Figure 7-3. Manifold Heat Control Valve

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Figure 7-2. Exhaust Manifold

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TM-9-8000 Principles of Automotive Vehicles Manual

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Figure 7-4. Muffler

TM 9-8000

Figure 7-3. Manifold Heat Control Valve

Hydrocarbons

(HC).

Hydrocarbons

are

gen are formed when the nitrogen and oxygen in the

unburned fuel. They are particulate in form (solid) and,

intake air combine when subjected to the high

like carbon monoxide, they are manufactured by

temperatures of combustion. Oxides of nitrogen are

insufficient oxygen in the combustion mixture and

harmful to all living things.

combustion chamber temperatures that are too low.

Hydrocarbons are harmful to all living things. In any

7-6. Controlling of Exhaust Emissions. The control

urban area where vehicular traffic is heavy, hydrocarbons

of exhaust emissions is a very difficult job. To eliminate

in heavy concentrations react with sunlight to produce a

carbon monoxide and hydrocarbon emissions, the

brown fog known as photochemical smog.

temperatures of the combustion chamber would have to

be raised to a point that would melt pistons and valves.

c. Oxides of Nitrogen (NOx). Oxides of nitro-

This Is compounded with the fact that oxides of nitrogen

TA233471

7-3