Z32 Turbo upgrade

Discussion in 'Technical' started by Blue300, Aug 16, 2019.

  1. Blue300

    Blue300 Member

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    Hi,

    I need advice as to which turbo is the better option between either a gt2860rs or the newer gtx2867 gen 2 and was wondering if there are any major differences in power delivery between the two.
    I'm currently running high flowed turbos on 15psi, it's very laggy but quite strong top end usually hitting max boost at about 5000rpm,
    I'm wanting a turbo that will give me the same boost levels at lower rpm and continue making power until redline,

    Thanks
     
  2. MagicMike

    MagicMike Moderator Staff Member

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    If you are expecting larger turbos to make more boost earlier, I think you will be disappointed.

    I don't know what your supporting mods are, but IMO, you should start there. If you plan them well, and still decide you want larger turbos, at least your supporting mods will carry over.

    Side note, full boost at 5k for high flows sounds terrible.
     
  3. Blue300

    Blue300 Member

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    I thought it was too laggy but im thinking how ive set the boost controller may be the cause, as the wastegates are opening only when the desired boost levels are reached with a turbosmart eboost street.

    This weekend I'll be fitting 740cc injectors and haltech plug in, it's already got larger smic, dw300 fuel pump, 2.5 inch dump pipes into 2.5 inch exhaust
     
  4. IB

    IB ?????

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    There is something wrong if your high flows reach full boost at 5k. Maybe wastegate actuators?
     
  5. Blue300

    Blue300 Member

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    Yeah it's definitely not right, I've checked for vacuum leaks and no problems. The wastegate springs are pre set at 23psi but I've only ever reached a maximum of about 16psi by setting the boost controller to obs
     
  6. IB

    IB ?????

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    Maybe one of the turbos has seized?
     
  7. Blue300

    Blue300 Member

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    I think maybe it has. I was under the car tonight and noticed a small oil leak on the bottom of the compressor housing coming from where it joins to the core, I can't see any leaks coming from the top at the oil feed line
     
  8. ProckyZ89

    ProckyZ89 Senior Member

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    Not sure what actuators you have but I’d strongly check that- internal actuators I don’t think even go up to 23psi on spring pressure.

    To answer your question

    There is a big price difference between those 2
    The GT2860 (or gtx2860 is your best option) will work amazingly well and you should be seeing full boost low to mid 4000rpm area.
     
  9. Blue300

    Blue300 Member

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    Ok that would make sense as to why the high flows are reaching max boost at higher rpm, the cores are 2860 - 5 with the compressor housings machined to the max but are still using thrust bearings which I guess would be less responsive than ball bearing.
    Once I get it running today I'll have to check exactly when it does hit full boost, maybe it's at 4500 or 4800, I haven't really taken alot of notice as when it does reach max boost I'm too busy looking at the road
     
  10. rob260

    rob260 Moderator Staff Member

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    Man I recommend dropping the wastegate pressure down around 1bar.

    If spring pressure is too low blow wastegates open. When you go too high you start to put flow the compressor housing.

    Have you played with the boost controller settings on the dyno? The last high flow build I did we set spring pressure at 16psi and I think the tuner managed to get 23psi using the boost controller before it started choking. He then went back and mapped gain through the RPM (boost controlled via link ECU) to improve response.

    You can do his via ECU or if you have a decent EBC (turbosmart eBoost series for eg) you can map gain against an RPM signal.

    2860 is a good turbo, GTX of course “better” but unless you’re running e85 you won’t be running enough boost to really notice the benefits. I can’t imagine a scenario in which a T28 is more responsive than a high flow simply due to physically larger housings. Of course context counts.

    Hope that helps.
     
  11. Blue300

    Blue300 Member

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    Good point I guess that would build boost faster but then again I do enjoy alot of lag then suddenly hitting max boost.

    I haven't had a chance to get it on a dyno yet but hopefully will be able to soon.
    I took it for a spin earlier and set the gate pressure to 17psi with over boost shutdown at 20psi, at 4500rpm it reached 17.8 and felt like it didn't have any more go after 6300rpm.

    I'm thinking of running e85 and going with the top feed fuel setup but I'm worried there's no space big enough to fit a decent size turbo to make the most of it
     
  12. Blue300

    Blue300 Member

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    Another option I had in mind that I can't really find any threads of anyone that outlines the fitting issues that arise when going for twin gt3076.
    With larger 2.5 inch intake piping this should be enough to make use of the extra force from the larger compressor housing even at the same 4000rpm from what the 28 series offers.

    If fitment issues did arise, it would almost be easier to go down the path of big single conversion
     
  13. jellybeans

    jellybeans Active Member

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    big singles are pretty easy.
     
  14. Martin Williams

    Martin Williams Well-Known Member

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    Please tell us the full extent of your modifications, then you will get more comprehensive advise. I had no problem getting 22psi with GT2860s but I did have a lot of supporting modifications. I raced my car, so had no problems with lag as the rpm never dropped below 3000rpm and we had rolling starts.
     
  15. ProckyZ89

    ProckyZ89 Senior Member

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    The reason you haven’t found any information on it is because there’s only 1 car to my knowledge that’s done a 3076 set up and that was after a custom gt3582 set up. Which is now on GTx2860 gen2 making 800rwhp (American)

    Apart from the fact you won’t be on boost at all until 4500 you wouldn’t see peak boost until mid 5000’s and that’s with a choked up .64 rear housing machined onto it.
    Physical sizing, on factory location manifolds the 3076 does not fit easily at all.

    The other issue is here that our engines don’t realllly have enough exhaust volume for the larger turbos without the tiny housing.
    We can’t really rev ours above 8000rpm either to overcome this.

    3071 have been done a handful of times but have similar fitment issues as above and again were with the smaller rear housings.

    Twin gTX2860 or 2863/67 are capable of 700+rwhp with peak boost being in by 4500rpm.
     
  16. Blue300

    Blue300 Member

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    Ok thanks I think I'll be much better off with the gtx2860 gen 2, it will offer the best overall experience. And I'll probably keep my license a little longer too.
    Full list of modifications are,

    Czp side mount intercoolers
    Pwr 42mm twin pass radiator
    740cc injectors
    340 lph fuel pump
    Haltech platinum pro plug in
    Complete rebuilt engine
    Stock cams
    Je Forged pistons
    H beam conrods
    Xp performance Bearings
    Arp head studs
    Reconditioned heads
    3 inch dump pipes
    2.5 inch front pipes
    2.5 inch exhaust
    Stock exhaust manifolds
    Hi flowed turbos using 2860-5 cores
    Turbosmart eboost street
    Innovative motorsports dlg1 wideband
    Auto to manual conversion
    Ultra lightweight flywheel
    Heavy duty clutch
    One piece tailshaft
    Tein flex z coilovers
    Front adjustable camber arms
    Rear adjustable camber arms
    Z1 pcv hoses
    Z1 silicone accordion pipes
    New fuel, pwr steering, oil, vacuum lines
    Wiring specialties efi harness

    There are still many parts that need replacing
     
  17. ProckyZ89

    ProckyZ89 Senior Member

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    Few issues above that may bite you
     
  18. Blue300

    Blue300 Member

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    I'll stay with the stock cams for now as replacing the cams are big $$$$ for only a move in torque curve, although I think the vct's are playing up a little at the moment.

    Rgs performance sell the e85 flex fuel conversion with top feed set up which I will probably go down that track

    I think there is a small amount of slip in the clutch at the moment.

    Changing these parts is something I am wanting to do but unfortunately it will mean the car being off the road for at least a month, and I really don't think I can go that long without driving it
     
  19. ProckyZ89

    ProckyZ89 Senior Member

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    Month is chump change mate, try 12 months
     
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  20. Martin Williams

    Martin Williams Well-Known Member

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    You are spending a lot of time and money. IMHO you need to also improve flow through the engine. You are reconditioning the heads, so go for oversized valves, port the heads, Fit some R400 cams and stronger valve springs. Change out the VCTs. You will see some real improvement and be more able to get the best out of all the other mods you are making.
     
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