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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. #51
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    Click here to enlarge Originally Posted by Rob@RBTurbo Click here to enlarge
    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.

    Rob
    Hey Rob, yes you're reading it right Click here to enlarge See the link I posted earlier. I saw your post from 2009 on e90post asking for someone to interpret/discuss/map out a TD04-15G compressor map (i guess because components of it are part of the RBs). The above article will explain it all really clearly if you're willing to give it a chance. Its a really great guide to approximate a turbo's ability to hit a certain pressure ratio for a certain RPM given certain displacement and VE. It also helps you visualize if a certain turbo will run left of the surge line which is quite important.

    Fitment is something that is easy to give up on until you get the measurements down and very possibly be surprised. How many thought we'd never see a single in there just a couple months ago? Too easy to give up without even trying..
    Last edited by dzenno@PTF; 06-20-2012 at 11:45 AM.
    Click here to enlarge

  2. #52
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    Well in actuality if you want to know the exact spool characteristics youll need the turbine map and the moment of inertia of the turbo rotating assembly, people rarely look at those but thats an important piece of the puzzle too.
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  3. #53
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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Well in actuality if you want to know the exact spool characteristics youll need the turbine map and the moment of inertia of the turbo rotating assembly, people rarely look at those but thats an important piece of the puzzle too.
    Looking at for instance the stock turbos and comparing with the performance of them to the Garrets it starts to all make sense. For those that doubt it give that link I posted above a chance and you'll see. Happy to discuss of course
    Last edited by dzenno@PTF; 06-20-2012 at 11:49 AM.
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  4. #54
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    Space is a serious issue, so having one DP as you said would be the only possible way.
    Keep in mind, with the ability to make a custom log style exhaust manifold who's to say that the merge collector HAS to stay in the middle of the manifold like stock. The collector (exit where the flange is) on each mani can be moved out to make the required space so the rear mani's collector is on the back of the mani while the front mani's collector is in the front. That way you get a ton of space, more than stock, in the middle between the two turbos.
    Click here to enlarge

  5. #55
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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Keep in mind, with the ability to make a custom log style exhaust manifold who's to say that the merge collector HAS to stay in the middle of the manifold like stock. The collector (exit where the flange is) on each mani can be moved out to make the required space so the rear mani's collector is on the back of the mani while the front mani's collector is in the front. That way you get a ton of space, more than stock, in the middle between the two turbos.
    The merge collectors cannot stay in the middle of the cylinders in the same location they are stock because the turbos are longer. The turbos cannot be directed straight towards each other as the turbines would clash into each other. The turbine ends must be tilted down towards DPs for the long turbos to fit and even in that case there is no room for two DPs in the middle of the turbine ends. One DP would need to suffice. Since the turbine ends run into where DPs used to begin, the DP is as much shorter as the turbos are longer than stock. Short tubular equal length primaries. I haven't measured anything so this is just speculation.

  6. #56
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    The merge collectors cannot stay in the middle of the cylinders in the same location they are stock because the turbos are longer. The turbos cannot be directed straight towards each other as the turbines would clash into each other. The turbine ends must be tilted down towards DPs for the long turbos to fit and even in that case there is no room for two DPs in the middle of the turbine ends. One DP would need to suffice. Since the turbine ends run into where DPs used to begin, the DP is as much shorter as the turbos are longer than stock. Short tubular equal length primaries. I haven't measured anything so this is just speculation.
    Exactly Click here to enlarge Once its all measured it'll be much easier to visualize.
    Click here to enlarge

  7. #57
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    It is just to look at the Dyno curves for vehicles that use the Vishnu Single Turbo. Linear power from 3 to 7000 RPM with more than 600 whp on the tap is much better than can be achieved with stock or upgraded twin turbos. The stock turbo housings are too small to facilitate 600+ whp.

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    Click here to enlarge Originally Posted by R1000K3 Click here to enlarge
    It is just to look at the Dyno curves for vehicles that use the Vishnu Single Turbo. Linear power from 3 to 7000 RPM with more than 600 whp on the tap is much better than can be achieved with stock or upgraded twin turbos. The stock turbo housings are too small to facilitate 600+ whp.
    This is not about stock housings nor below 700WHP Click here to enlarge
    Stock framed turbos spool a lot quicker than Vishnu single, so Vishnu is not better Click here to enlarge

  9. #59
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    This is not about stock housings nor below 700WHP Click here to enlarge
    Stock framed turbos spool a lot quicker than Vishnu single, so Vishnu is not better Click here to enlarge
    +1

    No one's talking about reusing any stock turbo components...new twin cast iron exhaust manifolds, lines, dps, hotside fmic pipe and intake tubes
    Click here to enlarge

  10. #60
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    1 out of 1 members liked this post. Yes Reputation No
    If only someone could do all that?

  11. #61
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    Dzenno - perhaps Ivo can take measurements and provide a feasible mani solution. We could put our heads together and come up with real solutions and put these speculation to bed.

  12. #62
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    By the way, total length of a disco potato is 196mm (7.72inches)...not a log longer than stockers it seems..the GTX28 turbos are the same external size/packaging so offsetting the manifold merge/collector/flange an inch or two towards the front on the front mani and inch or two towards the rear on the rear manifold would open up the same space as on the stock setup...on top of that, the flanges on both front and rear manis could be tilted so both turbos' turbine housings point down towards the say 7-8 o'clock position instead of looking straight at the other turbo

    http://www.turbobygarrett.com/turbob...48_1_5_new.pdf
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  13. #63
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    As always...Good stuff Dzenno...Props

  14. #64
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    The best thing to do is take off the stock turbos and hold the discos up and eyeball how they would fit. Man Dzenno, who hooked you up with that technical drawling from Garrett? Anyone got $2700 lying around?

  15. #65
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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    The best thing to do is take off the stock turbos and hold the discos up and eyeball how they would fit. Man Dzenno, who hooked you up with that technical drawling from Garrett? Anyone got $2700 lying around?
    Little birdie? lol
    Click here to enlarge

  16. #66
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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Little birdie? lol
    Man, you are like that fat bald guy from Game of Thrones. Are you sure you're not a unick?

  17. #67
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    Click here to enlarge Originally Posted by Mat Morkin Click here to enlarge
    Man, you are like that fat bald guy from Game of Thrones. Are you sure you're not a unick?
    Don't tell me you watch that retarded show man?
    Click here to enlarge

  18. #68
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    My car will likely be at Ivo's for a turbo swap sometime soon, I wouldn't mind if anyone wanted to come in and take a look around and take some measurements while the turbo's are already off.

    It could save somebody the hassle of getting their car up on a lift removing parts and taking measurements.

  19. #69
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    I'm sure we can trust Dzenno to show up Click here to enlarge

  20. #70
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    I forgot the physical dimensions being small when looking at the compressor map...

  21. #71
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    Do you think it'll be worth it to get the GTX vs. GT? It's about $800 more...which is almost another GT
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  22. #72
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    Click here to enlarge Originally Posted by nafoo Click here to enlarge
    Do you think it'll be worth it to get the GTX vs. GT? It's about $800 more...which is almost another GT
    I think its actually about 600 more for the pair of GTX than for the GT...they'd be worth in terms of even earlier spool, higher efficiency, anti-surge machining, and just overall latest tech built into them
    Click here to enlarge

  23. #73
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    A comparison would be awesome. I'd be happy with Disco's and someone else can try the GTX's. With everything else being equal -FBO sense- we should dyno and graph them to see how they measure up to each other. If the results are minor in terms of spool availability and power potential, then price factor will play a role for a lot of people wanting to upgrade their turbos. If I remember correctly, the Disco potato power comes on hard past 4K RPM.

  24. #74
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    Click here to enlarge Originally Posted by orange Click here to enlarge
    If I remember correctly, the Disco potato power comes on hard past 4K RPM.
    Power/torque at a certain RPM depend highly on your engine compression, boost, ability of the turbo to hit certain boost, timing, etc...every motor is different...a 9:1 motor won't boost the same and make the same torque at the same RPM as a 10:1 or an 11:1 motor...same thing goes for different turbine and compressor A/R setups...
    Click here to enlarge

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    Some good news...measured the RB turbos (same size externally as stock obviously)...

    FRONT TURBO ASSEMBLY (longer): 10" long
    REAR TURBO ASSEMBLY (shorter): 8 1/8th" long
    EACH EXHAUST MANIFOLD flange: 10.2" from/to the most outer edge
    DEPTH: from the most outer point to the other side with the turbo sitting on the flat surface: ~8"

    All the GT28/GTX28 turbos are (196mm) 7.72" long from the compressor inlet on one side to the turbine housing flange. On paper, no fitment issues as total length of both stock turbos is ~18.1" and two GT(x)28 are 15.4"...
    Click here to enlarge

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