Diesel smoke?

Discussion in 'OT (OFF Topic) Forums' started by ms500, Oct 17, 2008.

  1. ms500

    ms500 Banned

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    Not a problem for me since I drive a petrol engine, but I was curious to know what causes the small puffs of black smoke sometimes seen when a diesel engine accelerates suddenly.

    My understanding is that when suddenly accelerating, there is a momentary inbalance between the air / fuel mixture and some unburned diesel is expelled out of the exhaust, is this right?
     
  2. recycled

    recycled Hardcore MB Enthusiast

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    unburnt fuel from the forced induction.
     
  3. st4

    st4 Banned

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    It happens a lot with "chipped" cars which overfuel. I believe I was behind such an example last week, volvo S60 D5 in front of me accelerated hard to join the dual carriageway, and the smoke was so bad my visibility was seriosuly impaired.

    However his car was fast, and even with mine in kickdown he was gone.
     
  4. Smiley

    Smiley Hardcore MB Enthusiast

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    I think most diesel cars will do this for the first time that they are floored after being run around town for a bit. Certainly my 124 estate does it and always has done - I usually give it a good clear out every couple of weeks - runs better for it.
     
  5. cjab98

    cjab98 Hardcore MB Enthusiast

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    When I had my old 306 Diesel I used this to keep tailgaters back by gassing them with diesel fumes, worked a treat:D
     
  6. Smiley

    Smiley Hardcore MB Enthusiast

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    oh i would never dream of doing that.....:rolleyes: :D
     
  7. kjay

    kjay Hardcore MB Enthusiast

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    I'm up for anything that stops tailgaters.:devil:

    My van chucks out loads of smoke when I start it up in the morning - But that's just cos it's knackered:) .

    .
     
  8. jeremytaylor

    jeremytaylor Hardcore MB Enthusiast

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    I used to drive a Renault 18 Estate diesel in the days when diesels were not far removed from tractors and had emissions controls to match. That car had a 2.1 engine that pulled really well.

    And was good at smokescreens too :D :devil:
     
  9. Stratman

    Stratman Hardcore MB Enthusiast

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    Unlike a petrol engine which must maintain an air/fuel ratio of approximately 15:1 a Diesel engine flows full air all the time, ie, there is no butterfly in the air intake, the 'throttle' is wide open all the time. The accelerator pedal only regulates the amount of fuel entering the engine.
     
  10. Sp!ke

    Sp!ke Administrator Staff Member

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    Dieselman, the forum needs you.

    Definitive answer required.
     
  11. Leemc2008

    Leemc2008 Hardcore MB Enthusiast

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    BLUE SMOKE from exhaust - Causes: Engine is burning engine oil, injection timing is incorrectly set.

    BLACK SMOKE from exhaust - Causes: Too much fuel is being delivered to the engine or the fuel that is being delivered is not correctly atomised, Exhaust Gas Reciculation (EGR) system has failed or is incorrectly set of has become clogged with soot.

    WHITE SMOKE from exhaust - Causes: If the ambient temperature is low, steam which is normal and usually clears, if the smoke never clears, water is entering the engine (cylinder head, head gasket, liner problem).

    GREY SMOKE from exhaust - Causes: Injection timing is incorrectly set, fuel is not being atomised correctly, something other than diesel has been added to the the fuel tank.
     
  12. Sp!ke

    Sp!ke Administrator Staff Member

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    But almost all diesels do this so could it really be that they all have blocked or ineffective EGR systems?

    I'm particularly interested as my wifes D5 does this sometimes (not always).
     
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