- Honda Car Owner's Manual

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89
ADVANCEDCATALYSTSYSTEM
Theinsightisdesignedtooperateataveryleanairfuelratioduringlightthrottlecruiseconditions.The
mixturecanbeasleanas22:1ifconditionsallow.Thisprovidesverygoodfueleconomy,andlowHCand
CO emissions. However, the lean mixture also causes a rise in combustion temperature, and high NOx
productionistheresult.
Inorder to preventhigh NOxtailpipeemissionsduring leanburn operation,the Insightusesa dual
catalystsystemthatincludesanextraNOxstorage/NOxreductioncatalyst.
The3-waycatalystiscloselycoupledtotheexhaustmanifoldtominimizeheat-uptime,thusreducing
emissionsafteracoldstart.
TheleanNOxcatalystisintheconventionallocation,underneaththecar.
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LeanNOxCatalystFunctioning
The lean NOx catalytic converter is
comprised of a ceramic A1203 substrate, a
platinum(Pt)catalyzingsurface,andatitanium-
sodium(Ti-Na)NOxstoragesurface.
Duringlean burnoperation, theexhaustgas
containsalargerpercentageofoxygen(O2)and
NOx, the NOx being primarily nitrogen
monoxide (NO). The platinumcatalyzesthe O2
andNOtoproducenitrogendioxide(NO2),whichisabletobestoredontheTi-Nasurface.
WhenitdeterminesthattheTi-Nasurfaceissaturated,theInsighttemporarilyrichensthemixture.This
actiondecreasestheNOxandO2intheexhaust,andraisesthelevelsofhydrocarbons(HC)andcarbon
monoxide(CO).TheplatinumisthenabletousetheHCandCOtocatalyzetheNO2(thathasbeenstored)
intoharmlessnitrogengas(N2),carbondioxide(CO2)andwatervapor(H20).