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Compound Turbo Thread

Posted by RWD4G63, Oct 31, 2012

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  1. imagine-02

    imagine-02 Proven Member

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    Chippewa Falls, Wisconsin
    Well I'm gonna be running an HX30 with a 6cm single scroll housing and an hx40 with a 18cm^2 housing @ around 30-35 psi. I have that stuff right now, so I'm running it, We'll see how it performs.

    Edit:
    -Meant 30-35 psi overall, not just 30-35 psi on the hx40.
    -Brought my turbos home and realized the housing on my hx40 is 17cm^2 (T4).
     
    Last edited: Nov 8, 2012

    350  0

    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  2. caged

    caged Proven Member

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    Joined Jan 2, 2009
    Brisbane, Australia
    So you want to run 30-35psi on the hx40? what are you running for total boost then?
     
  3. viperlp01

    viperlp01 Proven Member

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    Joined Oct 9, 2006
    Kalamazoo, Michigan
    Whats crazy is that I ran 18psi on the large turbo and 18psi on the small and made enough power to run mid/high 9s with a extremely conservative tune. Running 42psi on a 67mm PTE vs 40psi on a BW75mm seems silly to even compare the at those boost levels. Is there any good reads on back pressure actually relating directly to running out of compressor wheel.

    From what I understand about compounds is back pressure is going to be there. Its amazing to see you at a 1:1 ratio but to say for sure up around 8-9k that back pressure up there on a 75mm compressor is the reason you run out of compressor is crazy to me. You should be laying down well over 1000hp on a charger that large running on the edge of the compressor map. Considering the 6766 makes about 950ish up in your boost level the 75mm should make 1100 pretty easily(LOL I know right!)
     

    2K  0

    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  4. 95GSXracer

    95GSXracer DSM Wiseman

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    LaRue, Ohio
    36 psi sounds about right to runs 9s in a typical auto car, assuming your boost pressures are additive. The S475 is running at 15-17 psi when I run 8s with it, and low 90s lbs/min airflow. Look at the map to see where that is. I'm also moving the same airflow on the 6766. No surprise there.

    Running the compressor off the map will raise back pressure. This is a known fact, but don't take my word for it! Or a random thread where people don't know what they're talking about. Hook up an appropriate sensor and run a compressor off the map. :) Watch where the airflow curve flat lines, then look at back pressure vs rpm.

    The 475 can do ~105 lbs/min, but not at 2:1 PR. The 6766 can do mid 90s airflow, and I'm running that at nearly 4:1 where it can do that. I don't know how else to explain this. The maps make it obvious.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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  5. RWD4G63

    RWD4G63 Proven Member

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    Mattawan, Michigan
    My question is this: How do you know you're running 90lb/min from the 475 when you have another compressor stage? Total flow is not precisely indicative of what the primary is flowing. And backpressure at 9000rpm could be due to that tiny little 50 trim haha. Have you tried turning the boost up on the 475? Sorry if it sounds like I'm trying to grill you man, I'm just curious because it seems like you have a pretty unique situation (at least in the dsm world) and I'm trying to wrap my head around it.
     
  6. 95GSXracer

    95GSXracer DSM Wiseman

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    LaRue, Ohio
    I'm on my phone (at mir for world cup finals) so this will be brief. Mass flow at all points in the compound turbo system must be the same, there's no way around that. Also, the big turbo's inlet is at standard atmospheric conditions so it can't move more than it would as a single turbo. I did turn up the boost on the 475 and it resulted in no increase in trap speed, from total boost of 45 to 50 psi. I traps nearly the same down at 40-42 psi for that matter.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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  7. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    Related to Paul's set up... He made 600 hp on a 60-1. I forgot airflow numbers but it seems like the compound setup indirect or directly makes the compressor on the big more efficient.

    Thanks for sharing information Kevin!
     

    2K  0

    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  8. bastarddsm

    bastarddsm Proven Member

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    Mendota, Illinois
    100% Take this logic an apply it to the little turbo, and you can see oh the little 50trim can flow 90lbs/min!
     

    Showcar Build 5K  1

    1991 Eagle Talon N/T
    9.805 @ 144.00 · 1G DSM
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  9. Devilsfutbol17

    Devilsfutbol17 Proven Member

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    Bellingham, Washington
    This may be a really stupid question, but would a compound setup work the same if the exhaust went through the larger turbo first? The compressor outlet and inlet still being the same, the larger feeding the smaller turbo.

    If the larger turbo's wastegate is set to open at a higher pressure than the smaller one, then the smaller turbo would see all of the exhaust gas until it reaches it's own wastegate pressure. The smaller wastegate would be on the crossover pipe, so the larger turbo would still see all of the exhaust until it's own wastegate opened.

    Sorry if this is a stupid idea, I'm still trying to wrap my brain around the pressure ratios and how this works exactly. I was just curious because fitment with two decent size turbos(HX52 & HX35) might be better when space is very limited(galant). Thanks
     

    568  3

    1991 Mitsubishi Galant VR-4
    manual · Galant VR-4
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  10. bastarddsm

    bastarddsm Proven Member

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    Doubtful. It would 'work' but it would be laggy, defeating the point. The big turbo would extract the energy out of the exhaust not leaving much for the lil guy to have, delaying it's spool.
     

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    1991 Eagle Talon N/T
    9.805 @ 144.00 · 1G DSM
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  11. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    I must say that the turbo's generally spool almost exactly the same as if it was by itself. We were planning on running twin scroll into a large one and then into a small.
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  12. Devilsfutbol17

    Devilsfutbol17 Proven Member

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    Joined Jul 27, 2007
    Bellingham, Washington
    That's exactly what I was brain storming. In the GVR4 it may fit better to have a larger turbo more to the passenger side with maybe a top mount TS manifold, then have that exhaust flow into another decent sized turbo like an HX35 in an BEP housing. I have and HX35 on my galant now and there is not much extra space between the head and scirocco radiator.
     

    568  3

    1991 Mitsubishi Galant VR-4
    manual · Galant VR-4
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  13. 95GSXracer

    95GSXracer DSM Wiseman

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    LaRue, Ohio
    I don't mind sharing info at all, I'm happy to help. I think I've shared everything I've ever found pushing this setup hard on the track for 3 seasons at one point or another on various forums.

    The big turbo is bound to slow down the spool of the small turbo with the turbines in reverse order, the question is how much. It might be tolerable, since the big turbo won't be taking much from the exhaust at low flow, it just free wheels. The biggest problem that comes to mind is what to do with the exhaust discharge of the big turbo. It's a 5" diameter pipe in my case. It would take a lot of wastegate on the small turbo to vent it all.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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  14. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    The outlet of the hx52 is normally a 4in outlet. I cut it off and welded a 3.5in onto it. But the transition from the 3in outlet of the hx35 into a T4 flange is almost perfect. Any bigger would be a pain to make.
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  15. 95GSXracer

    95GSXracer DSM Wiseman

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    Joined Jul 25, 2002
    LaRue, Ohio
    On my setup the 2.5 inch discharge of the 50 trim has to go to a T6 flange. I ran one of the WG outlets parallel to it to help fill the big flange, but it still came out like sh**. :) The next setup I will probably make use of the nice swedged adapters SPD Exhaust sells.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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  16. ceedawg

    ceedawg Supporting Member

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    laurelton, New York
    Not to offend anybody and with all respct due,I just want to learn. :thumb: And to each his own.
    However,due to the complexity of this setup,weight,expense is there a real advantage to this setup over just having a conventional big turbo setup and perhaps spraying the turbo just to get it up on boost? I get questioned about my dual wastegate Twinscroll manifold and TwinScroll turbo setup concerning weight and expense but I understand it's effectiveness vs a conventional setup so I really want to understand the compound setup and its rational. Looks mighty complex,heavy and expensive especially for a street setup especially compared to mines.Thanks guys!
     
    ceedawg

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  17. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    Because it is freaking bad ass!! In classes that require a no nitrous rule... Spool time and area under the curve..
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  18. 95GSXracer

    95GSXracer DSM Wiseman

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    Joined Jul 25, 2002
    LaRue, Ohio
    For me, it's about being able to spool a big turbo on the auto trans without having to rely on nitrous. The nitrous setup I ran this year is much better than previous years, so I hate it a little less, but I still intend to go back to compound turbo. I have several new ideas I need to test. The best way to learn about something like this is to build a setup and play with it. Even better, race with it. :)

    It does add weight and complexity, but it weighs no more than a big single with nitrous (I've weighed the car with both setups, it's within 5 lbs, though weight distribution is different), and the complexity never really turned into a problem. In 3 seasons with my setup I only had one issue and it was a split coupler at the 2011 Shootout, which can happen on any turbo system. Both turbos are still running strong. In fact, it's the 50 trim from this setup that just ran 10s in my mightymax. There is a little more time required to remove and install the setup, but mine was designed to go together and come apart in two pieces, it's quick and easy.

    I really haven't found any downsides, except for the relatively poor 60 foots on my first rev, which will be addressed when I do the next version. I'm expecting 60 foots in the 1.25 range. Not as good as my best of 1.20 on the single turbo (and I know it can go into the teens), but I've run low 8s in that range. There's also the chance that I can 60 foot just as well as a single on nitrous if I get the balance right with the next two turbos. I won't know about that until I try it though.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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  19. ceedawg

    ceedawg Supporting Member

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    laurelton, New York
    LOL Kool:thumb: Can you post a dyno on here I just want to see the curve This I have to see! I have to say this setup is different and quite interesting.

    Great answer! Seems like this setup would be a good deal for those running auto trannies then.

    I definitely would like to see a dyno of one of these setups.
     
    Last edited: Nov 6, 2012
    ceedawg

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    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  20. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    We are getting a dyno in the shop in 6 weeks so as soon as I get this engine built it will be on the rollers.
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  21. RWD4G63

    RWD4G63 Proven Member

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    Joined Dec 7, 2011
    Mattawan, Michigan
    A little update for you guys.

    56F84665-4727-4DC3-9D63-4010E35F6523-3666-0000050CBEA9C5C5.jpg
     
  22. bastarddsm

    bastarddsm Proven Member

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    Mendota, Illinois
    I'd see if your can get some interstage cooling in there if I were you.
     

    Showcar Build 5K  1

    1991 Eagle Talon N/T
    9.805 @ 144.00 · 1G DSM
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  23. viperlp01

    viperlp01 Proven Member

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    Kalamazoo, Michigan
    ANDY!!! That stuff looks dope!!! You bringing those pieces to get welded when Joey brings his Aluminum stuff? I like it man!
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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  24. RWD4G63

    RWD4G63 Proven Member

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    Joined Dec 7, 2011
    Mattawan, Michigan
    Haha thanks! I may do some meth injection between stages, but for now it will only be aftercooling.

    Nah man I wish! I need to get my trans in before I can final weld anything. Don't want it to tweek something that I can't fix :)
     
  25. viperlp01

    viperlp01 Proven Member

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    Hell ya man. That sounds sick!
     

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    1997 Eagle Talon TSi AWD
    9.737 @ 140.310 · 2G DSM
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