Nems NA to TT conversion, with an added suprise ;)

Discussion in 'Member's Garage' started by SRB-2NV, Jan 22, 2014.

  1. SRB-2NV


    Thats not really how compound turbo works, the large turbo is connected to the exhaust stream of the engine and small turbos. Therefore the large turbo isnt seeing an NA 3L v6 engine feeding it exhaust but an already turbocharged engine.

    Kevin Jewer in the states runs 7s on his setup and spools a GT45R sized turbo before 5000rpm on a 2L motor, because the pressure ratio of the small turbos allows a kind of artificial displacement increase.

    Id be fairly happy with full boost from the large turbo at 5000rpm simply due to the fact that thats where the boost and power fell off on the dyno. With the external wastegates the car holds 20+psi to redline compared to 14 before, so an extra kick in the guts from the GT42R should be enough to get me into the 10s and if not.... we still have the blue bottle hooked up!
  2. SrAfciGeR

    SrAfciGeR Member

    Ok I understand "compound" or 3rd turbo connected in series vs parallel setup that i was referring to...

    Essentially you feeding all the exhaust and all the pressure from stockies trough the GT42R, then coming back in to the intake manifold with that single 2.5" pipe...
    Lot of re-routing tho, donno how you gonna feed all those pipes pass dumpipes but yeah show us some pictures when you do so :)

    You can perhaps think of using few in-line "barrel style" (water to air intercoolers) on the way back from GT42R if the space below the car allows you so.

    And yeah I donno how hot that air get's at 20psi from stockies but i'm sure it's cooking your pistons...
    This is not daily, you only dragin it right?
  3. SRB-2NV


    Im actually tossing up using a water to air ic in the back. I may do it later on to try it out. As for the boost, E85 and a rich tune help a lot
  4. SRB-2NV


    E85 and external wastegates are hands down the best money ive spent on this car so far, the car held 23.8psi to 6500rpm and decided it didnt like holding traction in 4th gear. Need some new tyres!
  5. SRB-2NV


    General idea of how the pipe will run. Bought about $350 worth of stainless steel for the charge piping.
    2018-12-17 20.02.33.jpg
  6. SrAfciGeR

    SrAfciGeR Member

    Well composite turbo setup might just be a third best thing :)

    Forth best thing perhaps: Water/methanol injector? As you can't just always use nitrous...

    Did you get tour twin scroll valve from sound performance?
  7. SRB-2NV


    Water meth is also an option, just a few things non car related have popped up and slowed progess till february.

    Quick spool valve is actually just a twin scroll flange with one pipe going to one scroll and an external wastegate going to the second. Got the idea from yellowbullet, the idea is while the wastegate is closed all the gas will pass through one scroll until that turbos boost gets to whatever spring pressure we have in that gate, then itll open and allow the gas to pass through both scrolls. One guy claimed 800rpm improvement with it.

    Not too fussed tbh, the factory turbos are at 17psi by 3300RPM and will provide the engine plenty of boost till the large turbo spools up... and as its a compound system itll be on ~10psi from the large turbo.

    There's going to be 3 different ways ill be testing this system to see what works best.

    First: Have the small turbos drop off and the GT42R provide all the boost up top

    Second: Series compound, boost from the large turbo is hooked into the top ports of the wastegate so 10psi out of the stockers with 10psi added to the top ports will be 20psi for example.

    Third: a mixture of the two above, have the stockers set to 22psi and the big turbo adding 12psi, but without the top ports hooked up. So instead of adding 12psi boost it will drop the small turbos boost by the large turbos boost. That way will lower backpressure and boost response should be better as the large turbo will only have to spool up to 10-12psi and not 24.
  8. SrAfciGeR

    SrAfciGeR Member

    Is your flange looking like this ?


    Yeah it's a try and error kind of scenario, I would think that best results you'll see if you configure it so that stockies are bypassed as soon as you see boost from GT42R.

    Regarding backpressure I would imagine that backpressure would be highest in between stockies and exhaust port, so in my opinion you need to open wastegates sooner than later, as pressure side will overspin stockies impellers and ease that flow on the exhaust side, by doing so you'll widen that backpressure area to the rear, or where GT42R will be located.
    As well to spin GT42R. to 24psi you don't need that much energy so backpressure will be smaller.
  9. SRB-2NV


    Had an injector failure yesterday so im chasing another one. Took the fuel rail off and cleaned the others.
  10. SRB-2NV


    New injector in, also decided to remove the flex fuel sensor as ive never used it anyway.

    Got to say this car is super fun in current configuration, my R33 with a GTX35 sized turbo is nowhere near as fun to drive and i dare say the zed would eat it without an issue.
  11. SRB-2NV


    Ran 12.1 @ 116MPH last night with a 1.8 60ft. Car pulls like an animal to 6200rpm then just flattens off. I suspect theres a restriction somewhere so next time ill make a few changes to try and get an 11.
  12. Boll!

    Boll! Well-Known Member

    Good stuff!!
    So that was with the 42 set up?
    Your using a manual yeah?
  13. SRB-2NV


    Nope, stock turbos and E85. Rear mount setup hasnt been installed yet. I want an 11 on stock turbos first!

    Yes 5spd manual and brass button clutch.
  14. Boll!

    Boll! Well-Known Member

    That’s a good effort mate, well done
  15. SRB-2NV


    Found out my cats have delaminated at were rattling about, not sure how long theyve been like that or if it was like that at the drags but they're now "high flow"

    I've bought a 3" catback exhaust as i suspect my old 2.5" was a restriction to power. Also need to sort out my tune at lower boost levels(~6psi) as when i launched at high rpm the AFR dipped to 10:1 and the car cut out.

    Few other changes ill be making soon are:
    55mm throttle bodies
    AMS lightweight crank pulley
    Along with the 3" catback
    Add a 2nd MAC valve for the external wastegates so i can add pressure to the top ports to keep them shut for longer.
  16. SRB-2NV


    Well the compound setup is up and running.. infact ive driven it twice. Haven't gone full throttle as there are things i need to sort out before that, however at half throttle i can get the GT42 making boost at under 3500rpm and by 4000 the turbo is screaming. This is also only running wastegate pressure(7psi creeping to 11psi) out of the stock turbos, im fairly confident if i turned the stockers up to 15psi the 42R would be on full noise before 4000rpm.

    Have the usual leak here and there that i need to sort out, a filter for the big turbo and getting a flat sheet welded in where my boot floor was but the car is actually driveable and can spool this 1000hp turbo like nothing. My R33 with a GTX35R was nowhere near as responsive.

    My exhaust currently goes:
    Dual 3" dumps > dual 2.5" front pipes > single 3" pipe > 2.5" pipe > wastegate and quick spool valve > GT42. Charge piping is 2.5" with a metal T piece.
    harty likes this.
  17. SRB-2NV


    Had to install a check valve into the turbo oil feed, turns out if you let a rearmount sit over night itll leak like a mofo. Installed a check valve and not a drop out the exhaust at all.
  18. SRB-2NV


    More updates:

    As the turbo drain is in a not so great spot the big turbo smokes like a mofo so ill need to add a catch can and mount my scavenge pump lower.

    Car has a million exhaust leaks but so far the system as a whole seems to be working, we made custom intake pipes for the stock turbos with a pressure feed to see how much boost we are getting out of the GT42. With leaks the GT42 is hitting 0.60bar or so, so ill be putting new gaskets in and adding an mbc to raise that to 15psi(1.0bar).

    My quick spool valve idea has failed so far as the spring pressure seems to be higher than the 60mm i am using for boost control so no matter how much boost i pump into it, having what is effectively a 0.52a/r turbine is killing top end power.

    Next step is to either remove the qsv spring or install a ~3psi one for testing and increase the GT42Rs boost beyond the 8ish psi its creating now to 14-16psi.

    Progress is progress and ill be updating this thread as i find more issues with the system.
  19. SRB-2NV


    Also as a quick reference ive had the car over 26psi with the GT42 only adding about 8psi. I believe the qsv spring is 10-12psi so ill remove it and test again or replace it with a 3-5psi spring. With the qsv closed the gt42 turbine a/r is only 0.52 so thats killing power.
  20. SRB-2NV


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