Question related to exhaust piping design...
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From: evil lair
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Ps - your setup looks great. I did a similar setup on a inline 4. A gt40 turbo with a flared transion from the v-band on the hotside to a 4" open pipe about 2ft long. It sounded very angry!
Last edited by evil 996tt; Jul 27, 2012 at 10:47 AM.
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Yes, it was. I agree with you. Space is scarce in our cars and things get tight quickly. A 4cylinder sounds good at least, the two banks of 3cylinders is.... If my ears had stomachs they would puke!!
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What I can't understand is why nobody proves their design by means of measururing backpressure. Backpressure = bad. The more backpressure the slower the spool. When I used to build exhausts and design turbo headers, we just put in an 1/8" bung and measured.
In my opinion, I can's see "blending" banks after the turbo being anything that will encourage scavanging. The pulses were already timed in the header. (flame suit on)..
In my opinion, I can's see "blending" banks after the turbo being anything that will encourage scavanging. The pulses were already timed in the header. (flame suit on)..
Had to chime in because this has been a ongoing debate over the years.
We have used a X type design since 2004 and it is one that was developed and proven in motorsport.
In terms of back pressure we were doing some back pressure testing on a997 GT2RS the other day and the factory system approx 11+lbs of back pressure. In comparison our World Challenge 997 GT2RS system is measured 2.2 psi of back pressure.
Everyone has their opinion on what works and what doesn't work and why.
I can only speak from experience and what has worked on our road cars and on the cars we run in pro racing. A close working relationship with Porsche Motorsport as well as top level engineers also helps us in designing our systems.
Bottom line there are a lot of good exhaust manufacturers. Do some research and find one that works best for your needs.
There is no one absolute.
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Here is a little history on the EBW X pipe, on how it became about.
The EBW x pipe was design with me in mind. There were a few things I was after, that NO other exhaust in the market cater to my needs, they are: 1) Great engine sound 2) lightweight exhaust.
On the quest to making our x pipe, the car that inspired Ben and myself was
this AWE's GT2rs.
http://www.awe-tuning.com/media/cata...haust_1280.jpg
Now the problem with that X pipe. is that it is so crunched up that it hurts flow. When we started off, Ben said, we can make that exhaust (AWE GT2rs) using some welder he knows that does a great job. I said if I'm going that route, I rather just buy it from AWE. I want something different because 1) that exhaust note does not sound good to ME. 2) You are very good with CAD/Comsol, why not use the technology that we have at our hands and make the best cross over exhaust for flow.
So the quest started. Not to look at other X pipes, until we see what we come up with using software. I asked him, to simulate a dual X pipe to see what would happen with flow and sound wave frequency, as theoretically, using physics, it would amplify the sound waves to a really high pitch. Witch also touches on the next subject we needed to tackle with an X pipe .Temperature. High temperature compressible flow. Witch effects, density, pressure, and sound, and the choke effect.
( If you want to know more about the acoustic theory, read up on the math- Google education is great
https://www.google.com/search?hl=en&...w=1366&bih=611 )
http://www.nd.edu/~pdunn/www.ame538/Chapt09.pdf
We found out the X pipe's would be very small (using a dual x pipe) because of the constraint room we have to work with, and the way the exhaust gasses would travel because of the way it would mounts on a 911, it would create a lot of heat (heat chokes flow (density) but increases high pitch sound- but it also increases velocity of air)- and one of the X pipes would just be hollow with very little flow going through. He then deleted the second X pipe and started flowing X one single x pipe. He spend A LOT of hours simulating the flow using Comsol Acoustics Module, Pipe flow module/ CFD module.
The hardest part finding out how much carving to do in the inner piping to cut off, for the angel of bend, when both banks hit, to make the flow not to hot, to it will not choke, but hot enough to create a high pitch sound and increase the velocity of air. You have to find the equilibrium. I’m at work and trust me, as much as I would like to blah about the physics behind it, because I LOVE physics. I have a job : (
All I can say is, the EBW x pipe was more than your typical guy welding pipes together and seeing which one sounds best( which is why our X pipe (over his straight pipes) helped BHT improve his 60-130 times on his 3.8 built motor). We have the same principal on our B7 RS4 and that is why we have the highest rated hp/tq B7 RS4 with our exhaust and intake. My fav post regarding x pipes is this one. Because it so true, at least that is what Comsol PFM/CFD told us
https://www.6speedonline.com/forums/996-turbo-gt2/279966-my-rendition-cross-flow-exhaust-3.html#post3582757
Google:
Compressible Flow Phenomena temperatures
Choking in change of cross section flow
Gas dynamics
The EBW x pipe was design with me in mind. There were a few things I was after, that NO other exhaust in the market cater to my needs, they are: 1) Great engine sound 2) lightweight exhaust.
On the quest to making our x pipe, the car that inspired Ben and myself was
this AWE's GT2rs.
http://www.awe-tuning.com/media/cata...haust_1280.jpg
Now the problem with that X pipe. is that it is so crunched up that it hurts flow. When we started off, Ben said, we can make that exhaust (AWE GT2rs) using some welder he knows that does a great job. I said if I'm going that route, I rather just buy it from AWE. I want something different because 1) that exhaust note does not sound good to ME. 2) You are very good with CAD/Comsol, why not use the technology that we have at our hands and make the best cross over exhaust for flow.
So the quest started. Not to look at other X pipes, until we see what we come up with using software. I asked him, to simulate a dual X pipe to see what would happen with flow and sound wave frequency, as theoretically, using physics, it would amplify the sound waves to a really high pitch. Witch also touches on the next subject we needed to tackle with an X pipe .Temperature. High temperature compressible flow. Witch effects, density, pressure, and sound, and the choke effect.
( If you want to know more about the acoustic theory, read up on the math- Google education is great
https://www.google.com/search?hl=en&...w=1366&bih=611 )
http://www.nd.edu/~pdunn/www.ame538/Chapt09.pdf
We found out the X pipe's would be very small (using a dual x pipe) because of the constraint room we have to work with, and the way the exhaust gasses would travel because of the way it would mounts on a 911, it would create a lot of heat (heat chokes flow (density) but increases high pitch sound- but it also increases velocity of air)- and one of the X pipes would just be hollow with very little flow going through. He then deleted the second X pipe and started flowing X one single x pipe. He spend A LOT of hours simulating the flow using Comsol Acoustics Module, Pipe flow module/ CFD module.
The hardest part finding out how much carving to do in the inner piping to cut off, for the angel of bend, when both banks hit, to make the flow not to hot, to it will not choke, but hot enough to create a high pitch sound and increase the velocity of air. You have to find the equilibrium. I’m at work and trust me, as much as I would like to blah about the physics behind it, because I LOVE physics. I have a job : (
All I can say is, the EBW x pipe was more than your typical guy welding pipes together and seeing which one sounds best( which is why our X pipe (over his straight pipes) helped BHT improve his 60-130 times on his 3.8 built motor). We have the same principal on our B7 RS4 and that is why we have the highest rated hp/tq B7 RS4 with our exhaust and intake. My fav post regarding x pipes is this one. Because it so true, at least that is what Comsol PFM/CFD told us
https://www.6speedonline.com/forums/996-turbo-gt2/279966-my-rendition-cross-flow-exhaust-3.html#post3582757
Google:
Compressible Flow Phenomena temperatures
Choking in change of cross section flow
Gas dynamics
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From: evil lair
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Fabryce,
Have you any data on the "x" systems vrs non "x" systems. Without giving any of your hard work and research away, I would just like a "yes this worked better" or no answer.
In a turbo application, I can't see the benifit at all. Fluid dynamics don't lie. In a N/A situation, I agree with the "x" benifit.
In a turbo and n/a, the proper merge collector will really help BUT that is BEFORE the turbo. Anything after is a restriction. In n/a design, the primary length, tube diamter and merge collector is VERY important. In a turbo application, it makes a difference but not much were you can't just run 1 extra lbs of boost to over come
Like I said, I will be testing an after market non "x" version for back pressure and I'll post the results. I should throw the stock setup on there just for a baseline.
Have you any data on the "x" systems vrs non "x" systems. Without giving any of your hard work and research away, I would just like a "yes this worked better" or no answer.
In a turbo application, I can't see the benifit at all. Fluid dynamics don't lie. In a N/A situation, I agree with the "x" benifit.
In a turbo and n/a, the proper merge collector will really help BUT that is BEFORE the turbo. Anything after is a restriction. In n/a design, the primary length, tube diamter and merge collector is VERY important. In a turbo application, it makes a difference but not much were you can't just run 1 extra lbs of boost to over come
Like I said, I will be testing an after market non "x" version for back pressure and I'll post the results. I should throw the stock setup on there just for a baseline.
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From: evil lair
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hey, aren't you supposed to be at the dyno! I want to see those results!
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Fabryce,
Have you any data on the "x" systems vrs non "x" systems. Without giving any of your hard work and research away, I would just like a "yes this worked better" or no answer.
In a turbo application, I can't see the benifit at all. Fluid dynamics don't lie. In a N/A situation, I agree with the "x" benifit.
In a turbo and n/a, the proper merge collector will really help BUT that is BEFORE the turbo. Anything after is a restriction. In n/a design, the primary length, tube diamter and merge collector is VERY important. In a turbo application, it makes a difference but not much were you can't just run 1 extra lbs of boost to over come
Like I said, I will be testing an after market non "x" version for back pressure and I'll post the results. I should throw the stock setup on there just for a baseline.
Have you any data on the "x" systems vrs non "x" systems. Without giving any of your hard work and research away, I would just like a "yes this worked better" or no answer.
In a turbo application, I can't see the benifit at all. Fluid dynamics don't lie. In a N/A situation, I agree with the "x" benifit.
In a turbo and n/a, the proper merge collector will really help BUT that is BEFORE the turbo. Anything after is a restriction. In n/a design, the primary length, tube diamter and merge collector is VERY important. In a turbo application, it makes a difference but not much were you can't just run 1 extra lbs of boost to over come
Like I said, I will be testing an after market non "x" version for back pressure and I'll post the results. I should throw the stock setup on there just for a baseline.
Dr. Evil,
I would like to see pre turbo back psi on k16, k24, and the array of there hybrids. I would have done it but I am passed those turbo sizes.
Tim
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As the original poster of this thread...
I apologize for starting any flames - hopefully the debate has been a healthy discussion.
I wanted to throw out another question which really was at the heart of the curiosity of the Sharkwerks exhaust of which I originally posted so hopefully Dan@ Sharkwerks or others might be able to shed some light.
Dan mentioned that the two reasons they went with that design for 997.2 TT's and not the 996 TT's was the fact that:
a) The piping was modular from the cat back.
b) The .2's are notoriously quiet.
Now, from hearing the Sharkwerks exhaust in their video clip, I thought the exhaust sound was great! So, what differences are there in the 996 TT's setup and the 997.2 TT's that would make such a design sound worse? I am assuming that the exhaust note coming out of a 996TT with a straight pipe design sounds horrible like a lot of people have been quoted as saying. This was kinda of a side question related to my original post. Thoughts?
I wanted to throw out another question which really was at the heart of the curiosity of the Sharkwerks exhaust of which I originally posted so hopefully Dan@ Sharkwerks or others might be able to shed some light.
Dan mentioned that the two reasons they went with that design for 997.2 TT's and not the 996 TT's was the fact that:
a) The piping was modular from the cat back.
b) The .2's are notoriously quiet.
Now, from hearing the Sharkwerks exhaust in their video clip, I thought the exhaust sound was great! So, what differences are there in the 996 TT's setup and the 997.2 TT's that would make such a design sound worse? I am assuming that the exhaust note coming out of a 996TT with a straight pipe design sounds horrible like a lot of people have been quoted as saying. This was kinda of a side question related to my original post. Thoughts?
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how bout the design that evom's uses on some cars where its not a actual x pipe but were the x pipe ussualy merges its only merged by a 3 inch straight balancing pipe.
heres a pic
https://www.6speedonline.com/forums/...ed-60-whp.html
heres a pic
https://www.6speedonline.com/forums/...ed-60-whp.html
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Had to chime in because this has been a ongoing debate over the years.
We have used a X type design since 2004 and it is one that was developed and proven in motorsport.
In terms of back pressure we were doing some back pressure testing on a997 GT2RS the other day and the factory system approx 11+lbs of back pressure. In comparison our World Challenge 997 GT2RS system is measured 2.2 psi of back pressure.
Everyone has their opinion on what works and what doesn't work and why.
I can only speak from experience and what has worked on our road cars and on the cars we run in pro racing. A close working relationship with Porsche Motorsport as well as top level engineers also helps us in designing our systems.
Bottom line there are a lot of good exhaust manufacturers. Do some research and find one that works best for your needs.
There is no one absolute.
We have used a X type design since 2004 and it is one that was developed and proven in motorsport.
In terms of back pressure we were doing some back pressure testing on a997 GT2RS the other day and the factory system approx 11+lbs of back pressure. In comparison our World Challenge 997 GT2RS system is measured 2.2 psi of back pressure.
Everyone has their opinion on what works and what doesn't work and why.
I can only speak from experience and what has worked on our road cars and on the cars we run in pro racing. A close working relationship with Porsche Motorsport as well as top level engineers also helps us in designing our systems.
Bottom line there are a lot of good exhaust manufacturers. Do some research and find one that works best for your needs.
There is no one absolute.
Your systems hands down sound the best. When I owned a shop we installed your system on a 997.1 C4S. It was simply the best sounding exhaust I ever heard, to date. The reality is that 10 hp is equal to 100 lbs so tell me if I put 100lbs in the average street car DD and see if that driver can tell me there is a difference. I don't think they will.
Tim
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I apologize for starting any flames - hopefully the debate has been a healthy discussion.
I wanted to throw out another question which really was at the heart of the curiosity of the Sharkwerks exhaust of which I originally posted so hopefully Dan@ Sharkwerks or others might be able to shed some light.
Dan mentioned that the two reasons they went with that design for 997.2 TT's and not the 996 TT's was the fact that:
a) The piping was modular from the cat back.
b) The .2's are notoriously quiet.
Now, from hearing the Sharkwerks exhaust in their video clip, I thought the exhaust sound was great! So, what differences are there in the 996 TT's setup and the 997.2 TT's that would make such a design sound worse? I am assuming that the exhaust note coming out of a 996TT with a straight pipe design sounds horrible like a lot of people have been quoted as saying. This was kinda of a side question related to my original post. Thoughts?
I wanted to throw out another question which really was at the heart of the curiosity of the Sharkwerks exhaust of which I originally posted so hopefully Dan@ Sharkwerks or others might be able to shed some light.
Dan mentioned that the two reasons they went with that design for 997.2 TT's and not the 996 TT's was the fact that:
a) The piping was modular from the cat back.
b) The .2's are notoriously quiet.
Now, from hearing the Sharkwerks exhaust in their video clip, I thought the exhaust sound was great! So, what differences are there in the 996 TT's setup and the 997.2 TT's that would make such a design sound worse? I am assuming that the exhaust note coming out of a 996TT with a straight pipe design sounds horrible like a lot of people have been quoted as saying. This was kinda of a side question related to my original post. Thoughts?
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From: evil lair
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BNG4GOD, sorry for the OT and no hard feelings here. Instead of just buying something because "x" vender says it works, I like to try things myself. I am fortunate enough were I can make a lot of things and it is just my own time and a little $ for material so, it is easy.
I am sure the exhaust venders here make a great product and this was not a slam on anyone nor the "x" design. I'm just new to the tt world and trying to learn myself.
