Technical SteamSpeed STX 78R BB N55 Turbo (aka stage 2.5) - specs & details

Discussion in 'N55' started by [email protected], Feb 8, 2018.

  1. sam@steamspeed

    [email protected] New Member Vendor

    3
    Focus RS, Impreza RSti
    One of our long-time BMW customers has been rolling with our STX 67 N55 (stage 1) turbo for a while putting down 400+ whp with pump gas + meth. He has been asking us to make a N55 turbo capable of over 550whp, so we did. We call it the STX 78R which has a ceramic ball bearing center section (hence the "R" designation), and large compressor wheel with a 78mm exducer (hence the 78). It has a an estimated flow over 70 lbs/min, which should be good for over 550 whp on a N55 engine.

    Why did we invest the money to have a BB CHRA when a compressor wheel will flow what if flows even using a cheaper JB CHRA and hypothetically make similar peak power?

    The BB CHRA in this application will be way more efficient than using JB turbos of similar size. In practice, the BB CHRA will come in sooner, and give you a lot more response all over the power curve. It will be very noticeable daily driving, but will also improve lap times in sections where you are on and off of the boost. Also because the CHRA is more efficient, it will make more power everywhere where a JB turbo is less efficient like high back pressure situations for example. The added BB efficiency will have a lower heat load vs JB which also makes it easier to make power and tune.

    Here are the core specs on the SteamSpeed N55 STX78R (aka stage 2.5) turbo:
    Bearing System: custom ceramic BB
    • Custom Compressor wheel In:59 / Ex:78 (the size is between GTX3076 and GT3582)
    • Custom Turbine wheel In:60 / Ex:57 (The size slightly bigger than GT3076 - In:60 / Ex:55).
    • Flow capacity: 70 lbs/min (est.)
    • Estimated WHP: ~550+ whp
    • Release Date: TBD
    • Estimated Pricing: ~$2500
    • Core Required: yes (just the comp & turbine housings only)
    Stay tuned for testing data, and final dyno results. Barring on scheduling issues, or other setbacks, we expect to have some final results for you in the next 4 weeks.

    Oh, and here are the pictures:
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    Last edited: Feb 8, 2018
  2. doublespaces

    doublespaces Administrator

    AZ
    2009 E93 335i
    Sweet, I look forward to some results!
     
  3. ChrisNeil5

    ChrisNeil5 Lurker

    15
    2008 BMW 135i
    Nice to see some more advancement in the n55 platform
     
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  4. Interesting in for results as well.
     
  5. N55uk

    N55uk New Member

    4
    Uk
    Looking foward to more info on this, we need more options on the n55
     
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  6. doublespaces

    doublespaces Administrator

    AZ
    2009 E93 335i
  7. sam@steamspeed

    [email protected] New Member Vendor

    3
    Focus RS, Impreza RSti
    Thanks everyone for the support. We will be doing some testing and validation in the next month or so. We'll try to keep this thread updated with useful install and testing data.
     
  8. terryd5150

    terryd5150 Specialist

    69
    2008 E92 335i 2009 E90 335i
    F-Series EWG application?
     
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