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How many of you guys have replaced your N75 valves?

Discussion in 'A4/S4 forum(B5 Chassis)' started by Soupie69uk, Mar 2, 2006.

  1. docurley
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    docurley Moderator Staff Member Moderator

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    I get your logic.
    #41
  2. madvw
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    madvw Active Member

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    The point is that the J valve does not allow higher boost through (although it may spike higer - which is bad) - it just allows a more sustained boost delivery, reacts more quickly, and doesnt drop the boost off early.

    If the boost curve changes significantly, like the people who've fitted one says it does, then you want to make sure that the fuel delivery is sufficient when the boost is being held at the top end - especially as this is where you'll do the most damage if its running lean.
    #42
  3. hop2407
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    hop2407 Active Member

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    Hmmmm too many what if's for me I guess especially as I have already been remapped..... Reckon I'll not bother. I'm known to be unlucky and don't want to risk busting something and causing more expense.....
    #43
  4. PhilR
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    PhilR One Ate Tea

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    I knew about the spiking problem apparently (the H version cases a spike so high it will cause limp mode in a chipped car)

    upon further reading i was thinking it was more a case of better controll rather than a higher boost level

    Think ill quiz jabba when i book it in i would imagine they have heard of this mod and will advise whats best
    #44
  5. RichA3Turbo
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    RichA3Turbo ...Watching you! Staff Member Moderator

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    fitting the J valve prior to mapping makes it a worthless mod!
    #45
  6. madvw
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    madvw Active Member

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    [ QUOTE ]
    fitting the J valve prior to mapping makes it a worthless mod!

    [/ QUOTE ]

    aww c'mon man, explanation please! /ubbthreads/images/graemlins/smile.gif
    #46
  7. JayB5UK
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    JayB5UK Member

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    And just to confuse me even more, have spoken to a guy with a Revo'd (like mine) Seat Ibiza who said the J valve caused limp mode!
    #47
  8. Kevint
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    Kevint Active Member

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    [ QUOTE ]
    fitting the J valve prior to mapping makes it a worthless mod!

    [/ QUOTE ]

    Sorry Rich, (I know typing is a pain for you atm)

    Are you saying there is no point fitting it to a standard 1.8T, or just no point fitting it first if you plan to have it mapped?

    Kev.
    #48
  9. Charlies604
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    Charlies604 Member

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    He said theres not point in fitting it before it is remapped.
    Im guessing this is because they will MAP OUT the benefits of the boost control.???
    #49
  10. imported_VaulterTim
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    imported_VaulterTim Guest

    [ QUOTE ]
    fitting the J valve prior to mapping makes it a worthless mod!

    [/ QUOTE ]

    Exactly.

    Same reason as quoted by PhilR above... he explained it perfectly.

    If you fit the 'J' before mapping then it will be mapped with that valve to the same boost level as it would have been with the OE valve and 'lost in the system' so-to-speak.

    Remember, the N75 just controls boost, it doesn't limit it. Your wastegate itself and the fuel/ignition/boost maps do that. It just happens to be slighlty higher rated than the OE one which means when fitted, it will increase boost levels (very slightly) across the range of the map that was written for the car.

    It will yield improvements on any car it is fitted to, they will just not be as noticeable on a standard (non-chipped) car.

    I fitted mine a while after having my car remapped and although I wouldn't say it made a massive difference, it did make a nice improvement across the rev-range with the car holding boost very slightly longer at the upper end of the rev-range. All but forgotten about now though since I got used to it /ubbthreads/images/graemlins/grin.gif

    A very cheap and worthwhile mod in anyone's book though I think /ubbthreads/images/graemlins/smile.gif

    Cheers

    T
    #50
  11. Soupie69uk
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    Soupie69uk Owner

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    Wish i could get one of these before sat when my car will prob be on the rollers at Star.
    #51
  12. RichA3Turbo
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    RichA3Turbo ...Watching you! Staff Member Moderator

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    [ QUOTE ]
    [ QUOTE ]
    fitting the J valve prior to mapping makes it a worthless mod!

    [/ QUOTE ]

    aww c'mon man, explanation please! /ubbthreads/images/graemlins/smile.gif

    [/ QUOTE ]

    As Tim says above!
    #52
  13. madvw
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    madvw Active Member

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    Cool, so replacing your N75 DOES increase your boost level.

    I can see how the ECU would cope with it, and automatically adjust fuel accordingly (within limits), but surely a preset map that took into account the increased boost already would be the best solution?

    I'm not trying to be deliberately annoying, just wanting to understand /ubbthreads/images/graemlins/beerchug.gif
    #53
  14. PhilR
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    PhilR One Ate Tea

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    [ QUOTE ]
    Cool, so replacing your N75 DOES increase your boost level.

    I can see how the ECU would cope with it, and automatically adjust fuel accordingly (within limits), but surely a preset map that took into account the increased boost already would be the best solution?

    I'm not trying to be deliberately annoying, just wanting to understand /ubbthreads/images/graemlins/beerchug.gif

    [/ QUOTE ]

    I think the logic is that if you run a std car you will be running what 7psi? If you get this chipped they will raise the boost level to say 14psi (~1bar)

    If you have a standard car and add a N75j you may well end up with for arguments sake 8psi of boost. If you get this chipped they will still only raise the boost to 14psi leaving you in the same situation as if you hadn’t bothered changing the valve,

    Applying the same logic having the car mapped on the standard valve will give 14psi of boost. Adding the n75j afterwards will raise this 1.0bar level slightly.
    #54
  15. madvw
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    madvw Active Member

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    so, what your effectively doing is raising the boost levels above what the remapper considers to be the safe upper boost limit?

    If it was me, i'd be happy with the higher boost limit from the remap, and then even happier with improved boost response and hold characteristics of the new valve. The slight boost increase from fitting the valve after the remap wouldn't interest me if it there was a risk of it going limp on me.
    #55
  16. docurley
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    docurley Moderator Staff Member Moderator

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    Yep agreed if its a preset map that they just flash on to your ECU chip or in my case they had to replace the chip then yes you will be ok,

    But if they are going to do a custom on the rollers map then from what I have read your best not fitting the J Valve till after the mapping.
    #56
  17. welshdragon
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    welshdragon Member

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    Guys,

    When fitting the N75J to my car either in chipped or K04 configuration (mapped with normal N75) I found a much more aggresive spool up of the turbo, a much greater increase in torque, and the car was by far so much smoother it was unreal.

    However as I guess most of you dont have boost gauges you havent realised that the 'j' makes a major overboost. My boost with the chip and K04 was a steady 15 psi in both cases. With the 'J' fitted it went upto 21psi in 1st-3rd and 24 psi in 4th & 5th. This is a major danger zone and as soon as I noticed this when my gauge was fitted I took the valve off. I retried it after my K04 & its remap but had exactly the same results.

    I tried and played with a boost controler with the N75J fitted but as soon as you can control the overboost the benifit from the 'J' seemed to disappear and hense I took it off. My thoughts are its a great quick win but far too dangerous for engine/turbo damage.

    P.S. I still have the valiable boost controller if anyone is interested.
    #57
  18. imported_VaulterTim
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    imported_VaulterTim Guest

    What kind of Boost controller were you using? If it was a simple bleed valve (which most are) then that means you are using static boost pressure and therefore totally removing the N75 from the equation... that will be why it (the N75) became in-effective.

    Again, PhilR has explained it perfectly, the same as he did the first time /ubbthreads/images/graemlins/tongue.gif

    If you had boost spikes of up to 24psi then there was something wrong with your map methinks... /ubbthreads/images/graemlins/confused.gif Mine gets nowhere near that. And if I remember correctly, didn't you have major issues with your maps and K04 installation?? Or was that someone else?

    madvw... I think the safe upper limits are well within the capabilities of the 'J' valve... most LIMP mode situations I have encountered usually tend to be as a result of fitting the more aggresive 'H' valves etc.

    Would be interesting to hear other people's opinions though... it's always good to learn of a new scenario for the knowledge bin /ubbthreads/images/graemlins/grin.gif

    Cheers

    T
    #58
  19. imported_VaulterTim
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    imported_VaulterTim Guest

    [ QUOTE ]
    Cool, so replacing your N75 DOES increase your boost level.

    I can see how the ECU would cope with it, and automatically adjust fuel accordingly (within limits), but surely a preset map that took into account the increased boost already would be the best solution?

    I'm not trying to be deliberately annoying, just wanting to understand /ubbthreads/images/graemlins/beerchug.gif

    [/ QUOTE ]

    Just read your post again... a few more comments since I now know what you're getting at /ubbthreads/images/graemlins/smile.gif

    I think initially that the addition of the 'J' valve was undertaken mostly by people who had already had their cars remapped and the 'J' valve was just another, cheap improvement without going back to the tuner for another remap.

    Having the knowledge of how this valve improves performance before remapping your car simply presents the decision of whether to request a slightly higher boost level from the tuner when having a car mapped for the first time or going for the extra option of the valve some time down the line.

    A totally individual decision I think... and more than likely an easier option to add the valve since most of us will be unlikely to know enough about ECU remapping to request and discuss the addition of extra boost and how to tweak fuel and ignition maps etc. with the tuner beforehand.

    Just a thought...

    Cheers

    T
    #59
  20. imported_billybravo
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    imported_billybravo Guest

    hiya im thinking about getting this n75 upgrade

    im going to buy from vagparts

    do i want this one

    part-no 034906283J

    Also does anyone have any tips to fitting /ubbthreads/images/graemlins/smile.gif



    thanks

    craig
    #60
  21. docurley
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    docurley Moderator Staff Member Moderator

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    When you order the valve make sure you get 3 good clips to replace the Audi ones as you will have to force them off.

    Also test fit it up as the clips are going to be tight plus try and free up as much slack as you can for the loom because when you fit it back on put cable on before you tighten the clips as you wont get it on other wise you will find that it near on impossible to reconnect.

    I'm hopping to get part of this loom from scrappers and extend the loom to help prevent any long-term issues.
    #61
  22. imported_billybravo
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    imported_billybravo Guest

    is there a way of knowing which way i fit it?

    thanks
    #62
  23. docurley
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    docurley Moderator Staff Member Moderator

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    Yes the plug connection points down instead of up.
    #63
  24. imported_billybravo
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    imported_billybravo Guest

    cheers im gonna order now i will let you know how it goes
    #64
  25. GT500
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    GT500 New Member

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    Just changed mine today.

    whoo hoo!!! it now goes like i thought it should.

    many thanks fellows, most pleased.
    #65
  26. imported_billybravo
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    imported_billybravo Guest

    mine ame today gonna fit tomoz will let you all know /ubbthreads/images/graemlins/smile.gif
    #66
  27. niggtv
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    niggtv Member

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    I asked vagparts.com about the N75J valve when I was on the phone to them today. they were very scathing - said it'd make no difference to the performance but would f*ck the ECU. Seems to be the opposite of what people on here are finding... not sure whether to go for one or not now!
    #67
  28. Soupie69uk
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    Soupie69uk Owner

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    I reckon they are just covering themselves.

    I have never ever heard of peoples ECU going because of a N75J valve.
    #68
  29. madkebab
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    madkebab Member

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    Just to add to the topic. I have been running a J valve for over a year and was very pleased. However recently my boost has dropped to 10psi. After replacing most of my vacuum hoses with silicone ones and also installing a Bailey DV30 things didnt improve.
    After speaking with MRC they said to try changing my N75 back to standard.
    I did this last night and now my boost is back to 14psi which is what I would expect with my 1 bar chip. So beware that these N75 valves can go faulty. I will be ordering another J valve though because before it went faulty I was getting a steady 17psi and the boost was alot smoother than with the standard valve.
    #69
  30. Soupie69uk
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    Soupie69uk Owner

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    Great news mate!!

    Least its not your turbo then like you feared.
    #70
  31. imported_billybravo
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    imported_billybravo Guest

    easy all ive fitted mine today and i must say im in love with it i can easy hold 1 bar now for a lot longer and the spike is around 18psi well pleased


    /ubbthreads/images/graemlins/laugh.gif
    #71
  32. docurley
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    docurley Moderator Staff Member Moderator

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    Another happy customer.
    #72
  33. gc48067
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    gc48067 Member

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    The N75 controls the point at which the wastegate opens on the Turbo, the faster valves supply more pressure to the back of the wastegate to keep it from blowing open when it normally would. I expect the DV is quieter because the extra boost is opening it faster and wider..

    You are basically upping the boost of the turbo.

    With my install I found I got 16psi with one valve, 18 with another and 26 with another - a lot of difference for simply changing a valve.

    I would expect all will be fine engine wise as long as the fuelling can keep pace (this will compensate as it is based on air flow rate through the engine) but you may find your turbo doesn't last quite as long - to be honest not necessarily a huge issue as they are relatively cheap.

    Would recommend fitting a boost guage so you can see what the differences are and ensure nothing silly is happening.

    Greg
    #73
  34. docurley
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    docurley Moderator Staff Member Moderator

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    Well all has settled down now and I am dumping like normal so I think it was the ECU not knowing the parameters of the new valve.
    #74
  35. imported_billybravo
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    imported_billybravo Guest

    im loving mine its so much better now /ubbthreads/images/graemlins/smile.gif
    #75

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