
58 Intelligent￿battery￿sensor￿IBS
59 Alternator
60 Coolant￿pump
9.2.￿Engine￿control￿unit
The￿N20￿engine￿features￿Digital￿Engine￿Electronics￿from￿Bosch￿with￿the￿designation￿MEVD17.2.4.￿It
is￿closely￿related￿to￿the￿DME￿of￿the￿N55￿engine￿(MEVD17.2)￿and￿is￿also￿engine-mounted￿on￿the￿intake
manifold.

N20￿Engine
9.￿Engine￿Electrical￿System
125
N20￿engine,￿Digital￿Engine￿Electronics
Index Explanation
1 Intake￿manifold
2 Digital￿Engine￿Electronics
3 Throttle￿valve
Do￿not￿attempt￿trial￿and￿error￿replacement￿of￿control￿units.
Because￿of￿the￿electronic￿immobilizer,￿a￿trial￿and￿error￿replacement￿of￿control￿units￿from￿other
vehicles￿must￿not￿be￿attempted￿under￿any￿circumstances.￿An￿immobilizer￿adjustment￿cannot
be￿reversed.
The￿N20￿engine￿DME￿(MEVD17.2.4)￿is￿designed￿to￿be￿mounted￿on￿the￿engine's￿intake￿manifold
on￿an￿aluminium￿heat￿sink￿plate.￿The￿DME￿is￿cooled￿through￿the￿heat￿sink￿plate￿by￿the￿air￿flowing
through￿the￿intake￿manifold.￿It￿is￿important￿for￿the￿DME￿to￿be￿correctly￿mounted￿on￿the￿heat￿sink￿plate
(tightening￿torque,￿good￿level￿contact)￿so￿as￿to￿ensure￿heat￿transfer￿to￿the￿plate￿and￿thereby￿cool￿the
DME.
The￿connection￿concept￿is￿identical￿to￿the￿MEVD17.2￿in￿the￿N55￿engine.￿There￿is￿a￿logical￿division￿into
six￿modules.

N20￿Engine
9.￿Engine￿Electrical￿System
126
N20￿engine,￿MEVD17.2.4￿connections
Index Explanation
1 Module￿100,￿vehicle￿connection,￿48￿pins
2 Module￿200,￿sensors￿and￿actuators￿1,￿58￿pins
3 Module￿300,￿sensors￿and￿actuators￿2,￿58￿pins
4 Module￿400,￿Valvetronic￿servomotor,￿11￿pins
5 Module￿500,￿DME￿supply,￿12￿pins
6 Module￿600,￿fuel￿injection￿and￿ignition,￿24￿pins
9.2.1.￿Overall￿function
The￿Digital￿Engine￿Electronics￿(DME)￿is￿the￿computing￿and￿switching￿center￿of￿the￿engine
management￿system.￿Sensors￿on￿the￿engine￿and￿the￿vehicle￿deliver￿the￿input￿signals.￿The￿signals
for￿activating￿the￿actuators￿are￿calculated￿from￿the￿input￿signals,￿the￿nominal￿values￿calculated￿using
a￿computing￿model￿in￿the￿DME￿control￿unit￿and￿the￿stored￿program￿maps.￿The￿DME￿control￿unit
activates￿the￿actuators￿directly￿or￿via￿relays.
The￿DME￿control￿unit￿is￿woken￿up￿via￿the￿wake-up￿line￿(terminal￿15￿Wake￿up)￿by￿the￿Car￿Access
System￿(CAS).

N20￿Engine
9.￿Engine￿Electrical￿System
127The￿after-run￿starts￿after￿terminal￿15￿OFF.￿The￿adaptation￿values￿are￿stored￿during￿the￿after-run.￿The
DME￿control￿unit￿uses￿a￿bus￿signal￿to￿signal￿its￿readiness￿to￿“go￿to￿sleep”.￿When￿all￿the￿participating
control￿units￿have￿signalled￿their￿readiness￿to￿“go￿to￿sleep”,￿the￿bus￿master￿outputs￿a￿bus￿signal￿and
the￿control￿units￿terminate￿communication￿five￿seconds￿later.
The￿printed￿circuit￿board￿in￿the￿DME￿control￿unit￿accommodates￿two￿sensors:￿a￿temperature￿sensor
and￿an￿ambient￿pressure￿sensor.￿The￿temperature￿sensor￿is￿used￿to￿monitor￿the￿temperature￿of￿the
components￿in￿the￿DME￿control￿unit.￿The￿ambient￿pressure￿is￿required￿for￿calculating￿the￿mixture
composition.

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