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diesel dump valve

Discussion in 'TDi - SEAT Diesel specific topics' started by English, Sep 15, 2009.

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  1. English

    English oi oi saveloy

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    Im looking for a dump valve for my 1.9 tdi leon whats the best one to buy and wheres the cheapest place to get it from.
     
  2. Viking

    Viking Insurance co's are crap.

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    Mate, this has been covered a dozen times before. A search would find you much detail, but as it's your first post I'll condense the findings from memory. About £250 for a piece of kit which does nothing but fart at you when you lift off the accelerator. No performance gains, lots of people laughing at you (including the people who sold you the fart pipe), and much embarrassment when you realise what you've done. :D

    Welcome to the forum btw.
     
  3. Viking

    Viking Insurance co's are crap.

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  4. MJ

    MJ Public transport abuser

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    I Have one fitted and as mentioned a thousand times - it does nothing for performance gains, just makes a noise, like when a fat bird jumps on an air bed. The children love it though ;)
     
    #4 MJ, Sep 15, 2009
    Last edited: Sep 22, 2009
  5. Muttley

    Muttley Catch that diesel!

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    Here is my sermon on diesel dump valves: submitted as the draft for a sticky thread, if the mods deem is suitable. Comments please - lets make this as accurate as we can :)



    Diesel dump valves:

    Petrol engines have a throttle mechanism which controls the flow of air between inlet (turbo-compressor) and the engine combustion chamber, so as to keep the air-fuel mixture in the ignitable range while throttling the engine's power output. The mass of air taken in and fuel added must both be carefully controlled.

    When you close the throttle on such an engine the compressor is still pushing air into the inlet and it suddenly has nowhere to go. The back pressure will inevitably slow the turbo down, and cause turbo lag when the throttle is opened again.

    The solution is to provide a pressure-actuated valve, which reacts to a difference in pressure between the two sides of the throttle. A dump valve opens to dump the excess pressure to the atmosphere. A recirculating blowoff valve diverts the air back into the inlet and does a much better job by equalising the pressure on both sides of the turbo. Without one of these, throttle response will be slower and throttles and turbos would have to be much more heavily engineered.

    So dump valves are about throttle response at gearchange and other sudden transient events, not about performance in the leadfoot top-speed way of thinking.

    The need for a dump valve is a weakness of turbocharged petrol engines, putting another contraption in the inlet which disturbs the gas flow and is a point of failure. I find it mildly astonishing that anyone should be proud of their car farting on the overrun. But then I llike my diesel so I'm probably disqualified from having an opinion :)

    Diesel engines have no throttle. Power output is controlled by the fuel quantity injected at each combustion stroke. Mass flow around the compressor-combustion chamber-turbine loop is always uniform. This makes diesels much better candidates for forced induction.

    A dump valve can only do harm to the performance of a diesel.

    Turbo wastegates are not dump valves, they limit the pressure on the exhaust turbine to prevent the turbo from overspeeding when the engine's gas flow becomes too high i.e. at high rev's. The higher-performing VAG turbos use variable-geometry inlet vanes and have no wastegate.

    There are "dump valves" for TDi's that are activated by the ECU, such as the Forge one. If fitted and adjusted properly they do not affect performance, they just make a noise. So you can fit them anywhere you like, wherever you want the noise to be heard best - say on the dashboard, or maybe on the roof.

    There is style, and there is substance. A noisy dump valve is a style choice, it has no substance, no usefulness on any diesel engine.

    Here endeth the first lesson
     
    #5 Muttley, Sep 15, 2009
    Last edited: Sep 20, 2009
    Redemption likes this.
  6. FRdan

    FRdan Guest

    I must say,What a description!!!

    Thats all the convincing i need NOT to put a dump valve on my belovered tdi.
     
  7. MJ

    MJ Public transport abuser

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    I'm not eating my words here but i have since this post decided to remove the Diesel dump valve, Blow off valve or what ever you wish to call it from my car. when i origionally fitted it i just wanted to see what it was like and i was quite happy with the overall effect but now that it is tried and tested i can tell you that they are niether use nor ornament

    Whilst fitted:

    I experieced a really lupy idle
    The car would 'chug' when driving at less the 1500rpm
    And whenever i decided to put my foot down i would create my own James Bond styled smoke screen.

    These faults (apart from very slight smoking on boost) have since vanished upon removal of the 'bov'.
    I found that when fitted and activated the solenoid would still suck the plunger which kept the valve open and allow excess air to be drawn in backwards through the dump valve into the intake!
    This was not down to shoddy fitting as i took every precaution nessesary to prevent air leaks - it was just down to the way it had to function.

    To be quite honest the best explanation is by MUTTLEY and is 2 posts above this one.
     
  8. brightsideteeem

    brightsideteeem I'm not like you guys...

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    if you want a "woosh" noise, search for "mufflerectomy"
     
  9. MW05

    MW05 Full Member

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    WOW!
    That's just saved me searching time AND money!
    I thought ALL turbo charged engines would benefit from a dump valve to stop the turbo from slowing down when the throttle closed...
    I can still have a big front mounted intercooler though can't I? :)
     
  10. 3gte

    3gte Full Member

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    Yes, yes you can
     
  11. mty12345

    mty12345 Senior Member

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    Diesels don't have a throttle. The pedal just controls when, and how much fuel is injected. There''s no butterfly like a petrol engine.
     
  12. stubby205

    stubby205 Full Member

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    That's convinced me not to get one :)
     

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