Compound turbo exhaust routing

Posted by viperlp01, Jan 13, 2012
Turbo System Tech - 4G63 turbos, Intercooling, Boost Control, Wastegates, etc.

  1. viperlp01

    viperlp01 Supporting Vendor

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    Hey guys, So I have been talking with Paul and another compound guy about running twin scroll into the big first and then into the small. I plan on controlling with twin 38s on the T.S and a single 44 for the small.

    I bought a HX52 billet 7 blade in a T5 twin scroll and a H1C with plans for a BEP T3 .70ar exhaust housing. I will still route the compressor with the big feeding the small. I know Paul had back pressure issues with his set up but was it because there wasn't enough gate, exhaust size, turbine size, ect ect....

    I know that Pauls 60-1 still had the same spool times by itself as when it was in the compound set up. The exhaust/heat energy argument is hard to believe with that experiment. With that being said regardless of where the turbos are they should spool the same. The biggest thing is utilizing the twin scroll and the possibility of me not having the sell my 2 38mms and buying a 44mm and a 60mm for gating.

    I guess it really comes down to where the turbos are going to be located in the engine compartment and ease of fabrication/install/removal. I am all for making things simple(LOL ya right) as I can for working on my car.

    Thanks for the input.
    John
    #1
  2. caged

    caged Proven Member

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    What boost are you planing to run? (eg total of 40psi with 10psi through the lager turbo). Iv almost finished my compound setup but have no clue on the best way to setup the boost on each turbo.
    Im running a custom twin scroll manifold into an Evo 4 twin scroll tdo5 turbo with a single 60mm gate (I modified it for 10mm more of valve travel) with a divider right up to the valve. Then iv got an HX40 pro with an 18.5cm rear and a single 45mm gate.
    #2
  3. gixrman

    gixrman Freelancer

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    I'm collecting parts for my compound setup and my question is about the proper WG size for the feed off of the primary turbo. Can you go to big or too small? I'm going with a Holset HX20 to a H1E. Going to be building my own manifold this summer hopefully.
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  4. LandSpeed-DSM

    LandSpeed-DSM Proven Member

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    It depends on how low you want to be able to run the PRs on both turbos.

    On my Honda I have a 60mm off the manifold before the small turbine and a 44mm between the small turbine and the big turbine in the hopes that I would be able to run single digit boost in the manifold if desired.
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  5. JusMX141

    JusMX141 Moderator

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    Perhaps, but he also netted a 75 lb/min log using a compressor that most guys struggle to get past 58 lb/min with. Applying those results to a H1C/HX52 compound, you could expect 110-115 lb/min of airflow without ever spooling later than what a single HX52 would.

    Paul's former 16G/60-1 compound setup is now a 16G/HX40 after the new owner experienced some reliability issues with the Turbonetics 60-1. The HX40 is capable of 70 lb/min by itself, so this revised setup has potential to make 85-90 lb/min while reaching full boost in the 4300-4500 range, and generating enough torque to do some serious transmission damage. LOL

    Hopefully we'll get some airflow logs from that combination when the weather improves!
    #5
  6. bsbllfit7

    bsbllfit7 Proven Member

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    Ha just a random question but what kind of transmission would you throw at this thing to last a semi decent life. Im guessing a dog box because i don't see how a standard rebuild with even slightly better parts could hold up!
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  7. viperlp01

    viperlp01 Supporting Vendor

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    I'm hoping to reach full spool before 3500 and turn the boost up as the year goes on. I am building the car for 9s(cage, D.S. hoop, ect.) The surface area of 2x 38mm Tials is more than one 60mm. The car is getting an auto trans that I am going to build. 100lb/min would be amazing but I wouldn't be reaching that with this engine this year.

    Regarding wastegates you can never go too big. A lot of people with compounds under estimate and have issues because they don't have enough gate.
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  8. caged

    caged Proven Member

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    I was under the impression that with a compound set up you wouldn't flow any more than what the large turbo would flow being a single??

    1 60mm will flow more than 2 38mm gates.
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  9. JusMX141

    JusMX141 Moderator

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    The smaller turbo is "compounding" by futher-compressing the airflow made by the larger turbo, hence the name. ;)
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  10. RWD4G63

    RWD4G63 Supporting Vendor

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    I believe Paul's 60-1 retained it's spool because the 16G was already shoving boosted exhaust gas down it's throat.

    However, since the HX52 won't really have any backpressure and the H1C is pretty quick spooling turbo even on a two liter, I don't think you'll have a problem reaching your goals.

    The real question is if you even need to route your dual 38's back into the exhaust. The H1C is obviously going to spool first, so you're not going to want any of the gates open. Once the target boost is reached and the 52 comes online, do you really want the gates to go back into the exhaust, only to come out of the 44 again? Since all the wastegates are basically going to come online at the same time, it seems much more simple to have all wastegates go to atmosphere. You'd have to test it out, but you might not need the 44 at all. This would be the advantage of running the 52 first. This also means you only need one boost controller.

    To me it seems like a better setup.
    Last edited: Jan 15, 2012
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  11. gixrman

    gixrman Freelancer

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    Thanks TiAL V60 it is.
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  12. turbotalon1g

    turbotalon1g Proven Member

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    Sounds like there will be a lot of compound turbo DSMs popping up in 2012!
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  13. caged

    caged Proven Member

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    Heres mine while I was building it if anyone is interested.

    Attached Files:

    #13
  14. FLASH1970

    FLASH1970 Proven Member

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    I know you already started on your manifold but I was thinking of maybe using an EVO9 turbo because it's backwards. Well, backwards to us. The EVO9 turbo would be off towards the driver's side, then the Holset would be more towards the passenger side. It'd be more of a straight shot for the exhaust to pass through both hotsides and might put the downpipe somewhere near the location it usually runs on our cars. Anyway you look at it, it'll be a tight fit.
    #14
  15. caged

    caged Proven Member

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    I thought I would revive this thread rather than fill up viperlp01's build Journal. This a quote from the kevin in the other thread that I copied to here---

    I Am redoing my setup after I lifted my head and had to pull it down anyway and going to transbraked auto. Iv stepped up my small turbo's rear housing from a 9cm evo 4 to a 10.5cm Evo 6 rear housing in hope of freeing up some back pressure at big rpm with my new kelford 280's. Iv also stepped the big turbo up to an Hx55 66mm(ish) with a 22cm rear housing (will run it with this housing and see how it goes). I'm not really keen to re invent the wheel as such but I am keen to look at running the exhaust from the small turbo into one scroll and the other scroll getting fed from the bypass wastegate. I would only have a wastegate off the scroll being feed from the turbo to try and stop any back pressure onto my small turbo's turbine. If I need to add a second wastegate to the other scroll then so be it but im not certain I will need to with such a large turbine wheel and housing. Do you think this will work? or not as great because my small turbo is reasonably small? Anyones input is apreciated.:thumb:
    #15
  16. 95GSXracer

    95GSXracer DSM Wiseman

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    That's probably how I would start with it, but I would put the other WG flange on just in case and block it off until you need it. ;) The bigger big turbine housing will help. but I can tell you though that even with a 96mm turbine and T6 1.32 housing, I still had boost creep on my S475. Seems crazy, but once you start to move some air it can still happen apparently. I ran the gate on the small turbo's gate outlet (still merged before the T6, not separated) thinking that most of the air I was moving would be bypassing the small turbine, but that also depends on how much of the small compressor you are using. It's also possible that 1 44mm gate was too small and where I put it wouldn't have mattered anyway. Best bet is probably to try to determine percentage of wastegating on the small turbo and then put the big gate wherever there is more flow. The WG outlet will also be hotter than the turbine outlet, so that will play a role as well. If that doesn't control it add another to the flange you installed in anticipation of this need. :)
    #16
  17. caged

    caged Proven Member

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    Yeah thats probably a good idea adding the flange for the extra gate now. I was only worried about the 22cm housing because im basically running a similar compressor wheel and cover as viperlp0's Hx52 but his turbine wheel exducer is smaller with a similar sized inducer and a smaller 19cm housing.
    I am going to try take my small wastegate feed off the manifold or housing this time as I was using the factory internal wastegate holes ported out to around 30mm each with a divider up to a 60mm wastegate that fed just before the big turbo. I dont think that will be anywhere near enough gate on this set up.

    How would I work out how much % of exhaust will flow through the turbine on a 16g tdo5hr @1.8-2 pressure ratio? Im thinking I will need to put the wastegate on the scroll that is fed from the bypass wastegate because that will flow way more than the tdo5 turbine.
    #17
  18. 95GSXracer

    95GSXracer DSM Wiseman

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    I agree.

    I could probably fumble through it and get an estimate, but I'm no expert, especially without a turbine map and in a compound situation. But if you keep the PR that low and keep from going off the right of the map (total airflow divided by big turbo PR is close enough), it's probably safe to say the majority will go out the wastegate. It's when you max out the compressor that the shift should occur, if it's going to. I'll bet you can tell by back pressure. As long as it's not much over 1:1 I would expect the most flow out the wastegate. In my case it didn't work, but I was also only venting one of two wastegates.
    #18

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