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Compound Turbo Thread

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That's good to hear. Do you have any issues with such a small turbine housing? What type of wastegate setup are you running? If I could get away with running the 14b and just using a 60 mm external gate it would be less work fabbing the piping since it's already setup that way...

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.
 
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.
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.
 
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.
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.
 
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.
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?
 
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?

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.
 
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.
 
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.
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!
 
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.
 
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...
 
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.
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?
 
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???
 
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.
 
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.
 
Engine displacement times small turbo PR is roughly what the big turbo will feel like it is attached to. Also, turbine drive pressure of the big turbo will be multiplied by the turbine expansion ratio of the small turbine, so you naturally want both as low as possible. If you run a restrictive exhaust it gets even worse. Exhaust back pressure x big turbine expansion ratio x small turbine expansion ratio will equal total turbine drive pressure at the exhaust manifold. It adds up fast!
That is a great nugget of info! 7 years later!
 
Awesome. And as a bonus when I eventually forget all this shit 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.
 
Bumping this thread. Anyone have updated on how their compound setups are doing? Anyone building a new setup? One of my regrets is not getting my setup together. I know new turbo tech has made this a less attractive option for a lot of people, but man is it cool!
 
I think the best way to reconcile new turbo tech with compound turbos is to combined them, but I'm sure that won't surprise anyone. :D I regularly dream of a new compound setup for the 2g using all XR turbos. It could happen. The prospect of keeping back pressure below 1:1 with a quick spooling compound setup is better now that it ever has been.
 
I think the best way to reconcile new turbo tech with compound turbos is to combined them, but I'm sure that won't surprise anyone. :D I regularly dream of a new compound setup for the 2g using all XR turbos. It could happen. The prospect of keeping back pressure below 1:1 with a quick spooling compound setup is better now that it ever has been.

YES. Not to mention all these new turbos are smaller and lighter, making packaging easier and a compound setup less cumbersome in the weight department. It would also be interesting to play with these new higher flowing internal gates everyone is making. If you could get it to work, an internally gated small turbo would make for a super slick setup!
 
An internal gate could work on the large turbo, but they're most likely to be found on the small turbo. If it flows well enough suspect it would still need an external WG, though only one instead of two perhaps. One possible side benefit is that if you max out the small turbo during spool, it's likely that the internal WG will blow open (or it could be set up that way), which is a good thing for spool. Ideally the boost control system would do this already, but it's one more way to make an internal gate useful.
 
We have been toying with the idea of moving away from our C53A chassis and putting all of the parts into a rear wheel drive chassis. One big thing is we are heavily considering going to compounds to keep it simple and maybe keep away from nitrous and tricky converter stuff.

we currently are running a T3 10cm 14b setup. I feel that would be a great base to start and having a cast manifold for the primary turbo would certainly help with strength for weight. And if and when we go that way, any of the TD05 turbos will be a great option if we outgrown the 14b. Not looking for anything crazy, just a consistent and reliable setup. One that does not have to be driven so hard and is fighting a 30 year old FWD chassis that won’t go straight with big tires and big power. Little tires and little power the car is drama free.
 
When I originally spec out the compound setup on the 2g for the previous owner I also selected a stock turbo footprint for the high pressure unit. Lots of options from 14b, to 68hta, to the larger bolt on stuff. Same turbine housing makes it easy, just need to leave room for a variety of compressor housings. We run it with a 68hta now, so there's room to go in both directions. I've yet to change the turbo after all these years, but it's nice to know we can.
 
We have been toying with the idea of moving away from our C53A chassis and putting all of the parts into a rear wheel drive chassis. One big thing is we are heavily considering going to compounds to keep it simple and maybe keep away from nitrous and tricky converter stuff.

we currently are running a T3 10cm 14b setup. I feel that would be a great base to start and having a cast manifold for the primary turbo would certainly help with strength for weight. And if and when we go that way, any of the TD05 turbos will be a great option if we outgrown the 14b. Not looking for anything crazy, just a consistent and reliable setup. One that does not have to be driven so hard and is fighting a 30 year old FWD chassis that won’t go straight with big tires and big power. Little tires and little power the car is drama free.

Yeah it is hard to justify compounds on a chassis that is greatly limited by it's drive configuration and transmission.
 
Bumping. I have always wanted to try a compound setup not sure it's worth it but recently my car was completely under water due to a flood so the it has to come apart anyways. I have a 68hta and a hx55 laying around does anyone think this would be a good combo. I have been eyeing up the 6466gen2 also. Like I said not sure it's worth the headache. Hx55 has a 25cn t6 turbine housing. Thanks
 
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