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  1. #1
    Senior Member Four Rings alphaVR's Avatar
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    Proper Exhaust System for Stage 3 2.0T

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    I apologize in advance if this topic seems to be beat to death... I assure you its not my intention to beat a dead horse, but to actually get some info on the subject that I haven't seen answered elsewhere.

    Car: 2008 Audi A4 Avant 2.0t 6MT
    Mods: AWE 2871r Stage 3 Kit w/ GIAC Pump Tune

    My car currently has the full AWE turboback system, including the high flow cat, except that the mufflers at the end have been replaced with Magnaflow Race mufflers (P.O. said the AWE mufflers droned a ton). While the car sounds great on the outside, the interior drone is a bit much and it just gets too loud inside. I've been doing a ton of searching around and it's hard to identify what new catback system would be best for what I am looking for based purely on the fact that I am running a Stage 3 kit - none of the videos I've seen so far have anything similar done to them.

    I am hoping someone here might have some experience with a similar setup and what exhaust systems actually sound good/don't drone. Even if its a different set of mufflers, I'd be open to it as long as its not compromising the sound outside of the car.

    If you have any info, it'd be greatly appreciated.
    -Tony-
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  2. #2
    Senior Member Three Rings midnight407's Avatar
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    from what i've read, you can try moving the mufflers a bit further out and/or doing some sound deadening material in the trunk
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  3. #3
    Senior Member Four Rings seal66's Avatar
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    Add in another resonator
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  4. #4
    Senior Member Four Rings jsandor91's Avatar
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    Re: Proper Exhaust System for Stage 3 2.0T

    You could gain a bit of performance by going 3 inch . but then drone will be even more of a issue .

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  5. #5
    Senior Member Four Rings alphaVR's Avatar
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    Not sure where you could move the mufflers to... theyre already at the far end of the system, about 2" from the tips haha

    I honestly dont know of anywhere you could put any more mufflers either... The Avant isnt much different underneath the car, but I dont see anywhere another muffler could go...

    http://www.awe-tuning.com/media/cata...car_1280_1.jpg

    Not looking to make the drone worse at all. Performance is near negligible since the 2871r makes enough power to make the thing really scoot. the 3" piping wouldn't gain me near as much.
    -Tony-
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  6. #6
    Senior Member Four Rings Charles.waite's Avatar
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    Add in a resonance cancelling pipe. Basically its what APR has done with their RSC system. They add in a certain length dead-end pipe split off the exhast and the sound pressure waves bounce off the end of the pipe, and travel back to the main exhaust trunk in reverse phase and cancel out the offending frequencies that cause drone.

    Its a bit of a complicated process to be honest, though you can measure the frequencies of the drone and calculate the pipe length more or less to eliminate trial and error.
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  7. #7
    Veteran Member Four Rings mr shickadance's Avatar
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    Quote Originally Posted by alphaVR View Post
    Not sure where you could move the mufflers to... theyre already at the far end of the system, about 2" from the tips haha

    I honestly dont know of anywhere you could put any more mufflers either... The Avant isnt much different underneath the car, but I dont see anywhere another muffler could go...


    http://www.awe-tuning.com/media/cata...car_1280_1.jpg

    Not looking to make the drone worse at all. Performance is near negligible since the 2871r makes enough power to make the thing really scoot. the 3" piping wouldn't gain me near as much.

    1) exhausts are very personal, one persons cup of tea may be another person bloodied eardrum. so the bare minimum for an exhaust for stage 3 would be at least a 3 inch down pipe and a hfc or test pipe situation.

    from then on, any exhaust you put on is going to add negligible amounts of power for sure (don't let anyone else tell you otherwise, we are talking sub-5hp gains past downpipe)

    you have an avant, and avants are drony, thats just how they are, fault by design, but whatever, so you obviously want something nice, but also quite. from what i have heard in youtube sound clips, the APR/Billyboat system appears to be decently quiet and is rather cheap.

    for a complete situation, i suppose you could fab up something similar to an akrapovic system, and activate flaps which can let you get loud when you want it, and quiet when you don't. it's going to be expensive but its an option (stage 3 baller over here so idk, just tossing it out there)


    as for the bolded portion, google a little bit about this, apparently sliding the exhaust tips to their very end has reported almost killed drone entirely.


    start with the tips, then explore other options.
    Scott

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  8. #8
    Senior Member Three Rings Jhad's Avatar
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    I have an Apr exhuast- its not too loud at all, and very little drone. However, when i first installed it the tips they were flush with the valence and droned alot- it was annoying because the exhuast was louder in the cabin than what was heard outside the car. I adjusted it and pulled it out a bit so that the tips stick out further- no more drone in the cabin. ( basically what Shick said)

    I know the AWE is much louder than APR, so I'd try to adjust the tips further or get some sound deadening materials. Probably the least expensive way to go.

  9. #9
    Senior Member Four Rings alphaVR's Avatar
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    Quote Originally Posted by Charles.waite View Post
    Its a bit of a complicated process to be honest, though you can measure the frequencies of the drone and calculate the pipe length more or less to eliminate trial and error.
    Im not at liberty to divulge much information of my connection to knowing this, but I've been given a full explanation of how it works by a friend and experienced it on multiple cars (Corvette, B6 S4, and a Subaru 2.5 turbo for example) and I swear by their technology. What they have to do to get it to sound like that takes a lot of engineering and isn't something you can buy off the shelf to fix it. But you are correct in the general theory of the application. The trouble is a) finding the space for it, and b) figuring out the right amount of pipe to get it to work

    Quote Originally Posted by mr shickadance View Post
    1) exhausts are very personal, one persons cup of tea may be another person bloodied eardrum. so the bare minimum for an exhaust for stage 3 would be at least a 3 inch down pipe and a hfc or test pipe situation.
    Indeed they are. As stated above, Ive been shown how loud exhausts can sound good and NOT drone the car out so I find myself expecting more from these exhaust systems than I am likely to find.
    I do already have the AWE 3" downpipe with a high-flow cat installed, so as you mentioned there are negligible (if any) performance gains to be made at this point. This is purely for the sound and aesthetics of the car.
    I have heard from a few people that the avants, for some reason, drone more than the Sedans. Whether thats due to the open rear cargo space to the interior of the car or not is beyond me, but there definitely is a difference.

    In regards to the tips, I dont have much ability there. At least on the magnaflow race mufflers, its all one assembly and theres nothing to allow for adjustment there. The AWE mufflers/tips arent installed on the car anymore, so I could at least see what theyre allowing me in terms of tip adjustment. I dont know if I can (very easily) get them remounted since they were cut off professionally right at the weld for the inlet pipe to the muffler.
    -Tony-
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  10. #10
    Senior Member Four Rings ericpaulyoung's Avatar
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    Quote Originally Posted by Charles.waite View Post
    Add in a resonance cancelling pipe. Basically its what APR has done with their RSC system. They add in a certain length dead-end pipe split off the exhast and the sound pressure waves bounce off the end of the pipe, and travel back to the main exhaust trunk in reverse phase and cancel out the offending frequencies that cause drone.

    Its a bit of a complicated process to be honest, though you can measure the frequencies of the drone and calculate the pipe length more or less to eliminate trial and error.
    ^^^ This x 1000000

    I run a 1/4 wavelength resonator and it is the cat's meow.








    Eric
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  11. #11
    Senior Member Four Rings ericpaulyoung's Avatar
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    Quote Originally Posted by alphaVR View Post
    Im not at liberty to divulge much information of my connection to knowing this, but I've been given a full explanation of how it works by a friend and experienced it on multiple cars (Corvette, B6 S4, and a Subaru 2.5 turbo for example) and I swear by their technology. What they have to do to get it to sound like that takes a lot of engineering and isn't something you can buy off the shelf to fix it. But you are correct in the general theory of the application. The trouble is a) finding the space for it, and b) figuring out the right amount of pipe to get it to work

    No need for secrecy, the patents are available for free online and if you search for industrial 1/4 wavelength resonator you can find several lectures on their design for industrial systems. They are actually quite common in industry.

    Eric
    Jesse "Eric is correct, that is not your bung hole"

  12. #12
    Senior Member Four Rings alphaVR's Avatar
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    Fair enough haha. He and I are close and he tells me things that sometimes aren't to be made public so I always play it safe. Don't want to cause any shit and possibly cost him his job just cuz we love to talk shop together.

    Those pics posted... Any more info? What car is that installed? If that's the underside of a B7 (looks close) then I might be really interested.... Doing research on the 1/4 wavelength resonator and there seems to be a TON of math involved (YAY!).
    -Tony-
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  13. #13
    Established Member Four Rings aluthman's Avatar
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    Quote Originally Posted by alphaVR View Post
    Those pics posted... Any more info? What car is that installed? If that's the underside of a B7 (looks close) then I might be really interested.... Doing research on the 1/4 wavelength resonator and there seems to be a TON of math involved (YAY!).
    I believe that's EPY's B7
    -Adam

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  14. #14
    Senior Member Four Rings ericpaulyoung's Avatar
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    Yup! It worked like magic fairy dust too. The STASIS exhaust drone was horrible, I put on the 1/4 length resonator, and the drone disappeared and I have a throaty growl with zero drone now. Notice the cap allows for the length of the 1/4 length dead end to be adjusted, that way you only have to get close with the calculated length, then go for a few drives and move it back and forth until your car is tuned like a guitar :)

    - Eric
    Jesse "Eric is correct, that is not your bung hole"

  15. #15
    Senior Member Four Rings ericpaulyoung's Avatar
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    I just downloaded a scope app for the iPhone, recorded my exhaust note when the drone was there, found the frequency (which is peaked at between 80 and 100 Hz) and calculated the wavelength for an approximate exhaust temperature in the side branch (can't remember, but I think I used like 140F or something). Then made the pipe like 95% of this length with a tip that would allow me to adjust the total length from 95% up to around 105% of the calculated length.
    Eric
    Jesse "Eric is correct, that is not your bung hole"

  16. #16
    Senior Member Four Rings ericpaulyoung's Avatar
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    Almost forgot the best part, the branch resonator add absolutely zero back pressure! One of the few time you get something for nothing.

    Notes of caution.
    1. There are Helmholtz chambers and 1/4 wavelength branch resonators. Familiarize youself with both. You want the 1/4 wavelength design. It actually wipes out a small range of frequencies around what it is tuned to treat. BUT a Helmholtz chamber is very specific to the frequency it will cancel out, and even worse can ADD DRONE if it starts resonating out of tune. Bad juju
    2. Make it so the dead end actually is a little uphill so the liquid condensing out of the exhaust can drain back into the exhaust and out the tailpipes. Otherwise it will be changing its effective length as it fills up. Mine points slightly downhill so I have a 1/16" drain hole on the tip to allow it to drain. It works great, but I think it is a little more elegant to not need the drain hole.

    - Eric
    Jesse "Eric is correct, that is not your bung hole"

  17. #17
    Senior Member Four Rings alphaVR's Avatar
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    Eric,

    thanks for all that info! Ran this by my buddy who designs exhausts and he confirms that this is a definite viable option. Going to start looking into it. I am aware of the two kinds (i think there's a 3rd kind too) and how they can be used differently. This one definitely looks to be the most direct way to remove the drone I am dealing with. I had a few questions though...


    1) If you dont mind my asking... how much did you invest into that to complete it?

    2) How did you go about making that adjustable "cap"? That looks like an awesome way to "fine tune" it.

    3) How did you go about attaching the branch onto the actual exhaust piping? I was thinking about a flange welded onto the exhaust so the branch is removable, but idk how useful that really is.

    thanks a ton!
    -Tony-
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  18. #18
    Senior Member Four Rings ericpaulyoung's Avatar
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    I just toll this right now on my way home.


    Jesse "Eric is correct, that is not your bung hole"

  19. #19
    Senior Member Two Rings PPLAPW's Avatar
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    Quote Originally Posted by ericpaulyoung View Post
    ^^^ This x 1000000

    I run a 1/4 wavelength resonator and it is the cat's meow.








    Eric
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    Senior Member Four Rings Axis's Avatar
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    Quote Originally Posted by ericpaulyoung View Post
    ^^^ This x 1000000

    I run a 1/4 wavelength resonator and it is the cat's meow.



    Eric
    Thats one nice muffler setup you have there.
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  21. #21
    Senior Member Four Rings canadianA4B7's Avatar
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    this is wonderful!! i need to have a custom 3" Downpipe made as no one offers it as a aftermarket parts. was wondering how i could go about losing the drone that was present when the RAI HFC/DP was installed. and i think this just might have to go onto my A4 thanx EPY!! im assuming some of this math is where you decided on the length of the 1/4 wave resonator? and we would need to input for our EGT, frequency and the RPM that is the issue?

    Lets assume EGT of 500*F (260*C) and frequency of 53.4hz at 800RPM. (Speed of sound = 331m/s+ 0.6m/s x 260*C) So the speed of sound should be 487m/s. (487m/s / 53.4hz / 4 =2.3m) So the total length of a wave resonator for 800rpm should be 2.3meters or 7.3 feet long. And for 1000RPM, (487m/s / 66.7 / 4=1.8M or 4.2 feet long)

  22. #22
    Senior Member Three Rings AudiFan6482's Avatar
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    Quote Originally Posted by canadianA4B7 View Post
    this is wonderful!! i need to have a custom 3" Downpipe made as no one offers it as a aftermarket parts. was wondering how i could go about losing the drone that was present when the RAI HFC/DP was installed. and i think this just might have to go onto my A4 thanx EPY!! im assuming some of this math is where you decided on the length of the 1/4 wave resonator? and we would need to input for our EGT, frequency and the RPM that is the issue?

    Lets assume EGT of 500*F (260*C) and frequency of 53.4hz at 800RPM. (Speed of sound = 331m/s+ 0.6m/s x 260*C) So the speed of sound should be 487m/s. (487m/s / 53.4hz / 4 =2.3m) So the total length of a wave resonator for 800rpm should be 2.3meters or 7.3 feet long. And for 1000RPM, (487m/s / 66.7 / 4=1.8M or 4.2 feet long)


    "Audi B7 a4 3 inch downpipe"...beep boop boo beep...
    and first result in google is.........
    http://www.raimotorsport.com/RAI-3-0...i-20man-dp.htm
    2008 A4 6MT Quattro... Monster mats...APR STG2...TP

  23. #23
    Senior Member Four Rings ericpaulyoung's Avatar
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    Well I have to go find the spreadsheet, but I think it came out around 36 inches. Hmmm I will go look for it.
    Jesse "Eric is correct, that is not your bung hole"

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    Senior Member Four Rings canadianA4B7's Avatar
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    I have the RAI HFC/DP and it doesnt fit to the K04, it was tried and the O2 bung is too close to the flange to have it fabricated to fit. sorry didnt include that detail in my post. but thanx for the help. i also contacted techtonic and Labree. but apparently they dont make a 3" DOWNPIPE.
    http://techtonicstuning.com/main/ind...roducts_id=973
    as seen through the link regarding downpipe, not including the Test pipe or Cat. i just need the pipe after the cat or test pipe. any other suggestions? serious if ive missed something please provide a link.

  25. #25
    Senior Member Four Rings alphaVR's Avatar
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    Quote Originally Posted by canadianA4B7 View Post
    Lets assume EGT of 500*F (260*C) and frequency of 53.4hz at 800RPM. (Speed of sound = 331m/s+ 0.6m/s x 260*C) So the speed of sound should be 487m/s. (487m/s / 53.4hz / 4 =2.3m) So the total length of a wave resonator for 800rpm should be 2.3meters or 7.3 feet long. And for 1000RPM, (487m/s / 66.7 / 4=1.8M or 4.2 feet long)
    Almost all of that is right, though this side pipe wont see full exhaust temps the main pipe would see (based simply on airflow and most of the hot gasses passing this)

    Your math is almost spot on. I highly doubt there would be drone at 800rpm, but the math works as you state.

    From my buddy, RPMs don't matter as much as people make it see. You can make an exhaust drone at different RPMs at differnent speeds in different gears (i.e. an RPM and speed in 5th may drone at a different RPM and speed in 4th, and so on). Thus, what you need to do is what Eric stated in which you take an audio recording of your cabin noise in various gears and RPMs. Then you plot the frequency and decibel readings to then begin to analyze where you need to target the 1/4 wave resonator. From there, you create a bell curve of the decibel readings for various frequencies and use that to target with.

    Thus, the math would work out as follows....

    If you determine 84Hz to be at the top of your bell curve and you find that the air temperature in the pipe will be around 200 degrees, which means the speed of sound at that temp is 383.751 m/s...
    Length = (speed of sound at temp)/(frequency targeted)...

    OR

    Length = 383.751/84....
    Length = 4.568464285714286 meters.
    Divide that by 4 (to get your 1/4 length), and get 1.142116071428571, which converts to 3.7471 feet - the length the pipe needs to be to cancel out the 84hz frequency

    This is all estimated/guessed and by no means FACT. But... it gives you an idea of how this should all work based on what I've read, what Eric has stated, and what I've confirmed from my buddy who's an engineer and designs exhausts like these for a living.
    -Tony-
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  26. #26
    Senior Member Four Rings canadianA4B7's Avatar
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    this is great stuff. the way it looks like EPY made his he made like a slider one pipe slightly larger then the other. which im assuming how he made his adjustments? so if the inner pipe is say 30" from the branch from the Dp and the other is about 20" or so then it could be slide one over the other to get that precision length that will cancel out the drone frequency. am i seeing your design correctly EPY? and will the size of the resonator pipe matter? i understand the calculation for lenght, but is there a measurement for volume aswell?

  27. #27
    Senior Member Four Rings alphaVR's Avatar
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    Youd be correct. He designed the two pieces in mind so their initial total length (aka the shortest length they could possibly combine to become) was 95% of the target length. By making the cap slide over the branch pipe, it allows him to slide it some to allow him to "fine tune" which frequency he wants to focus at just in case the math was slightly off. As he mentioned, it takes a few drives and playing with its length to get it where you want it. Bear in mind that this still only allows you to focus on a narrow scope of frequencies, but if you do your homework you should be able to be there within 95% accuracy.

    As far as pipe size, the jury is out IMO. I've heard it doesn't matter too much. If the exhaust pipe is 2.5", for sake of making things easier to weld on, I would go no larger than 2" for the branch pipe. Beyond that... not sure.
    -Tony-
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    Senior Member Four Rings ericpaulyoung's Avatar
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    Quote Originally Posted by alphaVR View Post
    Almost all of that is right, though this side pipe wont see full exhaust temps the main pipe would see (based simply on airflow and most of the hot gasses passing this)

    Your math is almost spot on. I highly doubt there would be drone at 800rpm, but the math works as you state.

    From my buddy, RPMs don't matter as much as people make it see. You can make an exhaust drone at different RPMs at differnent speeds in different gears (i.e. an RPM and speed in 5th may drone at a different RPM and speed in 4th, and so on). Thus, what you need to do is what Eric stated in which you take an audio recording of your cabin noise in various gears and RPMs. Then you plot the frequency and decibel readings to then begin to analyze where you need to target the 1/4 wave resonator. From there, you create a bell curve of the decibel readings for various frequencies and use that to target with.

    Thus, the math would work out as follows....

    If you determine 84Hz to be at the top of your bell curve and you find that the air temperature in the pipe will be around 200 degrees, which means the speed of sound at that temp is 383.751 m/s...
    Length = (speed of sound at temp)/(frequency targeted)...

    OR

    Length = 383.751/84....
    Length = 4.568464285714286 meters.
    Divide that by 4 (to get your 1/4 length), and get 1.142116071428571, which converts to 3.7471 feet - the length the pipe needs to be to cancel out the 84hz frequency

    This is all estimated/guessed and by no means FACT. But... it gives you an idea of how this should all work based on what I've read, what Eric has stated, and what I've confirmed from my buddy who's an engineer and designs exhausts like these for a living.
    Yup :) You got a high Midichlorian count in your system, and will do well!
    Jesse "Eric is correct, that is not your bung hole"

  29. #29
    Senior Member Four Rings canadianA4B7's Avatar
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    cool!! ive gotta save some of those pics from EPYs posts. will take to shop when i can afford the pipe and fab work!! but i think this will work with my setup. im also curious weather it would work on straight pipes? im thinking it would work just the same as with a system with mufflers. but clearly the mufflers will also reduce the volume of the exhaust. but if it were loud like straight pipe drone free....... i think im just dreaming! ill see what i can come up with on my setup. but i think ill likely end up changing the whole system with this new found drone reducer!!

  30. #30
    Senior Member Four Rings ericpaulyoung's Avatar
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    OK, two quickies. The amount of cancelation on a branch resonator is proportional to the diameter of the pipe. I used a 2 1/2" branch and it worked well, but a 3" would actually cancel even more of the resonant sounds. As an example, a 1" pipe would not really accomplish much and a 1/2" pipe would not do anything. You need the pressure fluctuation to be out of phase, and of equal displacement as the pressure wave that you are trying to cancel out. In principal you would use the same diameter branch as the diameter of the main duct you are trying to cancel out frequencies in. If you look at where I cut in my branch, the section is ovalized, so I had to go to a slightly smaller diameter to get the connection to work. I had the branch mandrel bent out of SS 304 tubing and welded into place. I don't know if you can see, but there is also a support that is at a location about 1/3 of the way down the branch so that the branch is supported at more than one location. This is to take stress away from the welded joint and hopefully prevent stress cracks.

    As for cost, I spent around a grand on the STASIS exhaust and $300 for the branch to be custom bent and welded into place. Took the shop about 3 hours total.

    Something that is not in the pictures is the exhaust clamp. The end piece indeed does simply slide over the outside of the main branch piece, but is held in place with a standard exhaust clamp. This is not shown in the pictures above where I was just test fitting the system.

    Eric
    Jesse "Eric is correct, that is not your bung hole"

  31. #31
    Senior Member Four Rings ericpaulyoung's Avatar
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    Quote Originally Posted by canadianA4B7 View Post
    cool!! ive gotta save some of those pics from EPYs posts. will take to shop when i can afford the pipe and fab work!! but i think this will work with my setup. im also curious weather it would work on straight pipes? im thinking it would work just the same as with a system with mufflers. but clearly the mufflers will also reduce the volume of the exhaust. but if it were loud like straight pipe drone free....... i think im just dreaming! ill see what i can come up with on my setup. but i think ill likely end up changing the whole system with this new found drone reducer!!
    Mufflers cancel (or rather absorb) the higher frequencies and the chambers/branch/Helmoltz geometries cancel out the lower frequencies. So you need both to properly tune the sound of your exhaust.
    - Eric
    Jesse "Eric is correct, that is not your bung hole"

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    Senior Member Four Rings mcpcartier's Avatar
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    Nice thread....been a while since I saw something I hadn't seen posted one way or another previously.

    Why I keep coming back and browse.
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    Senior Member Four Rings alphaVR's Avatar
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    Eric,

    makes a ton of sense now that you put it that way.

    I think these magnaflow race mufflers have to go. Ill do some audio recordings to confirm but I think I am dealing with drone at a ton of different RPMs/Speeds, so this solution wont be able to take care of all of them. Ill look into getting the AWE mufflers put back on so I can try to tune this exhaust to the correct frequencies.

    I figured $300 would be about what it cost to do this. Not cheap but also really good bang for your buck if you do it right. Eric, did you just have them weld a hangar from the branch pipe to the main exhaust pipes?
    -Tony-
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  34. #34
    Senior Member Four Rings ericpaulyoung's Avatar
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    The support actually clamps around the branch and then connects to one of the bolts on the exhaust. I will try to get a photo tonight, but will probably have to jack my car up to do it. I am pretty low :)

    There is some good news about the cancelation function of the branch design. It doesn't know if the drone is produced at one rpm or another, as long as it represents 1/4 or some other fractional multiplication of 1/2, it will still invert the pressure wave. So the beach will treat any drone for which the branch is 1/2, 1/4, 1/8, or 1/16 of the wavelengths of that drone. Anyways, you only need to target the main frequency which is somewhere between 80-100 Hz. Do this and your exhaust will sing to you in all gears at all speeds. :)

    Eric
    Jesse "Eric is correct, that is not your bung hole"

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    Established Member Two Rings
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    Re: Proper Exhaust System for Stage 3 2.0T

    But guys, are you sure this exhaust plus experimental resonance pipe really is a better choice than just picking up a good proven exhaust like a Miltek?

    I certainly sympathise with the urgent need to solve Stasis drone as mine was driving me up the wall - but surely avoiding the issue is smarter.

  36. #36
    Senior Member Four Rings ericpaulyoung's Avatar
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    Quote Originally Posted by kvitrafn View Post
    But guys, are you sure this exhaust plus experimental resonance pipe really is a better choice than just picking up a good proven exhaust like a Miltek?

    I certainly sympathise with the urgent need to solve Stasis drone as mine was driving me up the wall - but surely avoiding the issue is smarter.
    Ya, that is a very good point!

    I guess the question would then be, if Miltek solved the problem a different way, did the way they solve it require more back pressure? My STASIS exhaust with branch resonator is basically a set of straight pipes with very, very low back pressure resistance. If Miltek used chambered mufflers to kill the drone then they would be quieter, but also not offer as good of performance. I don't know. Does anyone have a picture of the inside of the Milltek mufflers?

    - Eric
    Jesse "Eric is correct, that is not your bung hole"

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    Veteran Member Four Rings mr shickadance's Avatar
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    Quote Originally Posted by kvitrafn View Post
    But guys, are you sure this exhaust plus experimental resonance pipe really is a better choice than just picking up a good proven exhaust like a Miltek?

    I certainly sympathise with the urgent need to solve Stasis drone as mine was driving me up the wall - but surely avoiding the issue is smarter.

    the smarter way was what EPY did, the most economic way is how milltek, stasis, etc have done it.

    the extra pipe, is an added cost, and the requirement to tune the exaust at the hands of some grease monkey is going to do not out weigh the simple "just-put-a-muffler-on-it" benefits

    it's too much a liability for a company to make what EPY did
    Scott

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  38. #38
    Senior Member Four Rings ericpaulyoung's Avatar
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    I thought of making a branch resonator insert that people can just decouple the mid placed clamp, place the insert in, then replace with longer bolts. Quick and simple. The problem is they would cost me around $400 to make with a clamp collar and would have to sell at $500 for a solid profit. Not a huge market though. But if I can convince Hugh to sport it for me... Hmmm. Maybe everyone can have one!
    Eric
    Jesse "Eric is correct, that is not your bung hole"

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    Senior Member Four Rings alphaVR's Avatar
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    APR's RSC exhausts (Along with other companies doing similar things), and the technology behind them, are pretty well-proven to not only perform well in the sense of no cabin drone, but also IMPROVE horsepower/torque numbers.

    Take for example Corsa Performance Exhausts. They just released an exhaust system for the 2012-2013 Jeep Grand Cherokee STR-8. They too have the noise-cancelling tech that makes for no drone, but it was proven on a dyno their exhaust added 42HP and about 75ft/lbs of torque. Just from an exhaust!

    Regarding Milltech... perhaps their does have less drone, but at what costs? More back pressure? A freer-flowing exhaust will always perform better and is what I need to run on my Stage 3 2.0t, but you then run into drone issues. This Branch resonator solves the drone problems while not impeding on the free-flowing exhaust benefits.

    I guess what this comes down to is user application and preference. I don't mind getting my hands dirty and coming up with a geeky solution to the problem. Im also not sold on whether any off-the-shelf systems would do anything to fix the drone.

    EPY... if you were ever to entertain the idea of having a few more produced, let me know... If I dont have one built already, I'd be interested.
    -Tony-
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  40. #40
    Senior Member Four Rings Charles.waite's Avatar
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    Some good info in here. So glad I brought it up...

    EPY, does it matter particularly where you branch the resonator off? I mean obviously from a ease of install standpoint, but I would assume it could technically be installed anywhere there is enough room for it right?
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