Exhaust System; Three-Way Catalyst - wsm wg972-e4 Workshop Manual

WG972-E4, WSM

5. EXHAUST SYSTEM

[1] THREE-WAY CATALYST

A three-way catalyst is a catalyst that removes CO,
HC and NOx at the same time by oxidation-reduction
reaction.
A three-way catalyst oxidizes HC to CO
and also CO to CO
2
reduces NOx to N near the stoichiometric ratio.
2
The main basic component of an exhaust gas
purification system is a three-way catalyst and it is
feedback control of air-fuel ratio by means of an oxygen
sensor.
The purpose is to make maximizing the emission
purification efficiency characteristic with reference to the
intake air-fuel ratio.
Because the good balance of carbon, hydrogen and
oxygen in exhaust gas is necessary to operate
three-way catalyst and oxidation-reduction reaction
successfully. Also the balanced condition is theoretical
air fuel ratio.
KUBOTA engines have two kinds of catalytic devices
which are catalytic muffler and catalytic converter. Both
of catalytic devices are attached after exhaust manifold.
If catalytic converter is adopted, additional muffler
should be assembled after catalytic converter.
(1) Catalytic Converter
(2) Catalytic Muffler
1-M21
and H
2
respectively and at the same time
[A] CATALYTIC CONVERTER
[B] CATALYTIC MUFFLER
9Y1211108ENM0038US0
KiSC issued 07, 2015 A
ENGINE
O,
2