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EGR Valve

Discussion in 'Engine' started by garymac, Jan 25, 2006.

  1. garymac

    garymac Member

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    Sep 21, 2005
    Location:
    North East
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    c250 TD auto - sold
    What exactly is the function of the EGR valve?

    Many I have spoken to suggest blanking it off, but what consequence would this have?
     
  2. Bazzle

    Bazzle Hardcore MB Enthusiast

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    Melbourne, Australia
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    SLK230 1998 auto, 2006 W169 A200 Sport
    You will help to pollute the air:

    EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Undernormal combustion, Nitrogen(N2)Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight,
    it combines with other compounds like Hydrocarbons and forms Smog. Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into
    the combustion chamber, it will lower combustion chamber temps enough so that
    the Nitrogen doesn’t react with the other compounds and is passed unchanged out
    the tailpipe thus not contributing to smog.

    Bazzle
     
  3. Dieselman

    Dieselman Banned

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    However as the conditions required for the production of Nox only really exist when the engine is running VERY lean, this only occurs at idle condition.

    As Bazzle has said the exhaust gas reduces the oxygen content in the "air" so reduces the condition. The problem is that this then reduces the engine output and creates smoke, so burns more fuel and creates more polution that way. This is why diesel cars tend to emit a puff of black smoke when pulling away from rest.
    In addition the recirculated gas polutes the oil and intake tract.

    If your car has a MAF sensor then you can't block the EGR as that would be detected by the MAF, otherwise you can block the vacuum tube as a test.
     
  4. mw_C32

    mw_C32 Hardcore MB Enthusiast

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    Not really sure what it does but....

    I had a Vauxhall Vivaro 1.9dti van a couple of years ago which broke down 2 months after new. I called the AA out.

    He knew exactly what was wrong as quite a few of these had broken down. What he did was to take out the egr valve turn it around 180 degrees and put it back.

    He did say that it was either permanently open or permanently closed cant remember which but that I would get much better performance and there would be more smoke.
    I had it like this for a week until the dealer fixed it, but wow!! what a difference, and it made a nice growl when flooring the throttle. That week was the best time I had with that van. :D

    M.
     
  5. blicky_1

    blicky_1 Hardcore MB Enthusiast

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    Mine was replaced at 36k under warranty, engine light came on and did not go off, MB replaced and has never come on since (done 70k now!)
     
  6. tamrsoft

    tamrsoft Hardcore MB Enthusiast

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    Note moved to the other EGR posting
     
    Last edited: Jan 26, 2006
  7. Parrot of Doom

    Parrot of Doom Hardcore MB Enthusiast

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  8. OP
    OP
    garymac

    garymac Member

    Messages:
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    Sep 21, 2005
    Location:
    North East
    Car:
    c250 TD auto - sold
    I have had on a couple of occasions when accelerating heavily the response from the engine as described in the above link. Have now disconnected the EGR and replicated the style of driving and had none of the ill effects. Lets hope it continues!!
     
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