Free Car Repair Advice by Professional Mechanics.
How Does it Work /
Emission
Control
How Emission Controls Work
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 gasses 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.
How
Does it Work /
Emission
Control
Check Manufacturer Specific Emission
Control Questions and Answers
Related Subjects
Got a Car Repair Question
we will answer it for FREE!
GET A
REPAIR MANUAL
FOR YOUR CAR. Get instant access to your vehicles drive belt routing, wiring
diagrams, trouble code information and other available updates and factory bulletins.
| 
