ENGINESYSTEMS13
Airow
Airowsthroughtheairlterassemblyandenters
theLow-Pressure(LP)turbocharger.TheLP
turbochargerincreasesairpressureandtemperature
beforeenteringtheLowPressureChargeAirCooler
(LPCAC).Cooledandcompressedairthenowsfrom
theLPCACintotheHighPressure(HP)turbocharger
(compressorinlet).Hotandhighlycompressedair
owsfromtheHPturbocharger(compressoroutlet)
intotheHighPressureChargeAirCooler(HPCAC)
whereitiscooled,andintotheintakethrottleduct,
andcontinuesthroughtheEngineThrottleValve
(ETV).TheHPandLPturbochargerscanincrease
pressuresupto345kPa(50psi).
IftheExhaustGasRecirculationValve(EGRV)is
open,exhaustgasespassthroughtheEGRcooler
andintotheintakethrottleductwhereitismixedwith
lteredair.Thismixtureowsintotheintakemanifold,
andthenthecylinderhead.Theintakemanifoldisan
integralpartofthecylinderheadcasting.
Duringcoldweather,theInletAirHeatersystem
activatestheheaterelement,vaporizingandigniting
smallquantitiesoffuelintotheairinletduct.
Aftercombustion,exhaustgasesexitthroughthe
cylinderheadexhaustvalvesandports.Theexhaust
gasisforcedthroughtheexhaustmanifoldwhere,
dependingonEGRVposition,itissplitbetween
theEGRsystemandtheexitpaththroughtheHP
turbocharger,LPturbocharger,andExhaustBack
PressureValve(EBPV).
TheEBPVisoperatedbytheAirControlValve(ACV),
apneumaticactuator.WhentheACVisapplied,
theEBPVrestrictsowandincreasesexhaustback
pressure.OperationoftheEBPViscontrolledbythe
ECMusingtheACVandtheTurbocharger1Turbine
OutletPressure(TC1TOP)sensor.WhentheEBPV
isopened,exhaustbackpressureisreleased.
Exhaustgasesexitingtheengineowthroughthe
EBPV,thenthroughthevehicleAftertreatment(AFT)
system,andouttheexhausttailpipe.