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

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

    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 isnt 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, lets begin.

    Engine cover off.



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



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



    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 (thats why mine isnt there. But I broke that fitting an alternator. Its been temporarily replaced with a wine bottle cork Pro bodge!).



    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)



    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.



    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.



    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.



    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).



    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 didnt however based on the fact that I dont like putting anything into the FPR vac line in case of leak. Ultimately meaning lean fuelling.



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



    I replaced second N112 vac line to the SAI with silicone for good measure. You dont have to do this.



    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.



    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.

    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 by Welly; 3rd December 2009 at 15:31. Reason: Forgot stuff.
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  3. #2
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    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

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    Can you refit the n249 without refitting the vac lines? Just a emty n249 only the electrical wire connected?

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    Quote Originally Posted by The Stig View Post
    Can you refit the n249 without refitting the vac lines? Just a emty n249 only the electrical wire connected?
    Yep, that's spot on, it needs to stay electrically connected as the ECU will be upset if it's not.
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    Nice! Just bought the materials and it try!

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    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

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



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


    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!!


    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

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    Or put the engine cover back on?
    S3, 4 wheels, magical B8's, Eibach, Pipewerx equipped, glass windows, metal engine, silver paint.

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    Quote Originally Posted by Kunit View Post
    Or put the engine cover back on?
    Details....
    glasgowal likes this.
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    Quote Originally Posted by Kunit View Post
    Or put the engine cover back on?
    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

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    Quote Originally Posted by jonny87 View Post
    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
    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...
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    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.
    S3, 4 wheels, magical B8's, Eibach, Pipewerx equipped, glass windows, metal engine, silver paint.

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    Quote Originally Posted by Kunit View Post
    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.
    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

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    Quote Originally Posted by Kunit View Post
    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.
    What exactly did you notice on performance doing this mate?

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    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..

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    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.
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    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?

  18. #17
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    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.
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  19. #18
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    Quote Originally Posted by jonny87 View Post




    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?
    It's better to burn up, than to fade away...

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    It makes it louder, apparently.

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    Welly's Avatar
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    Quote Originally Posted by JD09 View Post
    It makes it louder, apparently.
    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.
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    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 ??
    Ebony black 99 S3, Forge 007, cone filter, goodridge braided lines, apex lowering springs. More to come...

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    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

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    Correct.
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    awesome so does this mean i do not need a t piece?

    thanks mate

  26. #25
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    No, you can just run 1 pipe from the DV to the inlet mani.
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    I've done it, i too only had to use one pipe. What a difference its made
    Audi A3 Quattro Sport 180bhp

    Pic's comimng soon !

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    Gonna do this at the weekend... Wish me+ my basic car knowledge well lol

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    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?

  30. #29
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    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
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    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...
    2002 S3 8L, FORGE 007, R-TECH RE-MAPP, MILTEK CAT BACK NON-RESONATED, JETEX CONE FILTER AND 260 BHP ISH.......

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    Just done this, feels alot more responsive and only took 10 mins...... Complete removed N249 so never going back on!!!
    2002 S3 8L, FORGE 007, R-TECH RE-MAPP, MILTEK CAT BACK NON-RESONATED, JETEX CONE FILTER AND 260 BHP ISH.......

  33. #32
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    Quote Originally Posted by luke2702 View Post
    Just done this, feels alot more responsive and only took 10 mins...... Complete removed N249 so never going back on!!!
    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....
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    Quote Originally Posted by Welly View Post
    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....
    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!!!!
    2002 S3 8L, FORGE 007, R-TECH RE-MAPP, MILTEK CAT BACK NON-RESONATED, JETEX CONE FILTER AND 260 BHP ISH.......

  35. #34
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    Quote Originally Posted by luke2702 View Post
    Left the electric part plugged in if that is what you mean mate.
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    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!

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    Welly what type of plastic welder did you use to weld the nipple on to the n112 valve. Ive gone and broken mine of

  38. #37
    Welly's Avatar
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    Quote Originally Posted by s3 toe View Post
    Welly what type of plastic welder did you use to weld the nipple on to the n112 valve. Ive gone and broken mine of
    A lighter and a flat headed screw driver mate. Melt the plastics together.
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    What use was the flat headed srwedriver for mate sorry if i sound thick as anything

  40. #39
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    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.
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    Arr yea i see what you mean now thank you very much. Just hope it holds till my new on arrives

 

 
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