Monster MotorsportJMB Retrofits
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  1. #1
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    Surging problem now sorted

    Hi everyone. Replaced my DV today for peace of mind and now my surging issue has disappeared. Didn't think that a faulty DV would have caused it but touchwood its ok now but may have just been coincidence and it will probably happen again soon. Also did the N249 valve bypass mod whilst I was there. DV is definately working faster and gear changes smoother than before. Very happy with the outcome.

    One more question I have is regarding the DV fitment. Can these be mounted / fitted the other way round and if so what are the benefits of this? cheers
    2003 S4 Moro Blue Saloon

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  3. #2
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    Did you check to see if any of the hoses you removed were split?

    Yes you can run it the other way, none really, makes a slightly louder noise.
    Driving the most secretive S3 on ASN

  4. #3
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    Yeah louder, I run my Forge the opposite way
    Ebony black 99 S3, Forge 007, cone filter, goodridge braided lines, apex lowering springs. More to come...

  5. #4
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    Quote Originally Posted by Dani_B19 View Post
    Did you check to see if any of the hoses you removed were split?

    Yes you can run it the other way, none really, makes a slightly louder noise.
    Couldnt find any split hoses etc and all seemed tight. Thought i'd change the DV anyway as its not expensive.
    Does rotating the DV shorten its life at all. May try it but if its only the sound issue may not bother.
    2003 S4 Moro Blue Saloon

  6. #5
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    No at all.
    Driving the most secretive S3 on ASN

  7. #6
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    was wary of doing it earlier
    so just swap the two large hoses on the dv? sorry to sound thick but don't usually get involved in tinkering of this kind but starting to get a bit hooked
    2003 S4 Moro Blue Saloon

  8. #7
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    Undo valve, turn round & refit.. Simples
    Ebony black 99 S3, Forge 007, cone filter, goodridge braided lines, apex lowering springs. More to come...

  9. #8
    Dani_B19's Avatar
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    Like steve said, undo exsisting pipeing etc, turn DV around and reattach pipe's etc, done.
    Driving the most secretive S3 on ASN

  10. #9
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    i run mine the wroung way around also makes no difference to it being able to do the job its made to do, if itsfitted the correct way around the valve will work on vaccum so there is no chance of the valve opening under boost as it will be pulling more vaccum (i guess thats how they get away with making cheap plastic ones) with it the other way around your valve is having to stop the boost pressure pushing the valve open and leaking boost off, forge do different pressure springs so you can still maintain the correct boost by using the correct spec spring..

  11. #10
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    So what problem did you have with the car then ?
    Audi A3 Quattro Sport 180bhp

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  12. #11
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    What DV did you have before and what was it replaced with?

  13. #12
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    Quote Originally Posted by Dazboss View Post
    So what problem did you have with the car then ?
    surging on boost and very jerky when coming off the throttle
    2003 S4 Moro Blue Saloon

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    Quote Originally Posted by finesse View Post
    What DV did you have before and what was it replaced with?
    just the standard bosch one at the moment. Upgrading to a 007p when I get it remapped
    2003 S4 Moro Blue Saloon

  15. #14
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    Quote Originally Posted by s4mark View Post
    surging on boost and very jerky when coming off the throttle
    Mines kinda doing this but not the jerky'ness so much.
    Audi A3 Quattro Sport 180bhp

    Pic's comimng soon !

  16. #15
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    Quote Originally Posted by Dazboss View Post
    Mines kinda doing this but not the jerky'ness so much.
    personally I think the jerkiness was caused by the n249 myself and getting rid seems to have done the trick. Doubt the DV had anything to do with it, I only replaced it for peace of mind. If it does start playing up I would suspect the MAF as I had similar problems on my a4 and it was a knackered MAF.
    Unplugged the MAF on the S3 and took it for a drive and the surging was still there on boost so didn't really think that was at fault
    2003 S4 Moro Blue Saloon

  17. #16
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    Quote Originally Posted by s4mark View Post
    personally I think the jerkiness was caused by the n249 myself and getting rid seems to have done the trick. Doubt the DV had anything to do with it, I only replaced it for peace of mind. If it does start playing up I would suspect the MAF as I had similar problems on my a4 and it was a knackered MAF.
    Unplugged the MAF on the S3 and took it for a drive and the surging was still there on boost so didn't really think that was at fault
    dont you just hate making more than 1 change for a result....witch one cured it .....lol

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    Quote Originally Posted by s3_kev View Post
    i run mine the wroung way around also makes no difference to it being able to do the job its made to do, if itsfitted the correct way around the valve will work on vaccum so there is no chance of the valve opening under boost as it will be pulling more vaccum (i guess thats how they get away with making cheap plastic ones) with it the other way around your valve is having to stop the boost pressure pushing the valve open and leaking boost off, forge do different pressure springs so you can still maintain the correct boost by using the correct spec spring..

    Under boost conditions, there is no vacuum. The boost pressure in the inlet manifold finds it's way down the signal pipe, and equalizes the pressure coming from the other side of the diaphragm (charge pipe side), preventing the valve from opening. When you back off the throttle, you introduce vacuum which pulls the diaphragm open, releasing the charge air. Principal is the same whichever way around the valve is fitted.

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    id rather have the charge pipe trying to force air into the side of the dv rather than up against the diaphragm as its more likely to push the disphragm up

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    Quote Originally Posted by Matt82 View Post
    id rather have the charge pipe trying to force air into the side of the dv rather than up against the diaphragm as its more likely to push the disphragm up
    Yep, that's obviously the preffered way to fit the valve.

    Has anyone tried not running a valve at all, maybe in a track-day only or race application? you wouldn't lose as much metered air throught the turbo's compressor inlet as you would via an externally venting dump valve - I know they would run badly like this. In my experience with other blown motors, turbo response has a marked improvement without any type of BV/dump valve in place. Yeah you may get some compressor surge/stall between changes but I've never experienced any detrimental effects to the turbo from this. I'm not suggesting it's a good idea to remove the BV - I'm fully aware of the few reasons why it's fitted in the first place, just curious if it's been experimented with.

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    Quote Originally Posted by Matt82 View Post
    id rather have the charge pipe trying to force air into the side of the dv rather than up against the diaphragm as its more likely to push the disphragm up
    I actually misread what you put there Matt, I disagree. The design of the valve and how the diaphragm, cup and spring sit in the body really needs the air coming straight into the face of the diaphragm. I think the seal could be compromised the other way around.

  22. #21
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    Quote Originally Posted by 5teve L View Post
    Undo valve, turn round & refit.. Simples
    So just so I'm clear the bottom main section of the T (imagine that's the dump valve, brill I know) that sits in the tip still stays positioned there... Just the other 2 pipes either side of it are reversed?

  23. #22
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    Quote Originally Posted by Lee H View Post
    Yep, that's obviously the preffered way to fit the valve.

    Has anyone tried not running a valve at all, maybe in a track-day only or race application? you wouldn't lose as much metered air throught the turbo's compressor inlet as you would via an externally venting dump valve - I know they would run badly like this. In my experience with other blown motors, turbo response has a marked improvement without any type of BV/dump valve in place. Yeah you may get some compressor surge/stall between changes but I've never experienced any detrimental effects to the turbo from this. I'm not suggesting it's a good idea to remove the BV - I'm fully aware of the few reasons why it's fitted in the first place, just curious if it's been experimented with.
    it would run under actuator pressure only would it not?

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    Quote Originally Posted by Lee H View Post
    I actually misread what you put there Matt, I disagree. The design of the valve and how the diaphragm, cup and spring sit in the body really needs the air coming straight into the face of the diaphragm. I think the seal could be compromised the other way around.
    but if the charge pipe is pushing up against the valve it has a chance of lifting the valve and leaking. if it goes in sideway, itll have to push the valve through the side of the body (exagerated)

    i think wed need pics of the inside of the dv to see how the seal sits as you mentioned

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    a car im working on tonight has fun with no dv whatsoever for about 2-3 years. charge pipe is bunged and so is the return on the tip

    massive compressor surge every time she lifts off, sounds great, but no ill effects in that time

    ive had the tip off just to check for play in the impellor. none

    Quote Originally Posted by Lee H View Post
    Yep, that's obviously the preffered way to fit the valve.

    Has anyone tried not running a valve at all, maybe in a track-day only or race application? you wouldn't lose as much metered air throught the turbo's compressor inlet as you would via an externally venting dump valve - I know they would run badly like this. In my experience with other blown motors, turbo response has a marked improvement without any type of BV/dump valve in place. Yeah you may get some compressor surge/stall between changes but I've never experienced any detrimental effects to the turbo from this. I'm not suggesting it's a good idea to remove the BV - I'm fully aware of the few reasons why it's fitted in the first place, just curious if it's been experimented with.

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    Quote Originally Posted by s3dave View Post
    it would run under actuator pressure only would it not?
    Sorry, I should have said assuming there was no electronic boost control going on, N249 bypass. So yeah, actuator pressure only, maybe with a mechanical boost control device.

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    [QUOTE=Matt82;1041247]but if the charge pipe is pushing up against the valve it has a chance of lifting the valve and leaking. if it goes in sideway, itll have to push the valve through the side of the body (exagerated)

    Not when there's equal pressure applied the other side of the diaphragm via the signal pipe that's attached to the inlet manifold. That, combined with the spring that's helping to keep the valve closed also.

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    Quote Originally Posted by Matt82 View Post
    a car im working on tonight has fun with no dv whatsoever for about 2-3 years. charge pipe is bunged and so is the return on the tip

    massive compressor surge every time she lifts off, sounds great, but no ill effects in that time

    ive had the tip off just to check for play in the impellor. none

    I've had plenty of experience of turbocharged cars with no dv, never seen any evidence of that causing the turbo damage you hear talk of - snapped shafts, broken off vanes from the compressor wheel etc. Myth.

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    lots of interweb myths. love busting them

    hers is remapped by amd too. runs 15-16psi. ive seen her run 15.2s at pod too. she does death it.

    its a 98 AGU so its no spring chicken, but its coming up for a clutch change soon (dmf dying)

  30. #29
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    Quote Originally Posted by Matt82 View Post
    lots of interweb myths. love busting them

    hers is remapped by amd too. runs 15-16psi. ive seen her run 15.2s at pod too. she does death it.

    its a 98 AGU so its no spring chicken, but its coming up for a clutch change soon (dmf dying)
    What blower is on that AGU dude?
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  31. #30
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    Quote Originally Posted by Lee H View Post
    Under boost conditions, there is no vacuum. The boost pressure in the inlet manifold finds it's way down the signal pipe, and equalizes the pressure coming from the other side of the diaphragm (charge pipe side), preventing the valve from opening. When you back off the throttle, you introduce vacuum which pulls the diaphragm open, releasing the charge air. Principal is the same whichever way around the valve is fitted.
    ok i have heard of it being explained in the way i described which makes sense to me as with the valve the correct way one end that goes into the tip will be where the pull would be from the 'vacumm'??? surley if the turbo is pulling in air from the filter then there will be no pressre against the dump vlave piston as there is no positive pressure in the intake?? then when you let off the vacumm in the charge pipe would open the piston and draw the air into it??
    with it the other way surley you would have positive pressure in the charge pipe pushing the piston of the dv open?? then when you let off the vacumm would be pulled this time through the tip side to open the valve??

    thats how i have understood it sorry if im mistaken just made sense to me

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    Kev, the 'vent' part of the valve - which is fitted to the tip, regardless of which way around the valve is fitted is irrelevent in it's operation. As far as opening and closing is concerned. You could vent it to atmosphere and it wouldn't make a difference.

    The only vacuum the valve is making use of comes from the inlet manifold, via the small vacuum hose attached to the top of the valve. On closed throttle overrun, or very partially open throttle the engine is trying to pull air in but it is 'throttled'. This builds vacuum in the inlet manifold and the DV is open at this time. The second you open the throttle and allow the engine to breathe, the vacuum disappears. The valve closes. Boost pressure starts to rise as the turbo spools. This boost pressure fills the vacuum pipe attached to the valve and forces the valve to stay closed, despite the boost pressure in the charge pipe acting on the diaphragm trying to open it. It stays closed until you close the throttle, introducing vacuum again which opens the valve and vents the charge air into the tip.

    Quote Originally Posted by s3_kev View Post
    ok i have heard of it being explained in the way i described which makes sense to me as with the valve the correct way one end that goes into the tip will be where the pull would be from the 'vacumm'??? surley if the turbo is pulling in air from the filter then there will be no pressre against the dump vlave piston as there is no positive pressure in the intake?? then when you let off the vacumm in the charge pipe would open the piston and draw the air into it??
    with it the other way surley you would have positive pressure in the charge pipe pushing the piston of the dv open?? then when you let off the vacumm would be pulled this time through the tip side to open the valve??

    thats how i have understood it sorry if im mistaken just made sense to me

  33. #32
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    I used to run the dv reversed when i had a green cotton panel filter. It makes a loud chirp whistle sound which i liked! But then i got a BMC kit so i put it back to the normal way and i get a nice loud whoosh. The other day i reversed the dv to see what it'd sound like with the BMC kit and it sounded duff! It was like a metal against metal sound like a 'ching' kinda noise.
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  34. #33
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    Ok so can someone explain how to reverse it? Do all the pipes have to be undone including the top small breather hose?

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    Quote Originally Posted by fran-s3 View Post
    Ok so can someone explain how to reverse it? Do all the pipes have to be undone including the top small breather hose?
    Simple. You have 3 ports on the valve. #1 Vacuum connection (small one at the top), #2 going to the tip and #3 connected to the charge pipe.

    You leave #1 alone. Then just swap #1 and #2 around. job done.


  36. #35
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    Cool thanks Lee, do the pipes stretch out ok?

  37. #36
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    No problem dude, it will fit like a glove.
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