Eliot Silverman

Eliot Silverman
Owner

Tuesday, April 24, 2012

Emission Controls

The goal of the emission control system is simple, minimize pollution.

PVC Valve
The first emission control device was the positive crankcase ventilation valve, also known as the PCV valve.  It was federally mandated in 1963.  During the compression stroke a small percentage of the raw air/fuel mixture squeezes between the pitons and the cylinder walls and goes into the crankcase.  This raw mixture of air and fuel is very polluting.  Before 1963 these gasses were vented into the atmosphere.  With a PCV valve, these raw gases are put back into the engine where they are burned.  This reduces pollution while marginally increasing gas mileage.

EGR Valve
In 1972 the government mandated “Exhaust Gas Recirculation” valves, also know as EGR valves.  This valve opens when the engine is warmed-up and turning faster than the idle speed.  It allows a predetermined amount of burnt gases to be recycled back into the intake.  Over 98% of the exhaust gases are inert since they were ‘burnt’ in a previous combustion event.  Nitrous oxide is the main component of “Smog” and is caused by high combustion temperatures.  Mixing raw air/fuel with inert gas from the EGR valve decreases the combustion temperatures, preventing (limiting) the production of nitrous oxides.

Catalytic Converter
In 1975 catalytic converters were introduced.  Catalytic converters are very effective means to reduce air pollution.  When you burn gas, you produce H20 (water), carbon dioxide (C02) and Carbon Monoxide (C0) and some gasoline remains unburnt (HC).  H20 and CO2 are desirable results of combustion, but HC and C0 are very polluting and therefore undesirable. The catalytic converter converts CO into CO2 and converts HC into H2O and C02.  Catalytic converters can be destroyed instantly with leaded gas.  When they were introduced, the gasoline manufacturers also introduced lead free gas. 

Oxygen Sensor
Oxygen sensors are used to fine tune the air fuel mixture.  The ideal mixture is 14.7 parts of air to one part of gasoline.  This ratio is called stochiometric.  A rich running car means there is too much fuel for the amount of air, and a lean running condition means there is too much air for the amount of gasoline.  A very rich or very lean running engine will ruin a catalytic converter.  To keep the engine close to stochiometric, manufacturers added sensors to measure the amount of air going into the engine.  Knowing how much air is going into the engine, the computer can add the proper amount of gasoline.  The Oxygen sensor is a feedback device which tells the computer if the mixture is too lean or too rich.  Since the oxygen sensor helps the computer maintain stochiometric mixture it reduces pollution and increases gas mileage.

EVAP System
The EVAP system was introduced around 1996.  This system is designed to prevent gas vapors from escaping into the atmosphere.  Gasoline in your gas tank naturally vaporizes.  In older cars this vapor was vented into the atmosphere.  Since 1996 these vapors are collected in a canister filer.  When you are moving above a predetermined speed, two valves open up allowing the vapors in the canister filter to vent into the engine where they are burnt.  This devise increases gas mileage and decreases pollution. 

14 comments:

  1. I question whether one tank of leaded fuel will do any significant damage to a catalytic converter or an O2 sensor. In any case, an O2 sensor is not that expensive if it should need replacement. A damaged catalytic converter will of course reduce its emission control effectiveness, but it will make no difference at all to the performance of the car.

    ReplyDelete
  2. I question whether one tank of leaded fuel will do any significant damage to a catalytic converter or an O2 sensor.

    San Jose auto repair

    ReplyDelete
  3. Who knew that so much goes into emission control? I knew of the PVC Valve, but I didn't even know they had an Oxygen Sensor. So the sensor fine tune the air fuel mixture. Does it measure the ratio?

    Elisa Jed | http://www.qualitytransmission.com/

    ReplyDelete
  4. Thanks for this post! My check engine light came on twice in the last month, both times because the gas cap was loose. I didn't know that could cause the light to come on! I felt really silly when my mechanic told me that was the problem, but I feel better knowing a professional diagnosed the issue. It ended up being an emission problem. http://www.islandmuffler.com

    ReplyDelete
  5. I need to take my car into a repair shop. The check engine light is on, and it makes a very weird noise when I drive it. I use my car a lot, so I need to have it fixed ASAP. I'm sure that one of my local auto repair shops will be able to fix it quickly. http://www.dinardoforeignmotors.com/State_Inspections_Horsham_PA.html

    ReplyDelete
  6. Nice post! I am really in love with your blog thank you so0o much.
    auto repair

    ReplyDelete
  7. Great! We will be connecting to this enormous post on our site. Continue the good writing.UKdentalcare

    ReplyDelete
  8. Hey nice post man! Thanks for incredible info.

    Our Company Website

    ReplyDelete
  9. I have checked this link this is really important for the people to get benefit from.

    auto body repair

    ReplyDelete
  10. Love to read it,Waiting For More new Update and I Already Read your Recent Post its Great Thanks.
    auto repair brandon fl

    ReplyDelete
  11. Emission control system, in automobiles, means employed to limit the discharge of noxious gases from the internal-combustion engine and other components. There are three main sources of these gases: the engine exhaust, the crankcase, and the fuel tank and carburetor.

    Injectors: Set of 8 LS1 / LS6 / LT1 / EV1 Style High Impedance HPI Inj – High Performance Injectors

    ReplyDelete
  12. I think, in this post, you are providing many links to help in Auto Body Shop,So We have checked this link this is really important for the people to get benefit from.
    car repair triangle nc

    ReplyDelete
  13. Keep up the great work, love reading good materials State Inspection Mechanic

    ReplyDelete
  14. Contents of this website are good and appreciative. Congratulation

    Battery Installation Calgary

    ReplyDelete