Emission Control Systems

by
Russell Krick

Publisher

The Goodheart-Willcox Co., Inc.
Tinley Park, Illinois
© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


© Goodheart-Willcox Co., Inc.

Permission granted to reproduce for educational use only


(13 Topics)

 Air pollution
 Exhaust emissions
 Engine modifications
 Emission control systems
 Positive crankcase ventilation (PCV)
 Evaporative emissions control systems
 Exhaust gas recirculation (EGR)
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Permission granted to reproduce for educational use only

 Air injection system
 Pulse air system
 Thermostatic air cleaner system
 Catalytic converter
 Computerized emission control
systems
 OBD II emission system monitoring
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 Caused by an excess amount of
harmful chemicals in the atmosphere
 Emission control systems are used on
cars and trucks to reduce harmful
chemicals in the atmosphere

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Air Pollution

There are many sources, both
natural and man-made
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Natural Sources
 Volcanoes
 Forest fires
 Dust
 Decay of vegetation

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Man-Made Sources
 Factories
 Home furnaces
 Fireplaces
 Internal combustion engines

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Smog
 Visible cloud of airborne pollutants
 Derived from the words “smoke” and
“fog”
 Harmful to humans, animals, and
vegetation

 Formed when pollutants combine with
oxygen and nitrogen in the presence of
sunlight
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Smog
Common in large
cities and
industrial areas

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 Pollutants produced by internal
combustion engines:
 hydrocarbons (HC)
 carbon monoxide (CO)
 oxides of nitrogen (NOx)
 particulates

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Hydrocarbons (HC)
 Unburned fuel
 All petroleum products
 Produced by incomplete combustion or
fuel evaporation

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Carbon Monoxide (CO)
 Extremely toxic
 Colorless and odorless
 Prevents blood cells from carrying
oxygen to body tissues
 Caused by rich air-fuel mixtures

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Oxides of Nitrogen
(NOx)
 Air consists of 79% nitrogen and 21%
oxygen
 Above approximately 2500 ºF (1370 ºC),
nitrogen and oxygen combine
 Caused by high compression ratio, lean

mixture, and high operating temperature

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Particulates
 Solid particles of carbon soot and fuel
additives
 Serious problem with diesel engines
 Caused by rich air-fuel mixture or
mechanical problems
 About 30% of particles settle out of the
air quickly, 70% float for extended
periods
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Air-Fuel Ratio and
Emissions

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Vehicle Emission

Sources

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 Engine designs that can minimize
emissions:
 lower compression
 small combustion chamber surface
 reduced quench areas
 decreased valve overlap
 hardened valves and seats

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Permission granted to reproduce for educational use only


 Positive crankcase ventilation (PCV)
 Evaporative emissions control
 Exhaust gas recirculation (EGR)
 Air injection
 Thermostatic air cleaner
 Catalytic converter
 Computer control system
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 Uses engine vacuum to draw blowby
gases from the crankcase into the
intake manifold for burning
 Blowby is caused by leakage past the
piston rings
 Reduces HC, CO, and particulates
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PCV System

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PCV Valve
 Controls flow through the system
 Located in the valve cover, intake
manifold, or the side of the engine
block
 Varies flow for idle, cruise, acceleration,
wide open throttle, and engine-off
conditions

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PCV Valve

A. Idle
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B. Acceleration

C. Engine off
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Diesel PCV System

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Air-Oil Separator
 May be used instead of a PCV valve
 Makes oil vapors condense and flow
back into the oil pan

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Permission granted to reproduce for educational use only