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Compound Turbo Thread

Posted by RWD4G63, Oct 31, 2012

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  1. rrussell

    rrussell Proven Member

    304
    42
    Joined Jan 7, 2008
    coeur d' alene, Idaho
    No issues at all. I'm running a Tial 44 mm gate to bypass to the FP turbo. If anything I have to run the 13g at a higher pressure then I would of thought before the 44mm gate opens. When the 44 mm gate opens at a lower pressure it won't bring in the LP turbo fast enough. So the 13g hits around 22 psi then the 44 mm gate opens and instant 32 psi or what ever i want for my max boost level. I kinda want to try a larger LP turbo do to to much low end torque. At 10 psi launch boost it hits 16 psi instantly as soon as i let off the brake and spins all four tires when running the Blizzaks. With the slicks it spins just a little but is hard on them running on the street.
     

    Street Build 2K  16

    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  2. Derail20T

    Derail20T Proven Member

    144
    20
    Joined Apr 21, 2013
    Sarnia, ON, Canada
    That's interesting. So are you figuring that the low pressure turbo is only putting out 10psi? How did you set up your wastegates? I am planning on controlling the primary turbo by a mbc sensing the boost pressure after the first stage and controlling the secondary with a mbc sensing boost at the manifold. I'm not sure if this is the best way to do it though.
     

    Street Build 427  1

    1991 Mitsubishi Galant VR-4
    319 whp · 288 lb/ft · Galant VR-4

    Drag Race Build 3K  11

    1991 Eagle Talon TSi AWD
    10.84 @ 124.02 · 1G DSM
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  3. rrussell

    rrussell Proven Member

    304
    42
    Joined Jan 7, 2008
    coeur d' alene, Idaho
    The LP turbo runs around 10psi with the HP running around 22 psi for a total of 32 psi manifold on pump mix with VP C16. I have ran it as high as 26/16psi
    with a total of 42 psi. on straight VP C16.
    I'm running a MBC with its signal at the LP turbo. The HP turbo is control by a second MBC with its signal at the manifold.
     

    Street Build 2K  16

    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  4. Derail20T

    Derail20T Proven Member

    144
    20
    Joined Apr 21, 2013
    Sarnia, ON, Canada
    I would have thought that it would be better to run the low pressure turbo at a higher pressure so that it would be more in its efficiency zone and produce a higher flow rate. With only 10 psi the FP red would lucky to flowing 50 lb/min. I'm definitely not an expert and don't have any real world compound turbo experience I'm just going by what I've read and by compressor maps. It is interesting that at 22 psi on the high pressure turbo that it spools the red so much quicker than when it was at a lower pressure. Can you tell at what point the lp turbo kicks in? After thinking about this I'm contemplating about just using springs in the wastegate for the high pressure turbo to control it's boost at 15 psi, I'd have a line from the hp turbo inlet go to the top of the wastegate and a line from the hp turbo go to the bottom of the wastegate. This way there would always be a 15 psi delta on the hp turbo... How has your performance been with your setup? Any track times or dyno results?
     

    Street Build 427  1

    1991 Mitsubishi Galant VR-4
    319 whp · 288 lb/ft · Galant VR-4

    Drag Race Build 3K  11

    1991 Eagle Talon TSi AWD
    10.84 @ 124.02 · 1G DSM
    Loading...
  5. rrussell

    rrussell Proven Member

    304
    42
    Joined Jan 7, 2008
    coeur d' alene, Idaho
    I thought the same thing until I got it up and running. I'm still not sure why it likes the HP turbo PR around 2.0? With the LP at 10psi it only flows
    54 lbs/min @ 7500 rpm. I'm also running stock 5 speed cams at this time.

    I can defiantly tell when the LP turbo kicks in because of its location sound wise. LOL But I can't tell when it kicks in by how the car pulls. It feels like a big CI engine with a ton of torque.

    I'm still in the process of sorting out WG lines and there arrangement. One thing you will find out very quickly is back pressure plays a much greater roll in blowing open the gates. Even though my engine delta p is always 1 to 2 psi in the good it still has a huge effect on the WG.

    No track or dyno times yet just been street tuning. But the car seems to be around a low 10 second car by my but dyno. Turbo compound system are very cool but they have their cons also. Its hard on the drive train and tranny.
     

    Street Build 2K  16

    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  6. 95GSXracer

    95GSXracer DSM Wiseman

    1,363
    97
    Joined Jul 25, 2002
    LaRue, Ohio
    Any of the turbos from 14b to 68hta will use the same turbine wheel and housing. A more efficient wheel will need less backpressure from the same turbine to do the same work though, something to think about. The main concern for small compressor size is it's relation to the big turbo's turbine, since it will determine how easily the big turbo gets spooled up. Too big a gap there and the setup will be lazy.

    Regarding the small turbine side being a restriction I think everyone knows my position on that by now. :) It contributes to total back pressure by multiplying big turbine back pressure by its expansion ratio, so it does play a major role. Both turbines do. One is a multiplier for the other. But with enough WG ahead of it, you won't choke it. And if you did, it would boost creep so you'd probably know it.

    On my current setup, which is a 3582HTA and 4505HTA, I went with the small .68 housing on the 35R. Back pressure is still only 1:1 with boost. This is a ~120 lb/min setup and I'm not one bit worried with that turbine size. With this setup I also tightened up the gap between small compressor and big turbine, and the thing spools so fast I can easily get away with a bigger housing on that small turbo. I will likely try this at some point, we'll see what it does to back pressure.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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    Operate, rrussell and Derail20T like this.
  7. Derail20T

    Derail20T Proven Member

    144
    20
    Joined Apr 21, 2013
    Sarnia, ON, Canada
    I am hoping that my big 60mm wastegate will prevent either turbo from being choked. As of now I am pretty much going to be going by trial and error to find out what works the best for my setup!
     

    Street Build 427  1

    1991 Mitsubishi Galant VR-4
    319 whp · 288 lb/ft · Galant VR-4

    Drag Race Build 3K  11

    1991 Eagle Talon TSi AWD
    10.84 @ 124.02 · 1G DSM
    Loading...
  8. RWD4G63

    RWD4G63 Proven Member

    245
    10
    Joined Dec 7, 2011
    Mattawan, Michigan
    Nice to see this thread is still alive and guys are putting together new setups!
     
  9. TajMan

    TajMan Proven Member

    70
    1
    Joined Jan 20, 2005
    Salt lake City, Utah
    I'm still building cars, still have my 6-bolt 2.3 stroker and I have a 2G AWD automatic trans.. to go in a '99 3000GT!

    I'm extremely leaning towards a compound setup. I have 272 cams, ported head, 1mm oversize exhaust valves, BC springs/retainers.

    I really like your setup rrussell,
    what do you think about a setup with a FP black for DSM as the large (LP) turbo? Will 14b or 13G be best for the small (HP) turbo? I love that it can get right up on a stock converter. 44mm as the primary wastegate (from manifold bypassing HP turbo into the LP inlet) is that big enough? I have a 38mm external wastegate, is that big enough as the 2ndary wastegate and will that keep a FP black from overboosting?

    I'm considering if I can do something like this and get it running at least on a stock converter.. or if I'll just be better off with a restalled converter.
     
    familyMAN likes this.
  10. 95GSXracer

    95GSXracer DSM Wiseman

    1,363
    97
    Joined Jul 25, 2002
    LaRue, Ohio
    A single 44 might be big enough on that setup. With turbos in the size range I run, it's not. However, on my current setup I put a single 44mm for each turbo BEFORE the small turbine, and this is working well. That cuts out the third 44mm I used to run (two for the small turbine, one for the large).

    The 38mm is probably enough for the black, unless you intend to run really low boost. No different than running it as a single.

    Compounds can definitely let you get away with a very tight converter. On the 2g car, I run a FP 71HTA and a 4205 HTA. With a converter that only stalls to 2200 at 0 psi and is fully coupled by 5500 rpm, it's a little slow to spool but still works. For converter stall you're always at the mercy of that small turbo.

    On the race car I run a 3582HTA (.68 T3) and 4505HTA (1.44 T4) with my usual converter for that car, and I can go from idle to 60+ psi and 6000 rpm in about 3 seconds. That's quick enough that I can tighten up the converter and get some efficiency and torque multiplication back...
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
    Loading...
  11. rrussell

    rrussell Proven Member

    304
    42
    Joined Jan 7, 2008
    coeur d' alene, Idaho
    I think the 14b on a stock converter would work. I tried a 16g on my setup and it didn't get up on the stock converter. I tried a FP Black on my car and the Red and the Black acted the same. I saw no difference in the two?
     

    Street Build 2K  16

    1991 Eagle Talon TSi AWD
    automatic · 1G DSM
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  12. imagine-02

    imagine-02 Proven Member

    155
    1
    Joined Apr 19, 2008
    Chippewa Falls, Wisconsin
    Curious to hear your thoughts on this setup. Forewarning, it isn't for a 4G63. Coming back to the DSM world to ask this because you guys seem to know more than others.
    2.8L 6 cylinder gas engine
    Shooting for 700hp

    Small Turbo (basically an HY35)
    CHRA: from 7 blade HX35
    Comp Housing: from 7 blade HX35
    Comp Wheel: from 7 blade HX35/HY35 (54/78)
    Turbine Wheel: from HE351/HY35 (58/65)
    Turbine Housing: T3 .63 AR
    External Wastegate: what size???

    Large Turbo (basically an HX40 w/ HX50/52 size wheels)
    CHRA: from regular HX40
    Comp Housing: machined HX40
    Comp Wheel: aftermarket billet 7 blade (67/89)
    Turbine Wheel: from H1E (67/76)
    Turbine Housing: T3 1.06 AR
    External Wastegate: what size???
     

    351  0

    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  13. 95GSXracer

    95GSXracer DSM Wiseman

    1,363
    97
    Joined Jul 25, 2002
    LaRue, Ohio
    With that displacement, power goal, and modern turbos, I'm not sure I'd do compounds. But that said, any gate will probably work for the big turbo, whatever you would use on it as a single. For the small turbo you're probably on the fence between 1 or 2 44s. I don't recommend anything bigger than a 44, they blow open too easily at the back pressures we tend to run.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
    Loading...
    imagine-02 likes this.
  14. imagine-02

    imagine-02 Proven Member

    155
    1
    Joined Apr 19, 2008
    Chippewa Falls, Wisconsin
    Thanks for the info.
    The compound setup is desired because I want to build boost at low RPM for tight and technical courses without needing to shift.
    Do you think the turbos are too close to the same size for a compound setup even with the compressor and turbine modifications? I basically tried making the HX35 as small as possible and the HX40 as big as possible.
     

    351  0

    1995 Eagle Talon TSi AWD
    manual · 2G DSM
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  15. camocorvette

    camocorvette Probationary Member

    5
    0
    Joined Aug 5, 2012
    Spanaway, Washington
    That is a great nugget of info! 7 years later!
     

    Street Build 323  3

    1995 Mitsubishi Eclipse GST
    300 whp · 315 lb/ft · 2G DSM
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  16. 95GSXracer

    95GSXracer DSM Wiseman

    1,363
    97
    Joined Jul 25, 2002
    LaRue, Ohio
    Awesome. And as a bonus when I eventually forget all this sh** I'll be able to find it somewhere on the internet. :D

    My own setup is still going strong. The 4505 is now a 4580HTZ but otherwise it's pretty much unchanged in the turbo department. I don't get to make many passes these days, and a rod failure at the shootout this year isn't helping, but it's on the brink of finally being fast, I can feel it. The magic is the in the torque converter vs gear ratio and I've just about got my head around it, just need to throw large piles of money at it now to test this theory.
     

    Drag Race Build 2K  5

    1992 Eagle Talon TSi
    7.961 @ 171.10 · 1G DSM
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