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Thread: turbo sizing + e85/HG spacer questions

  1. #1
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    turbo sizing + e85/HG spacer questions

    M52b28 in an e30 325i
    Planning to run RK Tunes e85 tune.

    Trying to decide if should go with a spacer or not after I get the head back from having it decked/pressure tested.
    How close am I cutting it running e85 + stock compression + ARPs shooting for 15-20lbs boost/400-500whp?

    With those goals in mind - turbo sizing. Trying to keep it under $1000, or at least in that ballpark - which knocks out Garrett and Precision.

    Looks like I'm in Borg Warner territory, maybe s360? Any other recommendations for brand/size + A/R?

  2. #2
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    You can run 12:1 compression with boost on E85. No reason at all to lower the compression with E85.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  3. #3
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    This is probably what I would put on it for that budget or an S257sxe if you want to stay borg warner

    https://agpturbo.com/agp-turbo-z2-6262e-billet/


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  4. #4
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    .82 A/R sound right?

  5. #5
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    Quote Originally Posted by The Great Decay View Post
    .82 A/R sound right?
    Depends on what turbine and compressor wheel combination you are going with and what manifold flange you need


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  6. #6
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    Planning to go RSI manifold so either T3 or T4 would work and definitely Vband outlet

  7. #7
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    Quote Originally Posted by The Great Decay View Post
    Planning to go RSI manifold so either T3 or T4 would work and definitely Vband outlet
    If you think you will only ever be wanting like 400-600 whp then I would probably go with the T3. If you ever want to make more, like 700 or more, then there are more turbos available in T4 than T3.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  8. #8
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    Thanks for schooling me and confirming what I thought, but wasn't for sure on. Planning on the .81 a/r T4

    I'm sure I'm going to keep turning up the boost until something breaks but my intention is to run a stock motor w/ arps + e85 that will run in the low 11s for as long as it'll hold.
    Then I'll reevaluate if I need to go bigger/built but can't hurt to go T4 now.

    If I expand my turbo budget to $2k is the extra $1000+ spent really that justifiable? Dropping almost $2k on a GT35R going to really make that much difference in a 1/4 mile?
    Last edited by The Great Decay; 08-12-2021 at 02:58 PM.

  9. #9
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    Quote Originally Posted by The Great Decay View Post
    Thanks for schooling me and confirming what I thought, but wasn't for sure on. Planning on the .81 a/r T4

    I'm sure I'm going to keep turning up the boost until something breaks but my intention is to run a stock motor w/ arps + e85 that will run in the low 11s for as long as it'll hold.
    Then I'll reevaluate if I need to go bigger/built but can't hurt to go T4 now.

    If I expand my turbo budget to $2k is the extra $1000+ spent really that justifiable? Dropping almost $2k on a GT35R going to really make that much difference in a 1/4 mile?
    With turbos your are basically paying for response and the aerodynamics of the compressor and turbine wheels. A GT35R is a decent turbo but its literally 25 year old technology at this point. In general the stuff available in the $1000-$2000 class is legacy technology stuff with turbine technology from the 1990's but with ball bearing center sections and a billet compressor wheel. Both of those things will offer a little bit faster response than cheaper turbos with journal bearings or cast compressor wheels, because of less rolling resistance and weight.

    For right around $2000 and up you can get into some real new technology stuff. Something like an EFR8474 or a Xona Rotor 8464s. Both have brand new turbine and compressor technology in them. Both of those will spool faster than a GT35r, but will offer the potential to make a couple hundred more hp on top. You kind of get the best of both worlds with something like that and don't have to make much of any compromise between response time and having enough airflow to make a lot of power.

    https://www.turbokits.com/borg-warne...747100019.html

    https://forcedperformance.shop/produ...35852784271521


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  10. #10
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    I would look at a JB $1150 PT6266. If you look at the big torque thread, Litemup has two or three dyno graphs of his making major power. Granted, I think his was a BB turbo, but a JB should have similar response. 500wtq at 3500rpm. And the a second graph of over 800 whp/ torque.
    WOT

  11. #11
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    turbo sizing + e85/HG spacer questions

    Guess to update this a bit - ended up finding a solid deal on a used ball bearing Precision 6266 .82 A/R that was too good to pass up.

    Appreciate the knowledge from everyone. I’ll throw together a build thread once I get closer to getting everything stuffed in the e30
    Last edited by The Great Decay; 08-17-2021 at 06:55 AM.

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