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View Poll Results: Which Twin setup?

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  • Twin GT28RS

    27 65.85%
  • Twin GT2871R

    14 34.15%
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  1. #26
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    bigdnno98, I would just make new downpipes and use the internal wastegate that comes with the MHI turbo. Does the GT28rs come internally gated?

    If space is an issue there could be one downpipe that splits to each turbo, having the wide band O2's in the separated part just after the turbo and the other two after it is collected together. I have a set if TD04-15G's to compare our stock turbo's to and there is really only about .5" difference in external size, so space should be ok. Because of this I am going to look into the TD05-16G since the housing will allow more flow and options for further improvement later on if needed.

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    Click here to enlarge Originally Posted by streetluger Click here to enlarge
    I would go with the GT28rs for quick spool.

    I am planning on doing a twin turbo swap over the next 6 months also. I have been looking at using the TD04-19t or TD05-16G, both turbo's are cheap and will easily fit in there.

    Keep us posted, I would like to see how the project goes.

    Also has anyone considered cutting the stock turbo's off of the manifolds and welding an adapter on to bolt the new turbo to? I think the manifolds aren't too restrictive as long as the exhaust housing on the turbo isn't too small, I am considering this option since I have two stock turbos that won't sell.
    Hacking the factory exhaust manifolds wont be easy, they are a dual walled design like a Turvis or insulated coffee mug so it would be extremely difficult.

  3. #28
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    Click here to enlarge Originally Posted by streetluger Click here to enlarge
    bigdnno98, I would just make new downpipes and use the internal wastegate that comes with the MHI turbo. Does the GT28rs come internally gated?

    If space is an issue there could be one downpipe that splits to each turbo, having the wide band O2's in the separated part just after the turbo and the other two after it is collected together. I have a set if TD04-15G's to compare our stock turbo's to and there is really only about .5" difference in external size, so space should be ok. Because of this I am going to look into the TD05-16G since the housing will allow more flow and options for further improvement later on if needed.
    RB turbos are made out of TD04-15T components. If you're trying it I agree, at least try to go 16G or even 20G

    Funny enough our man Rob is mentioned here back in 2009 Click here to enlarge
    http://www.3si.org/forum/f35/td04-16...5/#post5361119
    Click here to enlarge

  4. #29
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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge
    Hacking the factory exhaust manifolds wont be easy, they are a dual walled design like a Turvis or insulated coffee mug so it would be extremely difficult.
    Definitely new manifolds or its too difficult/expensive
    Click here to enlarge

  5. #30
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    I am concerned about the double layer manifold also. It would probably take a very skilled welder to pull it off...that unfortunately is not me. I think it would be fairly easy to put together two log style manifolds as long as the flange that goes to the head can be replicated with the proper angle for the gaskets.

    Would it be possible to chop the old manifold off of the flange and use that as a starting point for a new one? The alternative would be to have a shop make a copy of it based on the stock one.

    Either way I don't see a true twin turbo upgrade costing that much aside from the turbo cost.

  6. #31
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    CP-E dropped their upgrade project? It looked challenging to say the least.

    What would be the plan for getting the wastegates to work?1
    What makes you say they dropped it?

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  7. #32
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    What makes you say they dropped it?
    Let me rephrase that. I heard the project was put on permanent hold for one reason or another. To me that says nothing is in the works anymore. Do you have any info to suggest otherwise?
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Let me rephrase that. I heard the project was put on permanent hold for one reason or another. To me that says nothing is in the works anymore. Do you have any info to suggest otherwise?
    Where did you hear this? I'll ask them.

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  9. #34
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Where did you hear this? I'll ask them.
    Little birdie
    Click here to enlarge

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Where did you hear this? I'll ask them.
    The exact reason would be interesting to know directly from them.

  11. #36
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    my guess is the profit margin. the r&d, tooling, advertising, it isn't worth it with competition having a good hold. and now with the single option available i think they said $#@! it, and moved on. but didnt i say it would be/was canned way back when?
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    dzenno, and others looking forward to an actual N54 twin turbo upgrade.........its coming

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    Click here to enlarge Originally Posted by farbmw Click here to enlarge
    And I see it is very diffacult to walk away from your 135i!
    Ya, I am still in the car although its bone stock and depressing that way. I am still sitting on the sidelines patiently waiting on the platform while I decide on whats next for me. Came close to pulling the trigger in a 996TT. Its been my dream since I can ever remember to own a Porsche but I just cant seem to quit my N54.
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  14. #39
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    Click here to enlarge Originally Posted by streetluger Click here to enlarge
    If space is an issue there could be one downpipe that splits to each turbo, having the wide band O2's in the separated part just after the turbo and the other two after it is collected together.
    Space is a serious issue, so having one DP as you said would be the only possible way.

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    GT28RS (i.e. disco potato) or GT2871R?
    The reply to the original question would be "neither". Funny enough, if you google the net you'll get your anwer: "The GTX2863R flows as much as the GT2871R but with GT2860RS boost response!" Click here to enlarge

    If you think of it, Disco Potato was amazing - and the spool is still great by modern standards, but it is 10 years old tech already, and Garrett finally upped their game with GTX-series by better aero which enhances the efficiency especially at higher boost pressures. If someone would really want to push it, two of these would beat traditional single scroll big single turbo in both spool and power.

  16. #41
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    The reply to the original question would be "neither". Funny enough, if you google the net you'll get your anwer: "The GTX2863R flows as much as the GT2871R but with GT2860RS boost response!" Click here to enlarge

    If you think of it, Disco Potato was amazing - and the spool is still great by modern standards, but it is 10 years old tech already, and Garrett finally upped their game with GTX-series by better aero which enhances the efficiency especially at higher boost pressures. If someone would really want to push it, two of these would beat traditional single scroll big single turbo in both spool and power.
    Mulling over compressor maps of a whole bunch of small/mid frame turbos and comparing with the N54 and finding how they'd spool in a twin configuration to the desired boost, ensuring no possible surge happening and also making the desired power as well as being able to make a flange that'd accept a couple different units and still be doable isn't a small feast but I've done quite a bit of research already. GT28R, GT28RS and the GT2871R twins would work amazingly well on the N54 with my personal favourite vote going to the GT28RS (i.e. GT2860R, aka disco potato). It'd spool to 2.22 PR (18psi) by 3500rpm and stay on the right of the surge line by taking the approximation of 20% of max CFM at redline (7200rpm) and connecting the dots from 1.0PR@20% of max cfm up to 2.22PR@3600rpm CFM. A twin disco potato could make upper 675hp at 18psi, 700 at 20psi, supporting up to 24psi absolute max in midrange. This is with a 60mm, 62trim, .60 A/R.

    I'll definitely have a look at the GTX series next and the GTX2863R and its compressor maps and do some calcs. How much different is this new GTX unit from a disco potato in terms of packaging? Is it internally wastegated, very important to ease up on packaging/fabrication as well as tuning?

    EDIT: Looked at the GTX2863R compressor map. It'd actually take about 3800rpm on our motor in a twin config to spool to 18psi but it does provide more efficiency and power than a disco potato. To me this would actually be a better option than a GT2871R but the disco potato, even though 10yrs old, is still a better match to me for the desired mid 3k rpm spool and desired power level (mid-high 600). I could always step up to the GTX2863R if I wanted to hit over 800.
    Last edited by dzenno@PTF; 06-20-2012 at 09:08 AM.
    Click here to enlarge

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    Here's the compressor map for the GTX2863R:<br><br>Click here to enlarge<br><br>It'd hit 17psi by 3600rpm...it has potential for 800hp at just 17psi with an efficiency of 71+%...i'm starting to like this one a lot Click here to enlarge anyone know if this is available internally wastegated?<br><br>Nice thing is that it has a compressor housing with built-in anti surge machining so that's a bonus too<br><br>Here's how it compares to the GT2860R (aka disco potato, aka GT28RS):<br><br>Click here to enlarge
    Click here to enlarge

  18. #43
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    I'll actually have the GTX2860R Click here to enlarge exceeds disco potatos perf down low and a ton more room and efficiency Click here to enlarge love it! New favourite for sure
    Click here to enlarge

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    That GTX turbo map is beautiful... Look at at the pressure ratio it can hit.
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    Click here to enlarge

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    That GTX turbo map is beautiful... Look at at the pressure ratio it can hit.
    Its pretty crazy yes, all while remaining highly efficient. But, without building the bottom end and lowering compression I don't think anyone in their right mind will attempt those pressure ratios Click here to enlarge The older GT28RS (original disco potato) is actually still very much a contender as you get the turbine housing+wastegate assembly with the wastegate all for $1100-1200 retail...with the GTX2860R it starts at $1280 retail without the turbine housing and the wastegate and its assembly (about $1500-$1600 fully assembled)...Disco potato is a more affordable option that should work very well I think as well for those on a tighter budget
    Click here to enlarge

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    Dzenno, I believe the actual figures for N54 can be even better than what the equations you use give. Have you checked what the stock turbo compressor maps give in theory? The maps are in the sticky on the other forum.

  22. #47
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    Dzenno, I believe the actual figures for N54 can be even better than what the equations you use give. Have you checked what the stock turbo compressor maps give in theory? The maps are in the sticky on the other forum.
    These are rough estimations of course based on compressor maps. There is no way of knowing 100% how a turbo will behave on a motor without actually trying it on the car...Precision for instance, good luck trying to get a compressor map out of them Click here to enlarge they've never and will never publish one for their units so stuff like this you have no idea of predicting/estimating/calculating

    In case anyone's interested in learning how to read compressor maps and match up turbo(s) to an engine take a look at this URL:
    http://www.lovehorsepower.com/joomla...id=4&Itemid=88

    Funny enough, the guy who owns that blog recently switched from his MR2 to a 135i Click here to enlarge I asked him what he thought about twin discos on this motor and he agreed provided there's space to fit they'd be an amazing upgrade. We all know fitment is a PITA but with a shorty twin log style manifold I'd like to think its very doable

    In terms of the downpipes or downpipe, it'll be whatever works out given space constraints obviously

    EDIT: Looking at the GTX2860R turbo you could be spooling ~13psi as early as 1500rpm..sick!
    Last edited by dzenno@PTF; 06-20-2012 at 11:26 AM.
    Click here to enlarge

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    as long as you dont intend to pass 2.5 pressure ratio then disco potato will work great if budget and fitment is a concern. Looking at the overlay of both maps, they look similar in performance at low pressure ratios.

    I do agree the GTX will spool much earlier though.
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    Click here to enlarge

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    as long as you dont intend to pass 2.5 pressure ratio then disco potato will work great if budget and fitment is a concern. Looking at the overlay of both maps, they look similar in performance at low pressure ratios.

    I do agree the GTX will spool much earlier though.
    When people say "spool" earlier it really comes down to what boost do you want to spool TO and at by what RPM. Just to clarify for others, this all depends pretty heavily on both displacement and VE. Both of them will spool similarly fast to 18psi, with the GTX "starting" to spool up and build boost significantly earlier than a regular disco potato.

    2.5PR is 22psi and up to that PR both perform very close, with the GTX being the spool up winner
    Click here to enlarge

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    Am I reading this right that you are determining spool characteristics from a compressor map? Please advise on how you are doing that... as I'd like to learn!

    As for space for a true twin turbo upgrade it really comes down to the the length of the turbo. You would need to find an ultra short turbo end to end (compressor snout to turbine housing flange). That is the biggest hangup on a good twin setup. It doesnt matter if you rotate them both forward, or in opposite directions with exhaust outletting together (like stock), you still really need a super stubby turbo to be able to mate it all together and get plumbing to and from each turbo and fit in these cars. I'd say if it is greater than 8" end to end it is too long, problem is most of these really nice modern turbos are 10"+ IIRC.

    One post for the day.

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