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G25-660 testing on 1.8t.... info here as more "sticky" than facebook

badger5 Oct 31, 2018

  1. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    Righto..
    those who follow badger5 on facebook will already have seen this but for those who dont, here's some info from first stage testing of the new Garrett G25-660 turbo. Much "hyped" online unit.. GT28 size, GT35 abilities.. (claims from garrett)

    So... Test engine is my poor little ibiza racecar.(as usual). Its engine spec in outline is 82.5mm bore, std stroke, 9.3:1 compression, ported smallport (largeport), dimpled cnc head, catcams,supertech etc etc.

    Previously running GTX3076Gen2/0.63 and HTA3076/0.63
    2bar ~500bhp region

    The G25-660/0.72 unit is garrett vband but fitted directly onto my current tial flanged manifold & downpipe, which was a pleasant surprise. Made installation a breeze. Clocked to fit my setup, all the lines fitted. Nice feature of this G25 series is the chra is vband clamped to the hotside so no more bolts to backout of the hotsides! yay! and easy to rotate.. Double yay!

    The size of the unit is indeed compact.. GT28 size.. small turbine but different slightly larger turbine than a 28, but way smaller than GT30xx turbine

    comparison plots are of different boosts and against the HTA3076 I removed to do this test. boost onset torque onset etc are what I am looking for.

    some plots... more to write when I get a mo to add to this.
    G25-660 at different boost levels
    [​IMG]
    [​IMG]

    HTA3076 compared to G25-660
    [​IMG]

    Some "wobbly boost" experienced from the G25.... Hmmm. Not good.
    [​IMG]

    Thoughts are currently that there is a potential wastegate issue here... possibly just sticking (inconsistent onset of boost), but also I believe back pressure related in the oscillation seen when higher boost at higher revs seen...
    the ecu is DTA S80 unit, running STC drive by wire... and boost control is fixed duty cycle driven, not closed loop, so the ringing of the boost is not a PID thing.. there is no PID control active. Its a physical thing. Back Pressure is my concern. Bad thing that.

    Wastegate is being replaced, it is as old as noah, and has served me well but we did have to weld its valve head back on a couple months ago where it detached itself. Early old large 44mm tial gate. Trying out a new 44mm GFB wastegate this time.. cos I have'nt tried one, and fancy seeing how it is. I will plumb the new gate in dual port tho, as was only ever single port up to now.

    So we will resume testing when parts are in and its modified to work again, this time with back pressure measurements measuring at turbo hotsides.

    more later...........
     
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  3. Prawn

    Prawn My other car is a MINI!!!!

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    Great work Bill!

    Thanks for taking the time to do testing like this.

    Without your testing all the claims just remain hype and speculation as usual. With you doing the this testing we can at least see soon enough if this new g25 meets the bold claims!

    Hope the wastegate replacement sorts the boost issues and you find good things from it
     
  4. Rainbird

    Rainbird Well-Known Member

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    Good stuff - great to see some real testing rather than sales pitch and hearsay and looks like a fairly promising unit. Interested to see what EGTs are like relative to the GT30s you've bene running before. Kudos, Bill!
     
  5. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    We've added a take off on the G25-660 and my HTA3076 so back pressure can be measured when next on the dyno to continue the testing.
    Wastegates (old Tial) is plumbed for dual port as a check also, but new GFB one has arrived today as replacement also.
    [​IMG]

    Even fixed the dynos data logger aquisition card.. one died a year or so again, all of them being obsolete, feared the worst but bought a new innovate card and with some rewiring made it work with the old cards so all back up to many channels of logging, so will be able to log boost and back pressure at same time with dyno.

    [​IMG]
    [​IMG]
     
    Rainbird, Alex C and Prawn like this.
  6. Prawn

    Prawn My other car is a MINI!!!!

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    Nice stuff Bill!

    What's the coiled tube off the back pressure take off? Some form of signal smoothing or isolation away from hot gasses?

    Can't wait to see the results.

    I swapped my tial 44mm gate from single port to dual wkth a mac valve early on in my road mapping and found boost control much better and more consistent.
     
  7. superkarl

    superkarl MAN OF STEEL

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    It’s to remove heat before it gets to some more conventional flexible tubing
     
  8. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    hopefully cool it down a little before the poor little silicon tube gets stuck over its end for measuring back pressure
     
  9. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    ok, so another weekends work testing this thing..
    Saturday pm had a few hours late afternoon, so stuck badgerwagen on the dyno again. Only change being dual ported the old Tial wastegate and now with back pressure measurement. It was inconsistent boost and boost onset again frustratingly.. but the oscillation seemed to have gone. Time to actually replace the old tial for the new GFB gate I bought to try.

    Sunday, removed old Tial and fitted new GFB... utter faf, and not a product I will use again.. Not well thought through product fitment wise at all.. Anyhow, it fitted, was also dual port configured and during the process we removed the chra/coldside from its vband for better access, and saw a rub mark on the hotside and turbine wheel. "feck"[​IMG]
    [​IMG]

    Guessing on previous assembly the chra did'nt get pushed in square enough.. but this would explain the weird boost onset and oscillation if catching. Maybe my old tail gates ok.. Too late now the gfb thing is on there.

    Resuming testing now with back pressure measurement and stable, consistent boost onset, we could do some more testing.

    First back pressure. Seems max boost run ~30psi we see a 1.5:1 pressure ratio: Tolerable level I believe.
    [​IMG]
    Power output and comparison to both the HTA3076 and GTX3076Gen2 I run.
    [​IMG]
    Onset of boost and torque plots below, violet G25-660,yellow hta3076,red GTX3076G2
    [​IMG]
     
    superkarl, Rainbird and Prawn like this.
  10. Rainbird

    Rainbird Well-Known Member

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    This is looking like a really promising option!
     
  11. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User TDi Audi A4 Audi Avant Owner Group quattro

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    Again thanks to Bill for doing this and freely sharing this information. I am really happy I believed what Garret were saying and bought one a few months ago. That was lucky, better go and buy a lottery ticket :) . Now with some shiny bits attached I really need to get this on the car.

    So how fast does a G25-550 spool on a 1.8T, as I can't really see it spooling that much better . Same size turbine just a 7mm smaller compressor wheel. And how long before Mamba / Kinagawa start knocking out copies. As there isn't anything really fancy or exotic in this except the Mar M turbine.
    DSC_4049.JPG
     
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  13. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    The hotside/chra being vband also is something else for the mamba's of the world to copy also..
     

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