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N249 Bypass/Removal

Discussion in 'A3/S3 Forum (8L Chassis)' started by Welly, Dec 2, 2009.

  1. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    OK.... Thinking of doing this as DV response not always fantastic. I am also having a few problems with car under boost (which I feel may be N75J related).

    Have been doing a bit of research into this and there appears to be about 65 million ways of doing it.

    I have found a lot of info on the VW forums about this - see links:

    http://uk-mkivs.net/forums/t/265883.aspx & http://uk-mkivs.net/forums/p/213950/1381524.aspx#1381524.

    Now these are two very different ways of doing this, and I notice that the N249 is actually on the metal plate that attaches to the manifold in these examples, where as mine is on the rocker cover with the vac chamber...

    Simply, I haven't got a definitive answer as to any benefit from this, aside from clearing up a sh*t load of pipework which I think looks awful.

    What are people's thoughts?
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 2, 2009]
    Connect the pipe coming off the inlet mani to the top of the DV, leave the N249 electrically connected, bin the rest....

    Check my build thread :)

    <tuffty/>
    #2
  4. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    As usual, spot on the money! Thats the one which runs up inside the inlet mani, up to to N249 on the rocker to give it it's vac feed I guess - then just T into it (ready for boost gauge)
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 2, 2009]
    Thats the fella :)

    <tuffty/>
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  6. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    OK cool, easy enough. You're a star.

    Last one then, what about the vac pipe from the 249 to the 112 bolted on the underside of the manifold plate the? Route a line from somewhere else (FPR or T into the 249 line again?)?

    Trying to get hold of a dipstick shroud from Audi at the moment, bloody broke mine last night.... Have whittled a wine bottle cork down to fit to get me to work this morning....!
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  7. 1animal1
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    1animal1 The Clar!! it mouves!!! VCDS Map User

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    [Dec 2, 2009]
    whats the downside to doing this.......
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  8. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 2, 2009]
    Guess so mate... not got a 112 on my S3 :)

    <tuffty/>
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  9. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    Fair enough, I'll just guess and see what happens. All it needs is a vac source so that should be fine.

    Animal - from what I've read there aren't really any massive downsides.

    Pros: It sharpens up DV response and eliminates the possibility of the ECU dumping boost mid rev (using the DV anyway).

    Cons: Limits the ways that the ECU has to control overboost (although the N75 & MAP sensor will keep the ECU in the know and in control). Also, it removes one of the ways that the Traction Control uses to limit power. Am I bovvered tho?
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  10. ex_scoobydoo
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    ex_scoobydoo Member

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    [Dec 2, 2009]
    the pipe comming off the n112 t that into the FPR pipe
    i did mine at the weekend.
    #9
  11. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    [Dec 2, 2009]
    Pics guys.
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  12. Welly
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    Welly VX220 SC Driver :)

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    I'm going to do mine later (despite the biting cold down here in wonderful Gloucestershire). I'll take some pics then and get them up later on.
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  13. rossbrownlee
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    rossbrownlee Ross_S4

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    [Dec 2, 2009]
    where you fit a new pipe to the inlet manifold (the one for th dv) then just tee in and run another pipe to the n112 sov. You can do the tee-in inderneath the inlet manifold where it would be hiddden by the mounting plate if you want it hidden.
    It is important to retain the functionality of the n112 as controls the secondary air injection.
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  14. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 2, 2009]
    [​IMG]

    [​IMG]

    <tuffty/>
    #13
  15. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    Nice work Tuffty, Like that. That's what I'm planning mine to end up looking like. Ultimately planning to remove all this stuff, including the N249 by using a resistor to trick the ECU (should be fine at the right voltage and resistance).

    Planning to get rid of the SAI and N112 as well in time, but thats a job for when I can get in my garage.... Approx 2016.
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  16. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    [Dec 2, 2009]
    Gets pics and a guide up on how you go welly, i want to gte rid of the entire n249 etc but not sure of the resistor idea.
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  17. Welly
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    Welly VX220 SC Driver :)

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    [Dec 2, 2009]
    Will do, I'm going to bypass it today, but the resistor idea I'm gonna lend some thought to and do a bit of research on I think....
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  18. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 2, 2009]
    If its all about the looks, I would just recommend extending the loom and reposition the N249 valve somewhere out of sight... ECU won't throw a wobbler due to a bit of russian roulette modding :)

    IIRC it can be coded out if you go stage 3 but I didn't do this with mine...

    <tuffty/>
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  19. Welly
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    Welly VX220 SC Driver :)

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    Yeah, thats not a bad shout in retrospect, it's easy enough to cable tie it out of the way... Coded out would be useful, I am planning to go down the same route as you once Ive squirreled enough money away to afford it so may look into that then.

    Genius.
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  20. Welly
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    Welly VX220 SC Driver :)

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    [Dec 3, 2009]
    #19
  21. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Dec 3, 2009]
    Nice guide Welly. I've read about this mod loads of times but could never understand it. Now you've done a decent guide with pics it makes more sense.

    Is there any diference with the N249 and N112 valves/circuits on the AMK, APY, and BAM engines?
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  22. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 3, 2009]
    AMK and BAM don't have N112/SAI so less involved to bypass the N249.

    Its as simple as unplugging the pipe from the inlet mani to the t-piece of the N249 and extending it to the top of the DV. Unplug all pipes connected to the N249 and remove the surplus hardware. Leave N249 electrically connected and mounted on the bracket and bingo.

    <tuffty/>
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  23. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Dec 3, 2009]
    Many thanks boss.

    I notice in some of the old threads that some people say that it could be harmfull to the engine if this is removed and the car is overboosting. Though I've never actually read anything about issues being caused due to this mod! What is the worst that could happen?
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  24. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    [Dec 3, 2009]
    Nice little guide welly.
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  25. Welly
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    Welly VX220 SC Driver :)

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    [Dec 3, 2009]
    There are many other counter measures to resolve overboosting. The N249 is one, but the engine is always aware of boost level via the map sensor.

    The N75 Valve is the obvious other counter measure for this - too much boost and the ECU will change the cycle time on the valve to counter act.

    Also if it reads too much boost over requested then it will go into limp mode as we all know - which is when the ECU opens the N75 fully, giving actuator controlled pressure of 5-6 PSI.

    So frankly, I cant see what the worst would happen is to be fair. My old AGU had a MBC, so the ECU was never in control of boost. And there was no problems until it saw too much boost, then it would cut the spark to stop the engine.

    These ECUs will simply NOT let you run more boost than they want to.

    Bastards.
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  26. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Dec 3, 2009]
    Performance change at all welly. What is the pros and cons to doing this.
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  27. Welly
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    Welly VX220 SC Driver :)

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    [Dec 3, 2009]
    Much more responsive DV, really noticeable for me. Revs drop down quicker at gear change also making them smoother. And I got rid of all of the gack on top of the rocker :).

    There are pros and cons for this both on the guide, and further up this thread...
    #26
  28. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Dec 3, 2009]
    http://www.seatcupra.net/forums/showthread.php?t=42406

    PROs: By removing N249 valve, you can prevent this bad habit of the ECU, and by removing N249 valve, you are removing an approximately 2mm narrow bottle neck restriction (ID of the N249 valve) in the line to the DV, which will result in a somewhat faster DV response. I am using the stock bosch DV, but it feels just as good as an aftermarket DV with N249 (restriction) inline. Boost curve is smooth and progressive.

    CONs: Boost overshots/spikes may grow higher, especially in high gear/low rpm situations (using the small K03), which can result in a leaner condition (for the moment). These spikes depend on N75 type, wastegate setting and software programming, but they usually don't last long (0.5-1s max). In the case these spikes are very high (car enters limp even), minor adjustment on the wastegate can be done. Ibiza engine covers cannot be used anymore (by removing the accessories above, two mounting points of the cover are removed aswell).
    #27
  29. Welly
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    Welly VX220 SC Driver :)

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    [Dec 3, 2009]
    None of the mentioned engines use this turbo.... K04s don't suffer as badly with lower down spikes in this scenario due to longer spooooooooooooool time.
    #28
  30. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Yeah sorry about that I just cut and pasted from the seat forum. I'm going to get myself some silicon and a T piece and rip this lot out this weekend hopefully!

    My list of things to do this weekend is growing:

    Ambient lighting mod
    change fuel filter
    tear out N249
    #29
  31. Welly
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    Welly VX220 SC Driver :)

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    I think it's worth doing. It's just a much smoother drive, more crisp like a turbo engine should be!
    #30
  32. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Dec 3, 2009]
    Thanks guys for the info. Im 50/50 wheather to do it.
    #31
  33. Welly
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    Welly VX220 SC Driver :)

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    [Dec 3, 2009]
    Look at it this way, it takes 15 mins to do, and it takes 15 mins to undo.

    Its a completely reversible process at the end of the day, it's worth giving it a go, and if unhappy with results, change it back.
    #32
  34. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Dec 3, 2009]
    yer you are right. The thing that makes me think is, if I keep it bypassed and few weeks down the line the engine fails, I would be wondering did it really do it any good.
    #33
  35. MintyS3
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    MintyS3 Works 60% the time, Everytime.

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    [Dec 3, 2009]
    My n249 failed resulting in my turbo fluttering. Got rid and all is well.
    #34
  36. Welly
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    Welly VX220 SC Driver :)

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    If the turbo fails in a few weeks after removing that valve then you have some slightly more pressing issues dude to be fair...

    There is no way this alone would cause complete turbo failure. Like I said, the engine will NOT let you boost at more than it deems safe, N249 or no N249.

    AGU engines don't have these, and last I checked they don't spontaneously combust...

    If you aren't living on the edge then you're taking up too much room... lol :)
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  37. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Dec 3, 2009]
    Yeah I have strange fluttering noise too and i'm wondering if this mod will eradicate it.
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  38. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Dec 3, 2009]
    I have a similar sort of noise too every now and then. I have a Forge DV so doubt its that.

    Im going to read the guide later and maybe give it ago next weekend.
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  39. Welly
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    Welly VX220 SC Driver :)

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    I would to see if it resolves your noise. Like I said, easy enough to switch back....

    Post results! :)
    #38
  40. jonny87
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    jonny87 Active Member

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    [Dec 3, 2009]
    in relation to pros of this little mod, im sure i read somewhere on here before that removing the vac chamber off the top of the rocker lets coilpack 3 & 4 breathe a bit more, reducing the risk of them overheating and blowing as is so common on our cars, not a cure just an aide!!

    also if you change your own plugs/coilpacks, doing this is going to make them that little bit more accessible ;)

    thanks welly for the guide, going to give it a bash this weekend, let ya know how i get on
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  41. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Dec 3, 2009]
    What's the resistor trick i've seen on a few other threads! It looks like the electrical part of the N249 can then be stashed away somewhere else instead of re-attaching to its mounting plate and looks neater?
    #40

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