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

N75 J or N75 H?

Discussion in 'A3/S3 Forum (8L Chassis)' started by HTC, Dec 8, 2005.

  1. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    I've worked out that my N75 valve is faulty, so I'm looking for a replacement.

    Has anyone had any experience of either valve on their car?

    Seems that the "H" version is the same valve the ECS sell as the "race valve".
    The "J" version is apparently less agressive.

    I'm thinking about the "H" version as my AGU doesn't have a MAP sensor in the intercooler and would be less likely to go limp (ooer :0)).

    Thanks.
    #1
  2. RichA3Turbo
    Offline

    RichA3Turbo ...Watching you! Staff Member Moderator

    Joined:
    Jan 6, 2003
    Messages:
    5,089
    Likes Received:
    4
    Give the ECS/H a go... Got some in stock if you want to try it.

    RIch
    #2
  3. Grant
    Online

    Grant Well-Known Member

    Joined:
    Dec 4, 2003
    Messages:
    1,144
    Likes Received:
    52
    I use the J. How different is the H Rich?
    #3
  4. Grant
    Online

    Grant Well-Known Member

    Joined:
    Dec 4, 2003
    Messages:
    1,144
    Likes Received:
    52
    Rich - can you organise a group buy?
    #4
  5. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    How much is the ECS/H from you Rich?
    #5
  6. Grant
    Online

    Grant Well-Known Member

    Joined:
    Dec 4, 2003
    Messages:
    1,144
    Likes Received:
    52
    [ QUOTE ]
    How much is the ECS/H from you Rich?

    [/ QUOTE ]
    Rich wears a mask, calls himself **** Turpin and says: £50 + vat and delivery.

    /ubbthreads/images/graemlins/lol.gif
    #6
  7. RichA3Turbo
    Offline

    RichA3Turbo ...Watching you! Staff Member Moderator

    Joined:
    Jan 6, 2003
    Messages:
    5,089
    Likes Received:
    4
    H is more aggressive than J, and as you say, i suspect it will work better on the AGU.

    £50+vat -5%


    Rich
    #7
  8. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    Okay doke, I'm gonna check the price of the H valve at me local VW before I commit.

    One more thing, is the "H" version orientated the same way as the original valve. Apparently the connector on the "J" is round the other way?
    #8
  9. RichA3Turbo
    Offline

    RichA3Turbo ...Watching you! Staff Member Moderator

    Joined:
    Jan 6, 2003
    Messages:
    5,089
    Likes Received:
    4
    Yeha i think its the opposite way to the standard valve.

    Rich
    #9
  10. S3DBW
    Offline

    S3DBW Member

    Joined:
    Jan 4, 2003
    Messages:
    160
    Likes Received:
    2
    H valve is the same orientation as the standard valve. On the S3 the H valve gives a bit more boost, but can be prone to spiking. J valve as previously mentioned is a bit less aggresive and has the wiring connector on the opposite side, however there is usually enough wire on the loom to reach it
    #10
  11. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    Thanks for that S3DBW, I've ordered the H valve for that reason and that it should be cool with my engine code.

    Hopefully it'll sort out my recent lack of boost.
    #11
  12. NWMark
    Offline

    NWMark Member

    Joined:
    May 7, 2003
    Messages:
    202
    Likes Received:
    1
    H gives huge initial boost spike i.e.1.7 - 1.8 bar and then is very similar to the standard after that.

    the J valves iniitial boost is lower than the H, but seems to hold boost better across the range.

    ive got boost graphs of them somewhere at home ill try and post them tonight.

    Mark
    #12
  13. JamS3
    Offline

    JamS3 Active Member

    Joined:
    Jun 17, 2003
    Messages:
    2,257
    Likes Received:
    12
    What would be the best one for my S3 do you think with a AMD remap?
    On my boost gauge I seem to spike at about 18-19psi.
    Would a change of valve make much difference or would I be risking going into the relms of limp mode?
    #13
  14. Grant
    Online

    Grant Well-Known Member

    Joined:
    Dec 4, 2003
    Messages:
    1,144
    Likes Received:
    52
    You should hit limp mode until you're spiking over 23psi I think.
    #14
  15. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    [ QUOTE ]
    H gives huge initial boost spike i.e.1.7 - 1.8 bar and then is very similar to the standard after that.

    the J valves iniitial boost is lower than the H, but seems to hold boost better across the range.

    ive got boost graphs of them somewhere at home ill try and post them tonight.

    Mark

    [/ QUOTE ]

    Mark, that would most helpful.
    #15
  16. NWMark
    Offline

    NWMark Member

    Joined:
    May 7, 2003
    Messages:
    202
    Likes Received:
    1
    [ QUOTE ]
    You should hit limp mode until you're spiking over 23psi I think.

    [/ QUOTE ]

    Had the H valve on my car for about 4 weeks and never hit limp mode once, even had a RR done with it on. I got 310lb/ft and 260bhp.

    Mark
    #16
  17. NWMark
    Offline

    NWMark Member

    Joined:
    May 7, 2003
    Messages:
    202
    Likes Received:
    1
    [ QUOTE ]


    Mark, that would most helpful.

    [/ QUOTE ]

    ive found the standard and H boost charts cant find the J valve one, must be here somewhere though.

    original
    [​IMG]

    H valve
    [​IMG]

    The solid straight line is due to boost sensor not being able to read above 1.55bar. but looking at the rate of clime its easywell into 1.6 and probably above 1.7, when i originally posted these charts others said using the H valve they have seen upto 1.8 bar of boost.

    Mark
    #17
  18. dummi
    Offline

    dummi smoking a6

    Joined:
    Mar 25, 2004
    Messages:
    1,210
    Likes Received:
    0
    do you disable limp mode to achieve 1.7 bar+?

    would that be of benifit on a big turbo or not? the early boost late lag vs. early lag late boost on the k04 atleast
    #18
  19. Ess_Three
    Offline

    Ess_Three Active Member

    Joined:
    Feb 19, 2001
    Messages:
    5,383
    Likes Received:
    6
    [ QUOTE ]

    H valve
    [​IMG]


    [/ QUOTE ]


    [​IMG]

    If you comapre the two plots above, you will see similarities.
    The lower pic is my S3 making 332 lb-ft of tirque, with the H valve fitted (along with a very aggressive map...and other mods)
    The shape of the boost curve is the same... (the black line that peaks soonest is actual boost recorded on the dyno - not VAG Com boost...but measured at the inlet manifold)



    [ QUOTE ]

    The solid straight line is due to boost sensor not being able to read above 1.55bar.


    [/ QUOTE ]

    This is roughly true...although MAP sensors do vary in theit accuracy and range...mine read slightly higher.

    The bottom line is...they do saturate...and when they do...you'll risk limp mode.



    [ QUOTE ]

    but looking at the rate of clime its easywell into 1.6 and probably above 1.7, when i originally posted these charts others said using the H valve they have seen upto 1.8 bar of boost.


    [/ QUOTE ]

    This is VERY dependant on the map you have installed...you will NOT get 1.6+ bar on a standard ECU map!

    I was running 1.6 to 1.65 bar peak boost on a standard N75...adding the H valve increased this by approx 0.2 bar peak...roughly 20 lb-ft of torque.

    I was running 1.85 to 1.89 peak boost with the H valve fitted...and to do this you need the trigger point for limp mode raising substantially, in the ECU map.
    Some tuners raise it higher than others...the answer seems to be that they raise it proportionally to the increase in boost (peak boost up by 0.4 bar, limp trigger up by 0.4 bar) but to run the H or J valves in all weathers and temperatures, you'll need one with the limp limit raised further.

    I could run the H valve perhaps 50% of the time...in cold weather and high ambient barometric pressure (both of which effect the limp trigger point) I would hit limp if you didn't drive round it.

    So, don't go thinking you'll get 1.8 bar from a H or J valve...you won't.

    But if you are running a 1.4 bar map, you may well see 1.6 / 1.65 bar peak - if there isn't a restriction elsewhere!

    With regard to the H and J valves...I dyno's both...back to back, and back to back with standard...on high boost and standard boost maps...and saw no noticable difference on my engine - despite expecting big differences!
    Peal torque on both occasions was 332 lb-ft.
    #19
  20. Ess_Three
    Offline

    Ess_Three Active Member

    Joined:
    Feb 19, 2001
    Messages:
    5,383
    Likes Received:
    6
    [ QUOTE ]
    do you disable limp mode to achieve 1.7 bar+?


    [/ QUOTE ]

    Hopefully some of the above post helps...but I would not be too keen on disabling limp mode...it's there to protect the engine if something fails...I've messed about with an adjustable voltage clamp on the MAP sensor to limit the signal the ECU sees...hence never hitting limp...but my balls aren't big enough to run this all the time...



    [ QUOTE ]

    would that be of benifit on a big turbo or not? the early boost late lag vs. early lag late boost on the k04 atleast

    [/ QUOTE ]

    The N75H or J?
    No, not really...the big turbo is the limit for low end boost (it's size) not the N75...and besides, if you are having a big turbo fitted, you are probably going for bespoke mapping anyway...so you can have the tuner tailor the boost curve to suit...you don't need to trick the ECU with a different N75!
    #20
  21. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    Some very good information there.

    I have a couple of questions.
    I'm running the K03s unit with peak boost of (i'm guessing) 1.3 bar ish. Mike T. at Jabba informed me that my car held boost at 1.24 bar so I'm assuming that it would peak slightly higher?

    What I need to know is, what pressure level would cause damage to my turbo etc. No point in pumping just hot air.

    Does the early AGU engine have a limp mode for boost as there is no MAP sensor. I don't want fit this valve if I'm going to cause myself problems.

    Thanks.
    #21
  22. RichA3Turbo
    Offline

    RichA3Turbo ...Watching you! Staff Member Moderator

    Joined:
    Jan 6, 2003
    Messages:
    5,089
    Likes Received:
    4
    The AGU has no such thing.. The only way it hits limp mode is if the mixture is out of boundaries. the 'H' valve will work just fine. Jason is running an ECS valve on his A4 (AEB, same as AGU!) and its made a substantial difference in torque (butt dyno)...It really kicks in the lower gears especially.

    Rich
    #22
  23. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    Cheers Rich, I thought that was the case.

    Even so, I don't want to be boosting to much.
    If the valve ever turns up, I'll guess I'll just fit it and see for a few days.

    Does anyone know where I can find a compressor map for the k03s. I've seen some for the early unit but not the later item.
    #23
  24. Ess_Three
    Offline

    Ess_Three Active Member

    Joined:
    Feb 19, 2001
    Messages:
    5,383
    Likes Received:
    6
    [ QUOTE ]

    I have a couple of questions.
    I'm running the K03s unit with peak boost of (i'm guessing) 1.3 bar ish. Mike T. at Jabba informed me that my car held boost at 1.24 bar so I'm assuming that it would peak slightly higher?


    [/ QUOTE ]

    Held boost at 1.24 bar?
    He can't mean 1.24 bar sustained to the redline as you struggle to get a larger K04 to do that.
    I doubt a K03 can...

    If it is holding boost like that to the redline...your turbo will be red hot....and your inlet charge likely to melt the internals!



    [ QUOTE ]

    What I need to know is, what pressure level would cause damage to my turbo etc. No point in pumping just hot air.


    [/ QUOTE ]

    Well that's the key: hot air!

    Do you have uprated ICs?

    If so, you can take liberties with the boost assuming you have some VERY efficientICs.

    My S3 running 1.4 bar peak was seeing 78 degrees at the inlet manifold - after the standard ICs - on the dyno.

    With uprated ICs you would not see any more that 23 degrees or so on the dyno...with peak boost running at 1.85+ bar.

    Needless to say, at 1.4 bar or above you get little by way of gains by cranking the boost up - all additional power gained by more boost is lost to the ECU winding back the timing to prevent meltdown.

    Sort the ICs out though, and you can run higher boost and pervent the ECU from retarding the timing...giving more power and torque despite the fact that the turbo is running way out of it's efficiency curve and has already progressed into 'hot air pump' mode.
    Not great for the life of the turbo though...
    #24
  25. dummi
    Offline

    dummi smoking a6

    Joined:
    Mar 25, 2004
    Messages:
    1,210
    Likes Received:
    0
    [ QUOTE ]
    [ QUOTE ]
    do you disable limp mode to achieve 1.7 bar+?


    [/ QUOTE ]

    Hopefully some of the above post helps...but I would not be too keen on disabling limp mode...it's there to protect the engine if something fails...I've messed about with an adjustable voltage clamp on the MAP sensor to limit the signal the ECU sees...hence never hitting limp...but my balls aren't big enough to run this all the time...

    <font color="red"> oh i see, i would not have the guts for that period, yep that answers my question </font>



    [ QUOTE ]

    would that be of benifit on a big turbo or not? the early boost late lag vs. early lag late boost on the k04 atleast

    [/ QUOTE ]

    The N75H or J?
    No, not really...the big turbo is the limit for low end boost (it's size) not the N75...and besides, if you are having a big turbo fitted, you are probably going for bespoke mapping anyway...so you can have the tuner tailor the boost curve to suit...you don't need to trick the ECU with a different N75!

    [/ QUOTE ]

    <font color="red"> right, that answers my question too /ubbthreads/images/graemlins/ok.gif so n75 is a bit of a DIY rather than something that needs to be considered with big turbo, good info as always /ubbthreads/images/graemlins/grin.gif</font>
    #25
  26. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    [ QUOTE ]

    Held boost at 1.24 bar?
    He can't mean 1.24 bar sustained to the redline as you struggle to get a larger K04 to do that.
    I doubt a K03 can...

    If it is holding boost like that to the redline...your turbo will be red hot....and your inlet charge likely to melt the internals!

    [/ QUOTE ]

    Indeed, boost does tail off at redline. I trust Mike to have done a good job on the remap. He seems to have good reviews from other 1.8T owners, and I don't think he would want to push a customers engine too far.

    Maybe his comment was a passing remark that the boost settles down to this amount before tailing off later in the rev range?

    [ QUOTE ]

    Do you have uprated ICs?


    [/ QUOTE ]

    At the moment no. But I also don't drive my car hard all the time. This is something I am lokking into. Hopefully before the weather warms up.

    I still need to do a bit more logging. I'll add inlet temps to the other variables I need to look at to sort my boost issues out.

    Hopefully I'll be able to sort this out soon when I get some more time out of work crimbo shopping etc!
    #26
  27. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    Finally got round to replacing my N75. Got the "H" valve from VW cost me £48.06.

    Anyways, my car is flying again! No surging of boost at all. Forgot how fast its was. Did a quick log with VAGCOM and the duty cycle for the valve is as it should be.

    Only downside is I've just wasted half a tank of petrol celebrating!!

    All for a good cause I suppose.

    /ubbthreads/images/graemlins/woohoo.gif
    #27
  28. Ryanc
    Offline

    Ryanc Active Member

    Joined:
    Feb 15, 2004
    Messages:
    1,321
    Likes Received:
    0
    Was the duty cycle hitting 100% before as you should see no more than 95%.
    Something i need to keep a eye on as i have been spiking boost to 1.6bar..ouch.
    #28
  29. docurley
    Offline

    docurley Moderator Staff Member Moderator

    Joined:
    Dec 12, 2003
    Messages:
    3,859
    Likes Received:
    25
    Sound like something I should have done ages ago.
    #29
  30. trevorb33
    Offline

    trevorb33 Member

    Joined:
    Aug 1, 2005
    Messages:
    33
    Likes Received:
    0
    Just put the H on Mine can't believe the difference for £40 probably the best thing ive brought
    #30
  31. HTC
    Offline

    HTC Active Member

    Joined:
    Jan 11, 2004
    Messages:
    3,413
    Likes Received:
    0
    The duty cycle wasn't too high, but I was told that it was changing about too much. But my load values for boost control were definately out of spec.

    I still might try the "J" valve as well, just because I'm curious.
    #31

Share This Page