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N75J/N75C/MBC Comparison - with graphs

Discussion in 'A3/S3 Forum (8L Chassis)' started by Welly, Aug 2, 2010.

  1. s3dave
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    s3dave TFSI Hybrid

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    [Aug 7, 2010]
    i fitted mine direct, left the n75 in place and electrically connected and blocked the pipes
    very solid with no tail off, took it off for the moment while my intercooler pipes have settled in, was running at 27 psi ... maybe i will put it back on tomoz as pipes have stopped on, and i have been caneing it
    #41
  2. Welly
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    Welly VX220 SC Driver :)

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    [Aug 7, 2010]
    Sorry dude, only just saw this - my liquid does it for me :). I would imagine it gets the data from 120 and converts it on the fly.
    #42
  3. Welly
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    Welly VX220 SC Driver :)

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    [Aug 7, 2010]
    Hybrid FTW - my K04 would eat itself at that pressure from the heat produced.
    #43
  4. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 7, 2010]
    gave mine some beans from 3rd gear upto 5th on the 1st run boost tailed off like mad when changing upto 4th hit hit 20psi initially then creped down to 15psi then down to 10 psi, on the 2nd run was much improved and held 20psi through the whole time every gear was pretty quick. but think i need to bypass the n75 as thats probably the reason for the boost drop??
    #44
  5. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Aug 8, 2010]
    27psi?

    eak!

    hows your egt's?
    #45
  6. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 8, 2010]
    thats another thing i noticed cant actually measure egt's as i have apy engine but i have an oil pressure gauge which normally reads 1.8 bar on normal driving then 1.6 bar on a little sprint. yesterday after hammering it down the dual gariage way it was at 1.2 bar so im guessing things are getting pretty warm to make the oil that much thinner
    #46
  7. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Aug 8, 2010]
    is yours pre-facelift then?
    tufftys has egt on apy engine
    #47
  8. Welly
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    Welly VX220 SC Driver :)

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    [Aug 8, 2010]
    Tuffty's is AMK dude....
    #48
  9. zseth
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    zseth Member

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    [Aug 8, 2010]
    bit off topic sorry guys, but if i am running a remap (260bhp) and need to get a new n75 valve, which should i go for J or F ? i have a 2001 AMK engine and dont want to over do it, just want smooth power delivery and comfy ride lol

    thanks
    #49
  10. Welly
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    Welly VX220 SC Driver :)

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    [Aug 8, 2010]
    Not if you're not having problems - no.
    #50
  11. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Aug 8, 2010]
    doh!
    #51
  12. Welly
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    Welly VX220 SC Driver :)

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    [Aug 9, 2010]
    [​IMG]
    #52
  13. DJ_Troopa
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    DJ_Troopa K1 Driver

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    [Aug 9, 2010]
    One of my friends on his Mk3 Ibiza Cupra has disconnected his N75 valve also. Hes taken the vacuum pipe off it and kept it electronically connected. He's done this because he says the actuator on his turbo is shagged. He's tried turning the actuator up for more boost but it doesn't do anything! Is it safe to run the N75 like that? He holds boost through the rev range big time, only seems to tail off just before the red line!
    #53
  14. Welly
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    Welly VX220 SC Driver :)

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    [Aug 9, 2010]
    As long as the engine is strong enough to take it - and going crazy with it isn't the best idea.

    I've set mine to 22 initially but it kept going into limp mode under very heavy load (in 6th on the motorway for example) so will drop down to 21 psi which is around the requested boost level anyway.

    Safe boost is OK - going mad will cause serious problems.
    #54
  15. DJ_Troopa
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    DJ_Troopa K1 Driver

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    [Aug 9, 2010]
    I hit 22.3 psi peak on my liquid gauge, is that all good? I have a few mods though but i don't know what psi i should be getting? Is there any point of me getting an MBC or should i just keep the N75F i have?
    #55
  16. Welly
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    Welly VX220 SC Driver :)

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    [Aug 9, 2010]
    I'd stick with what you've got mate, the reason I'm using an MBC is that the turbo wasn't making the requested pressure. It's old and tired... and I think the wastegate is creeping...

    So it needed a little help.
    #56
  17. Madeley
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    Madeley Member VCDS Map User

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    [Aug 9, 2010]
    Ok guys whats egt, these codes are doin my head in.
    #57
  18. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Aug 9, 2010]
    Exhaust Gas Temperature=EGT
    AFR=Air Fuel Ratio
    AIT=Air Inlet Temp
    MAF=Mass Air Flow meter

    to name but a few abbreviations you see
    #58
  19. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 11, 2010]
    here are my results from fitting my mbc

    std N75=
    259.02 BHP
    233.58 LB/FT

    MBC + N75=
    261.63 BHP
    250.99 LB/FT

    MBC only=
    262.4 BHP
    260.43 LB/FT

    note all these figures are taken from vagcom the calculated after so gs. was divided by 0.8 and nm was divided by 1.35582
    boost was @ 20psi on std which would drop to 18psi then hold 17psi to red line, n75 and mbc set @22psi peak hold 20psi to redline MBC only set @20-21psi hold 19-20 to redline.
    Last edited: Aug 11, 2010
    #59
  20. Danny Cawsey
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    Danny Cawsey Cawsey

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    [Aug 11, 2010]
    im running stage 2 map at 267hp but want to try and find a few more horses before going hybrid or bt,
    is it worth me getting an mbc? p.s how comes everybody uses mbcs and not ebcs on here?
    #60
  21. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 11, 2010]
    who's stage2 mapp is it?? mine was rr at 269bhp with amd mapp and 312lb/ft so mapping figures should be ignored imo as there not true figures they make them look good!
    no need to waste money on an ebc reallly mbc works and no lights if the n75 is left plugged in

    for the cost of the mbc its not too bad as you do get a slight gain and boost is held higher through out the revs @ the risk of bending rods though..it wont make such a difference that you will decide not to continue wanting a hybrid though if thats what your already wanting
    #61
  22. Danny Cawsey
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    Danny Cawsey Cawsey

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    [Aug 11, 2010]
    mines got an AMD map also, so i take it there isnt really anything els i can do before turbo except fit my fmic?
    how much psi can u actually run through the ko4 turbo could you reach 280-290 hp with out hybridizing it?
    #62
  23. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 11, 2010]
    i think there is a guy on seatcupra.net who runs those sort of figures he's using water methanol so thats whats needed to really help. but really a k04 would be doing well to reach those figures
    #63
  24. Matt82
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    Matt82 Active Member

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    [Aug 16, 2010]
    so just going on the raw figures (without seeing the plots) it seems the mbc makes it more diesel like with the higher torque spike.

    really tempted to fit one to mine and experiment with moving the boost up and down to see hwo it effects the output. i recon if you brought the boost down it would reduce that spike without killing the top end too much
    #64
  25. Welly
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    Welly VX220 SC Driver :)

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    [Aug 16, 2010]
    I'm battling with issue at the moment.

    Full throttle is fine with the MBC as I have set the boost to about 21.5 PSI which is requested boost level of the map.

    The issue is when on part throttle, especially on the motorway for example, the MBC is always trying to achieve 21.5 PSI boost.

    Map at this point is requesting about 3-4 psi and getting WAAAAAAAAAAY more, goes spakko and throws limp mode buy cutting one of the coils.

    A pain. A big big pain.
    #65
  26. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 16, 2010]
    took mine off today, went into limp mode with out even putting my foot down just starts boosting so easy with the MBC its hard to drive but at the same time its very smooth to drive..
    also doing vagcom logs the torque is peaking at very low revs in very quick plots then filters out to quick im scared for my rods so took it off.
    #66
  27. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 18, 2010]
    since refitting the std n75 my boost has dropped again to 17 18psi if im really lucky and im proper annoyed as prior to fitting the mbc i had just fixed my long term boost issue and boost was at 20psi easily 21 sometimes.

    can fitting the n75 pipes the wrong way around damage the n75?? as i made a mistake and got them the wrong way for a bit... also i think i may have a slight tear around the n75 where it goes into the TIP im going to silicone that tomoz to eliminate that but could that cause boost loss too???
    #67
  28. harty190486
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    harty190486 New Member

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    [Aug 18, 2010]
    i have a Lcr with cc stage 1 remap, fmic, decat, filter, descreened maff and have been playing with my unos and found i had the same problem on part throttle also getting maff signal to high due to part throttle boost deviation so fitted it in parrelel with my standard n75 f valve which is tweeked to give alittlke bit more initial boost, set the unos with stronger spring it comes on at 1.54 bar now and hold 1.2 at the red this is running 3 deg advance timing and slight fueling adjustment with a bit more pre load on the wastegate, the boost this way feels so strong compared to just running an n75 and has made the car even more responsive, i did the varios logs boost timing pull fueling egts etc and all looks good fueling is 0.830 troughout timing pull is no more than 5 egts no more than 910 on wot and boost is bang on heres a boost log to show you this is on a 25 degree day also when cooler boost timing and gs are better have seen 220gs with logs to prove
    [​IMG]
    Last edited: Aug 18, 2010
    #68
  29. Matt82
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    Matt82 Active Member

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    [Aug 18, 2010]
    good reading in this thread, not getting a lot of time to spend on the board lately though :S
    #69
  30. Welly
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    Welly VX220 SC Driver :)

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    [Aug 19, 2010]
    I get the same issue with lower logs in higher ambient temps.

    This liquid gauge I have now has proven to be a most useful tool for this....

    Car is broken at the moment and receiving a new prop and downpipe, but once done I shall take some photos.

    The interesting thing being my requested vs actual live graph. With it being a live display of actual boost with a smaller white line to show ECU request, it makes it easy to see what's happening there.

    On the N75 valve - of any type - my actual boost never meets the requested level. Requested on full throttle is ~21.5 PSI. Actual gets to around 19 PSI tops.

    I've set my MBC to 21.5 PSI now and it achieves it with now problems. If achievable with the MBC connected - this means that it's not the fact that the turbo is tired causing this problem.

    The main difference between the MBC and N75 is the simple fact that the actuator doesn't see ANY air at all untill set boost level is achieved - this is not true with the N75 valve.

    What I think is happening here is that the actuator has gone soft on the turbo, and is being blown open long before requested boost is achieved.

    I am planning to add more preload to the actuator and then retest to prove or disprove this theory. I also have a spare K04 actuator at home which I can fit if required for testing purposes.

    I shall post results when done.
    #70
  31. Welly
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    Welly VX220 SC Driver :)

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    [Aug 19, 2010]
    Fiting it the wrong way round won't do it any damage -it will just give you actuator pressure at all times basically....
    #71
  32. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 19, 2010]
    yeah i noticed i was only getting actuator pressure was only about 6psi peak... just woundered if it was posible to have damaged the n75 as that is all that has been messed with between using the mbc. iam going to pick up my old n75j i sold a mate this eve to see if this helps. if not all i can put it down to is tesco's momentum99 being cack and i will go fill up with sheel again.. thought id try the momentum after your recent thread and could'nt be arsed to drive 20 odd miles to get shell at the time
    #72
  33. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 19, 2010]
    changed n75 over and problem solved again lol, so my n75 must be intermitantly faulty too. so i won't be blaming tesco fuel haha however i have got a full tank of sheel in her now
    #73
  34. s3dave
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    s3dave TFSI Hybrid

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    [Aug 19, 2010]
    kev.. running my j valve makes mine run sweet and strong boost
    #74
  35. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Aug 20, 2010]
    yeah i had it on when i had mine stage2'd but swapped back to std after and made no real difference at the time so i sold it on but got to buy it back now hahaha
    #75
  36. Madeley
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    Madeley Member VCDS Map User

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    [Aug 30, 2010]
    I got a n75c and the nipple that goes into tip has been opened up(looks like its been done with a hot pin) ,makes a big differance, pulls like a train.
    #76
  37. Welly
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    Welly VX220 SC Driver :)

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    [Aug 30, 2010]
    ?? Pics!
    #77
  38. Madeley
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    Madeley Member VCDS Map User

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    [Aug 31, 2010]
    Theres no chance of a pic, it's tiny. l think it just gives the actuator more vacuum pressure, the hole is only about a mill bigger.
    If you look inside the nipple you will see the restriction.
    #78
  39. Danny Cawsey
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    Danny Cawsey Cawsey

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    [Sep 2, 2010]
    ive just ordered a forge unos mbc last night can somebody please give me some quick instructions on how and where is the best place to fit it?
    cheers
    #79
  40. Madeley
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    Madeley Member VCDS Map User

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    [Sep 3, 2010]
    #80

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