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Old 11-18-2010, 09:51 PM   #1
shutupnshift04
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Default turbo mani, how big is too big

I know theres been a lot of talk about header piping size and spool characteristics, how it holds power ect. I am thinking of building a custom rotated kit. You would think that the smaller the piping the more pressure is built up that would spin the turbo faster. Think of blowing into a small straw or a huge piece of pvc. The small straw flows the air faster but chokes your lungs up and stops them from flowing to full capacity. The big pvc pipe requires a lot more breathing power to move air at high speeds so would theoretically spool slower but the engine itself will breathe better.

However turbos spool on thermal expansion correct? So one would think smaller piping into a larger turbo would cause the exhaust to expand in the turbo? The only problem is chocking up the motors "breathing" which is what actually makes the power to begin with. So for a set up like a 35r or 40r which piping size is ideal? What about a smaller turbo like vf series? Also how big is too big on actual piping size? please discuss (and dont just say well full race uses this so its the best explain why.)
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Old 11-19-2010, 01:39 AM   #2
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I thought about this a lot while I was porting my exhaust manifolds. It is a complex problem and to find the optimal size I think one would have to build a model in some software program.

Are you thinking of having one pipe or multiple like in a twin scroll setup?
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Old 11-19-2010, 03:02 AM   #3
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I was leaning towards a twin scroll however its not set in stone so I would like opinions on both designs (even though im sure its similar diameter wise).
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Old 11-19-2010, 09:51 AM   #4
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make the pipe a slightly smaller diameter than the head port.
Use 316L stainless for the material. It is not much more expensive than **** 304, but is designed for high temperature applications.
If you can afford 321, do that. But 16L is more than enough.
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Old 11-19-2010, 11:09 AM   #5
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I appreciate you input however my topic wasnt discussing what material to use. I want to keep this topic as technical as possible. So please dont just write keep it slightly smaller then the head port, explain why and give exact piping size not material. Thanks in advance!

What if someone made a manifold the way larger in diameter by the head ports and slowly (or drastically) tapered to smaller piping closer to the turbo like a funnel effect?

http://www.motorcycle.com/how-to/how...care-3423.html
Please refere to the link i posted. I have a huge back round in motocross. With that said I always was interested in 2 stroke expansion chamber theory and harnessing engine pulses to extract exhaust gases faster and more effeciently. The main drawback is "light switch" power bands" with the 2 strokes but turbos are like that allready. Now the 2 stroke expansion chambers are called expansion chambers because of the sound wave pulses however it also expands the air and once it reaches the end of the expansion chamber it compresses and becomes denser. What if you put a turbo right where it became denser?
Back to turbo theory. They spool on thermal expansion however I don't really understand this. One would think that air velocity would spin a compressor wheel more then actual dense air expanding. Once again I don't understand thermal expansion I'm no scientist so i just choose to accept it. I mean it kind of make sense but at what point is thermal expansion more valuable then actual air velocity?
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Old 11-19-2010, 12:16 PM   #6
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Just copy Full-Races manifold(although personally I would just buy it). They've put more R&D into headers than anybody else on here.
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Old 11-19-2010, 01:43 PM   #7
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Please read original post. In my original post I stated that i didnt want someone to come in here and say just use full race's manifold there the best. I want technical info and theories not just buy this brand or that brand cause there the "best" I know full race makes great products, thats not what this is about. If you think inside the box nothing will ever get better. so no i will not purchase a full race manifold. Please only respond if you have good information to post or answers to my questions or something to add about one of the theories i posted. thanks in advance!
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Old 11-19-2010, 01:53 PM   #8
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Quote:
Originally Posted by shutupnshift04 View Post
Please read original post. In my original post I stated that i didnt want someone to come in here and say just use full race's manifold there the best. I want technical info and theories not just buy this brand or that brand cause there the "best" I know full race makes great products, thats not what this is about. If you think inside the box nothing will ever get better. so no i will not purchase a full race manifold. Please only respond if you have good information to post or answers to my questions or something to add about one of the theories i posted. thanks in advance!
What I'm getting at is the people who have access to that info spend countless hours and even more money testing. They don't just throw it out there for the world to see. Buy a book on exhausts and read if you want to learn for yourself.
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Old 11-19-2010, 02:01 PM   #9
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smart guy? Your really resulting to insults over the internet huh. MY ORIGINAL POST SAID TO NOT STATE EXACTLY WHAT YOU CAME IN HERE AND STATED (just buy full race). I know there geniuses. Does that mean i cant have an intelligent conversation on the internet about exhaust because full race is the best brand? I have read up on exhaust theories. I want to have a discussion, i dont want to read a book an talk to myself. people like you drag nasioc down, please exit my thread asap because im not here to argue with you I'm here to have an intelligent thread. Thank you back to topic please.
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Old 11-19-2010, 02:14 PM   #10
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LMAO did you really just edit half your post and delete you calling me smart guy to try and make me look bad? Back to topic! No name brands please and thank you
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Old 11-19-2010, 03:32 PM   #11
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you:
dont know anything about turbo applications or thermodynamics
expect someone to waste their time on your JERZAY THANG attitude to teach you
can't help yourself.

Nobody wants to help someone like you. Read a book.
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Old 11-19-2010, 05:35 PM   #12
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You:
know nothing about me or my knowledge of cars

think that just because im from jersey im an a-hole (prolly cause of that stupid show) even though i said please and thank you in advance in every one of my posts

and badler came into my thread and answered no questions asked and personally bashed me but I have the attitude?

would get your face bashed in if you ever tried talking to me like that in person.but hey anyone can be tough on the internet.

So please explain what makes me look like i know nothing about cars. its not like i came in here and said which sweet bov should i buy.

If you and badler are "subbey specialists" then i want to sell my car cause your ignorance is on that of a honda owners level.

ONCE AGAIN GET OUT OF MY THREAD if you have nothing to contribute. if your so knowledgable answer my questions instead of saying buy full race cause THERE THE BEST BRO! and oh buy this metal...I DIDNT ASK THAT. can you even read?
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Old 11-19-2010, 05:37 PM   #13
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for gods sakes can we get back on topic before this thread becomes worthless.
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Old 11-19-2010, 06:21 PM   #14
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You say you have a background in motorcycles.....well "tuning" a header is much like "tuning" a motorcycle exhaust.....and all the different brands they sell with different diameters and expansion chambers at different locations to basically move the torque curve wherever the end user wants it.

same theory applies here......(pretty much the same as turbine housing sizing also)

Larger runners = slower spool, higher topend

Smaller runners = faster spool, lower topend

Its not a simple question to answer......it really depends on what your total setup is going to be.....a td04 setup will benefit from a different design than a gt40 setup.

I also see you have a 2002 wrx.....so you have some other factors to take into account.....you cant use an EL style unless you get an STi oil pan.....or you can make a similar design to killer b's that works around the pan (im pretty sure there's requires a 2.5L pan though).

Theres pretty much only 2 ways you are going to get any concrete data....anything anyone says to you in here is going to be pure guesstimation based on theory (including myself) and not really anything concrete.

1) CFD and simulations

2) build a bunch of headers with different runner and up pipe diameter combos and test them out.


One thing that i've always wondered about was swapping the design approach.....most people use small runners/ups on small turbos and larger runners/ups on larger turbos......

I'd personally like to see a large runner header on a small td04......and a small header on a gt35 with a 1.06 housing.
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Old 11-19-2010, 07:30 PM   #15
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Quote:
Originally Posted by shutupnshift04 View Post
I appreciate you input however my topic wasnt discussing what material to use. I want to keep this topic as technical as possible. So please dont just write keep it slightly smaller then the head port, explain why and give exact piping size not material. Thanks in advance!

What if someone made a manifold the way larger in diameter by the head ports and slowly (or drastically) tapered to smaller piping closer to the turbo like a funnel effect?

http://www.motorcycle.com/how-to/how...care-3423.html
Please refere to the link i posted. I have a huge back round in motocross. With that said I always was interested in 2 stroke expansion chamber theory and harnessing engine pulses to extract exhaust gases faster and more effeciently. The main drawback is "light switch" power bands" with the 2 strokes but turbos are like that allready. Now the 2 stroke expansion chambers are called expansion chambers because of the sound wave pulses however it also expands the air and once it reaches the end of the expansion chamber it compresses and becomes denser. What if you put a turbo right where it became denser?
Back to turbo theory. They spool on thermal expansion however I don't really understand this. One would think that air velocity would spin a compressor wheel more then actual dense air expanding. Once again I don't understand thermal expansion I'm no scientist so i just choose to accept it. I mean it kind of make sense but at what point is thermal expansion more valuable then actual air velocity?
Never drastically do anything when you're talking about airflow. As smooth and gradual as possible.

As for the theory part, my understanding is that you want velocity (smaller pipes) as it enters the turbine. Then the shape of the housing diffuses it to create pressure, or something like that. But you don't want the pipes so small to the point of choking the volume of the flow. There are always trade-offs.

There may be more technical info in the 'Forced Induction' section, as this category is more about the 'how' of making something, and less of the 'why'.
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Old 11-19-2010, 07:33 PM   #16
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Thank you for the positive input! keep it coming
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Old 11-19-2010, 07:40 PM   #17
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http://www.amazon.com/Maximum-Boost-Turbocharger-Engineering-Performance/dp/0837601606
everything you need to know is in here.

if you are nice, maybe you'll get a pdf sent via email from me.
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Old 11-20-2010, 01:24 AM   #18
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Quote:
and don't just say well full race uses this
Yeah, that never works. The fundamental problem with this suggestion is that there is really only one type of person who is compelled to share such blindingly obvious observations, and that is not the type of person who will read the entire first post, nor follow instructions even if he does happen to read the whole thing by mistake. You cannot deter these people from stating the obvious. If you try, it just turns into a pissing match. The best thing you can do is to simply ask your question, hope for interesting answers, and ignore the useless ones.

I subscribed to this thread last night, hoping that it might get interesting, and fully expecting that it would start like... well, just like it did. I 'ed when I snuck a peek at lunchtime. It sucks, but welcome to NASIOC.

All I got is theory, and not even a whole lot of that, but here goes anyway...

With a good tuned pipe on a naturally aspirated single-cylinder two-stroke, you can do stuff like suck fresh charge through the chamber and into the pipe, and then cram the extra charge back into the chamber when the pressure wave bounces back. Resonance can give you huge gains, so a lot of exhaust design focuses on managing those pressure waves.

With four-cylinder turbocharged four-strokes, you've got LOTS of backpressure from the turbine, and four pulses interfering with each other, so I don't think resonance is going to be nearly as useful. Equal length headers minimize pulse interference between cylinders, and twin scroll does that even more. But I have yet to see expansion chambers used in between the heads and the turbo, and I'm guessing this is why. It's not about bouncing positive and negative pressure waves around, it's about propagating the exhaust pulses to the turbine so the turbine can drive the compressor, and the compressor can cram extra air into the chambers.

AMR makes some of the biggest headers Subaru headers available. Somewhere on this forum is a disappointing dyno chart from a car with those headers, followed by a pretty cool dyno chart after switching to more conventional headers. It seemed like a pretty controlled test too, even though they didn't really set out to do a test or prove anything. I searched for the link, but couldn't find it. Maybe you'll have better luck. I think it shows about where the upper range of useful diameter is.

Notice that you've got a guy above saying to leave a step between the heads and the headers, and a guy saying that all transitions should be smooth. Who to believe? Google and read and decide: http://www.google.com/search?q=anti-reversion+step

The problem with optimizing for exhaust speed at the turbine is that speed comes at the expense of backpressure. One of the key variables for turbines is the pressure at the turbine inlet vs. the pressure at the turbine outline. The higher that ratio is, the more work the turbine can provide to drive the compressor. (The other key variables are mass flow and temperature, if I remember right. I had a really cool paper describing those variables and their relative significance, and I can't find it, and that's driving me nuts. I'll keep looking.)

But anyway, I think Phatron was right - the bottom line is that you're going to have to build different headers and test them. Unless maybe you've got friends who are really fond of CFD simulation, and even that is fraught with peril. Just read the conclusion of this academic paper, and note that it's only a couple years old:

http://www.imeche.org/Libraries/Turb...s_on.sflb.ashx

Quote:
The operation of radial turbines in pulse flow conditions is a complex problem that has not yielded simple and readily applicable solutions. There is as yet no agreement about definitions of figures of merit that can be used to characterize turbine performance and inform future turbine development for this type of operation. It appears that simple concepts of “pulse flow efficiency” and “pulse flow performance maps” will be, at best, approximations, and at worst, very misleading for both engine simulation and turbine design purposes.
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Old 11-20-2010, 02:30 PM   #19
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Quote:
Originally Posted by Phatron View Post
You say you have a background in motorcycles.....well "tuning" a header is much like "tuning" a motorcycle exhaust.....and all the different brands they sell with different diameters and expansion chambers at different locations to basically move the torque curve wherever the end user wants it.

same theory applies here......(pretty much the same as turbine housing sizing also)

Larger runners = slower spool, higher topend

Smaller runners = faster spool, lower topend

Its not a simple question to answer......it really depends on what your total setup is going to be.....a td04 setup will benefit from a different design than a gt40 setup.

I also see you have a 2002 wrx.....so you have some other factors to take into account.....you cant use an EL style unless you get an STi oil pan.....or you can make a similar design to killer b's that works around the pan (im pretty sure there's requires a 2.5L pan though).

Theres pretty much only 2 ways you are going to get any concrete data....anything anyone says to you in here is going to be pure guesstimation based on theory (including myself) and not really anything concrete.

1) CFD and simulations

2) build a bunch of headers with different runner and up pipe diameter combos and test them out.


One thing that i've always wondered about was swapping the design approach.....most people use small runners/ups on small turbos and larger runners/ups on larger turbos......

I'd personally like to see a large runner header on a small td04......and a small header on a gt35 with a 1.06 housing.
I like where your going with that last statement. using a larger runner header on a td04 should shift its power a little more towards the top end. Using a smaller runner on a big turbo would theoretically make more power down low which would help in spool and "jumpstart" the turbo. The only thing i see that might conflict is: I would think you would want to complement the power band that the turbo is naturally looking for? I appreciate the input phatron!
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Old 11-20-2010, 02:37 PM   #20
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Quote:
Originally Posted by eg33GC View Post
Amazon.com: Maximum Boost: Designing, Testing, and Installing Turbocharger Systems (Engineering and Performance) (9780837601601): Corky Bell: Books

everything you need to know is in here.

if you are nice, maybe you'll get a pdf sent via email from me.
thanks for the link ill look into it
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Old 11-20-2010, 02:39 PM   #21
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Quote:
Originally Posted by NSFW View Post
AMR makes some of the biggest headers Subaru headers available. Somewhere on this forum is a disappointing dyno chart from a car with those headers, followed by a pretty cool dyno chart after switching to more conventional headers. It seemed like a pretty controlled test too, even though they didn't really set out to do a test or prove anything. I searched for the link, but couldn't find it.
Found it, and a summary too:
http://forums.nasioc.com/forums/show...8&postcount=30

2" primaries, if I remember right.
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Old 11-20-2010, 03:25 PM   #22
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Quote:
Originally Posted by NSFW View Post
Yeah, that never works. The fundamental problem with this suggestion is that there is really only one type of person who is compelled to share such blindingly obvious observations, and that is not the type of person who will read the entire first post, nor follow instructions even if he does happen to read the whole thing by mistake. You cannot deter these people from stating the obvious. If you try, it just turns into a pissing match. The best thing you can do is to simply ask your question, hope for interesting answers, and ignore the useless ones.

I subscribed to this thread last night, hoping that it might get interesting, and fully expecting that it would start like... well, just like it did. I 'ed when I snuck a peek at lunchtime. It sucks, but welcome to NASIOC.

All I got is theory, and not even a whole lot of that, but here goes anyway...

With a good tuned pipe on a naturally aspirated single-cylinder two-stroke, you can do stuff like suck fresh charge through the chamber and into the pipe, and then cram the extra charge back into the chamber when the pressure wave bounces back. Resonance can give you huge gains, so a lot of exhaust design focuses on managing those pressure waves.

With four-cylinder turbocharged four-strokes, you've got LOTS of backpressure from the turbine, and four pulses interfering with each other, so I don't think resonance is going to be nearly as useful. Equal length headers minimize pulse interference between cylinders, and twin scroll does that even more. But I have yet to see expansion chambers used in between the heads and the turbo, and I'm guessing this is why. It's not about bouncing positive and negative pressure waves around, it's about propagating the exhaust pulses to the turbine so the turbine can drive the compressor, and the compressor can cram extra air into the chambers.

AMR makes some of the biggest headers Subaru headers available. Somewhere on this forum is a disappointing dyno chart from a car with those headers, followed by a pretty cool dyno chart after switching to more conventional headers. It seemed like a pretty controlled test too, even though they didn't really set out to do a test or prove anything. I searched for the link, but couldn't find it. Maybe you'll have better luck. I think it shows about where the upper range of useful diameter is.

Notice that you've got a guy above saying to leave a step between the heads and the headers, and a guy saying that all transitions should be smooth. Who to believe? Google and read and decide: http://www.google.com/search?q=anti-reversion+step

The problem with optimizing for exhaust speed at the turbine is that speed comes at the expense of backpressure. One of the key variables for turbines is the pressure at the turbine inlet vs. the pressure at the turbine outline. The higher that ratio is, the more work the turbine can provide to drive the compressor. (The other key variables are mass flow and temperature, if I remember right. I had a really cool paper describing those variables and their relative significance, and I can't find it, and that's driving me nuts. I'll keep looking.)

But anyway, I think Phatron was right - the bottom line is that you're going to have to build different headers and test them. Unless maybe you've got friends who are really fond of CFD simulation, and even that is fraught with peril. Just read the conclusion of this academic paper, and note that it's only a couple years old:

http://www.imeche.org/Libraries/Turb...s_on.sflb.ashx
I wish i had the time and money to build a bunch of diff headers and dyno them. lol I understand why a expansion chamber would be a long shot to say the least I just kind of used that to try and get people thinking outside the box a little. Im going to read that link you posted asap and appreciate the info!

From what i understand the pulses plays a huge role in turbo spool and performance. I cant remember the name of the theory but on intake manifolds its idea to have omething that the sound can resonate and bounce back off of (liek a wall in the intake mani) which in turn grasps the sound waves to bounce back into the cylinders at the right time. would that be possible on an exhaust manifold? except reverse ofcoarse. i would assume youwould have to time it so the wave sucks the air out instead of assisting in pushing air in like intake manifolds? If anyone knows the name of this specific theory that would be great (for some reason its slipping my mind right now) if i remember ill post a link
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Old 11-20-2010, 05:08 PM   #23
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The main theory behind your overall question is basically captured in Bernoulli's Principle. Here is a link with a nice little animation where you can adjust the pipe size and see how the velocity changes. This is a good place to start.

http://home.earthlink.net/~mmc1919/venturi.html

The math behind all this can get complex especially when you start changing pipe direction, diameters and bring in exhaust pulses.

The best advice I can offer is try and imagine this stuff in your head. Unless you know a good Mechanical Engineer who has access to nice software.

Subaru probably did all of this engineering to begin with and with a stock turbo I would not venture to far away from OEM specs. Now if you are introducing bigger turbo's into the equation then yes you might need to adjust the flow characteristics of the exhaust manifold.

I truly hope this thread does not diverge into the typical NASIOC discussion.
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Old 11-20-2010, 08:44 PM   #24
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Quote:
Originally Posted by NSFW View Post
Yeah, that never works. The fundamental problem with this suggestion is that there is really only one type of person who is compelled to share such blindingly obvious observations, and that is not the type of person who will read the entire first post, nor follow instructions even if he does happen to read the whole thing by mistake. You cannot deter these people from stating the obvious. If you try, it just turns into a pissing match. The best thing you can do is to simply ask your question, hope for interesting answers, and ignore the useless ones.

I subscribed to this thread last night, hoping that it might get interesting, and fully expecting that it would start like... well, just like it did. I 'ed when I snuck a peek at lunchtime. It sucks, but welcome to NASIOC.

All I got is theory, and not even a whole lot of that, but here goes anyway...

With a good tuned pipe on a naturally aspirated single-cylinder two-stroke, you can do stuff like suck fresh charge through the chamber and into the pipe, and then cram the extra charge back into the chamber when the pressure wave bounces back. Resonance can give you huge gains, so a lot of exhaust design focuses on managing those pressure waves.

With four-cylinder turbocharged four-strokes, you've got LOTS of backpressure from the turbine, and four pulses interfering with each other, so I don't think resonance is going to be nearly as useful. Equal length headers minimize pulse interference between cylinders, and twin scroll does that even more. But I have yet to see expansion chambers used in between the heads and the turbo, and I'm guessing this is why. It's not about bouncing positive and negative pressure waves around, it's about propagating the exhaust pulses to the turbine so the turbine can drive the compressor, and the compressor can cram extra air into the chambers.

AMR makes some of the biggest headers Subaru headers available. Somewhere on this forum is a disappointing dyno chart from a car with those headers, followed by a pretty cool dyno chart after switching to more conventional headers. It seemed like a pretty controlled test too, even though they didn't really set out to do a test or prove anything. I searched for the link, but couldn't find it. Maybe you'll have better luck. I think it shows about where the upper range of useful diameter is.

Notice that you've got a guy above saying to leave a step between the heads and the headers, and a guy saying that all transitions should be smooth. Who to believe? Google and read and decide: http://www.google.com/search?q=anti-reversion+step

The problem with optimizing for exhaust speed at the turbine is that speed comes at the expense of backpressure. One of the key variables for turbines is the pressure at the turbine inlet vs. the pressure at the turbine outline. The higher that ratio is, the more work the turbine can provide to drive the compressor. (The other key variables are mass flow and temperature, if I remember right. I had a really cool paper describing those variables and their relative significance, and I can't find it, and that's driving me nuts. I'll keep looking.)

But anyway, I think Phatron was right - the bottom line is that you're going to have to build different headers and test them. Unless maybe you've got friends who are really fond of CFD simulation, and even that is fraught with peril. Just read the conclusion of this academic paper, and note that it's only a couple years old:

http://www.imeche.org/Libraries/Turb...s_on.sflb.ashx
Pressure wave tuning and resonance etc... is something I'm just starting to get into. As for reversion, my simple understanding is that it's not that big of a deal unless there is a substantial amount of overlap in the cams. But like I said, I'm basically a noob when it comes to this stuff.

For flow you still want smooth transitions though, right? The steps are used to change direction of pressure waves. Which has a bigger effect on spinning a turbine?

As for yourself and subscribing, you seem more like you will be a contributor to this than getting much out of it. Could you clarify for me what I was getting at about the velocity/diffusion in the turbine housing?
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Old 11-20-2010, 08:58 PM   #25
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Originally Posted by shutupnshift04 View Post
I wish i had the time and money to build a bunch of diff headers and dyno them. lol I understand why a expansion chamber would be a long shot to say the least I just kind of used that to try and get people thinking outside the box a little. Im going to read that link you posted asap and appreciate the info!

From what i understand the pulses plays a huge role in turbo spool and performance. I cant remember the name of the theory but on intake manifolds its idea to have omething that the sound can resonate and bounce back off of (liek a wall in the intake mani) which in turn grasps the sound waves to bounce back into the cylinders at the right time. would that be possible on an exhaust manifold? except reverse ofcoarse. i would assume youwould have to time it so the wave sucks the air out instead of assisting in pushing air in like intake manifolds? If anyone knows the name of this specific theory that would be great (for some reason its slipping my mind right now) if i remember ill post a link
The theory isn't wrong, but applying it sounds hard... With turbo engines, exhaust gas backpressure is much higher than with NA engines. Before you reach full power, you'll have more backpressure than boost pressure. So regardless what you do with the waves you've still got a pressure differential working against you.

http://forums.nasioc.com/forums/showthread.php?t=935698
http://forums.nasioc.com/forums/show....php?t=1854224

Also, I think you'll find that the length of pipe you need for that resonance is going to be difficult to work with. You want the turbo close to the motor so you don't lose exhaust heat. Also, unless you want to get really creative about where you put the turbo and/or how you route the headers, the distance from the heads to the turbo is pretty hard to change.

And you'd want four long primaries to keep the pulses from interfering. I wonder if there's any gains to be had from putting a 4-into-1 collector right at the turbine entry. And I also wonder if it's even possible to get four reasonably-sized tubes to pass through the 'cradle' that the up-pipe has to fit through.

So, I'm not optimistic about applying 2-stroke design theories to Subarus.

It would also be interesting to look at the when the exhaust valves open, relative to the exhaust stroke, on Subaru's turbo motors. And of course what options are readily available. And then there's the question of whether there's enough overlap between the intake and exhaust valves for exhaust tricks to pull extra charge into the chamber. I have no idea, but it doesn't seem likely.
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