1998 Subaru Legacy GT LTD Sedan AWD F4-25L DOHC Emission Control: Catalytic Converter Locations
Catalytic Converter: Description and Operation
PURPOSE/OPERATION
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The basic material of Three-Way Catalyst is Platinum (Pt) and Rhodium (Rh), and a thin coat of their mixture is applied onto honeycomb or
porous ceramics of an oval shape (carrier). To avoid damaging the Catalyst, only unleaded gasoline should be used.
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The catalyst is used to reduce Hydrocarbons (HC), Carbon Monoxide (CO) and Oxides of Nitrogen (NOx) in exhaust gases, and permits
simultaneous oxidation and reduction. To obtain an excellent purification efficiency on all components HC, CO and NOx, a balance should be
kept among the concentrations of the components. These concentrations vary with the air-fuel ratio.
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The air-fuel ratio needs to be controlled to a value within the very narrow range covering around the stoichiometric mixture ratio to purify the
components efficiently.