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Where does the combi valve vac hose go?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Bad Sir Culation, Dec 9, 2013.

  1. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 9, 2013]
    It's disconnected on my car. Should the hose be plugged back in? If not, should it be plugged as it isn't currently?
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  3. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    [Dec 9, 2013]
    It should be connected under the inlet manifold manifold off a small vac nipple. If its not then you need to find out whats on that nipple
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  4. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 10, 2013]
    Damn. I don't know where to start then, as I was looking at it tonight and couldn't see where it would go. I need pictures lol.

    In this photo from the other thread:
    View attachment 24383
    you can see the hose from the inlet to the DV. I *THINK* that the hose from the FPR is going to the inlet next to where the DV hose goes. Does that sound correct so far?

    You will also see the black hose going into the t-piece on the DV hose. I do not know where this black hose goes, what it's for or why its plumbed into the DV hose. Perhaps this goes to where the combi valve hose should go?

    Is there any good reason to do this?
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 10, 2013]
    Looks like a fairly poorly executed N249 bypass... there is a guide in the FAQ sticky that could help you tidy it up a but... APY engines are a little more involved as they have secondary air (the pipe loitering about off the jobber on the side of the head...) most peeps just remove this altogether to simplify the whole thing... later AMK/BAM S3's didn't come with SAI... its an emissions thing... won't affect MOT as its more for controlling emissions on cold start...

    Look in the FAQs and have a read of the N249 bypass/delete thread...

    Couple of reasons for doing this... makes the DV more responsive and cleans up a lot of the pipes that can split etc and cause other running issues... however... there is no real need to do it if you don't want/need to... most people do it as they are getting rid of split pipes etc already so a full clean up of stuff and replacement with silicon just makes it easier...

    The N249 is used as part of the ECU protection functionality... its a switch over valve... the DV is opened by vacuum and kept closed by boost... if the ECU detects an issue then it can use the N249 to switch to a vacuum feed from the vacuum store (plastic container that is missing from your picture) and operates the DV to dump boost while closing the throttle to reduce load...

    You lose this with the bypass but tbh the ECU can hold its own without it... biggest issues being more leaks and bad maps... I'd be more concerned about leaks and bad maps than re-plumbing the N249 back in..

    You do need to leave it electrically connected though as this messes with adaptions and can make the car fail emission test at MOT time

    <tuffty/>
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  6. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 10, 2013]
    Thanks Tufty. I've actually read through that, but thought I didn't need it as a result of this already being bypassed. Should I be looking for somewhere to plug this combi valve back in?

    I'll go back through that thread if you say it is going to yield the answers I need, but I could have sworn there was no mention of the vac hose for the combi. It is possible I am going mad, what with the amount of stuff I am having to jump on with this car all at once!
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 10, 2013]
    Lets get the terminology straight here... by 'combi' valve I am assuming you mean the grey valve in the centre of your pic above... if so this is the N249 valve

    The valve just needs to be plugged in electrically (as it is currently)... no need to pipe this up at all as this is now 'by passed'... just cable tie it out the way.. :)

    <tuffty/>
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  8. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 10, 2013]
    Ah no, I know what the N249 valve is (now, thanks to you guys on here!), no what I mean is the round item to the right of the FPR. It has a dark vac hose connected to it that isn't going anywhere now. I thought it was an EGR originally but then saw it referred to as a combi valve a couple of times during searches. Seems I may have got my wires crossed on its name.
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  9. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 11, 2013]
    Anymore for anymore? :p
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  10. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 11, 2013]
    Thats the Secondary Air Injection valve... bin it off...

    <tuffty/>
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  11. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 11, 2013]
    #10
  12. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Dec 11, 2013]
    http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/88299-sai-removal-guide.html

    Its used for emissions on cold start... binning off means less clutter, less pipes etc to leak, less to go wrong

    <tuffty/>
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  13. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 11, 2013]
    Thanks Tuffty, much appreciated. It's far easier to find these guides when you know what the parts are actually called!
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  14. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 11, 2013]
    Just one more quick question; if I leave the valve in place for now, should I plug the vac line on it, or just leave it unplugged?
    #13
  15. Bad Sir Culation
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    Bad Sir Culation Member

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    [Dec 15, 2013]
    Bump in case anyone can answer this for me.
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  16. Lavis89
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    Lavis89 Active Member

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    [Dec 15, 2013]
    If the car is running right and there isn't a check engine light then I would leave it for the moment until you do a SAI removal (if you do one). That's just me though, I don't like to fiddle with things that aint broken because I will tend to brake it!
    #15

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