Navistar MaxxForce 15 - High-Pressure Charge Air Cooler (HPCAC); Air Control Valve

ENGINESYSTEMS19
isconnectedtothelow-pressurecompressoroutlet
andusesenginecoolanttoregulatethechargeair
temperature.TheISCairoutletisconnectedtothe
compressorinletonthehigh-pressureturbocharger.
High-PressureChargeAirCooler(HPCAC)
TheHPCACisinstalledbetweenthehigh-pressure
turbochargercompressoroutletandtheEngine
ThrottleValve(ETV).TheHPCACusesambientair
owtoregulatethechargeairtemperature.The
HPCACairoutletisconnectedtotheETVbody.
AirControlValve
Figure10Aircontrolvalve
1.T ohigh-pressureturbochargerwastegateactuator
2.Turbocharger1TurbineOutputPressure(TC1TOP)
inputtosensor
3.Compressedregulatedairsupplyfromchassisair
tank
Theaircontrolvalvecontrolsairpressuretothe
high-pressurewastegateactuatorbasedonturbine
outputpressurefromaportontheoutputofthe
low-pressureturbocharger.Theturbineoutput
pressuresensorisintegraltotheaircontrolvalve.Air
pressuretotheaircontrolvalveissuppliedfroman
airtankmountedonthechassis.Theaircontrolvalve
iscontrolledbytheEngineControlModule(ECM).
Theaircontrolvalveisnormallyclosed.Thus,withno
PulseWidthModulated(PWM)signal,theaircontrol
valveremainsclosedandnoairpressureissupplied
tothewastegateactuatoronthehigh-pressure
turbocharger.Whenadecreaseinchargeairpressure
isrequired,theECMsuppliesaPWMgroundvoltage
tothenegativesideofthewastegatecontrolsolenoid.
Theothersideofthewastegatecontrolsolenoidis
connectedto12Vsupplyvoltage.Thiscausestheair
controlvalvetoopenwhichsuppliesairpressureto
thewastegateactuator.
ThelimitvaluesofthePWMsignalarebetween
approximately95%,correspondingtoanopenair
controlvalve,and5%,correspondingtoaclosedair
controlvalve.Whentheaircontrolvalvecloses,it
interruptstheairsupplytothewastegateactuator
andatthesametimerelievesairpressurefromthe
wastegatebyallowingittoventtoatmosphere.The
wastegateactuatorthencloses,resultinginincreased
chargeairpressure.