![MTD 61 series Скачать руководство пользователя страница 107](http://html1.mh-extra.com/html/mtd/61-series/61-series_shop-manual_1850092107.webp)
Exhaust
101
Catalytic converter muffler
The CARB (California) compliant engines use a cata-
lytic converter muffler. This muffler also has an air injector
to help with the catalytic reaction in the muffler. The Cata-
lytic muffler can be identified by the presence of this air
injector. See Figure 8.5.
NOTE:
The catalytic converter muffler is removed/
replaced by following the same procedures as the
conventional muffler.
The catalytic converter is most efficient when it receives
the exhaust of an engine running slightly above the stoi-
chiometric point. The catalytic converter breaks down the
exhaust, through chemical reactions, to reduce the nitro-
gen oxide, carbon monoxide and the hydrocarbon emis-
sions. The air injector adds oxygen to the converter so that
it can complete its chemical reaction inside the muffler.
NOTE:
Stoichiometric point is defined as the point where
the mass ratio of fuel to air is chemically balanced.
For gasoline, the stoichiometric point is approxi-
mately 14.7 to 1.
The air injector works as follows:
• Between the exhaust pulses of the engine, there is
low pressure in the exhaust.
• During these periods of low pressure, air is drawn
in to the converter through a reed valve in the air
injector. See Figure 8.6.
• This air provides the oxygen needed for the cata-
lyst to process the next power pulse.
• The reed valve also stops the exhaust from by-
passing the catalytic converter and escaping
through the air injector.
The air injector has an inlet screen. This screen acts as
a filter to keep debris from entering the converter, should
this screen become blocked, the converter will not function
properly.
Figure 8.5
Air injector
Figure 8.6
Reed valve
Inlet screen
Содержание 61 series
Страница 2: ......
Страница 6: ...IV...
Страница 22: ...61 65 and 70 Series Vertical Shaft Engines 16...
Страница 34: ...61 65 and 70 Series Vertical Shaft Engines 28...
Страница 42: ...61 65 and 70 Series Vertical Shaft Engines 36...
Страница 78: ...61 65 and 70 Series Vertical Shaft Engines 72...
Страница 90: ...61 65 and 70 Series Vertical Shaft Engines 84...
Страница 114: ...61 65 and 70 Series Vertical Shaft Engines 108...
Страница 141: ......
Страница 142: ...MTD Products Inc Product Training and Education Department FORM NUMBER 769 03354 02 12 2013...