1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

N249 Bypass How To (2000 S3 - but same for many)

Discussion in 'General Technical / How To' started by Welly, Dec 3, 2009.

  1. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Dec 3, 2009]
    N249 Bypass.

    Car: 2000 S3 with APY.

    Time taken: Approx 1 hour 30 mins (would have been less but we were messing about, and broke something).

    Attempted by: Welly & his mate Jonny.

    Needed: 4mm internal diameter vac hose. Allen keys. 10 MM socket. T piece.

    Difficulty: A trained chimp could complete.

    OK. This isn’t a difficult task, and to anyone with even a flicker of mechanical know-how will, (once knowing what pipe is what) have this done with ease.

    Pros and Cons:

    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.

    The three items in question are a) the re-circ valve b) the N249 valve and c) the N112 valve (not on AMK or BAM engines)

    So, let’s begin….

    Engine cover off….

    [​IMG]

    N249 is readily obvious on the APY engine as shown in image 1.

    [​IMG]

    In image 2 you can see the three pipes that we need to keep on the engine.

    [​IMG]

    Image 3 simply shows the vac chamber that we will be getting rid of.

    Removal of the metal plate attached to the inlet manifold is necessary at this point – two Allen key bolts. Forgot to note what size – sorry. Be VERY careful when removing plate as it has a lug which connects onto the dipstick shroud – this will usually be brittle and easily broken (that’s why mine isn’t there. But I broke that fitting an alternator. It’s been temporarily replaced with a wine bottle cork… Pro bodge!).

    [​IMG]

    Image 4 is showing you the underside of said metal plate. N112 pipe work is readily visible. Cut pipe to N249 as close to the nipple as possible. If replacing vac line to SAI also (if you have a bit of spare hose) the cut the second vac line. If not, simply pull off (be careful not to damage valve – more on this later)

    [​IMG]

    Image 5 shows the pipe to the N249 that was cut off in the previous step. This will need to be cut back – but not yet.

    [​IMG]

    Image 6 shows cutting into the vac feed from the inlet manifold. Again, will need to be cut for a good fit, but not yet.

    [​IMG]

    As shown in image 7, once this line is cut, you can unbolt the vac chamber (1 x 10mm bolt) and remove from the car along with the valve and pipe assembly.

    [​IMG]

    Once out of the car, remove the clips from the two pipes connected to the N249 valve and pull free. Keep somewhere handy (and clean if you have OCD).

    [​IMG]

    Image 10 is trying to show a few bits all at once… T piece connecting (top) Recirc vac line (left) vac feed from inlet manifold (bottom) Vac feed to N112 valve.

    It is worth mentioning here that you CAN T into the FPR vac line for the N112. I didn’t however based on the fact that I don’t like putting anything into the FPR vac line – in case of leak. Ultimately meaning lean fuelling.

    [​IMG]

    Refit N249 valve to rocker cover as shown in image 11. Make sure you reconnect wire.

    [​IMG]

    I replaced second N112 vac line to the SAI with silicone for good measure…. You don’t have to do this.

    [​IMG]

    As mentioned before, this is the repair that we had to make to my N112 valve after the nipple breaking off…. 1 x T Piece pipe cut down and plastic welded to the snapped stub.

    [​IMG]

    Reconnect N112 pipe work in the same way it was removed – one to the new T piece and one to the SAI. Ensure N112 electrical plug is refitted.

    Remove all equipment from engine bay and start engine.

    Local test.

    You should notice improved DV response at gear change, as it no longer has a third party interfering. You SHOULD NOT have any warning lights etc with this bypass. If you do stop and check all plugs correctly refitted.

    Job Done. :whistle2:

    Please note that SOME (I'm not fully aware of what engine codes) 1.8T engines have the N249 valve on the underside of the attached plate (next to N112 valve). The basic process for those is the same, you'll just have to figure out what pipes correspond to the pictures... And count yourselves lucky that yours is hidden!!

    If anyone spots anything I've missed, please add it.

    (NB. I take no responsibility for any damage you do whilst attempting this mod. But you should be fine!)
    Last edited: Dec 3, 2009
    #1
  2. Ads

    Ads

    [Sep 18, 2014]

  3. jonny87
    Offline

    jonny87 Active Member

    Joined:
    Sep 24, 2009
    Messages:
    1,098
    Likes Received:
    3
    [Dec 3, 2009]
    gonna give this a bash on the weekend mate, my n249 is underneath the metal plate jobber, so il have fun figuring out which pipe should go where etc

    thanks for the guide though dude, always much much easier after someone has taken the time to do things like this :)
    #2
  4. The Stig
    Offline

    The Stig Member

    Joined:
    Nov 17, 2009
    Messages:
    33
    Likes Received:
    0
    [Dec 12, 2009]
    Can you refit the n249 without refitting the vac lines? Just a emty n249 only the electrical wire connected?
    #3
  5. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Dec 13, 2009]
    Yep, that's spot on, it needs to stay electrically connected as the ECU will be upset if it's not.
    #4
  6. The Stig
    Offline

    The Stig Member

    Joined:
    Nov 17, 2009
    Messages:
    33
    Likes Received:
    0
    [Dec 14, 2009]
    Nice! Just bought the materials and it try!
    #5
  7. jonny87
    Offline

    jonny87 Active Member

    Joined:
    Sep 24, 2009
    Messages:
    1,098
    Likes Received:
    3
    [Dec 28, 2009]
    well i finally got round to doing the n249 bypass mate, following your guide was easy as anything so kudos there bud, to be fair once i got started it became pretty obvious what needed doing, took me about an hour to do so not too much time spent in the cold lol :cold:

    heres some pics, i forgot to take a before pic but im sure you all know what it looks like :)

    [​IMG]

    i tee'd mine underneath the inlet manifold so that its not so visible, just makes it look that little bit neater imo
    [​IMG]

    also with my n249 valve i managed to sort of hide mine between the chargepipe and some heatproof material/matting whatever you want to call it!!
    [​IMG]

    i suppose if you wanted to be really fussy you could extended the two wires to the valve and then you could place where ever you so wished to, like your's welly is still on show above the coilpacks, depends if it bothers you or not

    i didnt have enough hosing to replace the one from the n112 to the sai, but this is easy enough for me to do at a later date

    so big shout out to welly for taking the time to do the how to guide, made the job a hundred times easier ;) :respekt:
    #6
  8. Kunit
    Offline

    Kunit Member

    Joined:
    Aug 22, 2009
    Messages:
    170
    Likes Received:
    0
    [Dec 28, 2009]
    Or put the engine cover back on?
    #7
  9. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Dec 28, 2009]
    Details....
    #8
    glasgowal likes this.
  10. jonny87
    Offline

    jonny87 Active Member

    Joined:
    Sep 24, 2009
    Messages:
    1,098
    Likes Received:
    3
    [Dec 28, 2009]
    yep, but some people will do this for the pro's of doing it, others will do it to make it look neater and not need to have cover, plus its one less thing to remove when doing coilpacks/plugs ;)
    #9
  11. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Dec 28, 2009]
    Ha, I've just had to change two myself actually. Another point to note is that I cut the N249 bracket in half, meaning you only have to bolt it on in 2 places instead of all the way across...
    #10
  12. Kunit
    Offline

    Kunit Member

    Joined:
    Aug 22, 2009
    Messages:
    170
    Likes Received:
    0
    [Dec 28, 2009]
    I did mine for performance and there is no way the top of the engine looks better than the cover, especially with the two other covers in the bay, just looks ridiculous.
    #11
  13. jonny87
    Offline

    jonny87 Active Member

    Joined:
    Sep 24, 2009
    Messages:
    1,098
    Likes Received:
    3
    [Dec 29, 2009]
    yer but if you done some more tidying up in there, polished/painted the rocker etc etc you could have a very nice looking bay, its just something different to look at rather than some dull black plastic

    but hey, not everyone does it for the same reason
    #12
  14. fran-s3
    Offline

    fran-s3 Active Member VCDS Map User

    Joined:
    Jan 29, 2008
    Messages:
    1,103
    Likes Received:
    1
    [Mar 4, 2010]
    What exactly did you notice on performance doing this mate?
    #13
  15. warleydaddy
    Offline

    warleydaddy Member

    Joined:
    Oct 14, 2008
    Messages:
    211
    Likes Received:
    0
    [Mar 28, 2010]
    Just been out and done this,took 30mins.. No real gains.. Spool up is a td louder,but thats about it... But has got rid of ALOT of mess on top of the engine..

    Pete..
    #14
  16. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Apr 4, 2010]
    Just a note to all.

    Leave the N249 valve electrically connected.

    If you don't, this can stop adaptive fueling from working resulting in HIGH EMISSIONS and MOT failure.

    Like me. LOL. :icon_thumright:
    #15
  17. drewlad
    Offline

    drewlad mr

    Joined:
    Apr 4, 2010
    Messages:
    6
    Likes Received:
    0
    [Apr 5, 2010]
    hi there i came to do the N249 Bypass on mr 2003 s3 and i noticed there is a little diferance i can't figure it out any clues?
    #16
  18. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Apr 5, 2010]
    The 225 BAM and the 210 AMK don't have the SAI system. This also means they don't have an N112 valve, which is why you don't have the tube there.

    No problemo, just ignore that portion of the guide.

    Also sent this via PM.
    #17
  19. mark_sarah
    Offline

    mark_sarah Limp mode!

    Joined:
    Nov 3, 2009
    Messages:
    203
    Likes Received:
    0
    [Jun 6, 2010]

    I see you have the Diverter Valve a different way round to mine! Is this how they are suppose to be fitted? Or does it boost better that way?
    #18
  20. JD09
    Offline

    JD09 I'm not modding, I'm improving VCDS Map User

    Joined:
    Dec 20, 2009
    Messages:
    3,080
    Likes Received:
    35
    [Jun 7, 2010]
    It makes it louder, apparently.
    #19
  21. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Jun 7, 2010]
    Yep, it does make a slight difference - still works in the same way though.

    Forge say this can be done with the 007P without affecting performance of the valve.
    #20
  22. 5teve L
    Offline

    5teve L Member

    Joined:
    May 15, 2010
    Messages:
    152
    Likes Received:
    1
    [Jul 13, 2010]
    Just did this on mine, got rid of all that mess on the top of the engine, looks much tidier :)
    I just chopped into the two hoses & used them to T into, then a bit of hose to the DV.... was there any reason why you took the hose off the other valve under the metal tray OP ??
    #21
  23. IOM-S3
    Offline

    IOM-S3 Member

    Joined:
    Jul 15, 2010
    Messages:
    109
    Likes Received:
    0
    [Jul 22, 2010]
    hey guys, i was going to attempt this mod, however i only have 1 vac pipe coming up from the inlet area? why is this, is it because some models do not have the n112 valve??

    cheers
    lee
    #22
  24. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Jul 22, 2010]
    Correct.
    #23
  25. IOM-S3
    Offline

    IOM-S3 Member

    Joined:
    Jul 15, 2010
    Messages:
    109
    Likes Received:
    0
    [Jul 22, 2010]
    awesome so does this mean i do not need a t piece?

    thanks mate
    #24
  26. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Jul 22, 2010]
    No, you can just run 1 pipe from the DV to the inlet mani.
    #25
  27. Dazboss
    Offline

    Dazboss Like A Thristy Dingo ;)

    Joined:
    Jul 10, 2010
    Messages:
    366
    Likes Received:
    0
    [Aug 24, 2010]
    I've done it, i too only had to use one pipe. What a difference its made :)
    #26
  28. djarchive
    Offline

    djarchive Member

    Joined:
    Apr 28, 2009
    Messages:
    248
    Likes Received:
    4
    [Oct 4, 2010]
    Gonna do this at the weekend... Wish me+ my basic car knowledge well lol :)
    #27
  29. The Doctor
    Online

    The Doctor Well-Known Member

    Joined:
    Jul 25, 2009
    Messages:
    1,284
    Likes Received:
    109
    [Oct 9, 2010]
    Was talking to G60dan about this at ADI today. Welly, apart from tidying up yet more pipework under the bonnet, what are the tangible performance advantages? Less lag or what? I understand from G60dan that the risk is that the effect of the traction control is affected in some situations?
    #28
  30. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Oct 9, 2010]
    To be honest mate, performance advantages are negligible. Some people who have tried this have reported changes, but I think that to say it will increase performance isn't true.

    It will crispen up your DV response time, which is nice, as there is no valve and vac chamber for it to go through. It will also eliminate the possibility of boost/vac leaks from the pipework assembly.

    Anyway, with regard to the traction control, it will disable the traction control's ability to dump boost if it sees fit. I'm a bit funny like that, and don't like the idea the car can decide to do something I don't want it to....

    With regard
    #29
  31. luke2702
    Offline

    luke2702 Member

    Joined:
    Apr 22, 2010
    Messages:
    446
    Likes Received:
    0
    [Oct 20, 2010]
    I am doing this at the weekend, not doing it for looks as i like the look of the covers!!(sorry). Doing it to improve DV response...
    #30
  32. luke2702
    Offline

    luke2702 Member

    Joined:
    Apr 22, 2010
    Messages:
    446
    Likes Received:
    0
    [Oct 24, 2010]
    Just done this, feels alot more responsive and only took 10 mins...... Complete removed N249 so never going back on!!!
    #31
  33. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Oct 24, 2010]
    Make sure you leave the N249 connected though dude, as if you don't adaptive fuelling will turn off....

    I found this out come MOT time....
    #32
  34. luke2702
    Offline

    luke2702 Member

    Joined:
    Apr 22, 2010
    Messages:
    446
    Likes Received:
    0
    [Oct 24, 2010]
    Left the electric part plugged in if that is what you mean mate.

    1 thing i did notice is my MPG on the computer takes longer to adjust!!!!
    #33
  35. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Oct 24, 2010]
    :thumbsup:
    #34
  36. supreme
    Offline

    supreme Member

    Joined:
    Oct 28, 2010
    Messages:
    55
    Likes Received:
    5
    [Nov 21, 2010]
    Big Thanks to the OP for posting this guide up!

    Did this at the same time as fitting my 007P. There must be a resistor to bridge the electical connection of the valve to proper bin it off?

    I hate the thought of something redundant sitting in the bay hidden out of site or not!
    #35
  37. s3 toe
    Offline

    s3 toe Member

    Joined:
    Jan 12, 2011
    Messages:
    37
    Likes Received:
    0
    [Feb 16, 2011]
    Welly what type of plastic welder did you use to weld the nipple on to the n112 valve. Ive gone and broken mine of :(
    #36
  38. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Feb 16, 2011]
    A lighter and a flat headed screw driver mate. Melt the plastics together.
    #37
  39. s3 toe
    Offline

    s3 toe Member

    Joined:
    Jan 12, 2011
    Messages:
    37
    Likes Received:
    0
    [Feb 16, 2011]
    What use was the flat headed srwedriver for mate sorry if i sound thick as anything
    #38
  40. Welly
    Offline

    Welly VX220 SC Driver :)

    Joined:
    Aug 5, 2009
    Messages:
    10,699
    Likes Received:
    117
    [Feb 16, 2011]
    Heat the screwdriver to a reasonable degree with the screwdriver, and then use it to melt the plastics if you see what I mean. It acts as a sort of spatula.
    #39
  41. s3 toe
    Offline

    s3 toe Member

    Joined:
    Jan 12, 2011
    Messages:
    37
    Likes Received:
    0
    [Feb 16, 2011]
    Arr yea i see what you mean now thank you very much. Just hope it holds till my new on arrives :)
    #40

Share This Page