Figure 7-2. Exhaust Manifold
A typical muffler has several concentric
economy and also cause overheating.
chambers with openings between them. The gas enters
the inner chamber and expands as it works its way
e. Exhaust system components usually are made
through a series of holes in the other chambers and
of steel. They usually are coated with aluminum or zinc
finally to the atmosphere.
to retard corrosion. Stainless steel also is used in
exhaust systems in limited quantities due to its high cost.
d. Mufflers must be designed to quiet exhaust noise
A stainless steel exhaust system will last indefinitely.
while creating a minimum of back pressure. This could
cause loss of engine power and
Section II. EMISSION CONTROL SYSTEMS
however, this is not what happens. The fuel never
7-5. Purpose (Fig. 7-5). When the fuel is burned In the
combines completely with the oxygen and undesirable
combustion chamber, the ideal situation would be to
exhaust emissions are created as a result. The major
have the fuel combine completely with the oxygen from
the intake air. The carbon would then combine to form
carbon dioxide (COI, the hydrogen would combine to
a. Carbon Monoxide (CO). Carbon monoxide is
form water (H20), and the nitrogen that is present In the
formed as a result of insufficient oxygen in the
intake air would stand alone. The only other product
present in the exhaust would be any oxygen from the
temperatures that are too low. Carbon monoxide Is a
intake air that was not used in the burning of the fuel. In
colorless, odorless gas that is poisonous
a real life situation