Power nosing over at high RPM

Discussion in 'Technical' started by SRB-2NV, Feb 21, 2015.

  1. SRB-2NV


    Hey guys, since doing my TT conversion i've noticed the zed doesn't pull very well in the high RPM range(5500+rpm). I've driven many many variants(auto/man etc) but none have nosed over as bad as mine up top. The car pulls like a train to 5000rpm and then its almost as if its an NA after that. Boost holds a steady 12PSI from 2800-7000rpm.

    I'm planning tomorrow:
    Drop the exhaust + check for collapsed cats/mufflers
    Change fuel filter
    Try different fuel pump
    Inspect FMIC and all pipes/hoses/clamps
    Fix all possible boost leaks

    More details:
    Base timing is 15*
    Auto VG30DETT with manual turbos
    2.5" AMS Turbo inlets
    Boost is at 12PSI
    Compression test had good results
    On its last hard run ECUtalk showed 98% IDC and 4.535v AFM.

    Any idea's on what else to check?
  2. Z32 TT

    Z32 TT Active Member

    Afr you got a wideband?
  3. SRB-2NV


    I have a wideband but haven't checked AFR's on 12PSI, still haven't gotten around to installing it :eek:
  4. Fists

    Fists Well-Known Member

    You've fixed up the auto ECU extra idle timing thing right? Either using manual ECU or turned it off in nistune?
  5. SRB-2NV


    Its running a borrowed manual ECU atm. Before anyone asks, no there are no bloody error codes.
  6. Z32 TT

    Z32 TT Active Member

    I changed at 6.4

    Power drops of with stock cams. You sure it's just not that?

    Install the wideband aswell LOL a guy like you I thought it would be the first thing you do
  7. Fists

    Fists Well-Known Member

    Haha, its always worth checking the easy things first when trouble shooting online.

    Only other thing that comes to mind is ignition breakdown but I have a feeling you would notice if it was missing not just bogging down.
  8. SRB-2NV


    I had a cheap ebay exhaust bracket for it before but thats gone missing. On 7psi it was dipping into the 10.6-10.90 mark but never checked on 12. Nah its worse than an auto tt with stock turbos, it really feels like an NA.
  9. rollin

    rollin First 9

    I think you are on the right track checking for an exhaust blockage
  10. Tektrader

    Tektrader Z32 Hoe, service me baby

    1) Recircs blowing open at upper boost levels ( seems a bit low for that)

    2) Wastegates blowing open because they haven't been synced during refit
  11. ZYTRAM

    ZYTRAM Formerly known as martini_Z

    Are you still running an NA fuel pump?
  12. zx299

    zx299 Well-Known Member

    Good question.......

    That could point to the lack of topend power, especially if the NA pump is 20yrs old. A fuel pressure gauge will tell you soon enough.

    Do you like playing russian roulette with your motor SRB-2NV, winding up the boost without the aid of a WB :eek:
  13. SRB-2NV


    TT fuel pump and the car has a knock detection device fitted.
  14. Shane001

    Shane001 Well-Known Member

    What knock detection device do you have fitted?

    Unless it's a very expensive one, they are next to worthless.

    WB should be the first thing installed.
  15. beaver

    beaver southern zeds


    tt pump will only work properly with a tt pump control unit, an na pump control unit will not send the correct voltage to a tt pump, and fuel pressure will drop away quickly at anything over 14psi. Not a good thing, if you have that setup?

  16. SRB-2NV


    Ok some results

    Afrs hit the 10.50 mark 5krpm then 5500rpm it leans out to 11.3 - 100% idc

    Intercooler is fine, changing to another one did nothing.

    Fuel pump and filter changed

    Changed the std pipes from ic to tb's with hard pipes and it pulls like a train to 6krpm. The ones i had were bare as they had no shielding/covering and were soft as anything.

    didnt have a chance to check the exhaust today as it rained for a lot of the day.

    At 6400rpm the car hits a brick wall, will not pull past that no matter what. Afrs stay in the 11s.

    4.565v afm
  17. Shane001

    Shane001 Well-Known Member

    I'm assuming idc = injector duty cycle? 100% - there's your problem.
  18. SRB-2NV


    Im changing the fpr to my spare turbosmart fpr800 tomorrow and will re check. Also may pull the exhaust pending weather.
  19. rollin

    rollin First 9

    Nothing wrong really with 100% duty cycle really if the wideband still reads ok. Yes it will be off the map but still getting enough fuel
  20. rollin

    rollin First 9

    Shouldn't be that high on the afm at that boost level either

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