N20 Engine PDF

Technicaltraining.
Productinformation.
N20Engine
BMWService
Generalinformation
Symbolsused
Thefollowingsymbol/signisusedinthisdocumenttofacilitatebettercomprehensionandtodraw
attentiontoparticularlyimportantinformation:
Containsimportantsafetyguidanceandinformationthatisnecessaryforpropersystemfunctioning
andwhichitisimperativetofollow.
Informationstatusandnational-marketversions
TheBMWGroupproducesvehiclestomeettheveryhigheststandardsofsafetyandquality.Changes
intermsofenvironmentalprotection,customerbenefitsanddesignmakeitnecessarytodevelop
systemsandcomponentsonacontinuousbasis.Consequently,thismayresultindifferencesbetween
thecontentofthisdocumentandthevehiclesavailableinthetrainingcourse.
Asageneralprinciple,thisdocumentdescribesleft-handdrivevehiclesintheEuropeanversion.Some
controlsorcomponentsarearrangeddifferentlyinright-handdrivevehiclesthanthoseshownonthe
graphicsinthisdocument.Furtherdiscrepanciesmayarisefrommarketspecificorcountry-specific
equipmentspecifications.
Additionalsourcesofinformation
Furtherinformationontheindividualtopicscanbefoundinthefollowing:
Owner'sHandbook
IntegratedServiceTechnicalApplication.
Contact:conceptinfo@bmw.de
2010BMWAG,Munich,Germany
ReprintsofthispublicationoritspartsrequirethewrittenapprovalofBMWAG,Munich
TheinformationinthedocumentispartoftheBMWGrouptechnicaltrainingcourseandisintended
foritstrainersandparticipants.RefertothelatestrelevantBMWGroupinformationsystemsforany
changes/supplementstothetechnicaldata.
Contacts
GernotNehmeyer/UdoMetz
Telephone+49(0)8938234059/+49(0)8938258506
gernot.nehmeyer@bmw.de/udo.metz@bmw.de
Informationstatus:November2010
BV-72/TechnicalTraining
N20Engine
Contents
1. Introduction............................................................................................................................................................................................................................................. 1
1.1. History...................................................................................................................................................................................................................................... 1
1.1.1. HistoricBMWAGengines..................................................................................................................................... 1
1.1.2. HistoricBMWMengines........................................................................................................................................ 3
1.2. Technicaldata............................................................................................................................................................................................................. 3
1.2.1. Comparison ................................................................................................................................................................................. 4
1.3. Newfeatures/changes....................................................................................................................................................................................6
1.3.1. Overview............................................................................................................................................................................................. 6
1.4. Engineidentification......................................................................................................................................................................................... 7
1.4.1. Enginedesignation............................................................................................................................................................ 7
1.4.2. Engineidentification........................................................................................................................................................ 8
2. EngineComponents........................................................................................................................................................................................................... 11
2.1. Enginehousing..................................................................................................................................................................................................... 11
2.1.1. Engineblock............................................................................................................................................................................ 12
2.1.2. Cylinderheadgasket................................................................................................................................................. 16
2.1.3. Cylinderhead......................................................................................................................................................................... 17
2.1.4. Cylinderheadcover..................................................................................................................................................... 18
2.1.5. Oilsump......................................................................................................................................................................................... 24
2.2. Crankshaftdrive................................................................................................................................................................................................... 27
2.2.1. Crankshaftwithbearings..................................................................................................................................... 27
2.2.2. Connectingrod ................................................................................................................................................................. 42
2.2.3. Pistonwithpistonrings......................................................................................................................................... 43
2.3. Camshaftdrive....................................................................................................................................................................................................... 45
2.4. Counterbalanceshafts.............................................................................................................................................................................. 46
2.5. Valvegear.......................................................................................................................................................................................................................50
2.5.1. Design................................................................................................................................................................................................ 50
2.5.2. Valvetronic................................................................................................................................................................................... 55
2.6. Beltdrive......................................................................................................................................................................................................................... 63
3. Oil Supply...............................................................................................................................................................................................................................................65
3.1. Overview.......................................................................................................................................................................................................................... 65
3.1.1. Hydrauliccircuitdiagram..................................................................................................................................... 66
3.1.2. Oilpassages.............................................................................................................................................................................68
3.2. Oilpumpandpressurecontrol.................................................................................................................................................... 73
3.2.1. Oilpump......................................................................................................................................................................................... 73
3.2.2. Control............................................................................................................................................................................................... 75
3.2.3. Pressure-limitingvalve............................................................................................................................................ 83
3.3. Oilfilteringandcooling............................................................................................................................................................................ 84
3.3.1. Oilcooling.................................................................................................................................................................................... 84
3.3.2. Oilfiltering................................................................................................................................................................................... 85
N20Engine
Contents
3.4. Oilmonitoring.......................................................................................................................................................................................................... 86
3.4.1. Oilpressureandtemperaturesensor.............................................................................................. 86
3.4.2. Oillevelmonitoring....................................................................................................................................................... 87
3.5. Oilspraynozzles.................................................................................................................................................................................................87
3.5.1. Pistoncrowncooling..................................................................................................................................................87
3.5.2. Chaindrive.................................................................................................................................................................................. 88
3.5.3. Camshaft........................................................................................................................................................................................89
3.5.4. Gearing,Valvetronicservomotor..............................................................................................................91
4. Cooling.........................................................................................................................................................................................................................................................93
4.1. Overview.......................................................................................................................................................................................................................... 93
4.2. Heatmanagement........................................................................................................................................................................................... 96
4.2.1. Coolantpump........................................................................................................................................................................ 96
4.2.2. Mapthermostat.................................................................................................................................................................. 97
4.2.3. Heatmanagementfunction............................................................................................................................. 97
4.3. Internalenginecooling............................................................................................................................................................................. 98
5. AirIntake/ExhaustEmissionSystems.............................................................................................................................................. 99
5.1. Overview.......................................................................................................................................................................................................................... 99
5.2. Intakeairsystem............................................................................................................................................................................................ 101
5.2.1. Hot-filmairmassmeter..................................................................................................................................... 102
5.2.2. Intakemanifold................................................................................................................................................................ 102
5.3. Exhaustturbocharger............................................................................................................................................................................. 103
5.3.1. FunctionofTwinScrollexhaustturbocharger................................................................. 105
5.4. Exhaustemissionsystem................................................................................................................................................................ 108
5.4.1. Exhaustmanifold.......................................................................................................................................................... 108
5.4.2. Catalyticconverter..................................................................................................................................................... 108
6. VacuumSystem...................................................................................................................................................................................................................... 110
7. FuelPreparation.................................................................................................................................................................................................................... 112
7.1. Overview...................................................................................................................................................................................................................... 112
7.2. Fuelpumpcontrol........................................................................................................................................................................................113
7.3. High-pressurepump................................................................................................................................................................................ 113
7.4. Injectors........................................................................................................................................................................................................................ 114
8. FuelSupply..................................................................................................................................................................................................................................... 117
8.1. Tankventilation................................................................................................................................................................................................. 117
8.1.1. Two-stagetankventilation............................................................................................................................117
8.1.2. Two-stagetankventilationwithshutoffvalve.................................................................119
9. EngineElectricalSystem..................................................................................................................................................................................... 122
N20Engine
Contents
9.1. Overview...................................................................................................................................................................................................................... 122
9.2. Enginecontrolunit..................................................................................................................................................................................... 124
9.2.1. Overallfunction............................................................................................................................................................... 126
N20Engine
1.Introduction
BMWhasdecidedtobringbackthe4cylinderenginetotheUSmarket.ThelastBMW4cylinder
engineintheUSwastheM44,thislasteduntil1999andwasinstalledintheE36318is/318ti/Z3.
SincethenBMWintheUShasnothada4cylinderengine.TheN20enginerepresentsthenew
generationofBMW4-cylindergasolineengines.ItwillgraduallybephasedinonanumberofBMW
modelsstartinginSeptember2011.TheN20willreplacetheN526-cylindernaturallyaspirated
engines.TheN20engineisequippedwiththelatesttechnology,suchasTVDI(Turbocharged
ValvetronicDirectInjection)inconjunctionwithaTwinScrollexhaustturbocharger.Asawhole,itis
closelyrelatedtotheN55engine,thisiswhyconstantreferenceismadetotheN55engineinthis
document.
1.1.History
ThehistoryofBMW4-cylinderenginesbeganbackin1927withtheBMW3/15.Fromthatpointon,
apartfromaninterruptionstretchingfrom1936to1962,the4-cylindergasolineengineshaveagain
andagainbeentheprecursorstonewtechnologiesandhaveoftenalsobeenforerunners.Thus,
theM31engine(predecessoroftheM10engine)wastheworld'sfirst4-cylinderproductionengine
tofeatureaTwinScrollexhaustturbochargerandbackin1973alreadyachievingapoweroutputof
125kW/167bhpfromadisplacementof2liters.InmotorsportthecrankcaseoftheM10witha
displacementof1.5litersproducedthefirstFormula1worldchampionwithaturbochargedengine.In
theworldofmotorracingperformancefiguresofupto1350bhpfromadisplacementof1.5literswere
achieved,figureswhichtodatehaveonlybeenachievedbyBMW.
1.1.1.HistoricBMWAGengines
Designation Power Displacement Yearof Model Series

outputin in[cm] launch
bhp/rpm
DA1,2,4* 15/3000 748 1927 BMW3/15 3/15
DA3* 18/3500 748 1930 Wartburg 3/15
M68* 20/3500 782 1932 BMW3/20 3/20
M68* 22/4000 845 1934 BMW309 309
M115** 75/5700 1499 1961 BMW1500 115
M115** 80/5500 1499 1962 BMW1500 115
Availablein
theUS
M116** 83/5500 1573 1964 BMW1600 116
Availablein
theUS
M116** 85/5700 1573 1966 BMW 114C
1600-2
M116** 105/6000 1573 1967 BMW1600ti 116
M116** 75/5800 1573 1975 BMW1502 114
M118** 90/5250 1773 1963 BMW1800 118
M118** 110/5800 1773 1964 BMW1800ti 118
1
N20Engine
1.Introduction
bhp/rpm
M118** 130/6100 1773 1965 BMW 118
Availablein 1800tiSA
theUS
M118** 90/5250 1766 1968 BMW1800 118
short-stroke
M118** 90/5500 1766 1974 BMW518 E12/4
short-stroke
M05** 100/5500 1990 19651972 BMW 121
Availablein 2000/2002
theUS
M05** 120/5500 1990 1965 BMW2000ti 121
M15** 130/5800 1990 1968 BMW 121
Availablein 2000tii/2002tii
theUS
M17** 115/5800 1990 1972 BMW520 E12/4
M31** 170/5800 1990 1974 BMW E20
2002turbo
M41** 90/6000 1573 1975 BMW316 E21
M42** 98/5800 1766 1975 BMW318 E12
M42** 90/5500 1766 1976 BMW518 E12
M43/1** 109/5800 1990 1975 BMW320 E21
M64** 125/5700 1990 1975 BMW320i E21
M10(M92**) 105/5800 1766 1980 BMW318i E30
M10(M99**) 90/5500 1766 1980 BMW E30/E28
316/518
M98** 75/5800 1573 1981 BMW315 E21
M10 102/5800 1766 1984 BMW E30
Availablein 318iCat
theUS
M40B16 102/5500 1596 1988 BMW316i E30
M40B16 99/5500 1596 1988 BMW E30
316iCat
M40B18 116/5500 1796 1987 BMW318i E30
M40B18 113/5500 1796 1987 BMW E28/
318iCat E30/E34
BMW
518iCat
M42B18O0 140/6000 1796 1989 318is/318ti E36
Availablein
theUS
2
N20Engine
1.Introduction
bhp/rpm
M43B16O0 102/5500 1596 1993 316i E36
M43B16O0 87/5500 1596 1996 316g E36
M43B18O0 116/5500 1796 1993 318i/518i/ E34/E36
Z31.8
M43B19U1 105/5300 1895 2000 316i E46
M43B19O1 118/5500 1895 1998 318i/Z31.8 E36/E46
M44B19O0 149/6000 1895 1995 318is/318ti/ E36
Availablein Z31.9
theUS
*denotesenginesupto1933,**denotesenginesfrom19571980,Cat=catalyticconverterfrom
M42/1989datawithandwithoutcatalyticconverter.
Note:NotallenginesinthechartabovewereavailableintheUSmarket.TheM44B19O0was
thelast4cylinderengineavailableintheUSuptotheintroductionoftheN20in9/2011.
1.1.2.HistoricBMWMengines

bhp/rpm
S14B23 197/6750 2302 1986 BMWM3 E30
1.2.Technicaldata
Modeldesignation Enginedesignation Seriesintroduction
VariousBMWmodels N20B20O0 2012Modelyear
3
N20Engine
1.Introduction
1.2.1.Comparison
N20B20O0enginecomparedwithN52B30O1engine
Full-loaddiagram,N20B20O0enginecomparedwithN52B30O1engine
4
N20Engine
1.Introduction
Unit N52B30O1 N20B20O0
Design Inline6 Inline4
Displacement [cm] 2996 1997
Bore/stroke [mm] 85/88 84/90.091
Poweroutput kW/bhp 190/254 180/240
atenginespeed [rpm] 6600 5000-6500
Poweroutputperliter [kW/l] 63.4 90.14
Torque Nm/ft-lbs 310/228 350/255
atenginespeed [rpm] 2600-3000 1250-4800
Compressionratio [] 10.7 10.0:1
Valvespercylinder 4 4
Fuelconsumption l/100km 9.9 7,9
CO2emissions [g/km] 230 183
DigitalEngineElectronics MSV80 MEVD17.2.4
Exhaustemissionslegislation ULEVII ULEVII
5
N20Engine
1.Introduction
1.3.Newfeatures/changes
1.3.1.Overview
System Comment
Enginemechanical Aluminiumcrankcasewithcoatedcylinderbore
components
Optimizedcoolingjackets
UseoftheTVDItechnology
TwinScrollexhaustturbocharger
3rdgenerationValvetronicwithnewintermediatelevers
NewgenerationVANOSwithcentralvalves
Assembledcamshafts
Twomodecrankcaseventilation
Forgedcrankshaft
Positivecrankshaftoffset
Pistonwithnegativepinoffset
Chaindriveforcounterbalanceshaftswithchaintensioner
Counterbalanceshaftsarrangedontopofoneanother.
Oilsupply Map-controlledoilpump
Newpendulum-slideoilpumpdesign
Unfilteredoilcooling
Newcombinedoilpressureandtemperaturesensor.
Cooling Electriccoolantpump
Mapcontrolledthermostat.
Airintakeandexhaust TwinScrollexhaustturbocharger
emissionsystems
Hot-filmairmassmeter
Enhancedcrankcaseventilation.
6
N20Engine
1.Introduction
System Comment
Vacuumsystem Two-stagevacuumpump
Vacuumreservoirforthewastegatevalveisbuiltintothe
enginecover.
Fuelpreparation High-pressureinjection(asN55)
Solenoidvalveinjectors
Boschhigh-pressurepump
High-pressurelinestotheinjectorsaresolderedtotherail
Nofuellow-pressuresensor.
Engineelectricalsystem BoschMEVD17.2.4enginecontrolunit.
1.4.Engineidentification
1.4.1.Enginedesignation
TheN20engineisdescribedinthefollowingversion:N20B20O0.
ThetechnicaldocumentationalsofeaturestheshortformoftheenginedesignationN20,whichonly
allowsassignmentoftheenginetype.
Item Meaning Index/explanation

1 Enginedeveloper M,N=BMWGroup
P=BMWMotorsport
S=BMWMGmbH
W=non-BMWengines
2 Enginetype 1=Inline4(e.g.N12)
2=Inline4(e.g.N20)
4=Inline4(e.g.N43)
5=Inline6(e.g.N53)
6=V8(e.g.N63)
7=V12(e.g.N73)
8=V102(e.g.S85)
3 Changetothebasicengine 0=basicengine
concept 1to9=changes,e.g.
combustionprocess
4 Workingmethodorfueltype B=gasoline,longitudinal
andpossiblyinstallation installation
position D=diesel,longitudinal
installation
H=hydrogen
5 Displacementinliters 1=1liter+
7
N20Engine
1.Introduction
6 Displacementin1/10liter 8=0.8liters=1.8liters
7 Performanceclass K=Smallest
U=Lower
M=Middle
O=Upper(standard)
T=Top
S=Super
8 Revisionrelevanttoapproval 0=Newdevelopment
19=Revision
BreakdownofN20enginedesignation
Index Explanation
N BMWGroupDevelopment
2 4-cylinderin-lineengine
0 Enginewithexhaustturbocharger,Valvetronic
anddirectfuelinjection(TVDI)
B Gasolineengine,longitudinallyinstalled
20 2.0litersdisplacement
O Upperperformanceclass
0 Newdevelopment
1.4.2.Engineidentification
Theengineshaveanidentificationmarkonthecrankcasetoensureproperidentificationand
classification.
WiththeN55engine,thisidentificationwassubjecttoafurtherdevelopment,withthepreviouseight
positionsbeingreducedtoseven.Theenginenumbercanbefoundontheenginebelowtheengine
identification.Thisconsecutivenumber,inconjunctionwiththeengineidentification,allowsproper
identificationofeachindividualengine.
8
N20Engine
1.Introduction
1 Enginedeveloper M,N=BMWGroup
P=BMWMotorsport
S=BMWMGmbH
W=non-BMWengines
2 Enginetype 1=Inline4(e.g.N12)
2=Inline4(e.g.N20)
4=Inline4(e.g.N43)
5=Inline6(e.g.N53)
6=V8(e.g.N63)
7=V12(e.g.N73)
8=V102(e.g.S85)
3 Changetothebasicengine 0=basicengine
concept 1to9=changes,e.g.
combustionprocess
4 Workingmethodorfueltype B=gasoline,longitudinal
andpossiblyinstallation installation
position D=diesel,longitudinal
installation
H=hydrogen
5 Displacementinliters 1=1liter+
6 Displacementin1/10liter 8=0.8liters=1.8liters
7 Typetestconcerns(changes A=Standard
thatrequireanewtypetest) B-Z=dependingon
requirement,e.g.RON87
9
N20Engine
1.Introduction
N20enginenumber,engineidentificationandenginenumber
Index Explanation
00034772 Individualconsecutiveenginenumber
N Enginedeveloper,BMWGroup
2 Enginetype,Inline4
0 Changetothebasicengineconcept,TurbochargedValvetronicDirectInjection
B Operatingprincipleorfueltypeandinstallationposition,gasolinelongitudinal
installation
20 Displacementin1/10liter,2liters
A Typetestconcerns,standard
10
N20Engine
2.EngineComponents
2.1.Enginehousing
Theenginehousingcomprisestheengineblock(crankcaseandbedplate),thecylinderhead,the
cylinderheadcover,theoilsumpandthegaskets.
N20engine,structureofenginehousing
Index Explanation
1 Cylinderheadcover
2 Cylinderheadcovergasket
3 Cylinderhead
4 Cylinderheadgasket
5 Crankcase
11
N20Engine
2.EngineComponents
Index Explanation
6 Sealant
7 Bedplate
8 Oilsumpgasket
9 Oilsump
2.1.1.Engineblock
TheengineblockismadefromdiecastaluminiumAlSi9Cu3alongwiththecrankcaseandthe
bedplate.AnewcoatingforthecylinderwallisbeingusedforthefirsttimebyBMW.Itsreferredtoas
electricarcwirespraying.
Thecoolingjackethasalsobeenoptimizedtoimprovecoolingbetweenthecylinders,thisisdueto
therequirementsofaturbochargedengine.
Oilpassages
Thegraphicbelowshowstheoilpassagesintheengineblock.
N20engine,oilpassages
12
N20Engine
2.EngineComponents
Index Explanation
1 Oilreturnduct
2 Blow-byduct
3 Cleanoilpassages
4 Unfilteredoilpassages
Coolantducts
Thegraphicbelowshowsthecoolantpassagesintheengineblock.
N20engine,coolingjacketandcoolantpassages
Index Explanation
1 Coolingjacket,exhaustside
2 Coolingjacket,intakeside
3+4 Coolantpassagesbetweenthecylinders
Compensationopenings
Thecrankcasefeatureslargemilledlongitudinalventilationholes.Theseventilationholesimprove
thepressurecompensationoftheoscillatingaircolumnscreatedbytheupanddownstrokesofthe
pistons.
Additionalopeningsontheintakesideonthebearingseatbetweenthecylindersalsoimprove
crankcasepressure.
13
N20Engine
2.EngineComponents
N20engine,compensationopeningsinthebearingseat
Index Explanation
1+2+3 Openings
4+5 Ventilationholes
Cylinder
Anironwireisusedintheelectricarcwiresprayingprocess(arcsprayprocess)tocoatthealuminium
cylinderbores.Highvoltageisusedtoigniteanelectricarcatbothendsofthewire.Thetemperatures
generatedintheprocessareintheregionof3000C/5432F.Thehightemperaturesmeltthewire,
whichiscontinuallyfedbythewirefeedunit.Themoltenironisblastedontothecylinderwallsurface
atpressureviathecentralandsecondarycompressed-airsupplies.
Theliquidironadherestothealuminiumsurfacethrough:
Mechanicalbonding:
Moltenparticlespenetrateasaresultofhighkineticenergyandcapillaryactioninto
depressionsandundercuts,wheretheysolidifytocreateaverystrongcoating.
14
N20Engine
2.EngineComponents
Electricarcspraying
Index Explanation
1 Directionofmovement
2 Coatedcylindersurface
3 EASunit
4 Sprayjet
5 Nozzle
6 Secondarycompressed-airsupply
7 Spraywire
8 Powersupply
15
N20Engine
2.EngineComponents
Index Explanation
9 Centralcompressed-airsupply
10 Contacttube
11 Wirefeedunit
12 Electricarc
Advantages:
Sprayparticlesadherewiththebasemetal
Idealforthickcoatingsorlargesurfaces
Greatestapplicationrateperhourofallthethermalsprayingprocesses
Thearcspraycoatingcanbarelybedistinguishedintermsofcolorfromthebasemetal
Thelow-oxidespraycoatingcanbeprocessedduringmanufacturinglikeasolidmaterial
Hightensilestrengthandlowercontractionstrain
Micro-poroussurfacereducesfriction
Coatingpropertiessuchascoatinghardnessorsurfacequalitycanbedetermined
Allmaterialscanbeaddedascoatings,suchasforexampleferrous/nonferrousalloyoncast
iron
Lowthermalstressthankstooptimizedheattransfer.
Thelowcoatingthicknessofabout1mmproducesoptimumheattransferbutdoesnotallow
reworkingofthecylinderboresurfaceinservice.
Ifacylinderisdeterminedoutofspecificationtheentireengineblockmustbereplaced.
2.1.2.Cylinderheadgasket
Athree-layerspringsteelgasketisusedforthecylinderheadgasket.Astopperplate(2)isweldedon
intheareaofthecylinderboresinordertoachievesufficientcontactpressureforsealing.Allthelayers
ofthegasketarecoated,thecylinderheadandtheengineblockcontactsurfacesarecoatedwitha
partialfluorocaoutchouc(elastomer)withnon-stickcoating.
N20engine,cylinderheadgasket
16
N20Engine
2.EngineComponents
Index Explanation
1 Topspringsteellayerwithnon-stickcoating
2 Welded-onstopperplate
3 Middlespringsteellayerwithcoating
4 Bottomspringsteellayerwithnon-stickcoating
2.1.3.Cylinderhead
ThecylinderheadintheN20engineissimilartothecylinderheadintheN55.The3rdgeneration
ValvetronicsystemintroducedintheN55isalsousedintheN20engine.
TheclassicVANOSwithseparatesolenoidvalveintheN55enginehasbeenreplacedintheN20
enginebyacentralVANOSwithintegratedsolenoidvalve.Thebenefitofthissystemisareduced
numberofoilpassagesinthecylinderhead.
AsintheN55enginetheN20alsousesTVDItechnology.
Thecombinationofexhaustturbocharger,ValvetronicanddirectfuelinjectionisknownasTurbo
ValvetronicDirectInjection(TVDI).
N20engine,cylinderhead
17
N20Engine
2.EngineComponents
Index Explanation
1 VANOSsolenoidactuator,intake
2 VANOSsolenoidactuator,exhaust
3 Rollertappet,high-pressurepump
4 Valvetronicservomotor
5 Spring
6 Guideblock
7 Intermediatelever
8 Eccentricshaft
2.1.4.Cylinderheadcover
Design
Thecylinderheadcoverisanewdevelopment.Allthecomponentsforcrankcaseventilationandthe
blow-byductsareintegratedintothecover.Apressurecontrolvalvepreventsanexcessivevacuum
frombeinggeneratedinthecrankcase.Ventilationisperformedviadifferentductsdependingon
whethertheengineisrunninginturbocharged(Boost)ornormallyaspirated(NA)mode.
InNAmode,ventilationisperformedviathepressurecontrolvalveatabout38mbar.
18
N20Engine
2.EngineComponents
N20engine,cylinderheadcoverwithcrankcaseventilation
Index Explanation
A SectionA
B SectionB
C SectionC
1 Connectiontocleanairpipeaheadofexhaustturbocharger
19
N20Engine
2.EngineComponents
Index Explanation
2 Non-returnvalve
3 Pressurecontrolvalve
4 Springtabseparator
5 Oilseparator
6 Settlingchamber
7 Non-returnvalve
8 Non-returnvalve
9 Blow-byducttotheintakeportsinthecylinderhead
Theblow-bygasespassthroughtheopeningintheintakesideareaofcylinderonetothethreespring
tabseparators.Theoilintheblow-bygasisseparatedbythespringtabseparators,andflowsalong
thewallsdownthroughanon-returnvalveandbackintothecylinderhead.Theblow-bygasseparated
fromtheoilnowpassesintotheairintakesystemportsorfreshairpipe(dependingontheoperating
mode).
Function
Innaturallyaspiratedmode,thenon-returnvalveintheblow-byductofthecylinderheadcoveris
openedbythevacuumpressureintheairintakesystemandtheblow-bygasesaredrawnoffviathe
pressurecontrolvalve.Thevacuumpressuresimultaneouslyclosesthesecondnon-returnvalveinthe
ducttocharge-airsuction/freshairline.
Theblow-bygasesarerouteddirectlyintothecylinderheadintakeportsviathepassagesintegrated
inthecylinderheadcover.
Apurgeairline,whichisconnectedtothefreshairpipeaheadoftheturbochargerandtothe
crankcase,routesfreshairviaanon-returnvalvedirectlyintothecrankcase.Thegreaterthevacuum
inthecrankcase,thehighertheairmassintroduced.Thispurgingpreventsthepressurecontrolvalve
fromicingupbyreducingmoistureinthesystem.
20
N20Engine
2.EngineComponents
N20engine,crankcaseventilation,naturallyaspiratedmode
Index Explanation
B Ambientpressure
C Vacuum
D Exhaustgas
E Oil
F Blow-bygas
1 Airfilter
2 Intakeplenum
21
N20Engine
2.EngineComponents
Index Explanation
3 Perforatedplates
4 Passagesincylinderheadandcylinderheadcover
5 Blow-bygasduct
6 Purgeairline
7 Non-returnvalve
8 Crankcase
9 Oilsump
10 Oilreturnpassage
11 Turbocharger
12 Non-returnvalve,oilreturn
13 Charge-airsuctionline/freshairpipe
14 Connectiontocharge-airsuctionline
15 Non-returnvalvewithrestrictor
16 Throttlevalve
Onceinboostmodethepressureintheintakeplenumrisesthusitisnolongerpossibleforthe
blow-bygasestobeintroducedviathisroute.Anon-returnvalveintheblow-byductofthecylinder
headcoverclosestheducttotheintakeplenumandtherebyprotectsthecrankcaseagainstexcess
pressure.
Thenowgreaterfresh-airdemandgeneratesavacuuminthefreshairpipebetweentheturbocharger
andtheintakesilencer.Thisvacuumissufficienttoopenthenon-returnvalveinthecylinderhead
coveranddrawofftheblow-bygasesdirectlywithoutregulation.Thepressurecontrolvalve(17)is
bypassedinthismode,sinceonlyalowvacuumisgeneratedwhichdoesnothavetobelimited.
22
N20Engine
2.EngineComponents
N20engine,crankcaseventilation,boostmode
Index Explanation
A Chargingpressure
C Vacuum
D Exhaustgas
E Oil
F Blow-bygas
1 Airfilter
2 Intakeplenum
23
N20Engine
2.EngineComponents
Index Explanation
3 Perforatedplates
4 Passagesincylinderheadandcylinderheadcover
5 Blow-bygasduct
6 Purgeairline
7 Non-returnvalve
8 Crankchamber
9 Oilsump
10 Oilreturnpassage
11 Turbocharger
12 Non-returnvalve,oilreturn
13 Charge-airsuctionline/cleanairpipe
14 Connectiontocharge-airsuctionline
16 Throttlevalve
2.1.5.Oilsump
TheoilsumpismadefromplasticforrearwheeldrivevehiclesandcastaluminiumforxDrivemodels.
ForxDrivevehiclestheoilsumphasbeenmodifiedduetotheinputshaftsandattachmentpointsfor
theaxledrive.
Theoilpumpwiththecounterbalanceshaftscoverstheentireoilsumpandtherebyprotectsthe
crankshaftagainstoilsplashingbydoublingasawindagetray.Theoilflowingbackthroughtheoil
returnpassagesisrouteddirectlyintotheoilsumpandthereforecannotcomeintocontactwiththe
crankshaft.
24
N20Engine
2.EngineComponents
N20engine,oilpumpwithcounterbalanceshafts
Index Explanation
1 Chaindrive
2 Counterbalanceshaft
3 Oilreturnducts,intakeside
4 Oilpump
5 Oilreturnducts,exhaustside
25
N20Engine
2.EngineComponents
N20engine,oilsumpwithoilpumpandcounterbalanceshafts
Index Explanation
1 Chaindrive
2 Housing,counterbalanceshafts
3 Oilsump
4 Oilpump
26
N20Engine
2.EngineComponents
2.2.Crankshaftdrive
2.2.1.Crankshaftwithbearings
Crankshaft
ThecrankshaftoftheN20enginehasastrokeof89.6mmandismadeofthematerialC38modBY.Itis
aforgedcrankshaftwithfourbalanceweightsandweighs13.9kg/30.6lbs.
N20engine,crankshaft
Crankshaftbearingsandrodbearings
Thecrankshaftissupportedbyfive(lead-freetwocomponent)bearings.Thethrustbearingislocated
inthemiddleatthethirdbearingposition.Thethrustbearingisonlydesignedfor180andislocated
inthebearingseat.Thebearinginthebearingcapdoesnotprovideanyaxialguidance.
27
N20Engine
2.EngineComponents
N20engine,crankshaftbearings
Index Explanation
1 Upperbearingshellwithgrooveandoilhole
2 Thrustbearingwithgrooveandoilhole
3 Lowerbearingshellwithoutgroove
TheN20usesthesameprocedureaswithN55forcalculatingthecorrectbearingsizebyusingthe
crankcaseandcrankshaftcodes.
Theidentificationmarkingsfortheupperbearingsarefoundstampedonthecrankcaseandforthe
lowerbearingsonthecrankshaft.Ifthecrankshaftistobefittedwithnewbearingsrefertotherepair
instructionsformoreinformationontheproceduretodeterminethecorrectbearingsize/color.
28
N20Engine
2.EngineComponents
N20engine,bearingidentification,crankshaftcode
Index Explanation
1 Codedigitsforcrankshaftbearings(21211)
2 Codelettersforconnectingrodbearings(rrrr)
Twobearingcategoriesareused.Thesebearingcategoriesarerandb.
Thefollowingappliestothebearingpositionandbearingallocation:
Bearingcategoryorcode Installationlocation Bearingcolor

letter
b Rodend Violet
Bearingcapend Blue
r Rodend Yellow
Bearingcapend Red
ThebearingshellsareidenticalpartstothoseusedintheN54andN55engines.Alocatinggroove
preventsthewrongbearingshellfrombeinginstalled.
29
N20Engine
2.EngineComponents
N20engine,bearingidentification,crankcase
Index Explanation
1 Kstandsforclutchend
2 Bearing5
3 Bearing4
4 Bearing3
5 Bearing2
6 Bearing1
TheKdesignationinposition(1)standsforclutchend(German:Kupplungsseite).Thusthefirst
codedigit(2)istheIDcodeforbearing5inthecrankcase.Thesecondcodedigit(3)standsfor
bearing4,etc.
Thefollowingisanexampleofhowtocalculatethecorrectcrankshaftmainandrodbearingsusingthe
stampingcodes.
30
N20Engine
2.EngineComponents
Exampleofthecrankshaftbearingselectionprocedure.
Exampleoftheconnectingrodbearingselectionprocedure.
31
N20Engine
2.EngineComponents
Note:Thistrainingmaterialisintendedforclassroominstructiononly.Itisnotmeantto
replacecurrentlyavailablerepairinstructions.Alwaysrefertothemostcurrentversionof
repairinstructions,technicaldataandtorquespecifications.Refertothelatestversionof
ISTA.
Pinoffset
Pistonsalwaysrequirearunningclearance.Therunningclearancemeansthatthereisalwaysacertain
degreeoflateralmovement(pistonslap)asthepistonchangesdirectionfromup-stroketodown-
stroke.Thegreatertheforceactingonthepistonandthegreatertherunningclearance,thegreater
thepistonslap.
Pinoffsetinvolvesadvancingthetimewhenthepistonchangesbetweenthecompressionandpower
stroketothelowerpressurerangebeforetopdeadcenter.Thisresultsinareductionofnoiseand
friction.
Pinoffsetreferstothedisplacementofthewristpinaxisfromthecylindercenterlineofthepiston.A
positiveoffsetindicatesoffsettothemajorthrustface,anegativeoffsetdenotesoffsettotheminor
thrustface.Themajorthrustfacereferstothatsideofthepistononwhichthepistonrestsinthe
combustionstrokeonitswaytobottomdeadcenter(seearrowofIII).Minorthrustisthepiston's
thrustagainsttheoppositecylinderwallduringthecompressionstroke(seearrowofI).
Thefollowinggraphicshowsaconventionalcrankshaftdrivewithoutpinandcrankshaftoffset.
32
N20Engine
2.EngineComponents
Conventionalcrankshaftdrive
Index Explanation
I Pistonpositionandcrankshaftpositionshortlybeforetopdeadcenter(TDC)
II Pistonpositionandcrankshaftpositionattopdeadcenter
III Pistonpositionandcrankshaftpositionaftertopdeadcenter
A Majorthrustface
B Minorthrustface
C Directionofenginerotation
1 Wristpin
2 Centerofcrankshaftrotation
3 Thrustforce
Asthegraphicshows,inaconventionalcrankshaftdriveassemblythewristpinboss,theconnecting
rodandthecenterofcrankshaftrotationareinlineattopdeadcenter(TDC).Becauseofthis
arrangement,thepistonisforcedagainsttheminorthrustface(B)duringtheup-stroke.AtTDCthe
forcesarecompensatedbecausethepressureontheminorthrustfacedecreasesasthecrankshaft
rotatesawayfromTDCandthepistontiltstowardsthemajorthrustface(A).Becausethereisalready
highpressureatTDC,thisabruptchangeoffacecausesanoisewhichisreferredtoaspistonslap.
Pinoffsetcanbeeffectedtowardsthemajorthrustface(positive)andalsotowardstheminorthrust
side(negative).Major-thrust-facepinoffsetisalsoreferredtoasnoiseoffset.
33
N20Engine
2.EngineComponents
Minor-thrust-facepinoffsetisalsoreferredtoasthermaloffset.Inthispositionthesealingeffectof
thepistonringsisimproved.
Pinoffset
Index Explanation
A Major-thrust-facepinoffset(positive)
B Minor-thrustfacepinoffset(negative)
OT Topdeadcenter
UT Bottomdeadcenter
Becausethenoisecanbeheardduringthechangeoffaces,technicalmeasuresareusedtoshiftthis
changeoffacesasfaraspossibletoarange(pistonposition)inwhichtheactingforcesarelower.This
isdoneincurrentBMWenginesbyoffsettingthewristpintowardsthemajorthrustface.
Theoffsetisabout.0.3-0.8mminconventionalenginesandisthereforevirtuallyimperceptibletothe
eye.Thisisalsothereasonwhythepistonshaveadirectionalmarkingatthetop.Incorrectinstallation
mayresultinextremenoisesimilartothatgeneratedbypistondamage.
34
N20Engine
2.EngineComponents
Pistonrockinginanenginewithpinoffset
Index Explanation
I Pistonpositionandcrankshaftpositionbeforetopdeadcenter
II Pistonpositionandcrankshaftpositionshortlybeforetopdeadcenter,with
perpendicularconnectingrod
III Pistonpositionandcrankshaftpositionattopdeadcenter
A Majorthrustface
B Minorthrustface
1 Wristpin
2 Centerofcrankshaftrotation
3 Thrustforce
Thepistonrestsagainsttheminorthrustfaceduringtheup-stroke.Aneutralpistonpositionisalready
achievedbeforeTDCbyoffsettingthewristpin.Thisisthecasewhenthecenterlinesofthecylinder
andofthebigandsmallconnectingrodeyesareparalleltoeachother.AlreadybeforeTDCthepiston
changesfromtheminorthrustfacetothemajorthrustface.Inthisphasetheforceonthepistonis
stilllow.Duetotheoff-centersupportofthepiston,theforceactingonthepistonfromabovehasa
higherleverarmontheonefacethanontheother.Inthisway,thepistonisalreadytiltedduringtheup-
35
N20Engine
2.EngineComponents
stroke,resultingincontactwiththemajorthrustfaceattheupperedge.Initssubsequentmovement
thepistonagaintravelsstraightahead,sothatthepistonrestscompletelyonthemajorthrustface.
Thechangeoffacesismuchquieterthaninaconventionalcrankshaftdrive.
Thedownsideofpinoffsetisthatthereisaslightincreaseinfrictiononthemajorthrustface.This
minordownside,however,ismadeupforbythereducednoise.
Crankshaftoffset
AcrankcasewithcrankshaftoffsetisusedforthefirsttimebyBMW.
Crankshaftoffsetdenotestheoffsetofthecrankshaftaxisfromthecylindercenterline.Thisoffsetcan
effectonboththemajorthrustfaceandtheminorthrustface.Apositiveoffsetdenotesoffsettothe
majorthrustface,anegativeoffsetdenotesoffsettotheminorthrustface.
Crankshaftoffsetcanbasicallybeeffectedinbothdirections,butuptonowonlythevariationinthe
positivedirection(A)hasbeenused.
Crankshaftoffset
Index Explanation
A Positiveoffset
B Negativeoffset
OT Topdeadcenter
UT Bottomdeadcenter
36
N20Engine
2.EngineComponents
Thefollowinggraphicclearlyshowsthatpositivecrankshaftoffset,whencomparedwithpositivepin
offset,hasanopposedeffectonpistonrocking.Thuspistonrockingoccursmuchlaterandinthe
rangeofahighcylinderpressure.
Pistonrockinginanenginewithcrankshaftoffset
Index Explanation
I Pistonpositionandcrankshaftpositionshortlyaftertopdeadcenter
II Pistonpositionandcrankshaftpositionwithperpendicularconnectingrod
III Pistonpositionandcrankshaftpositionafterpistonrocking
A Majorthrustface
B Minorthrustface
1 Wristpin
2 Crankshaft
OT Topdeadcenter
UT Bottomdeadcenter
37
N20Engine
2.EngineComponents
Thetopandbottomdeadcentersarealsoshiftedbythecrankshaftoffset.Thetopandbottomdead
centersareachievedintheextendedandoverlappositionsrespectively.Theconnectingrodandthe
crankshaftpointgeometricallyinthesamedirection.
TDCpositioninanenginewithcrankshaftoffset
Index Explanation
OT Topdeadcenter
UT Bottomdeadcenter
l Connectingrodlength
r Crankthrow
y Crankshaftoffset
sOT DistanceTDC
h Pistonstroke
1 AngleinTDCpositionTDC
Bottomdeadcenterlikewisechangesitspositionandrunstoacrankangleofover180.
38
N20Engine
2.EngineComponents
BDCpositioninanenginewithcrankshaftoffset
Index Explanation
OT Topdeadcenter
UT Bottomdeadcenter
r Crankthrow
y Crankshaftoffset
sUT DistanceBDC
h Pistonstroke
2 AngleinBDCpositionBDC
AcombinationofpositivecrankshaftoffsetandnegativepinoffsetisusedintheN20engine.
Bothnegativeandpositivepinoffsetaffectthepistonrockingbehavior.Inresponsetothedistribution
offorcesduringpistonrocking,thisoccurslaterandmorequietly.
39
N20Engine
2.EngineComponents
Combinationofcrankshaftandpinoffset
Index Explanation
OT Topdeadcenter
UT Bottomdeadcenter
r Crankthrow
y Crankshaftoffset
sD Pinoffset
sOT DistanceTDC
h Pistonstroke
TheN20enginefeaturesconnectingrods144.35mmlong,withacrankthrowof44.8mm.Crankshaft
offsetis+14mm,offsetofthewristpinis-0.3mm.
40
N20Engine
2.EngineComponents
Data Value
Stroke 90.09mm
TDC +4.336
BDC +188.259
Inductioncycleangleandpowercycleangle 183.923
Compressioncycleangleandexhaustcycle 176.077
angle
Advantages
Inanenginewithcrankshaftoffset,theconnectingrodinthepowerstrokeisinaroughly
perpendicularposition(seethegraphicontheright)incontrasttoanenginewithoutcrankshaftoffset
(seethegraphicontheleft).Thisdesignsignificantlyreducesthethrustforce(5)andthefrictionofthe
pistononthecylinderwallwhichresultisincreasedefficiency.ThecrankshaftoffsetintheN20engine
isthusconsideredonemoreBMWEfficientDynamicsmeasure.
Systemdiagramofactingforces,left:normalengine,right:enginewithcrankshaftoffset
41
N20Engine
2.EngineComponents
Index Explanation
1 Pressureforcefromcombustion
2 Normalpistonforce
3 Oppositepistonforce
4 Lateralpistonforce
5 Thrustforce
6 Resultingforce
7 Crankshaftoffset
2.2.2.Connectingrod
Connectingrod
TheconnectingrodoftheN20enginehasaninsidediameterof144.35mm.AswiththeN55theN20
usesaspeciallyformedholeinthesmallendoftheconnectingrod.Thisformedholeismachined
widerontheloweredgesofthewristpinbushing/bore.Thisdesignevenlydistributestheforceacting
onthewristpinovertheentiresurfaceoftherodbushingandreducestheloadattheedges,asthe
pistonisforceddownwardonthepowerstroke.
42
N20Engine
2.EngineComponents
N20engine,connectingrod
2.2.3.Pistonwithpistonrings
AfullslipperskirtpistonmanufacturedbythecompanyFMisused.Thepistondiameteris84mm.
Thefirstpistonringisasteel-nitridedplaincompressionring.Thesecondpistonringisastepped
compressionring.Theoilscraperringisasteelbandringwithaspring,whichisalsoknownasanMF
systemring.
Aspreviouslydiscussedthewristpinaxishasanegativeoffsettotheminorthrustface.
Aninstallationpositionarrowisstampedonthepiston.Thisarrowalwayspointstotheinstallationof
thepistoninalongitudinaldirectionfacingthetimingchain.Itisnecessarytoinstallthepistoninthe
correctposition,sincetheasymmetricvalvereliefsontheintakeandexhaustsideswillresultinvalve
andcylinderwalldamage.
43
N20Engine
2.EngineComponents
N20engine,piston
N20engine,pistonrings
44
N20Engine
2.EngineComponents
Index Explanation
1 Plaincompressionring
2 Steppedcompressionring
3 MFsystemring
4 Piston
2.3.Camshaftdrive
Thecamshaftdrivedesignissimilartopreviousengines.Theoilpumpisgeardrivenviathe
counterbalanceshafts.Toensurethatthecounterbalanceshaftsarecorrectlypositionedinrelation
tothecrankshaft,asecondarychaindriveisusedwhichisalsoequippedwithachaintensioner.Both
chainshavetooth-typedesign.
N20engine,camshaftdrive
45
N20Engine
2.EngineComponents
Index Explanation
1 ExhaustVANOS
2 IntakeVANOS
3 Chaintensioner
4 Primarychain
5 Tensioningrail
6 Sprocket,drivenbycrankshaft
7 Secondarychain(tooth-typechain)
8 Chaintensioner
9 Sprocketforcounterbalanceshaftandoilpumpdrive
2.4.Counterbalanceshafts
Thepurposeofthecounterbalanceshaftsistoimprovetheengine'ssmoothrunningandacoustic
performance.Thisisachievedusingtwocounter-rotatingshaftswhicharefittedwithbalanceweights.
Thecounterbalanceshaftsaredrivenbythecrankshaftviaatooth-typechain.Thetooth-typechain
requirestheuseofspecialgearsonthecrankshaftandthecounterbalanceshafts.Thetooth-type
chainoptimizestherollingofthedrivechainonthesprockets,therebyreducingnoise.
N20engine,counterbalanceshaftandoilpumpdrive
46
N20Engine
2.EngineComponents
Index Explanation
1 Crankshaftsprocket
2 Tooth-typechain
3 Chaintensioner
4 Counterbalanceshaftsprocket
N20engine,counterbalanceshafts
Index Explanation
1 Sprocketoncrankshaft
2 Uppercounterbalanceshaft
3 Lowercounterbalanceshaft
4 Gear,uppercounterbalanceshaft
5 Gear,oilpump
6 Oilpump
7 Tooth-typechain,counterbalanceshaftandoilpumpdrive
47
N20Engine
2.EngineComponents
Beforeremovingandinstallingthecounterbalancedrivesprocketthelowercounterbalanceshaft
mustbesecuredwitha4.5mmthickalignmentpin(specialtool#2212825)tosecurelypositionthe
counterbalanceshaftswiththecrankshaft.
Counterbalanceshaftalignmentpintool2212825
Asealplugwhichisinsertedinthelocatingholemustberemovedforthispurpose.Thissealplug
preventsoilfromflowingintothecounterbalanceshaftchamberduringoperation,asituationwhich
wouldcauseoilfoaming.Itisthusimperativethatthissealplugbereinstalledduringfinalassembly.
Theexcessoilinthechamberiscarriedalongbytherotationofthebalanceweightsandreturnedviaa
dischargeopeningtotheoilsump.
Counterbalanceshaftsealplug
Positioningofthecounterbalanceshaftsinalignmentisnecessarytoensuresmooth,fault-
freeengineoperation.Pleaserefertotherepairinstructionsformoreinformation.
48
N20Engine
2.EngineComponents
N20engine,cutawayviewofcounterbalanceshafts
Index Explanation
1 Dischargeopening
4 Alignmentpin,lowercounterbalanceshaft
5 Sealplug
49
N20Engine
2.EngineComponents
2.5.Valvegear
2.5.1.Design
N20engine,valvegear
Index Explanation
1 Intakecamshaft
2 Rollercamfollower
3 Intermediatelever
4 Guideblock
5 Torsionspring
6 Eccentricshaft
8 Exhaustcamshaft
50
N20Engine
2.EngineComponents
N20engine,valvegear
Index Explanation
1 Torsionspring
2 Intermediatelever
3 Eccentricshaft
4 VANOSunit,intake
5 Intakecamshaft
6 HVCCelement,intake
7 Rollercamfollower,intake
8 Valvespring,intakevalve
51
N20Engine
2.EngineComponents
Index Explanation
9 Intakevalve
11 Exhaustvalve
12 Valvespring,exhaustvalve
13 Rollercamfollower,exhaust
14 HVCCelement,exhaust
15 Exhaustcamshaft
16 VANOSunit,exhaust
Therollercamfollowersontheintakesidearemadefromsheetmetalandsubdividedintofive
classes,Class1toClass5.Theintermediateleversarenowalsomadefromsheetmetalandare
subdividedintosixclasses,Class00toClass05.
Camshafts
TheN20engineisfittedwiththeassembledcamshaftsalreadyknownfromtheM73engine.Allthe
componentsareshrink-fittedontotheshaft.Thetimingofthecamshaftsrequiresnewspecialtool,#
2212831.Pleaserefertotherepairinstructionsforpropertimingprocedures.
N20engine,assembledcamshafts
Index Explanation
1 Exhaustcamshaft
2 Intakecamshaft
52
N20Engine
2.EngineComponents
N20engine,assembledcamshafts
Index Explanation
1 FlangeforVANOSunit,exhaust
2 Cam
3 Camforhigh-pressurepump
4 Sealingcap
5 Pipe
6 Hexagonhead
7 FlangeforVANOSunit,intake
8 Cam
53
N20Engine
2.EngineComponents
Index Explanation
9 Sealingcap
10 Pipe
11 Hexagonhead
12 Vacuumpumpdrive
Valvetiming
N20engine,valvetimingdiagram
N55B30M0 N20B20O0
Intakevalvedia./stemdia. [mm] 32/5 32/5
Exhaustvalvedia./stemdia. [mm] 28/6 28/6
Maximumvalvelift,intake/exhaustvalve [mm] 9.9/9.7 9.9/9.3
VANOSadjustmentrange,intake [CA] 70 70
VANOSadjustmentrange,exhaust [CA] 55 55
Spread,intakecamshaft [CA] 12050 12050
Spread,exhaustcamshaft [CA] 11560 11560
Openingperiod,intakecamshaft [CA] 258 258
Openingperiod,exhaustcamshaft [CA] 261 252
54
N20Engine
2.EngineComponents
Intakeandexhaustvalves
TheintakeandexhaustvalvesarecarryoverpartsfromtheN55engine.Theintakevalvehasastem
diameterof5mm.Theexhaustvalvehasastemdiameterof6mm,becauseitishollowandsodium
filled.Theexhaustvalveseatsaremadefromhardenedmaterialandtheintakevalveseatsare
induction-hardened.
Valvesprings
Thevalvespringsusedfortheintakeandexhaustvalvesaredifferent.Theintakevalvespringshave
alreadybeenusedintheN52,N52TUandN55engines.Theexhaustvalvespringsarefamiliarfrom
theN51,N52,N52TU,N54andN55engines.
2.5.2.Valvetronic
TheValvetroniccomprisesfullyvariablevalveliftcontrolandvariablecamshaftcontrol(double
VANOS),whichmakestheclosingtimeoftheintakevalvefreelyadjustable.
Valveliftcontrolisperformedontheintakeside,whilecamshaftcontrolisperformedonboththe
intakeandexhaustsides.
Throttle-freeloadcontrolisonlypossibleif:
theliftoftheintakevalve
andcamshaftadjustmentoftheintakeandexhaustcamshaftsarevariablycontrollable.
Result:
Theopeningandclosingtimesandthustheopeningperiodandtheliftoftheintakevalvearefreely
adjustable.
VANOS
TheVANOSsystemhasbeenmodified.ThismodificationnowprovidesforevenfasterVANOSunit
settingspeeds.Themodificationhasalsofurtherreducedsystemfailure.Thefollowingcomparisonof
theVANOSsystemsofN55andN20enginesshowsthatfeweroilpassagesarenecessary.
55
N20Engine
2.EngineComponents
N55engine,VANOSwithoilsupply
Index Explanation
1 Mainoilpassage
2 VANOSsolenoidvalve,intakeside
3 VANOSsolenoidvalve,exhaustside
4 Chaintensioner
5 VANOSunit,exhaustside
6 VANOSunit,intakeside
56
N20Engine
2.EngineComponents
N20engine,VANOSwithoilsupply
Index Explanation
1 OilpassagetoVANOSunit,intakeside
2 VANOSunit,intakeside
3 Camshaftsensorwheel,intakecamshaft
4 VANOSsolenoidactuator,intakeside
5 Mainoilpassage
6 OilpassageforintakecamshaftandHVCCelements
7 Camshaftsensorwheel,exhaustcamshaft
8 VANOSsolenoidactuator,exhaustside
9 VANOSunit,exhaustside
10 OilpassagetoVANOSunit,intakeside
11 OilpassageforexhaustcamshaftandHVCCelements
12 Chaintensioner
57
N20Engine
2.EngineComponents
ThefollowinggraphicshowstheoilpassagesintheVANOSunit.Theintakecamshaftcanbe
advancedwiththepassagesshadedlightyellow;theVANOSunitcanberetardedwiththe
passagesshadeddarkyellow.
Thecamshaftsensorwheelsrequireanewspecialtoolforproperpositioning,tool#2212830.
Pleaserefertotherepairinstructionsformoreinformation.
N20engine,VANOSunit,intakecamshaft
Index Explanation
1 Rotor
2 Oilpassageforadvancingthetiming
3 Oilpassageforretardingthetiming
4 Oilpassageforadvancingthetiming
5 Oilpassageforretardingthetiming
ThelockingpinensuresthattheVANOSunitislockedinasetpositionwheninthedepressurized
state.Thespiralortorsionspring(notshownhere)isdesignedtocompensatethemiddlecamshaft
friction,becausewithoutthespringtheVANOSadjustsmuchfastertoretarded(withfriction)than
toadvanced(againstfriction).Thelockingeffectisprovidedbytheoilpressure,whichwhenthe
58
N20Engine
2.EngineComponents
actuatorisnonregisteredalwaysforcestheVANOSunitintothelockingposition(wherethelocking
pinengagesandblockstheVANOSunit).Thetimingcanbeadjustedinthisway.Thisisimportant
whentheengineisstartedtoensureexacttiming.Thelockingpinissimultaneouslysuppliedwith
theoilpressureavailablefortimingadvanceviaoilpassagesintheVANOSunit.Ifthecamshaftisto
beadvanced,thelockingpinisthenforcedbytheappliedoilpressureagainstthelockingspring
towardsthecartridgeandthelockingcoverisreleasedforVANOSadjustment.
N20engine,lockingpin
Index Explanation
1 Lockingcover
2 Lockingpin
3 Lockingspring
4 Cartridge
59
N20Engine
2.EngineComponents
Index Explanation
5 Oilpassage
6 Lockingcover
7 Oilpassage
8 VANOScentralvalve
TheVANOSunitissecuredtothecamshaftbytheVANOScentralvalve.TheoilflowintotheVANOS
unitissimultaneouslycontrolledbythisVANOScentralvalve.Thesystemisactuatedbyasolenoid
actuator(whichpressesagainsttheplunger(4)oftheVANOScentralvalve)therebyswitchingthis
valvefromadvancetotheretardposition.
Theplungerinthecentralvalvecontrolstheoilflow.Intheillustrationbelowtheplungerisshown
extended.ThelargegraphicshowstheflowofoilfromthemainoilpassageintotheVANOSunit,while
thesmallgraphicshowstheflowofoilfromtheVANOSunitintothecylinderhead.
60
N20Engine
2.EngineComponents
N20engine,VANOScentralvalve,intakecamshaft
Index Explanation
1 Filter
2 Ball
3 Spring
4 Plunger
5 Sleeve
6 Housing
61
N20Engine
2.EngineComponents
Index Explanation
7 Openinginplunger
8 Oilsupplyfrommainoilpassage
9 BoretooilpassageinVANOS(timingadvance)
10 BoretooilpassageinVANOS(timingretard)
N20engine,VANOScentralvalve,intakecamshaft
Valveliftcontrol
Ascanbeenseenfromthefollowinggraphic,valveliftcontrolwiththeValvetronicservomotoris
identicalintermsofdesigntothatoftheN55engine.Theeccentricshaftsensorisintegratedinthe
Valvetronicservomotor.
ThesystemusesValvetronicIII,whichisalreadyusedintheN55engine.
62
N20Engine
2.EngineComponents
N20engine,cylinderhead
Index Explanation
1 VANOSsolenoidactuator,intake
2 VANOSsolenoidactuator,exhaust
3 Rollertappet,high-pressurepump
5 Spring
6 Guideblock
7 Intermediatelever
8 Eccentricshaft
2.6.Beltdrive
ThebeltdriveconsistsofamainbeltdrivewithalternatorandA/Ccompressorandanauxiliarybelt
drivewiththepowersteeringpump.Themainbeltdriveisequippedwithabelttensioner,theauxiliary
beltdriveisanelasto-belttensioningsystem.
63
N20Engine
2.EngineComponents
N20engine,beltdrive
Index Explanation
1 Beltpulley,powersteeringpump
2 Belt,powersteeringpump
3 Beltpulleys,crankshaft
4 Belttensioner
5 Beltpulley,alternator
6 Beltpulley,A/Ccompressor
7 Belt
64
N20Engine
3.OilSupply
TheoilsupplyintheN20engineisverysimilartothatintheN55engine.Thereareafewchanges
tothedesignwithsomeslightdifferencesinoperation.Duetothecomplexityofthissystem,itis
discussedagainingreaterdetailinthistrainingmaterial.
ThespecialfeaturesoftheoilsupplyintheN20engineare:
Map-controlledoilpump
Newpendulum-slideoilpumpdesign
NewVANOSvalves
Chaintensionerforcounterbalanceshaft/oilpumpdrive
Unfilteredoilcooling
Newcombinedoilpressureandtemperaturesensor.
3.1.Overview
ThefollowinghydrauliccircuitdiagramandgraphicsprovideanoverviewoftheN20oilsupplyanda
betterunderstandingoftheactuallayoutoftheoilpassagesintheengine.
65
N20Engine
3.OilSupply
3.1.1.Hydrauliccircuitdiagram
N20engine,hydrauliccircuitdiagram
Index Explanation
A Oilsump
B Crankcase
C Cylinderhead
D Oilfiltermodule
66
N20Engine
3.OilSupply
Index Explanation
E VANOScentralvalve,intakecamshaft(alsooilsupply,lubricationpoint,
camshaftthrustbearing)
F VANOScentralvalve,exhaustcamshaft(alsooilsupply,lubricationpoint,
camshaftthrustbearing)
1 Oilpump
2 Pressure-limitingvalve
3 Chaintensioner,counterbalanceshaftandoilpumpdrive
4 Engineoil-to-coolantheatexchanger
5 Permanentbypass
6 Non-returnvalve
7 Oilfilter
8 Filterbypassvalve
9 Lubricationpoints,intakecamshaftbearings(via4thbearing,supplyof
vacuumpump)
10 Oilspraynozzle,gearing,Valvetronicservomotor
11 Oilspraynozzles,cams,intakecamshaft
12 Hydraulicvalveclearancecompensation(HVCC),intakeside
13 Lubricationpoints,bearings,exhaustcamshaft
14 Hydraulicvalveclearancecompensation(HVCC),exhaustside
15 Non-returnvalve
16 Filter
17 4/3-wayvalve
18 VANOSunit,intakecamshaft
19 VANOSunit,exhaustcamshaft
20 Oilspraynozzles,cams,exhaustcamshaft
21 Chaintensioner,timingchain
22 Oilspraynozzlesforpistoncrowncooling
23 Combinedoilpressureandtemperaturesensor
24 Lubricationpoints,crankshaftmainbearings
25 Mapcontrolvalve
26 Emergencyvalve/pressurelimitingblowoffvalve
27 Lubricationpoints,bearings,counterbalanceshafts
67
N20Engine
3.OilSupply
3.1.2.Oilpassages
N20engine,oilpassages(phantomrearleftview)
Index Explanation
1 Oilfilter
2 Lubricationpointsincylinderhead(details,seebelow)
4 Mainoilpassage
5 Lubricationpoints,connectingrodbearings
68
N20Engine
3.OilSupply
Index Explanation
7 Oilpump
8 Emergencyvalve/pressurelimitingblowoffvalve
9 Mapcontrolvalve
10 Unfilteredoilpassage
N20engine,oilpassages(phantomrightfrontview)
69
N20Engine
3.OilSupply
Index Explanation
1 Lubricationpointsincylinderhead(details,seebelow)
2 VANOSactuatorunit,exhaustcamshaft
3 VANOSactuatorunit,intakecamshaft
4 Unfilteredoilpassage
6 Chaintensioner,counterbalanceshaftandoilpumpdrive
7 Oilsuctionpipe
8 Lubricationpoints,counterbalanceshaftbearings
10 Lubricationpoints,connectingrodbearings
N20engine,oilpassagesincylinderhead(phantomleftview)
70
N20Engine
3.OilSupply
Index Explanation
1 Lubricationpoints,intakecamshaftbearings
2 OilspraynozzlesinGuideblockforintermediateleversandintakecams
3 Oilspraynozzle,gearing,Valvetronicservomotor
4 HVCCelements,intakevalves
5 VANOSactuatorunit,intakecamshaft
6 VANOSactuatorunit,exhaustcamshaft
8 Oilpipeforoilspraynozzles,exhaustcams
9 HVCCelements,exhaustvalves
10 Lubricationpoints,exhaustcamshaftbearings
71
N20Engine
3.OilSupply
N20engine,oilreturnpassages(phantomleftrearview)
Index Explanation
1 Ventilationpassagesincylinderhead
2 Ventilationpassagesincrankcase
3 Ventilationpassagesinbedplate
4 Oilreturnpassagesinbedplate
5 Oilreturnpassagesincrankcase
6 Oilreturnpassagesincylinderhead
72
N20Engine
3.OilSupply
3.2.Oilpumpandpressurecontrol
Avariable-volumetric-flowslideoilpumpisusedintheN20engine.Despiteitsshapebeingmodified,
itsfunctionisfamiliartothatoftheN63andN55engines.Althoughthesetwoenginesshareasimilar
oilpump,theydifferinhowtheyarecontrolled.WhiletheoilpumpintheN63engineisvolumetric-
flow-controlled,intheN55andN20enginesitsmap-controlled.
3.2.1.Oilpump
Theoilpumpisconnectedtothecounterbalanceshafthousing.Theoilpumpislocatedatthe
flywheelsideoftheengine,butisdrivenatthefrontoftheenginebythecrankshaftviaachain.
Thechainsprocketconnectstotheoilpumpviaalongshaft.Thisshaftformspartofthefirst
counterbalanceshaftwhichrotatesinthesamedirectionasthecrankshaft.Therotationalspeedis
steppeddownfromthecounterbalanceshaftfortheoilpumpviaapairofgears.
N20engine,oilpumpwithcounterbalanceshafts
Index Explanation
1 Sprocketoncrankshaft
4 Gear,uppercounterbalanceshaft
5 Gear,oilpump
6 Oilpump
7 Tooth-typechain,counterbalanceshaftandoilpumpdrive
73
N20Engine
3.OilSupply
Asalreadymentioned,thefunctionoftheslideoilpumphasnotchanged.Themaindifferenceisthat
theslidemechanismnolongerpivotsonanaxisduringadjustment,butinsteadismovedinparallel.
N20engine,innerworkingsofoilpump
Index Explanation
1 Pressureside
2 slidingblock
3 Outerrotor
4 Pendulum
5 Innerrotor
6 Controloilchamber
7 Suctionside
8 Housing
9 Mainspring
Asinallnewergenerationslideoilpumpstheoilactsdirectlyontheslidemechanism.Thehigherthe
pressurehere,themoretheslidingblockisforcedagainstthespringinthedirectionofthecenterof
thepump,whichreducesthevolumetricdisplacement.Thisreducesthepumpdeliveryrateandlimits
74
N20Engine
3.OilSupply
thepressureinthesystem.Inthisway,itispossibletoachievepurelyhydraulic/mechanicalcontrolof
thevolumetricflow,allowingsufficientoperatingpressuretobeset.Thispressureisdeterminedby
thestrengthofthemainspringintheoilpumpwhichactsontheslidingblock.
AswiththeN55theN20enginefeaturesamapcontrolvalvewhichtheDMEactivatestoinfluencethe
pumpdeliveryrate.
Theoilpumpcannotbereplacedseparately.Theentireunitincludingthecounterbalanceshaftsmust
bereplacediftheoilpumpfails.
3.2.2.Control
ControllingthedeliveryrateoftheoilsupplypumpiscrucialcomponentoftheBMW
EfficientDynamicsstrategy.Essentially,engineersattempttodesignapumpwithregardtoitspower
inputassmallaspossibleinordertokeepenginelossesaslowaspossible.Ontheotherhand,the
pumpmustalsobedesignedinsuchawayastodeliversufficientvolumeandpressureunderall
operatingconditions.Aconventional,non-variablepumpwouldthereforehavetobedesignedin
accordancewiththesecondstandpoint,i.e.largeenoughtobeabletodeliversufficientamountsofoil
atalltimes.However,thismeansthatthepumpmaydeliverfartoomuchoilvolumeandpressureover
alargeportionofitsservicelifeandtherebydrawmoreenergythannecessaryfromthepowertrain.
Forthisreason,moreandmorepumpsarenowvariableindesignandtheircontrolisbecoming
increasinglymorefine-tuned.Thustheconventionalpumpwasfollowedbyvolumetricflowcontrol,
whichwassubsequentlyextendedtoincludedmapcontrol.
Volumetricflowcontrol
TheN20usesavanetypeoilpump.Thecoreofthisvariable-volumetric-flowoilpumpisthesliding
mechanism.Itcanbedisplacedwithrespecttothepumpshafttovarythepump'sdeliveryrate.
N20engine,oilpump(leftatmaximumdelivery,rightatminimumdelivery)
75
N20Engine
3.OilSupply
Index Explanation
1 Controloilchamber
2 Pressureside
3 Slidingblock
4 Mainspring
5 Suctionside
Inthemaximumdeliverysettingtheslidingblockispositionedoff-centerwithrespecttothepump
shaft.Inthisway,anincreaseinvolumeoccursonthesuctionsideandcorrespondinglyadecreasein
volumeoccursonthepressureside.Thisgenerateshighpumpcapacity.
Whentheslidingblockisdisplacedtowardsthepumpshaft,thepumpvolumeisreduced.Therefore,
thepumpcapacityisreduceduntilfinallytheminimumdeliveryisreached.
Thepositionoftheslidingblockisdependentontheoilpressureinthepump'scontroloilchamber.
Thispressurepushesontheslidingblockagainsttheforceofaspring.Whenthepressureislowinthe
controlchamber,theslidingblockismovedoff-centerbytheforceofthespringandthedeliveryrate
ishigh.Whenthepressureishighinthecontrolchamber,theslidingblockisdisplacedtowardsthe
centerofthepumpasthespringiscompressedandthedeliveryratedecreases.
Withpurevolumetricflowcontrol,thepressureinthecontroloilchambercorrespondstothatinthe
mainoilpassage.Inthisway,itispossibletomaintainarelativelyuniformpressureirrespectiveofthe
necessaryvolumetricflow.Onereasonforlargedifferencesinthenecessaryvolumetricflowinthe
oilcircuitistheVANOSvariablecamshafttimingcontrolsystem.IntheVANOSunitstheoilisused
notonlyforlubricationpurposesbutalsoforhydraulicactuationofthecamtiming.Alargeoilvolume
isthusnecessaryduringtheadjustmentphase,whichcausesthepressureinthesystemtodrop.
Thefallingpressurecausestheslidingblockintheoilpumptobedisplacedinthedirectionofhigher
delivery.Inthisway,ahighervolumetricflowismadeavailableandthepressuredropiscompensated
for.
Asalreadymentioned,thepressurethatissetintheoilsystemisdependentontheforceofthespring
whichcounteractsthepressureinthecontroloilchamber.Withasofterspring,theslidingblockcan
bedisplacedmoreeasily,i.e.withalowerpressure,towardsthecenter.Withaharderspring,more
pressureisrequiredtoreducethevolumetricdisplacementofthepump.Thustheappropriatespring
wascalculatedandselectedtoproperlyoperatetheN20oilsystem.
Mapcontrolrepresentsafurtherfine-tuningofvolumetricflowcontrol.
Mapcontrol
Mapcontrolisusedtoinfluencethepressureinthecontroloilchamberofthepump.Twovalvesare
involvedinthisprocess,asolenoidvalvecalledthemapcontrolvalveandahydraulicvalvewhichalso
actsasafail-safe.Thisfailsafevalveisalsoreferredtoasanemergencyvalveorasecond-level
modecontrolvalve.
Themapcontrolvalveislocatedontheleftsideoftheengine(boltedtobedplate)andchannelsthe
oilpressurefromthemainoilpassagetothecontroloilchamberwithinthepump.Itspurposeisto
influencepumpvolumeoutputbygraduallyandsmoothlyreducingtheoilpressureinthecontroloil
chamber.
76
N20Engine
3.OilSupply
Mapcontrolvalve
Thefurtheritreducesthepressure,themorevolumeisdeliveredbytheoilpumpastheslidingblock
movesfurtheroffcenter.However,thismodedoesnotproduceapositiveeffectonenergysaving.
Thereforethemainspringintheoilpumpwhichactsontheslidingblockissofterthantheoneused
inapurelyvolumetric-flow-controlledsystem.Inotherwords,theslidingblockcanbemovedtoa
centredpositionveryeasily,asthepumpswitchestominimumdelivery.Inthisway,therearelower
pressureconditionsintheoilsystem,whichinturntranslatesintolessenergyspenttodrivetheoil
pump.Wherenecessary,thepressureinthecontroloilchambercannowbereducedbythemap
controlvalvewhichalsoreducesthedeliveryrate.
Thesecondstageofmapcontrolisahydraulic/emergencyvalvewhichislocatedintheoilpump
housing.
77
N20Engine
3.OilSupply
N20engine,oilpumpwithhydraulicemergencyvalve
Index Explanation
1 Connectionfrommainoilpassage
2 Connectionfrommapcontrolvalve
3 Hydraulic/Emergencyvalve
4 Channeltocontroloilchamber
5 Connectiontocounterbalanceshafts
6 Controloilchamber
Thisis3/2-wayvalveisusedtochannelthemainoilpressureintotheoilpump'scontroloilchamber.
Theoilfromthemainoilpassageforcesaplungeragainstaspringuntilthepassagetotheoilpump
controlchamberisopened.Theoilpressurefromthemapcontrolvalveactsontheotherendofthe
plunger.Thepressureinthemapcontrolvalveportcounteractsthemainoilpassagepressuretofine
tunetheoilpressurewithintheoilpump'svolumecontrolchamberwhichinturnvariestheoildelivery
rateofthepump.
78
N20Engine
3.OilSupply
N20engine,emergencyvalve
Index Explanation
1 Oilpumphousing
2 Emergencyspring
3 Plunger
4 Frommainoilpassage
5 Tocontroloilchamberinoilpump
6 Frommapcontrolvalve
Thehydraulicvalveislocatedbetweenthemapcontrolvalveandthecontroloilchamberintheoil
pump.Thefollowinggraphicshowsthisinasimplifiedoilcircuit.
N20engine,simplifiedmapcontroloilcircuit
79
N20Engine
3.OilSupply
Index Explanation
1 Oilpump
2 Mainoilpassage
3 Mapcontrolvalve
4 Emergencyvalve
Inmapcontrolmodeoilpressureactsonbothendsoftheplunger.Theoilpressuredirectlyfromthe
mainoilpassageactsagainsttheemergencyvalvespring.Atthesametimetheoilpressurereleased
bythemapcontrolvalveactsontheotherend,i.e.alongwiththeemergencyvalvespring.
N20engine,hydraulic3/2-wayvalvewithmapcontrol
Theplungerremainsconstantlyinitsendpositionduringmapcontrol.Todisplacetheplunger,there
wouldhavetobeapressureof5.5barinthemainoilporttocounteractthespring.Thisneverarises
inmapcontrolmode,sincethemaximumsetpressureinthesystemis4.5barinthecircuit.Inthis
settingtheemergencyvalveformsaconnectionbetweenthemapcontrolvalveandtheoilpump's
controloilchamber(thevalveisclosedtothemainoilduct).
N20engine,simplifiedoilcircuitwithmapcontrol
Thepumpdeliveryrateiscontrolledbythepressureinthepump'scontroloilchamberwhichinturnis
determineddirectlybytheDMEviathemapcontrolvalve.
Mapcontrolistheoilsystem'sstandardoperatingmode.Itisalwaysengagedwhentherearenofaults
inthesystemandtheoperatingconditionsdonotexceedordropbelowcertainvalues(seebelow).
Uptonowmapcontrolsystemwouldmanagewithouttheemergencyvalve.Thisishoweverasecond
stageofmapcontrolakindoffailsafemode.
80
N20Engine
3.OilSupply
Ifthemapcontrolvalveisdeactivated,thechamberattheendofthespringintheemergencyvalve
isdepressurized.Becausetheplungerisnowonlybeingheldbythespringthemainoilpressure
displacesitandmakesitswayintothepump'scontrolchamber.Apressuredifferenceof5.5baris
requiredtoswitchtheemergencyvalveintothisposition.
N20engine,emergencyvalvewithsecond-levelcontrol
Inthismodethepressureischannelledfromthemainoilpassagedirectlyintotheoilpump'scontrol
oilchamber.
N20engine,simplifiedoilcircuitinemergencymode
Thereisnomapcontrolinemergencymodebecausetheoilpressureissetto5.5barmax.andthere
isnooiladmittedintotheoilpump'scontroloilchamberbelowthislevel.
Themapcontrolvalveisclosedatzerocurrent.Therefore,shouldthemapcontrolvalvefail,the
systemisautomaticallyinemergencymode,guaranteeingpressurelimitationto5.5bar.Asalready
mentioned,mapcontrolmodeisthenormalmodeofoperation.Thereare,however,severalreasons
whytheDMEwillswitchtoemergencymode.
Emergencymodeisappliedinthefollowingconditions:
Mapcontrolvalvefaulty
Oilpressuresensorfaulty
Outsidetemperaturelessthan-20C/-4F
Highengineoilorcoolanttemperature
Drivingprofile(e.g.highenginerevsforalongtime)
81
N20Engine
3.OilSupply
TheoilpressuresensorsignalallowstheDMEtoidentifywhethertheemergencyvalveisstuck.Ifthis
isthecase,theDMEattemptstofreetheemergencyvalvebyapplyingavaryingpressurebuildup.
Iftheemergencyvalveisstuckintheclosedposition,itispossibletocontinuemapcontrol.If,
however,theemergencyvalveisstuckintheopenpositionsufficientpressurebuildupisnolonger
possible.Theoilpressureindicatorlightisactivatedandtheenginemustbeshutdownimmediately.
Summary
Byapplyingoilpumpmapcontrol,itispossibletodeliveranoilsupplytomatchdemandandto
reducetheaveragepressurelevelintheoilcircuit.Thisensuresthattheoilpumphasalowerenergy
requirement.
Themapcontrolvalvecontrolsthepressureinthesystemandinturnallowsthedeliveryratetobe
controlledbytheDME.
Thefollowingdiagramshows(insimplifiedform)thepressurecurvesplottedagainstenginespeedfor
differentoilpumps.
Simplifiedpressurecurvesfordifferentoilpumps
82
N20Engine
3.OilSupply
Index Explanation
A Oilpressure
B Enginespeed
1 Non-controlledoilpump
2 Volumetric-flow-controlledoilpump
3 Map-controlledoilpumpatfullload
4 Map-controlledoilpumpatpartialload
Thediagramillustratestheadvantageofcontrolledoilpumps.Whenasufficientoilpressureis
reached,thedeliveryrateoftheoilpumpcanbereduced.Lowerpressureissynonymouswith
fuelsaving.Thusthemap-controlledoilpumpoffersthegreatestadvantagehere,sinceitcanbe
controlledregardlessofenginespeed.Atpartialload,forexample,onlylowerpressuresarerequired,
becausethecrankshaftmainbearingshavetobearlessload.Accordingly,aloweroilpressurecan
besetinthepartialloadrange,whichillustratesevenmoreclearlytheadvantageoverthevolumetric-
flow-controlledoilpump.
Theoilpressureinmapmoderangesbetween1.5and4.5bar.
Theemergencyvalvehasbeenintegratedinthesystemasafailsafeandtofacilitateahigherpressure
incertainconditions.Forexampleifthemapcontrolvalvefails,itensuresthenecessarypressureis
builtupandtheoilpumppressurecontrolof5.5bar.
3.2.3.Pressure-limitingvalve
Additionallyavailabletocontroltheoilpumpisapressure-limitingvalve,whichisoftenalsoknownasa
cold-startvalve.
N20engine,pressure-limitingvalveinoilpump
Index Explanation
1 Oilpumphousing
2 Oilpumpcover
3 Pressure-limitingvalve
83
N20Engine
3.OilSupply
Thepressure-limitingvalveislocatedintheoilpumphousingandintheoilcircuitasthefirst
componentafterthepump.Itopensatapressureofroughly12to13baranddischargestheoil
directlyintotheoilsump.Itisnecessaryatlowtemperaturesandwhentheoilhasahigherviscosity.
Inthesesituationsthepressure-limitingvalvepreventsdamagetocomponents,inparticulartotheoil
filtermoduleanditsseals.Thisisrelevantattemperaturesofbelow-20C/-4F,sincemapcontrolis
alreadyactiveabovethistemperature.
3.3.Oilfilteringandcooling
TheN20enginehasasimilarplasticoilfilterhousingastheN55engine,towhichtheengineoil-to-
coolantheatexchangerisalsodirectlymounted.Thisentireunitisknownastheoilfiltermodule.
N20engine,oilfiltermodule
Index Explanation
1 Oilfilter
3.3.1.Oilcooling
IntheN20enginetheengineoil-to-coolantheatexchangerislocatedintheoilcircuitaheadoftheoil
filter.Thisisknownasraw/unfilteredoilcooling,incontrasttocleanoilcooling.Thisisduetothelead-
freecrankshaftandconnectingrodbearings.Becausethesecomponentsareextremelysensitiveto
dirtparticles,thisarrangementbringstheoilfilterevenclosertojustbeforethebearingpositions.The
importanceisevengreatershouldauxiliaryengineoilcoolersbeusedinlatermodels,asherethereis
alwaystheriskofdirtgettingintotheoilcircuitafteranaccident.
Permanentbypass
TheN20enginedoesnothaveaheatexchangerbypassvalve.Instead,astheN55,ithasapermanent
bypass.Thisisapermanentlyopenbypassaroundtheengineoil-to-coolantheatexchanger.The
bypassincorporatesaflowrestrictortoensurethatthemajorityoftheoilflowsthroughtheengineoil-
to-coolantheatexchanger.
84
N20Engine
3.OilSupply
3.3.2.Oilfiltering
Thefull-flowoilfilterusedintheN20engine.Insteadofanon-returnvalve,anon-returndiaphragmis
mounteddirectlyonthefilterelement.Thefunctionofthisdiaphragmistopreventtheoilfilterfrom
drainingaftertheengineisshutdown.
N20engine,oilfilter
Index Explanation
1 Oilfilter
2 Non-returndiaphragm
Thenon-returndiaphragmismadeofrubberandisraisedbytheoilpressuretoadmitoilintothefilter.
Whentheengineisshutdownandtheoilpressuredrops,thenon-returndiaphragmusesitsshape
andelasticitytosealofftheoilduct.Theengineoilisunabletoflowoutofthefilter.Thenon-return
diaphragmispartoftheoilfilterandisthereforeautomaticallyreplacedeachtimethefilterischanged.
TheN20enginehasafilterbypassvalvewhichcanopenabypassaroundthefilterif,forexample,the
engineoiliscoldandhasahigherviscosity.Thisoccursifthepressuredifferencebetweenbeforeand
afterthefilterexceedsabout.2.5bar.Theallowablepressuredifferencehasbeenincreasedfrom2.0
to2.5barinordertoprotectthelead-freecrankshaftandconnectingrodbearings.Thisensuresthat
thefilterisbypassedmuchlessfrequentlyandanydirtparticlesarereliablyfilteredout.
85
N20Engine
3.OilSupply
3.4.Oilmonitoring
3.4.1.Oilpressureandtemperaturesensor
N20engine,oilpressureandtemperaturesensor
Anewcombinedoilpressureandtemperaturesensorisused.Thepressuresignalisrequiredforoil
pumpmapcontrol,thetemperaturesignalforengineheatmanagement.
Thesensorisexposedinthemainoilpassagetotheoilpressureprevailingthereandtheoil
temperature.Thus,whatismeasuredisnolongertheoiltemperatureintheoilsump,butinsteadthe
actualoiltemperatureintheengine.
Combinedpressureandtemperaturesensorsusuallyhavefourconnections(powersupply,ground,
temperaturesignal,pressuresignal).Theoilpressureandtemperaturesensorhasonlythree
connections.Thetemperatureandpressuresignalsarenottransmittedonseparatewires.Instead,
thesensoroutputsapulse-width-modulated(PWM)signal.ThisPWMsignalissplitintothreefixed
cycles.Thefirstcycleisforsynchronizationanddiagnosis,thesecondtransmitsthetemperature,and
thethirdthepressure.Thedurationofthehighlevelofarespectivecycledeterminesthevalue.
Cycle Function Durationofcycle Durationofhigh

level
1 Synchronizationand 1024s 256640s
diagnosis
2 Temperature 4096s 1283968s
3 Pressure 4096s 1283968s
Thelengthofthehighlevelisforthediagnosticsignalalwaysamultipleof128s(microsecond=
0.000001seconds),asisshowninthetablebelow:
Durationofhighsignal Pulsewidth Meaning

256s 25% DiagnosisOK
384s 37.5% Pressuremeasurementfailed
512s 50% Temperaturemeasurement
failed
640s 62.5% Hardwarefault
Forthispurposethesensoriscapableofself-diagnosisandcanidentifysensor-internalmechanical
andelectricalfaults.
86
N20Engine
3.OilSupply
Forthetemperaturesignal:
128s(3.125%pulsewidth)=-40C/-40F
3968s(96.875%pulsewidth)=160C/320F
Forthepressuresignal:
128s(3.125%pulsewidth)=0.5bar(absolute)
3968s(96.875%pulsewidth)=10.5bar(absolute)
Thetimesindicatedarenominalvalues.Actuallythedurationsofeachcycleandoftherespectivehigh
levelaremeasureandcomparedwitheachother.Theresultingpulsewidthproducestherespective
measuredvalue.
Theactualoilpressurecanbemeasuredbyinstallingspecialtool#2212823.Pleasereferto
therepairinstructions.
3.4.2.Oillevelmonitoring
Theestablishedthermaloillevelsensorisusedtomonitortheoillevelandtheoiltemperature.
3.5.Oilspraynozzles
AswithpreviousBMWenginesthosecomponentswhichcannotbereacheddirectlybyanoilpassage
arelubricatedand/orcooledbyoilspraynozzles.
3.5.1.Pistoncrowncooling
TheoilspraynozzlesforpistoncrowncoolingareusedintheN20engine.Theyincorporateanon-
returnvalvetoenablethemtoopenandcloseonlyfromaspecificoilpressure.
Aswellascoolingthepistoncrowns,theyarealsoresponsibleforlubricatingthewristpins,whichis
whyitisveryimportantforthemtobepreciselyaligned.
N20engine,oilspraynozzlesforpistoncrowncooling
Openingpressure 2.52.9bar
Closingpressure 2.1bar
87
N20Engine
3.OilSupply
TheoilspraynozzlesforpistoncrowncoolingintheN20enginemustbecorrectlypositionedusinga
specialtool#2212829afterbeinginstalled.Refertotherepairinstructions.
TherearetwodifferentvariantsofoilspraynozzleforpistoncrowncoolingfortheN20engine,
dependingontheirarrangementintheengine.Onevariantforcylinders1and3andonevariantfor
cylinders2and4.
3.5.2.Chaindrive
ThechaindriveintheN20engineisdividedintoanuppersection(thecamshaftdrive)andalower
section(theoilpumpdrive).
Camshaftdrive
Thetimingchainislubricatedbyanoilspraynozzlelocatedinthechaintensioner.Thereisanopening
inthetensioningrailthroughwhichtheoilcanbesprayedforthispurpose.
N20engine,chaintensionerwithoilspraynozzlefortimingchain
88
N20Engine
3.OilSupply
Counterbalanceshaftandoilpumpdrive
N20engine,counterbalanceshaftandoilpumpdrive
Index Explanation
1 Crankshaftsprocket
2 Chain
3 Chaintensioner
Oilissprayedontothechainthroughthechaintensionerforthecounterbalanceshaftandoilpump
drive.Thisishowevernotnecessaryforlubrication,sincethechainisimmersedintheoilsump.Inthis
case,thishelpstheoiltodrainfromthechaintensioner.
3.5.3.Camshaft
Thelobesonthecamshaftarealsolubricatedviaoilspraynozzles.Fortheintakecamshaftthereare
finegroovesinthegateswhicharesuppliedwithoilfromthescrewhole.
89
N20Engine
3.OilSupply
N20engine,guideblockwithoilspraynozzlesforintakecams
Index Explanation
1 Screwconnection,gates
2 Oilspraynozzlesforintakecams
3 Oilsupplyforoilspraynozzles
Whenfittingtheguideblockitisessentialtoworkinabsolutelycleanconditions,asanysoilingcould
blocktheoilspraynozzles.Lubricationofthecamlobeswouldnolongerbeguaranteedandcould
resultindamagetothevalvetrain.
Fortheexhaustcamshaft,thecylinderheadfeaturesanoilpipewhichspraysoilthroughsmallholes
directlyontothecamlobes.Accordingly,thereareeightholesforlubricatingtheexhaustvalvelobes
andanextraholeforlubricatingthetriplecamwhichdrivesthehigh-pressurefuelpump.
N20engine,oilpipewithoilspraynozzlesforexhaustcamlobes
90
N20Engine
3.OilSupply
Index Explanation
1 Oilpipe
2 Hole
3.5.4.Gearing,Valvetronicservomotor
N20engine,oilspraynozzleforValvetronicservomotor
TheN20enginefeaturesthesameValvetronicservomotorastheN55engineincludingthesame
installationposition.Thewormgearforadjustingtheeccentricshaftisalsolubricatedbyanoilspray
nozzle.Thisnozzlemustbecorrectlyalignedwhenfitted.However,thisdoesnotrequiretheuseofa
specialtool.Insteadthenozzlehastobecarefullyandnoticeablyengagedinthedesignatedguideon
theValvetronicservomotor.
91
N20Engine
3.OilSupply
N20engine,engagedoilspraynozzleforValvetronicservomotorgearing
Index Explanation
1 OilspraynozzleforValvetronicservomotorgearing
3 Correctlyengagedoilspraynozzle
Duetothesizeoftheoilspraynozzleandthefactthatthemotorcanbeassembledwithouttheoil
spraynozzle,thereisthedangerofitbeingforgottenduringfitting.
Makesurewhenfittingtheoilspraynozzlethatitiscorrectlypositionedandengaged.Anincorrectly
engagedoilspraynozzlewillbesubjectedtovibrationsandmaybreak.Refertotherepairinstructions.
92
N20Engine
4.Cooling
ThecoolingsystemisverysimilartotheN55engine.IntheN20engineanengineoil-to-coolantheat
exchangerisusedtocooltheengineoil.Thecoolingsystemiscontrolled(e.g.electriccoolantpump,
mapthermostatandelectricfan)bytheheatmanagementcoordinatorintheDME.
4.1.Overview
N20engine,coolingcircuit
Index Explanation
1 Radiator
2 Electricfan
3 Mapthermostat
4 Heaterformapthermostat
5 Filllevelsensorinexpansiontank
6 Expansiontank
7 Exhaustturbocharger
93
N20Engine
4.Cooling
Index Explanation
8 Heatercore
10 Coolanttemperaturesensor
11 Electriccoolantpump
Thecoolingmoduleitselfonlycomesinonevariant.Anauxiliaryradiator(intherightwheelarch)is
usedinvehiclesusedinhotclimatesmarketsandincombinationwiththemaximumspeedoptional
equipment.
Theelectricfanhasanominalpowerof600W.
Thefollowinggraphicsshowtheinstallationlocationsandlayoutsofthecomponents.
N20engine,coolingsystemcomponentsfromrear
94
N20Engine
4.Cooling
Index Explanation
2 Enginereturn,bypasscircuit
3 Mapthermostat
4 Radiator
5 Ventilationline
6 Expansiontank
7 Enginefeed
9 Auxiliaryradiator(notinstalledinallmodels)
10 Feed,heatercore
11 Return,heatercore
N20engine,coolingsystemcomponentsonenginefrontview
95
N20Engine
4.Cooling
Index Explanation
1 Expansiontank
2 Mapthermostat
3 Enginereturn,bypasscircuit
5 Connection,feed,heatercore
6 Feed,radiator
7 Return,heatercore
9 Return,radiator
4.2.Heatmanagement
TheN20enginehasthesameheatmanagementfunctionsintheDMEastheN55.Thisallows
independentcontroloftheelectriccoolingcomponentsofelectricfan,mapthermostatandcoolant
pump.
4.2.1.Coolantpump
TheN20enginehasanelectriccoolantpump,asisthecasewithmanyBMWengines.Itsnominal
powerconsumptionis400W.
N20engine,coolantpump
Ifthecoolantpumpisremovedbutistobereused,itisimportanttoensurethatitissetdownstillfilled
withcoolant.Dryingoutmaycausethebearingstostick.Notfollowingthisprocedurecanpossibly
causethecoolantpumpnotstart,whichinturnmayresultindamagetotheengine.
Beforeinstalling,turnthepumpimpellermanuallytoensurethatitmovesfreely.
96
N20Engine
4.Cooling
4.2.2.Mapthermostat
TheN20engineisfittedwithaconventionalmapthermostatwhichhasthefollowingtechnicaldatain
non-electricallycontrolledmode:
Settingofmapthermostat Coolanttemperature
Startstoopen 972C/2062F
Fullyopen 109C/2282F
Inaddition,anelectricheaterinthemapthermostatcanbeusedtomakethethermostatopenata
lowercoolanttemperature.
4.2.3.Heatmanagementfunction
Theheatmanagementdeterminesthecurrentcoolingrequirementandcontrolsthecoolingsystem
accordingly.Undercertaincircumstancesthecoolantpumpcanevenbeshutdownentirely,for
exampleinordertoheatthecoolantmorequicklyinthewarm-upphase.Thecoolantpumpcontinues
todeliverwhentheengineisstoppedandveryhottocooltheexhaustturbochargers.Thecooling
outputcanthereforeberequestedindependentlyoftheenginespeed.Inadditiontothemap
thermostattheheatmanagementisabletoactivatethecoolantpumpusingdifferentprogrammaps.
Theenginemanagementisthusabletoadaptthecoolanttemperaturetothedrivingsituation.
Thefollowingtemperaturerangesareadjustedbytheenginemanagement:
109C/2282F=Economyoperation
106C/2222F=Normaloperation
95C/2032F=Highoperation
80C/1762F=Highoperationandcurrentsupplytothemapthermostat.
IftheenginecontrolunitidentifiestheEconomyoperatingrangeonthebasisofrunning
performance,theenginemanagementadjuststoahighertemperature(109C/228F).Inthis
temperaturerangetheengineistobeoperatedwitharelativelylowfuelrequirement.Internalengine
frictionisreducedathighertemperature.Thetemperatureincreasethereforefavorsthelowerfuel
consumptioninthelowloadrange.InHighoperationandcurrentsupplytothemapthermostat
modethedriverwouldliketoutilizetheengine'soptimumpowerdevelopment.Thusthetemperature
inthecylinderheadisreducedto80C/176Fforthispurpose.Thisreductionimprovesvolumetric
efficiency,whichresultsinanenginetorqueincrease.Theenginecontrolunitcannow(adaptedto
therelevantdrivingsituation)adjustaspecificoperatingrange.Itisthereforepossibletoinfluence
consumptionandpoweroutputviathecoolingsystem.
Systemprotection
Ifthecoolantorengineoilissubjecttoexcessivetemperaturesduringengineoperation,certain
functionsinthevehicleareinfluencedinsuchawaythatmoreenergyismadeavailableforengine
cooling.
Themeasuresaresplitintotwooperatingmodes:
Componentprotection
97
N20Engine
4.Cooling
- Coolanttemperaturefrom117C/242F
- Engineoiltemperaturefrom143C/289Fattheoilpressureandtemperaturesensorin
themainoilpassage
- Measure:e.g.powerreductionofclimatecontrolandofengine
Emergency
- Coolanttemperaturefrom122C/251F
- Engineoiltemperaturefrom151C/303Fattheoilpressureandtemperaturesensorin
themainoilpassage
- Measure:e.g.powerreductionofengine(uptoabout.90%)
4.3.Internalenginecooling
AsintheN55engine,thecoolantpassagesinthecylinderheadalsosurroundtheinjectors,whichare
cooledinthisway.
UnliketheN55engine,theN20enginehasnogroovesontheblockdeckbetweenthecylinders.
Instead,theN20enginehasboreholesbetweenthecylinders,twooneachside,whichmeetinthe
middle.
N20engine,coolingjacketandcoolantpassages
Index Explanation
1 Coolingjacket,exhaustside
2 Coolingjacket,intakeside
3+4 Coolantpassagesinthelands
98
N20Engine
5.AirIntake/ExhaustEmissionSystems
TheairintakeandexhaustemissionsystemsareinprinciplesimilartotheN55.Thelistbelowitemizes
themostimportantfeaturesoftheairintakeandexhaustemissionsystems:
Permanentlyattachedintakesilencer
Hot-filmairmassmeter
TwinScrollexhaustturbochargerwithintegratedwastegateandblowoffvalves
Threeconnectionsforcrankcaseventilation
5.1.Overview
N20engine,airintakeandexhaustemissionsystems
Index Explanation
1 Chargeaircooler
2 Blowoffvalve
3 Intakesilencer
4 Hot-filmairmassmeter
99
N20Engine
Index Explanation
6 Wastegatevalve
7 Oxygensensorbeforecatalyticconverter
8 Catalyticconverter
9 Oxygensensoraftercatalyticconverter
10 DigitalEngineElectronics(DME)
11 Intakemanifoldpressuresensor
12 Throttlevalve
13 Chargeairtemperatureandpressuresensor
100
N20Engine
5.2.Intakeairsystem
N20engine,airintakesystem
Index Explanation
1 Intakemanifold
3 Throttlevalve
6 Intakesilencer
101
N20Engine
Index Explanation
7 Unfilteredairintake
8 Chargeaircooler
9 Connection,crankcaseventilation,turbochargedmode
10 Connection,purgeairline,crankcaseventilation
11 Blowoffvalve
5.2.1.Hot-filmairmassmeter
TheN20engineisequippedwithahot-filmairmassmeter,whichisverysimilartothatintheN74
engine.
Itcangenerallybesaidthatthequalityofairmassdeterminationbymeasurementusingahot-filmair
massmeterandbycalculationofthesubstitutevalue(ofintakeairtemperature,chargingpressure,
enginespeed,etc.)istobeconsideredasequalinthecurrentstateofdevelopment.Thecalculated
substitutevalueisneverthelessusedforengineloadcontrol.Thisvalueishoweverregularlyadjusted
withthevalueofthehot-filmairmassmeterinordertocompensatefortoleranceswhichariseon
accountofthecomplexflowconditionsintheairintakesystem.Themoresophisticatedthemixture
preparationmethod(Valvetronic,HighPrecisionInjection(especiallyinconjunctionwithstratified
chargemode),TVDI),themoreimportantitistoadjustthesubstitutevaluewiththehot-filmairmass
meter.TVDIiscurrentlythemostsophisticatedmixturepreparationmethod.Forthisreason,allTVDI
enginesarealsoequippedwithahot-filmairmassmeter.
Theuseofahot-filmairmassmeteralsoofferstheopportunityofextendeddiagnostics,e.g.fortank
orcrankcaseventilation,asthesesystemscreateadeviationintheairmassthatcanbeinterpreted
andusedtodiagnoserunningfaults.
Failureordisconnectionofthehot-filmairmassmeterdoesnotimmediatelyresultinemergency
engineoperation.However,impairedmixturepreparationandthereforepooreremissionvaluesare
possible,whichiswhytheemissionswarninglamp(CheckEngineLight)lightsup.
5.2.2.Intakemanifold
AsintheN55engine,theDigitalEngineElectronics(DME)ismountedontheintakemanifold.
However,therearedifferences.First,theDMEislocatedontheintakemanifoldandnotunderit.
Second,theintakemanifoldisnotopenaftertheDMEisremoved.Locatedbetweentheintake
manifoldandtheDMEisametalplate(heatsink)whichconductsheatawayfromtheDMEthisplateis
cooledbytheairflowoftheintakemanifold.
102
N20Engine
N20engine,intakemanifoldwiththrottlevalve
Index Explanation
1 Throttlevalve
3 Connectionfromtankventvalve
4 MetalplateforaccommodatingtheDME
5 Intakemanifold
Intakemanifoldpressuresensor
Locateddirectlybehindthethrottlevalve,attheentrytotheintakemanifold,istheintakemanifold
pressuresensor.Oncloserinspection,itcanbeseentobeacombinedpressureandtemperature
sensor.Thetemperaturesignalisthereforenotreadout.Thereasonforusingthissensorliesinthe
conceptofcommonparts.Itisbettertousethesamesensorwhichisalsousedasthechargeair
temperatureandpressuresensorandsimplynottoreadoutthetemperaturesignalthantointroducea
separatesensor.
5.3.Exhaustturbocharger
TheN20enginefeaturesanexhaustturbochargerwithTwinScrolltechnology.Itincludesatthe
turbineinlettwoseparateportsinwhichtheexhaustgasisroutedfromtwocylinderstotheturbine
vanes.
103
N20Engine
N20engine,turbocharger
Index Explanation
A Exhaustport,cylinders2and3
B Exhaustport,cylinders1and4
C Outlettocatalyticconverter
D Inletfromintakesilencer
E Ringport
F Outlettochargeaircooler
1 Vacuumunitforwastegatevalve
2 Oilsupply
3 Wastegatevalve
4 Turbinewheel
104
N20Engine
Index Explanation
5 Coolingpassage
6 Oilpassage
7 Coolantreturn
8 Blowoffvalve
Theturbochargerhasafamiliardesignwithanelectricblowoffvalveandavacuum-controlled
wastegatevalve.
5.3.1.FunctionofTwinScrollexhaustturbocharger
ThedesignationTwinScrolldenotesanexhaustturbochargerwithatwin-scrollturbinehousing.The
exhaustgasfromtwocylindersineachcaseisroutedseparatelytotheturbine.IntheN20engine(as
isusualin4-cylinderengines)cylinders1and4andcylinders2and3arebroughttogethertoformtwo
portseachfeedingonescroll.Thisresultsinpulsechargingwhichisusedtogreatereffect.
Pressureandpulsecharging
Twoprinciplesofforcedinductionareusedinengineswithexhaustturbochargerspressureand
pulsecharging.Pressurechargingmeansthatthepressureaheadoftheturbineisapproximately
constant.Theenergywhichdrivestheexhaustturbochargerisobtainedfromthepressuredifference
beforeandaftertheturbine.
Inthecaseofpulsecharging,thepressurebeforetheturbineishigh-speedandgreatlyfluctuating,or
pulsatingbythedischargeoftheexhaustgasfromthecombustionchamber.Thepressureincrease
resultsinapressurewavewhichstrikestheturbine.Inthiscase,thekineticenergyoftheexhaustgas
isused,wherebythepressurewavesdrivetheturbocharger.
Pulsechargingprovidesforafastresponsebytheturbocharger,especiallyatlowspeeds,because
pulsationisatitsstrongesthere,whereasinthecaseofpressurechargingthepressuredifference
betweenbeforeandaftertheturbineisstilllow.
Inactualfact,bothprinciplesarealwaysusedinexhaustturbochargersinpassengercarengines.The
proportionofpulsechargingishigherorlower,dependingonthesizefactors,theexhaustportguides
andthenumberofcylinders.
Dependenceonthenumberofcylinders
Inasingle-cylinderenginethereisanexhaustcycleeverytworevolutionsofthecrankshaft.
Theoretically,exhaustgasisthereforedischargedfor180every720crankangle.Thegraphicbelow
showsinhighlysimplifiedformthepressureconditionsbeforetheexhaustturbochargerinasingle-
cylinderengine.
105
N20Engine
Pressurediagraminexhaustportbeforetheturbochargerina1-cylinderengine
Index Explanation
A Bottomdeadcenter,exhaustvalveopens
B Topdeadcenter,exhaustvalvecloses,intakevalveopens
C Bottomdeadcenter,intakevalvecloses
D Topdeadcenter,ignition
Ascanbeseenhere,every720CAthereisapressurewavewhichstrikestheturbine.Thispulse
acceleratestheturbine.
Thenextgraphicshowsthepressureconditionsbeforetheturbineina4-cylinderengine.
Pressurediagraminexhaustportbeforeexhaustturbochargerina4-cylinderengine
Index Explanation
1 Exhaustvalve,1stcylinder,opens
2 Exhaustvalve,2ndcylinder,opens
3 Exhaustvalve,3rdcylinder,opens
4 Exhaustvalve,4thcylinder,opens
Becauseeachcylinderhaditsexhaustcycleaftertwofullcrankshaftrevolutions,therearefour
pressurewaveswithinthe720CA.Becauseofthefiringinterval,theyaredistributedevenlyatan
intervalof180CA.Thepressurewavesaresuperimposedhere.Whilethepressureofonecylinder
decreases,thepressureofthenextcylinderisalreadyincreasing.
Thisproducesasuperimposedpressurebeforetheturbine,asthenextgraphicshows.
106
N20Engine
Pressurediagraminexhaustportbeforetheturbochargerina4-cylinderengine,superimposed
Becausetheyaresuperimposed,thepressuredifferencefromminimumtomaximumisclearlylower.
Inthisway,thepulsebythepressurewaveontheturbinealsodecreases.Inthiscases,theproportion
ofpulsesuperchargingintheexhaustturbochargerislower.
Onewayofpreventingthisina4-cylinderengineistheTwinScrollexhaustturbocharger.Bysplitting
thefourcylindersintotwoports,thepressureconditionsofa2-cylinderenginearedepictedinthetwo
portsineachcase,asthefollowinggraphicshows.
Pressurediagraminexhaustportbeforetheturbochargerina4-cylinderengine,individuallyandsuperimposed
Index Explanation
1 Exhaustvalve,1stcylinder,opens
4 Exhaustvalve,4thcylinder,opens
Heretoothepressuresofthetwocylindersaresuperimposed.However,cylinders1and4and2and3
arecombinedinthetwoports.Becauseofthefiringorderofa4-cylinderengine,thereisineachcase
anintervalof360CAbetweentheexhaustcyclesofaport.Thusthereisalargepressuredifference
andthekineticenergyoftheexhaustgascanbebetterutilized.
Aspeciallyshapedexhaustmanifoldisusedtocombinetheexhaustpipesfromcylinders1and4and
2and3.
Intheturbochargerthesetwoportsrunseparatelyfromeachotheruptotheturbine.TheTwinScroll
exhaustturbochargerdiffersfromaconventionalexhaustturbochargerinthattheturbinehousing
separatesintwoformingaringchannelaroundtheturbine.
107
N20Engine
5.4.Exhaustemissionsystem
5.4.1.Exhaustmanifold
TheexhaustmanifoldisidenticalindesigntothatoftheN55engine.Itisair-gap-insulatedand
weldedtotheturbocharger.TheexhaustmanifoldintheN20engineisafour-into-twotype,which
isnecessaryforthespecialfunctionoftheTwinScrollturbocharger.Heretheexhaustoutletpipesof
cylinders1and4and2and3arecombinedineachcaseintooneportaspreviouslydiscussed.
N20engine,exhaustmanifoldwithexhaustturbocharger
Index Explanation
1 Exhaustports,cylinders1and4
2 Exhaustports,cylinders2and3
5.4.2.Catalyticconverter
TheN20enginehasanupstreamcatalyticconverterwithtwoceramicmonoliths.
108
N20Engine
Cutawayviewofcatalyticconverter
Index Explanation
1 Connectiontoexhaustsystem
2 De-couplingelement
3 Monitoringsensor
4 Controlsensor
5 Connectiontoturbine
6 Ceramicmonolith1
7 Ceramicmonolith2
Volume Diameter Numberofcells

Ceramicmonolith1 0.75 118.4 600
Ceramicmonolith2 0.99 125 400
Oxygensensors
TheBoschoxygensensorsusedarefamiliarfrompreviousengines:
Preoxygensensor:LSUADV
Postoxygensensor:LSF4.2.
Thepreoxygensensorislocatedaheadoftheprimarycatalyticconverter,ascloseaspossibletothe
turbineoutlet.Itspositionhasbeenchosensothatallthecylinderscanberecordedseparately.The
postoxygensensorispositionedbetweenthefirstandsecondceramicmonoliths.
109
N20Engine
6.VacuumSystem
ThevacuumsystemoftheN20engineiscomparablewiththatoftheN55engine.Aswellassupplying
thebrakeservo,itisneededprimarilytoactivatethewastegatevalveontheturbocharger.Inaddition,
theexhaustflapisactuatedbyvacuumintheN20engine.
N20engine,vacuumsystem
Index Explanation
1 Connection,brakeservo
2 Vacuumpump
3 Connection,exhaustflap
4 Vacuumreservoir
5 Electro-pneumaticpressureconverterforwastegatevalve
6 Vacuumunit,wastegatevalve
110
N20Engine
6.VacuumSystem
Thevacuumpumpasusualisdesignedtohavetwostagessothatthemajorityofthegenerated
vacuumismadeavailabletothebrakeservo.Avacuumreservoirisusedtoprovidesufficientvacuum
foractuatingthewastegatevalve.Thisreservoirisbuiltintotheenginecover.
Disconnectthevacuumlinebeforeremovingtheenginecover,asotherwisethereisariskofdamage.
111
N20Engine
7.FuelPreparation
TheN20engineuseshigh-pressureinjection,whichwasintroducedintheN55engine.Itdiffersfrom
high-precisioninjection(HPI)inthatitusessolenoidvalveinjectorswithmulti-holenozzlesinsteadof
thepiezoelectrictype.
7.1.Overview
ThefollowingoverviewshowsthefuelpreparationsystemoftheN20engine.Itessentially
correspondstothesystemswithdirectfuelinjectionfamiliarinBMWmodels.
N20engine,fuelpreparation
112
N20Engine
7.FuelPreparation
Index Explanation
1 Connection,quantitycontrolvalve
2 High-pressurepump
3 Low-pressureline
4 High-pressureline,rail-injector
5 High-pressureline,high-pressurepump-rail
6 Rail
7 Solenoidvalveinjector
Boschhigh-pressurefuelinjectorswiththedesignationHDEV5.2areused.Thehighpressurepumpis
alreadyknownfromthe8and12cylinderengines.AninnovationintheN20engineisthefactthatthe
high-pressurelinesfromrailtoinjectorarenownolongerscrewedattherailend,butwelded.Another
featurewhencomparedwithestablishedBMWfuelsystemsistheomissionofthefuellow-pressure
sensor.
Workonthefuelsystemisonlypermittedaftertheenginehascooleddown.Thecoolant
temperaturemustbebelow40C/104F,toavoidriskofinjuryduetospraybackfrom
residualpressureinthehigh-pressurefuelsystem.
Whenworkingonthehigh-pressurefuelsystem,itisessentialtoadheretoconditionsof
absolutecleanlinessandtoobservetheworksequencesdescribedintherepairinstructions.
Eventheslightestcontaminationanddamagetothethreadedfittingsofthehigh-pressure
linescancauseleaks.
WhenworkingonthefuelsystemoftheN20engine,itisimportanttoensurethattheignitioncoils
arenotwetwithfuel.Theresistanceoftheinsulatingsiliconematerialisgreatlyreducedbysustained
contactwithfuel.Thismayresultinarcingonthesparkplugconnectionandthusinmisfires.
Beforemakinganymodificationstothefuelsystem,removetheignitioncoilsandprotectthe
sparkplugsbycoveringwithacloth
Beforereinstallingthesolenoidvalveinjectors,removetheignitioncoilsandensurethatthe
cleanestpossibleconditionsaremaintained.
Ignitioncoilsheavilysaturatedbyfuelmustbereplaced.
7.2.Fuelpumpcontrol
Asalreadymentioned,thereisnofuellow-pressuresensorintheN20engine.Thefuelpressureis
calculatedbymonitoringpumpspeedandload.
7.3.High-pressurepump
TheBoschhigh-pressurepump,familiarfromtheN63andN74isused.Thisisasingle-plungerpump
whichisdrivenfromtheexhaustcamshaftviaatriplelobeonthecam.
113
N20Engine
7.FuelPreparation
Forfurtherinformationonthehigh-pressurepump,pleaserefertotheN63andN74enginetraining
informationavailableonTISandICP.
7.4.Injectors
TheBoschHDEV5.2solenoidvalveinjectorisaninward-openingmulti-holevalveunliketheoutward-
openingpiezoinjectorusedinHPIengines.TheHDEV5.2isalsocharacterizedbyhighvariabilitywith
regardtosprayangleandspraypattern,andisconfiguredforasystempressureofupto200bar.
TheseinjectorsarealreadyusedintheN55engine.However,theiroperatingprincipleisthesameas
thatoftheinjectorsusedintheN73engines.
Note:TheN73HDEVcontrolmodulescontainpulsewidthmodulatedfinaloutputstages
withhighperformancecapacitorstotransformthesystemvoltageupto85to100volts.See
ST042E65CompleteVehicle/N73enginetrainingmaterialavailableonTISandICP.
114
N20Engine
7.FuelPreparation
Index Explanation
1 Fuellineconnection
2 Electricalconnection
3 Stem
4 Compressionspring
5 Solenoidcoil
6 Armature
7 Nozzlepintle
8 6-holenozzle
Amagneticfieldisgeneratedwhenthecoilisenergized.Thismagneticfieldliftsthenozzlepintle
againstspringpressureoffthevalveseatandopensthedischargeholesoftheinjectornozzle.The
highpressureintherailforcesthefuelthroughdischargeholesathighspeedintothecylinder.To
terminateinjection,currentisshutoff,thenozzlepintleisforcedclosedbyspringforcebackontothe
valveseat.
115
N20Engine
7.FuelPreparation
Thevalveopensandclosesatveryhighspeedandensuresaconstantopeningcross-sectionduring
theopeningperiod.Theinjectedfuelquantityisdependentontherailpressure,thebackpressurein
thecombustionchamberandtheopeningperiodoftheinjector.
Forfurtherinformationoninjectoractivation,refertothesectionentitledEngineElectricalSystemof
thistrainingmaterial.
Unliketheinjectorspreviouslyused,thesolenoidvalveinjectorsoftheN55andN20engineshave
longandrelativelysensitivestemsmadenecessarybytheshapeofthecylinderhead.Eachstemis
madeofplasticontheoutsidebutontheinsidethereisametaltubeservesasafuelline.
Thestemsofthesolenoidvalveinjectorscanonlywithstand6Nmoftorquewhichtranslates
to2000Noftensileforce.Itisessentialwhenremovingandinstallingtheinjectorstofollow
thespecificproceduresetoutintherepairinstructions,alongwiththeuseofspecialtool#0
496885forinjectorremoval.Ifthistoolisnotusedtheinjectorswillbedamaged.
116
N20Engine
8.FuelSupply
Thefuelsupplyisvehicle-specific.Hardlyanychangeshavebeenmadetothealreadyexisting
models.Thereforeonlythetankventilationsystemontheenginewillbedescribedingreaterdetail
here.
8.1.Tankventilation
SimilartotheN55
8.1.1.Two-stagetankventilation
Thetwo-stagetankventingisusedontheN20engine.Thissophisticatedsystemismadenecessary
bytheTVDItechnology,becauseinthiscasesufficientvacuumintheintakemanifoldismuchless
common.ThiswasintroducedwiththeN55engine.
117
N20Engine
8.FuelSupply
N20engine,tankventilation
Index Explanation
1 Intakesilencer
2 Chargeairpipe(fromchargeaircoolertothrottlevalve)
3 T-connectorwithsuctionjetpump
4 Cleanairpipe(fromintakesilencertoexhaustturbocharger)
5 Connectionofpurgeairline,crankcaseventilation
118
N20Engine
8.FuelSupply
Index Explanation
6 Connectionoftankventilationtocleanairpipe
7 Intakemanifold
8 Linefromcarboncanisteroftankventilationsystem
9 Tankventvalvewithshutoffvalve
10 Throttlevalve
11 Connectionbeforethrottlevalvefordrivingsuctionjetpump
However,asuctionjetpumpisadditionallyusedinviewofthefactthatsufficientvacuumcannot
alwaysbeguaranteedinthecleanairpipe.Inordertodrivethispump,thelinetothesuctionjetpump
isconnectedbeforethethrottlevalve.Thiscreatesaconnectionbetweenthechargeairpipeandthe
cleanairpipe.Inturbochargedmodethepressureinthechargeairpipeisalwayshigherthaninthe
cleanairpipe,whichgeneratesinthislineaflowtothecleanairpipe.
N20engine,T-connectorwithsuctionjetpumpfortankventilation
Index Explanation
1 Linetocleanairpipe
2 Linefromtankventvalve
4 Linefromchargeairpipe
Thelinefromthetankventvalveisconnectedtothissuctionjetpump.Theventurieffectensuresthat
thecarboncanisterissafelypurged.
Non-returnvalvesonbothlinesfromthetankventvalveensurethatthereisnoreturnflowintothe
tankventvalveintheeventofexcesspressureintheselines.
8.1.2.Two-stagetankventilationwithshutoffvalve
Thetwostagetankventilationhasasecondelectricalvalvewhichisverysimilarindesigntothetank
ventvalve.Thisisknownasashutoffvalve.
119
N20Engine
8.FuelSupply
Theshutoffvalveservestodiagnosethesecondpointofadmissionandisdesignedtocloseoffthe
firstadmissionintotheintakemanifoldundercertainconditions.
N20engine,tankventvalve
Index Explanation
1 Connectionafterthrottlevalve
2 Lineforconnectiontocleanairpipe
3 Tankventvalve
4 Connectionfromcarboncanister
5 Shutoffvalve
Itismounteddirectlybelowthetankventvalveandisabletosealoffthelinetothethrottlevalve.
120
N20Engine
8.FuelSupply
N20engine,overview,two-stageversionoftankventilationwithsecondvalve
Index Explanation
1 Intakesilencer
4 Throttlevalve
5 Non-returnvalveforconnectiontocleanairpipe
6 Tankventvalve
7 Non-returnvalveforconnectionafterthrottlevalve
8 Shutoffvalve
Theshutoffvalveispoweredclosedandspringloadedopenatzerocurrent.
121
N20Engine
9.EngineElectricalSystem
9.1.Overview
N20engine,systemwiringdiagramMEVD17.2.4
122
N20Engine
Index Explanation
1 EngineelectronicsValvetronicdirectfuelinjectionMEVD17.2.4
2 Ambientpressuresensor
3 Temperaturesensor
4 A/Ccompressor
5 Junctionboxelectronics
6 Refrigerantpressuresensor
7 Electronicfuelpumpcontrol
8 Electricfuelpump
9 CarAccessSystemCAS
10 Brakelightswitch
11 Startermotor
12 DMEmainrelay
13 Clutchmodule
14 Relay,Valvetronic
15 Relay,ignitionandinjectors
16 Relay,terminal30switched
17 Diagnosismodule,tankventilation
18 Relayforelectricfan
19 Electricfan
20 Mapthermostat
21 Blowoffvalve
22 Tankventvalve
23 VANOSsolenoidactuator,intakecamshaft
24 VANOSsolenoidactuator,exhaustcamshaft
25 Switchableenginesoundsystem
26 Mapcontrolvalve
27 Electro-pneumaticpressureconverterforwastegatevalve
28 Quantitycontrolvalve
2932 Injectors
3336 Ignitioncoils
37 Engineventilationheating
38 Groundconnections
39 Oxygensensoraftercatalyticconverter(monitoringsensor)
40 Oxygensensorbeforecatalyticconverter(controlsensor)
41 Diagnosticsocket
123
N20Engine
Index Explanation
43 Railpressuresensor
45 Knocksensor12
46 Knocksensor34
48 Camshaftsensor,intakecamshaft
49 Camshaftsensor,exhaustcamshaft
50 Crankshaftsensor
51 Acceleratorpedalmodule
52 Throttlevalve
53 Coolanttemperaturesensor
54 Oilpressureandtemperaturesensor
55 Thermaloillevelsensor
57 DynamicStabilityControlDSC
58 IntelligentbatterysensorIBS
59 Alternator
60 Coolantpump
9.2.Enginecontrolunit
TheN20enginefeaturesDigitalEngineElectronicsfromBoschwiththedesignationMEVD17.2.4.It
iscloselyrelatedtotheDMEoftheN55engine(MEVD17.2)andisalsoengine-mountedontheintake
manifold.
124
N20Engine
N20engine,DigitalEngineElectronics
Index Explanation
1 Intakemanifold
2 DigitalEngineElectronics
3 Throttlevalve
Donotattempttrialanderrorreplacementofcontrolunits.
Becauseoftheelectronicimmobilizer,atrialanderrorreplacementofcontrolunitsfromother
vehiclesmustnotbeattemptedunderanycircumstances.Animmobilizeradjustmentcannot
bereversed.
TheN20engineDME(MEVD17.2.4)isdesignedtobemountedontheengine'sintakemanifold
onanaluminiumheatsinkplate.TheDMEiscooledthroughtheheatsinkplatebytheairflowing
throughtheintakemanifold.ItisimportantfortheDMEtobecorrectlymountedontheheatsinkplate
(tighteningtorque,goodlevelcontact)soastoensureheattransfertotheplateandtherebycoolthe
DME.
TheconnectionconceptisidenticaltotheMEVD17.2intheN55engine.Thereisalogicaldivisioninto
sixmodules.
125
N20Engine
N20engine,MEVD17.2.4connections
Index Explanation
1 Module100,vehicleconnection,48pins
2 Module200,sensorsandactuators1,58pins
3 Module300,sensorsandactuators2,58pins
4 Module400,Valvetronicservomotor,11pins
5 Module500,DMEsupply,12pins
6 Module600,fuelinjectionandignition,24pins
9.2.1.Overallfunction
TheDigitalEngineElectronics(DME)isthecomputingandswitchingcenteroftheengine
managementsystem.Sensorsontheengineandthevehicledelivertheinputsignals.Thesignals
foractivatingtheactuatorsarecalculatedfromtheinputsignals,thenominalvaluescalculatedusing
acomputingmodelintheDMEcontrolunitandthestoredprogrammaps.TheDMEcontrolunit
activatestheactuatorsdirectlyorviarelays.
TheDMEcontrolunitiswokenupviathewake-upline(terminal15Wakeup)bytheCarAccess
System(CAS).
126
N20Engine
Theafter-runstartsafterterminal15OFF.Theadaptationvaluesarestoredduringtheafter-run.The
DMEcontrolunitusesabussignaltosignalitsreadinesstogotosleep.Whenalltheparticipating
controlunitshavesignalledtheirreadinesstogotosleep,thebusmasteroutputsabussignaland
thecontrolunitsterminatecommunicationfivesecondslater.
TheprintedcircuitboardintheDMEcontrolunitaccommodatestwosensors:atemperaturesensor
andanambientpressuresensor.Thetemperaturesensorisusedtomonitorthetemperatureofthe
componentsintheDMEcontrolunit.Theambientpressureisrequiredforcalculatingthemixture
composition.
127
BayerischeMotorenwerkeAktiengesellschaft
QualifizierungundTraining
Rntgenstrae7
85716Unterschleiheim,Germany

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Designation Power Displacement Yearof Model Series

Designation Power Displacement Yearof Model Series

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