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N249 Bypass Guide for ARY Engine and all other A3 Engines

Discussion in 'A3/S3 Forum (8L Chassis)' started by Syvo, Jun 27, 2011.

  1. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jun 27, 2011]
    i decided to create this guide due to the number of guides showing how to do the bypass using the fpr as a tee point for the dv so to help with confusion i created the correct way to set the bypass up.

    ok first open the bonnet and you will see.
    [​IMG]

    then take off the engine covers there will be 8 twist/push in screws.
    [​IMG]

    the part you will be getting rid off from the top of the engine bay would be the vac chamber which is held in with 2x 10mm screws and there would be one pipe coming off this going next to the dv this needs disconecting also.
    [​IMG]

    once the vac chamber is removed and the pipe from the top of the dv is removed you should be left with 2 metal pipes with neither the dv or the vac chamber connected.
    [​IMG]

    next step is to disconect the plastic pipe which goes to the airbox this is so you can move the metal plate infront of the inlet manifold.
    [​IMG]

    next is to remove the 2x 10mm nuts ontop of the metal plate infront of the inlet manifold so the other part of the plastic pipe can be moved out of the way and also remove the two allen key bolts holding the plate to the manifold.
    [​IMG]
    [​IMG]

    now there should be three pipes running along the side of the engine bay to the metal plate two will be coming from the vac chamber and the dv as you removed the other end off these before they can now be cut. there is also another pipe which is a braded pipe this goes to the SAI unit this can also be removed (be careful as the pipe that connects to this is small brittal metal pipe)
    once removed the rest of the SAi pipe will look like so.
    [​IMG]

    there should only be one pipe holding the metal plate to the car this pipe can also be disconected as it runs from the metal plate to the underside of the inlet manifold.
    [​IMG]

    with everything disconected the metal plate can be reomved now and will be left with.
    [​IMG]

    the box in the centre of the metal plate is the n249 which we will be disconecting and the other is the n112.
    i found it easyer to cut the pipes to the n112 and unscrew the part from the plate to remove the metal clips holding the last bit of the pipe to the n112 to save breaking the nozzle of the n112.
    [​IMG]
    [​IMG]
    [​IMG]

    now disconect all the pipes from the metal plate and make sure you remember which way the one way valve went i put a lil bit of tape on mine so i knew which end went which way.
    with all pipes removed it should look like this.
    [​IMG]

    now you need to get the silicone hose out and some tie wraps first connect the silicone hose to the SAI.
    [​IMG]

    with that end connected connect it to the n112 make sure you have enough hose for when the metal plate is put back where you disconnected it trial fit to make sure it allways best.
    [​IMG]

    now remembering the way the one way valve went connect the n112 to the 1 way valve.
    [​IMG]

    then connect a small piece of pipe to the nipple to the underside of the inlet manifold which you freed up by removing all the piping the metal plate.

    with the small piece of tubing connected put a tee piece in the end of the small tubing comming off the nipple then connect one end to the one way valve and the other end will be connected to the dv.

    make sure you tie wrap the one way valve up so it does not dangle all around the engine bay.
    [​IMG]

    now with the metal plate put back and the two plugs connected back for the n112 and the n249 you can start to put the engine bay back together this is what you should be left with (excuse the white tee piece this is the pipe for my boost guage.
    [​IMG]

    while i had some spare hose i decide to change the fpr hose for some silicone hose.

    with engine covers back on this is what i was left with.

    Tools Used:
    10mm socket
    3/8 Rachet
    extension bar
    size 5 Allen key
    flat head screw driver
    straight pick
    hook shapped pick

    Time Taken:
    1 hour including taking pictures

    Experiance needed:
    Non only a case of disconeting some pipes and changing the pipe work over for new pipes.

    Cost:
    £5 for 2m silicone pipe.
    £1.50 for tee Piece ( although i had one spare so i did not need to buy this.)
    £2 pack of 10 tie wraps ( Already had these in tool box so did not have to buy.)

    What the Bypass Does.
    eliminates the ECU controlling boost in which the ECU dumps boost unexpectedly resulting is poor control in car the Traction Control is not affected by this i tested this out on a field and yeh the traction contol still kicks in, the dv is more responsive and slightly louder, minimal throttle response inprovement, reduced risk of split pipes or boost leaks as changed more orginal pipes for silicone pipes.

    hope this helps out people this guide is mainly for A3 Owners as welly has done a great guide for S3 owners this can be used for the A3's any thing i have missed please let me know.
    #1
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  3. A3 T
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    A3 T Lord Of The Rings

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    [Jun 28, 2011]
    Thanks for the guide mate :)


    Ill definitely be doing this as soon as i find time to get some 4mm hose.


    Maybe this should be made a sticky ?
    #2
  4. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jun 29, 2011]
    good idea yeh can we make this a sticky for a3 owners
    #3
  5. Jay A3
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    Jay A3 More power

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    [Jun 29, 2011]
    Thanks for the guide! well defo be looking into this :thumbsup:
    #4
  6. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jun 29, 2011]
    no worries hope it nice and easy to follow
    #5
  7. A3 T
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    A3 T Lord Of The Rings

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    [Jun 29, 2011]

    I think youll need to pm a mod mate ;)
    #6
  8. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jun 30, 2011]
    pm'd mod hopefully will be made as a sticky
    #7
  9. voorhees
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    voorhees Moderator Staff Member Moderator

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    [Jul 3, 2011]
    Stuck...I'll edit it so its incorporated with other bypass guides as said Paul
    #8
  10. dannyh
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    dannyh Nogaro S3

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    [Jul 4, 2011]
    Is this of more benefit for a remapped car, would there be any benefit to a standard 150??
    #9
  11. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jul 4, 2011]
    it would be a benifit for any as it bypasses the ecu having control over the boost so no lag between gear changes.
    #10
  12. dannyh
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    dannyh Nogaro S3

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    [Jul 4, 2011]
    No Lag at all :uhm:
    #11
  13. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jul 4, 2011]
    the ecu controls the boost with the n249 conected so potentailly the ecu can steal boost from you and give it back causing lag so by bypassing the n249 the ecu can't control the boost and you will have a smoother feel i.e no lag
    #12
  14. dannyh
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    dannyh Nogaro S3

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    [Jul 4, 2011]
    Nice!!! i will add this to the lis of things to do!!!!! great guide cant wait to do it
    #13
  15. Steveo_A3_1.8t
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    Steveo_A3_1.8t Member

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    [Jul 5, 2011]
    Nice guide mate! Just waiting for my hose and tee to aarove then I'll do this.

    Sorry to sound like a noob but what does SAI stand for??
    #14
  16. Alex C
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    Alex C Well-Known Member

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    [Jul 5, 2011]
    secondary air injection
    #15
  17. A3 T
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    A3 T Lord Of The Rings

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    [Jul 5, 2011]
    #16
  18. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jul 5, 2011]
    ive put mine back to standard as couldnt find the problem checked all pipes and dv etc this guide is the same as the one of mkivs only addition i didnt tee from the fpr so it should work my car just didnt like it
    #17
  19. dannyh
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    dannyh Nogaro S3

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    [Jul 5, 2011]
    A friend has done this on hi LCR and he said it is a great mod and he has had no issues.
    #18
  20. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Jul 5, 2011]
    true lots of people have done the mod with no issues it created the guide for A3's as people were getting confused with the S3 guide on ere and other A3 guides people had done when they had hooked up to the fpr.

    mine had issues duno why but the guide is correct all set up the correct way just guess my car didnt like the conversion
    #19
  21. Cmorebutt6969
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    Cmorebutt6969 New Member

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    [Jul 23, 2011]
    Stupid question can you do this with the 1.9 tdi?
    #20
  22. Chlippo
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    Chlippo Member

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    [Jul 28, 2011]
    would someone let us know if this is the same over for A3 S3 and different engine codes plz?
    #21
  23. Steveo_A3_1.8t
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    Steveo_A3_1.8t Member

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    [Jul 29, 2011]
    Syvo, what spring have you got in your 007p?? Also Ive just done the bypass using your guide and all is well. Cheers
    #22
  24. Welly
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    Welly VX220 SC Driver :)

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    [Aug 5, 2011]
    An additional note, having just done this on the TT.

    If you want to, you can also disconnect and block off the pipework for the N112 valve/SAI (as my mate broke mine).

    If this happens, then just make sure that you leave the valve electrically connected or you will NOT get any fuelling adaptation. MOT fail big time.
    #23
  25. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Aug 5, 2011]
    the green spring m8
    #24
  26. Steveo_A3_1.8t
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    Steveo_A3_1.8t Member

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    [Aug 9, 2011]
    I've got a yellow spring in mine, my car is standard apart from remap. Could your spring be the wrong weight?? Just a thought. I'm a complete novice when it comes to turbos etc never had one till now.
    #25
  27. Welly
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    Welly VX220 SC Driver :)

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    [Aug 9, 2011]
    Yellow is a bit much for that application mate, green is what you should have in there really....
    #26
  28. Steveo_A3_1.8t
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    Steveo_A3_1.8t Member

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    [Aug 19, 2011]
    Righto, cheers for the heads up mate. Am I correct in thinking that the lighter the spring weight, the less vacuum pressure is required to open the valve?? If so, what are the benefits of having the right spring for your specific application fitted?? And what the downside of having the wrong one is??

    Cheers
    #27
  29. A3 T
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    A3 T Lord Of The Rings

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    [Aug 24, 2011]
    I've ordered some hose and I've been looking at your guide and this guide (because it has all the bits circled in red...lol):



    http://www.golfgtiforum.co.uk/index.php?topic=113646.0


    But I'm still confused where you T the hose from the DV into.

    Is it one of the nipples under the manifold?
    #28
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  30. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Aug 25, 2011]
    if you look at picture 9 it shows the nipple of the inlet manifold basically the n112 will go to that nipple so you tee the n112 pipe to the dump valve under the inlet manifold
    #29
  31. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Aug 25, 2011]
    with the small piece of tubing connected put a tee piece in the end of the small tubing comming off the nipple then connect one end to the one way valve and the other end will be connected to the dv.
    #30
  32. Smokey_clark
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    Smokey_clark 12th Gear

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    [Aug 25, 2011]
    The spring works against the vacuum to close the DV after each operation. The spring strength is in relation to boost pressure, when your car is mapped the boost is increased. Eventually this is a greater pressure than the DV spring and the DV will be opened at the wrong time (full boost). This is when you uprate the spring so it can hold the DV closed at full boost. If you have too strong a spring in the DV it will not be able to operate with normal Vac pressure and the divertable air will run back through the turbo, causing compresser stall/flutter and ultimately damaging your turbo shaft.
    #31
  33. A3 T
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    A3 T Lord Of The Rings

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    [Aug 25, 2011]


    Thanks mate :thumbsup:

    So i can go with the guide i posted but then T the hose coming from the n112 (looks like the end nipple) to the manifold ?
    #32
  34. A3 T
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    A3 T Lord Of The Rings

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    [Aug 26, 2011]
    Am i right in thinking its hose 1 that we T off ?

    Where does hose 2 lead to and would it be worth changing it to silicone at the same time ?


    [​IMG]
    #33
  35. Syvo
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    Syvo IF IN DOUBT GO FLAT OUT

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    [Aug 26, 2011]
    yep hose 1 use for tee hose 2 leads to the fpr yeh worth chainging that while you there m8 i did mine
    #34
  36. A3 T
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    A3 T Lord Of The Rings

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    [Aug 28, 2011]
    Ok thanks mate , ill let you know how i get on ;)
    #35
  37. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Nov 23, 2011]
    Did this job on an A3 TQS (ARY) last night and thought that this little pic might help make the above guide a bit clearer:

    [​IMG]
    #36
  38. A3 T
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    A3 T Lord Of The Rings

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    [Nov 23, 2011]


    That's how i did mine but i still had a slight flutter.

    The hose you marked “SAI” do you mean the skinny metal pipe?
    #37
  39. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Nov 23, 2011]
    Yes I do mate. It's the hose to the SAI ;)
    #38
  40. Grazam
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    Grazam Member

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    [Feb 4, 2012]
    Going to give this ago when my Coilovers turn up as Im gonna use my friends ramp for the coilovers might aswell use the work shop facilities while im there :)
    #39
  41. Alais DJA
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    Alais DJA Member

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    [Mar 12, 2012]
    #40

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