Emission control systems have been incorporated into automobiles to
prevent pollution
by limiting the amount of partially burned and evaporated gases into the
atmosphere.
These systems have been efficient in reducing the pollution caused by
automobiles
to a large extent. Automobiles were first manufactured with exhaust
emissions control
systems in 1966. Since then technology has undergone several changes
that has increased
the number of cars which use this technology. The emission released is
calculated
by quantity released per distance traveled. The types of emissions are
tailpipe
emissions, life cycle emissions and evaporative fuel emissions.
Catalytic Converter
The catalytic converter was developed in the early 70's when severe
air pollution
was emanate, but wasn't made mandatory by the US government until 1976.
The catalytic
converter or "cat" for short is one of your vehicles main emission
control devices.
The name was derived from the operation the catalytic converter
performs, it takes
a catalyst and converts the unburned gases to burned gases, "catalytic
converter".
EGR Valve
EGR valves are used is to lower KNOX (NO2)
gases which occur when the combustion chamber when temperature reaches
over 3,500 degrees Fahrenheit. KNOX gases have proven to cause brain damage and
have been mandatory
on most vehicles since 1976. An EGR (exhaust gas re-circulation) this
valve
controls exhaust gases to enter the intake manifold and flow into the
combustion
chamber at certain times in the operation of the vehicle. To test your
EGR valve
remove the vacuum line that is connected to the valve, apply vacuum
using a vacuum
pump to the valve while the engine is running. If the engine stalls the
EGR system
is working, if not, the EGR valve may have failed.
Tailpipe emissions are released as bi-products of spent fuel that is
combusted
inside the cylinders of the
engine.
These omitted gases consist of carbon monoxide, hydrocarbons, carbon
dioxide and
nitrogen oxides. To control tailpipe emissions measures have been taken
to increasing
engine efficiency. This efficiency involves technologies such as
lightweight vehicle
design, regenerative braking, decreased rolling resistance, increased
ignition voltage,
minimizing air resistance and improving power train efficiency.
Lifecycle emissions are products which are released during the
manufacturing,
maintenance and disposal of the vehicle. The products include volatile
solvents
such as auto paint and lubricants, manufacturing plant power waste, oil
filter and
oil changes, heavy metals, tires, landfills, etc. These kinds of
emissions are responsible
for creating urban smog which consists of heavy molecular gases which
pollute our
environment.
Temperature change can result in the evaporation of fuel in the tank
because
of the development of pressure, this is known as gas tank venting.
Recently fuel
systems have been equipped with a closed system called EVAP, this allows
the vapor
to be stored in a charcoal canister until it can condense into a liquid
and then
returned to the fuel tank.
Another emission control system known as the air injection reactor or
AIR, oxygen
is injected in the exhaust manifold. This system decreases the
bi-products of incomplete
fuel consumption.
If the emission control system malfunctions the "check
engine" light will illuminate. Scan the PCM for trouble codes,
repair the problem,
then clear codes to re-test system. Most automobile's have an emission
system information
label under the hood, or consult a
repair
manual.
The emission system performs regular test while the
car is in
use called a "test cycle". Tailpipe emission are measured in parts per
million or
PPM. Presently, the limit for evaporated gases is two grams of HC per
hour, which
is about one liter per month. At first, the idle test, which was a
two-speed test
was conducted in the 1980s. Then it was substituted by the dynamometer
test in the
late 90's, in the accelerated simulated mode or ASM three gases are
tested. Various
states and countries have developed unique laws about pollution testing
of vehicles.
Good luck, and remember rated this help.
Here is a link explaining it
http://www.familycar.com/CLASSROOM/emission.htm
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