Man D2862 LE221 - Page 22

INTRODUCTION
Theenginecontrolunitsprocesstheinformationreceivedfromthesensorsandcontroltheoutputsignals
whicharesenttotheactuators.Theactuatorsconvertthesignalsintomechanicalvariables.Anactuatoris,
forexample,themeteringunitonthehigh-pressurepump.
Crankcase
Thecrankcaseconsistsofthecrankcaseuppersectionandthecrankcaselowersection.Bothsectionscast
fromdifferentspecialcastirons.Thewetcylinderlinersmadefromspecial,highlywear-resistantcentrifugal
castingareexchangeable.Thecylinderlinersaresealedatthebottomusingelastomersealingrings.Atthe
rearofthecrankcase,thereisaywheelhousing.Atthefrontofthecrankcase,thereisahousingcover.
Theywheelhousingandhousingcoveraremadeofaluminium.Theradialshaftsealsareinstalledinthe
housingcoverandtheywheelhousing.
Positivecrankcaseventilation
Thecrankcaseblow-bygasesarereturnedtothecombustionairviatwooilseparatorswithpressurecontrol
valveonthesuctionsideoftheturbochargers.
Crankshaft
Thecrankshaftisforgedinadieusinghigh-quality,micro-alloyedsteel.Ithas8mountedcounterweights
tobalancethemasses.Thecrankshaftismountedinsevenbearingsinthecrankcase.Thecrankshaft
journalsandconnectingrodbearingjournalsaremountedinready-to-installthree-componentbearings.The
axialbearingisprovidedbythrustbearingsinthelastbearingseatattheywheelend.Theconnectingrod
bearingsaresuppliedwithoilviaaboreinthecrankshaftbearing.
Connectingrods("cracked"connectingrods)
The"cracked"connectingrodsareprecisionforgedinadieusingquenchedandtemperedsteel.Thelarge
connectingrodeyeissplitdiagonallyby"cracking"theconnectingrodbearingcap.Thesurfacestructure
resultingfromcrackingresultsinatoothengagementeffectbetweentheconnectingrodbearingcapandthe
connectingrodwithaprecise,non-interchangeabletandhighlateralstability.
Pistons
3-ringsteelpistonsareused.Thepistonshaveacoolingductforrelievingthethermalload.Thisareais
coveredbyexiblemetalcontainingaboreintowhichtheoiljetfromtheoilinjectionnozzlesisinjectedfor
cooling.Theringsetcomprisesonehalfkeystoneringandtaper-faceringeachascompressionringsas
wellasadouble-bevelledringasoilscraperring.Thepistonscanberemovedfromabovetogetherwiththe
connectingrods.
Camshaft
Thecamshaftisforgedfromsteelandisinductionhardened.Itismountedinsevenbearingsinthecrankcase.
Thecamshaftisdrivenbytiminggearsthatareinstalledintheywheelhousing.
Cylinderhead
TheD28engineisequippedwithacamshaftwithoverheadvalves(OHV).EnginesinseriesD28areequipped
withindividualcylinderheadsmadefromspecialcastironaswellasshrink-ttedvalveseatringsand
pressed-inexchangeablevalveguides.Thevalveguideshavevalvestemsealsatallfourvalves.The
cylinderheadsaresecuredwithsixhigh-strengthexternalhexagonroundbolts(cylinderheadbolts).The
single-layersteelcylinderheadgasketwithelastomerelementshasaspeciallydesignedcombustionchamber
seal.
Enginelubrication
Theengineislubricatedbyforced-feedlubricationforallbearingpoints.Theengineoillterandtheoilcooler
aregroupedtogetherasanoilmodule.Theoillevelintheoilsumpismeasuredusingadipstick.
Coolingsystem
Thecoolingcircuitisathermostat-controlledforced-circulationcoolingsystem.Themaintenance-freecoolant
pumpisinstalledontheendfaceinthehousingcoverandisdrivenbyaseparategearset.Thethermostats
arehousedaboveinthetwo-sectionthermostathousing.Thethermostatsconsistofanexchangeableinsert
withexpansionelement.
Intakeandexhaustsystem
Thetwo-pieceexhaustmanifoldsarecastfromhightemperature-resistantspheroidalgraphitecastironand
aresecuredonthecylinderheadswithheatresistantbolts.Twomaintenance-freeturbochargersaremounted
ontheexhaustmanifolds.Theturbochargersarelubricatedbytheengineoilcircuit.
20AE63stedition