My compound turbo set-up

[99gst_racer]

Probably because not everyone has heard of it. Lol. I for one haven't heard of the compound setup until, well, this thread. Learn something new everyday I guess. Really hope it works out well for ya. I for one though want bolt-on parts cause the fab stuff can be a pain in the ass or trying to replace something that broke. Want everything as easy as I can get these days. Don't wanna spend 10 years trying to figure out the best tune for my ride. But hoping it won't be difficult for ya and hoping to see good numbers. I'd like to see vids of this thing running though.

I think it's funny though that you're talking about noise levels yet you're running the side exit exhaust. Lol. That's what I wanna do though but with a muffler on it. You doing anything for the rear bumper? Looking into the best ideas of not having the naked gaping hole in the back for where the exhaust is suppose to be. Anyway, good luck on this thing.

Tuning the car shouldn't be too bad. As long as the wastegates keep their respective turbos in check, tuning will be a breeze. Simply put, it's only more air and more fuel - sooner.

I have a Race Ready electric cut-out for that side exit exhaust. Both wastegates recirculate, so it's definitely not for them. I figure that if I ever want to be loud, I can be at the push of a button. Otherwise, I can drive relatively quietly also having a full exhaust.

Insane to say the least. 1600cc's right?

1200's for now. But I wouldn't be surprised if I ended up with a set of 1600's very soon.

I think it is amazing that no one has tried this yet

Me too! It will begin to get much more popular with the aftermarket performance guys in the years to come. It's already growing popularity with the OE group. The new Ford 6.4L hosts a compound turbo set-up and IIRC, Benz is introducing a compound turbo'd 4-cyl diesel car pretty soon.

Did you make it to the company meet?

I was there, but my car wasn't. There was just too much to get done and not enough time. Ohh well; at least it will be done in about a week anyway.

 

[94awdcoupe]

I think this setup fails in design. the first turbo is simply in the way of making power. The compressor side is fine. Its the exhaust side that will not work like you hope. The 16g will overspin and die very quickly, the second turbo will not recieve enough exhaust energy through that small wastegate Compound turbo setups work well on diesels where they should stay. Diesels tolerate very high boost pressures because the engine itself runs off autoignition point of fuel/air charge.

The AMS design staged twin turbo was brilliant by design compared to this setup. They only had a few days to get car ready for event . they feared they wouldnt have enough time to work out bugs so they had to abandon the project.

I cant find pictures of that but a quick search found this new 1.9tdi with staged chargers
Fiat Powertrain: 1.9 JTD Twin Stage Turbo with 100 hp/liter

I will respond to my own observation as I have done a bit of research on the subject.
My first sentence stands. There are only two paths for the exhaust heat to reach the second turbo. Through the 7cm/5h wheel and through the 44mm wastegate. The wastegate hole itself is going to flow very poorly as gases do not make 90 degree turns well. You are in attempting to make 600hp through those two small openings. The result will be the small turbo getting too much ex heat and the large turbo not getting enough.

Here are some pictures of how important the design of setup is. This is the supra setup that boost logic sells.
www.neons.org • View topic - Compound Turbo Setup? Crazy power... lots of low-end Torque

My comment this should stay with diesels should be discarded. It was uneducated one.

The AMS kit was a staged turbo kit. while brilliant in design is not in same category as compound turbo. Not sure which route I would take if I were to twin turbo. The jury is still out on that.

 

[RipperXX]

I wonder how it would effect the setup to put a larger exhaust housing on the 16g and a little smaller one on the T-61?

 

[dsm-onster]

A td05h 7cm^2 16g and a 1.75" pipe bypassing it is plenty of flow to the t4 turbine of the 60-1. Assuming backpressure in the 40-50psi range a 1.75" pipe flows PLENTY of mass for the the second turbine to extact plenty of work. 94awdcoupe, I know you already know the equation per our PMs. But for everyone else: Turbine work = Specific heat X Massflow X (temp in - temp out). A derivative of the Euler Turbomachinery Equation that applies to automotive turbochargers.

Those wastegates pictured in that neon forum link are chosen because of the volume of the 6cylinder supra motor and the much higher horsepower potential for which the system is intended. Paul is running a 60-1 compressor wheel. Not a t61.

 

[94awdcoupe]

I am basing my observation on real world experience. All his exhaust is going through 5h wheel/7cm housing and 44mm hole off two runners. I built a 25g setup that was exhausting through huge 6h wheel/ 8cm housing and my wastegate was fed through same 44mm hole as this setup. What I thought was a great design proved to have marginal flow through wastegate.

Heat is what powers a turbine. If he wants to make 550whp he has to move 55lb per minute of air through the 60-1. The exhaust heat required to power that second turbine is what is in question here.

I hope that this setup works. I think its awesome idea. And I praise the efforts of anyone who takes the time to bring new ideas in to play.

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[99gst_racer]

That BoostLogic kit is dead sexy, but I'm not able to fit that size package in the engine bay of my 2G. I specifically choose some of my components due to price and overall size and compactness. If it proves to work well, a more appropriate manifold and turbo set-up may be in order.

I'll have some more pictures and updates at the end of this week.

Here's a shot of both compressors on the car:

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[99gst_racer]

I am basing my observation on real world experience. All his exhaust is going through 5h wheel/7cm housing and 44mm hole off two runners. I built a 25g setup that was exhausting through huge 6h wheel/ 8cm housing and my wastegate was fed through same 44mm hole as this setup. What I thought was a great design proved to have marginal flow through wastegate.

What was the issue with the set-up on the left of your picture? What problems were you having with it?

Heat is what powers a turbine. If he wants to make 550whp he has to move 55lb per minute of air through the 60-1. The exhaust heat required to power that second turbine is what is in question here.

That's incorrect. It's a common misconception that the larger turbo needs to flow the total output of the entire system, or that the larger turbo needs to be gated to match the output pressure that you want to see. Both are incorrect. The 60-1 only needs to flow what I have it set to (just under one atmospheric bar) and will be gated so. The smaller turbo is doing most of the work in a compound set-up, and it receives the engine's exhaust heat quickly and efficiently, so I don't forsee any issues with it.

 

[wishihadatalon]

I still say that if it works like it should, Paul is going to be picking up a whole lot of drivetrain parts off of the nice long straight road by his house

 

[94awdcoupe]

What was the issue with the set-up on the left of your picture? What problems were you having with it?


That's incorrect. It's a common misconception that the larger turbo needs to flow the total output of the entire system, or that the larger turbo needs to be gated to match the output pressure that you want to see. Both are incorrect. The 60-1 only needs to flow what I have it set to (just under one atmospheric bar) and will be gated so. The smaller turbo is doing most of the work in a compound set-up, and it receives the engine's exhaust heat quickly and efficiently, so I don't forsee any issues with it.

The issue I was having was wastegate did not flow enough. Had boost crept from 25-29psi. had a heck of a time fixing problem by porting waste tube entrance once welded on.

I dont understand how the second turbo at 1 bar will flow 55lb per minute? If you want to make 550whp that is the amount of air you will need..All the air enters system through big turbo. From what you are saying the first turbo at 1bar will move 30lbs and the second will multiply the weight to 55lbs?

 

[99gst_racer]

I still say that if it works like it should, Paul is going to be picking up a whole lot of drivetrain parts off of the nice long straight road by his house

I sure hope not! I'd like to think that my clutch will be a nice fuse that won't allow for complete drivetrain destruction. We'll soon find out.

That reminds me - I still need to get those DSS rear axles in too.

The issue I was having was wastegate did not flow enough. Had boost crept from 25-29psi. had a heck of a time fixing problem by porting waste tube entrance once welded on.

Sounds like something wasn't working right. I don't think it was a design flaw.
Years ago, I had a ported 2G manifold and I had the #1 runner flanged for a 38mm wastegate. I could run 14 psi on a 50-trim with no creep issues at all. Pic of my manifold

I dont understand how the second turbo at 1 bar will flow 55lb per minute? If you want to make 550whp that is the amount of air you will need..All the air enters system through big turbo. From what you are saying the first turbo at 1bar will move 30lbs and the second will magically multiply the weight to 55lbs?

The second turbo (60-1) won't be flowing that kind of airflow. Like I said, the smaller turbo (B16G) is the primary turbo in a compound set-up. It does the majority of the work. With the increased inlet pressure, it's goal will be to flow that kind of airflow.

 

[94awdcoupe]

Sounds like something wasn't working right. I don't think it was a design flaw.
Years ago, I had a ported 2G manifold and I had the #1 runner flanged for a 38mm wastegate. I could run 14 psi on a 50-trim with no creep issues at all. Pic of my manifold


The second turbo (60-1) won't be flowing that kind of airflow. Like I said, the smaller turbo (B16G) is the primary turbo in a compound set-up. It does the majority of the work. With the increased inlet pressure, it's goal will be to flow that kind of airflow.

The port location is very important and it was a design flaw. gasses flow like water at high velocity. Gasses flow out the no.1 runner port very well. Try picturing this. Take a water hose on full blast and shoot into the number one runner. you will see alot of water coming out that wastegate hole. Now try shooting the water through the manifold with the hole in the spot you have it at. not much water will come out. Most will just pass by because water has mass and the majority will be following the wall from centrifugal force. Your 44mm gate has a lot bigger job than just controlling boost of first turbo. The first turbo will be moving way more air than it can normally by itself. The wastegate capacity is 200% of what it normally would be at.

If the smaller turbo is doing the majority of the work and moving 55lbs air then that 55lbs of air has to come from inlet on big turbo. you can have 55lbs of air inside ten cubic foot box, and you can have 55lbs of air inside a one cubic foot box. thats what turbos do. they compress air into smaller boxes. The big turbo definitely has to flow the air needed to make the desired HP level.

The correct answer is the box in front of big turbo (air inlet form first turbo) is at lower than atmospheric pressure. It therefore does not have to work as hard to move 55 pounds of air.

 

[dsm-onster]

It's good to see this project coming to completion. So many questions. . .

 

[99gst_racer]

The port location is very important and it was a design flaw. gasses flow like water at high velocity. Gasses flow out the no.1 runner port very well. Try picturing this. Take a water hose on full blast and shoot into the number one runner. you will see alot of water coming out that wastegate hole. Now try shooting the water through the manifold with the hole in the spot you have it at. not much water will come out. Most will just pass by because water has mass and the majority will be following the wall from centrifugal force.

Pressurized liquid/gas will take the path of least resistance. In the case of my set-up, the wastegate poses lesser resistance than the turbine section of the turbo. Nevertheless, that doesn't explain why you feel your turbo set-up didn't work well when gated off of the #1 runner and mine was just fine.

If the smaller turbo is doing the majority of the work and moving 55lbs air then that 55lbs of air has to come from inlet on big turbo.

So, you're saying that the only way to get 55 lbs/min of of the smaller turbo is by forcing 55 lbs/min into it? Don't you see that that doesn't make any sense? Knowing that pressure ratios multiply, one should be able to imagine that is a pressure charge is entering a compressor, a higher pressure charge will exit.

you can have 55lbs of air inside ten cubic foot box, and you can have 55lbs of air inside a one cubic foot box. thats what turbos do. they compress air into smaller boxes.

It's called "volume".

The big turbo definitely has to flow the air needed to make the desired HP level. The correct answer is the box in front of big turbo (air inlet form first turbo) is at lower than atmospheric pressure. It therefore does not have to work as hard to move 55 pounds of air.

I have a really good feeling that you don't have a 100% grasp on how a compound set-up works.

 

[dsm-onster]

Hey Paul, when this is up and working, will you be logging MAP? Are you going to be able or willing to log boost at the different stages?

 

[99gst_racer]

I do plan to log MAP - I still need to buy the sensor though. (thanks for the reminder )
I have two boost gauges in the car already. One for pre-stage and the other for manifold pressure. I hadn't considered datalogging pre-stage boost before though. I would need an additional MAP sensor for that, so I probably won't do it due to the cost of MAP sensors.

 

[SpeedAddict62]

Ok, I think people are getting confused here.

Mass can not be created or destroyed. What goes in, must come out. If you are flowing 55 lb/min of air into the engine, you are flowing 55 lb through BOTH turbos, regardless of anything else. The volume can change (and it will), but the number of molecules can not.

94awdcoupe, first off, the air is going through the big turbo first in his setup. Secondly, the air inlet to the first turbo might be slightly lower than atmospheric due to pressure drops in the piping, but it will be multiplied by the first turbo's pressure ratio. Then the second turbo will multiply the outlet pressure of the first turbo by its pressure ratio. So your final pressure is P = P(in)*PR1*PR2, neglecting pressure losses in the pipes.

The other thing that I am curious about is efficiency. The way I see it, if both turbos are running at 70%, your overall efficiency is 49%, which is pretty poor. You are going to be flowing some awfully hot air.

 

[99gst_racer]

The other thing that I am curious about is efficiency. The way I see it, if both turbos are running at 70%, your overall efficiency is 48%, which is pretty poor. You are going to be flowing some awfully hot air.

How did you calculate overall efficiency?

 

[SpeedAddict62]

I meant 49%

All I did was .7 (70%) x .7 = .49. Unless I'm completely missing something.

 

[94awdcoupe]

Pressurized liquid/gas will take the path of least resistance. In the case of my set-up, the wastegate poses lesser resistance than the turbine section of the turbo. Nevertheless, that doesn't explain why you feel your turbo set-up didn't work well when gated off of the #1 runner and mine was just fine.


So, you're saying that the only way to get 55 lbs/min of of the smaller turbo is by forcing 55 lbs/min into it? Don't you see that that doesn't make any sense? Knowing that pressure ratios multiply, one should be able to imagine that is a pressure charge is entering a compressor, a higher pressure charge will exit.


It's called "volume".


I have a really good feeling that you don't have a 100% grasp on how a compound set-up works. Keep studying up on it.

My 25g setup had same tube mounted between two runners as you do. You saw the picture posted. The path of least resistance was not through the wastegate. thats why there was creep. It was easier for the gasses to go to the turbine and over spool it.

You are missing that you need ~55 pounds of air to make your 550whp goal. Yes that 55 lbs goes through both turbos. If anyone has a misunderstanding on this point it is you Paul. I politely asked in my first post how the big turbo can run at 1 bar and pass 55pounds of air. You didnt answer correctly. and still havent. so I can only infer that you dont have a complete understanding about how basic turbo charging works.

volume is a poor term to use with turbo charging. volume is temperature and pressure defendant. You need to use the term lbs of air. lbs/min describes volume independently of pressure and temperature. this statement is correct. If the smaller turbo is doing the majority of the work and moving 55lbs air then that 55lbs of air has to come from inlet on big turbo.

 

[rush2252]

Wow... seriously it doesnt matter how many numbers you throw at paul Im going to laugh my ass off IF this thing works. Paul has mad skills and I think the rest of you need to keep your negative comments to yourselves.

I believe we as a community our here to help each other out and give each other inspiration. I dont recall ONE TIME during this post Paul simply asking "do you think this will work?" so stop saying IMO because he probably doesnt care.

Im sure if this keeps up he wont be willing to share projects like this with the rest of us who actually ENJOY reading these and live for this kinda shit!


I remember when people were saying the 4g63 was weak and would never run 9's now its running 7.70s and 6.90s in drag cars


Paul I admire your fabrication skills fellow dsmer


Kolby

 

[99gst_racer]

My 25g setup had same tube mounted between two runners as you do. You saw the picture posted. The path of least resistance was not through the wastegate. thats why there was creep. It was easier for the gasses to go to the turbine and over spool it.

Well, if your point is that plumbing a wastegate off that part of the manifold is bad, then I'm not worried. I've already sucessfully accomplished that on a previous build. Along with thousands of other DSMers. Like I said, your issue doesn't sound like a design flaw. But we can agree to disagree at this point.

You are missing that you need ~55 pounds of air to make your 550whp goal. Yes that 55 lbs goes through both turbos. If anyone has a misunderstanding on this point it is you Paul.

No, not missing it at all. The 60-1 compresses atmposheric pressure at pressure ratio higher than 1:1 and forces it into the 16G's compressor which multiply's that pressure ratio by it's own ratio to further compress the air charge to eventually reach the target pressure. The outlet pressure of each compressor is not even close to the same in a compound set-up.

I politely asked in my first post how the big turbo can run at 1 bar and pass 55pounds of air. You didnt answer correctly. and still havent.

And my point is that if you understand the very concept of how a compound turbocharger system works, you wouldn't be asking a question like this. There's no other way of saying the same thing over and over again that's going to make it more correct.

volume is a poor term to use with turbo charging. volume is temperature and pressure defendant. You need to use the term lbs of air. lbs/min describes volume independently of pressure and temperature.

So, volume is the proper term then... lbs/min is a ratio of volume and time. By the way, my goal is to break 60 lbs/min with this set-up. I just don't yet know how much boost I need to get there.

this statement is correct. If the smaller turbo is doing the majority of the work and moving 55lbs air then that 55lbs of air has to come from inlet on big turbo.

No dude, that is definitely not correct. The smaller turbo isn't "moving" air. It's multiplying it. What in the World make you think that for 55 lbs/min to come out of a turbo that 55 lbs/min has to enter it first? The 16G receives a volume of air and further compresses it to a higher volume. That's the way ANY compressor works. On a single turbo set-up, it pulls in atmospheric air and futher compresses it to create boost (which is only compressed atmosphere). The ONLY difference with a compound setup is that the primary turbo is fed a higher atmosphere via the largr turbo.

Maybe you're a picture person. Unfortunately, this is the best artwork you'll ever get out of me.

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[turbo addict]

Ok, I had been kicking this idea around a few years ago, and had sent you a few pm's about this before.
I think that the point that that other guy is trying to make is that in order to make 550hp you need about 55lbs/min of flow. What you want to do is think of the air flow from the standpoint of an airflow meter. When an airflow meter(mas) is metering the air before the turbo it doesn't know that there is a turbo there, it just reads the flow, so a 2.0 with flow like a 4.0 at 15psi(give or take) what you are doing here is the same thing, the big turbo doesn't know that there is a little turbo in there, it just flows air like it is going into a 4.0 not a turbocharged 2.0. So you still need to flow 55lbs/min of air before or into the big turbo (if you were reading airflow before the big turbo) you are just doing it at a lower pressure ratio like it is in a bigger motor.
The way you are explaining it is the 16g is magically making more (oxygen or air) in between the turbos and this is impossible.

I also understand that you are going to be opening up the wastegate once you make boost to effectively change the ve of the set up or to put it another way you are using 2 turbos to make a variable turbine effect where you are going to lower the backpressure once the 16g gets going to flow exhaust energy around the 16g and into the 60-1. then use the 60-1 to do more work and lessen the pressure ratio of the 16g and raise it on the 60-1 at higher revs.

Because a well built 4g63 can out flow a 60-1.

Just looking at the 60-1compressor map, it wants to be at 16to18psi or 2.2ish pressure ratio to flow 55 to 60lbs/min. and that is on the very outside of the map, you are looking at chokeflow almost. (like putting a 16g on a 502big block)

I really like the idea of this but think that the 60-1 is not a great choice. If it were me I would use the biggest T4 turbine housing that I could get my hands on for the 60-1. But I wouldn't use the 60-1 in the first place, I do however understand the money constraint, but something bigger would work much better.

If you are stuck with the 60-1 though, try to free up the inlet to the compressor as much as possible, cold air or ram air and a huge filter.

 

[knochgoon24]

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This is what's happening, if you assume 100% efficient so the temps don't rise, and a 1.5:1 pressure ratio through both compressors.

 

[turbo addict]

yep that is what i was saying.

 

[viperlp01]

Well man i just dont understand why you wont stop. This is not the first time this has been done. I mean honestly.... It is a proven design and has actually physics to back it up... The 16g is pulling air from a turbo that already compressed the air. Instead of pulling air from the atmosphere.

Im positive he will post every thing he can to show people exactly what this setup is doing. So until this is proven wrong on his 2g then stop doubting him. I talked to him in Nov last year and he was telling me about his research and how is should diffidently work.