Pictures are the iteration in the video here:
[video=youtube;DR7h7tjNTc4]http://www.youtube.com/watch?v=DR7h7tjNTc4[/video]
I promised photos ages ago on my original write-up - sorry it took so long. I'm constantly adjusting and revising the tail section, everything before that I am a fan of. Once I get it all set I'll do final installation of the tailpipe with a better exhaust tip and fewer transitions, then cut and vband it all. My goal is to retain a swappable tail section, since I get bored easily I'm still working out kinks with my switch to a full helmholtz chamber, but I had been asked for photos of my quarter wave resonated exhaust. This iteration rotated things downward so you can actually see it in pics. It's 33.25" long cancelling ~106.67 hz. The sloppy welds are ones I did, and I used non-stainless wire (oops). When I switch to a full helmholtz chamber it'll be slightly less peak cancellation, but it will cover a broader range (probably from 100hz to 120hz or so, all the worst resonant frequencies I've found in the FiST). The ultra quiet kills a lot of high frequencies so it *does* kill turbo impeller sounds (no whistling) but you can hear the wastegate just fine. I have driven this around next to overly sensitive Orange County police and only got attention due to blowoff sounds and some crackling.
Future exhaust plans:
- Adjust the exhaust hangers because at present the exhaust is "squeaky" when the car is cold
- Finish new t304 helmholtz chamber
- Chop it up and vband it (I'll probably vband the stock exhaust too for easier reinstallation).
- New rear section with an interesting sounding muffler. Maybe a vibrant muffler or a borla x1? I dunno, I'll probably try a few.
- Pay a fab welder to fix my crappy welds.
Here's how I figured out the length of the quarter wave resonator:
RPM w/ resonant drone 3200
Pulses per rev 2
Resonant frequency 106.6666667hz
107hz (easier than 106.6666667)
1210.11 (assumed 71 degrees f)
11.30943925 (speed of sound@71f)/(frequency)
2.827359813 (wave length/4 (feet))
33.92831776 (chamber length in inches)
Here's how I'm planning the size of my helmholtz chamber:
Frequency 106.67 hz
Port area 0.0381 meters = 1.5 inches
Port length 0.1016 meters = 4 inches
Velocity of sound@expected temp 343.4 m/s
Volume 9.97E-02 cu meters = 333.2521 c/i
I'm not 100% on the sizing of the helmholtz; I have the necessary dimensions, I just have to figure out how I am going to fit it in near the rear section
I'm playing with hydro-forming it but getting exact dimensions is not easy there. So far I've just ruptured a bunch of sheet metal balloons. If there are any enginerds that read this and my math/dimensions are obviously wrong, feel free to chime in.
[video=youtube;DR7h7tjNTc4]http://www.youtube.com/watch?v=DR7h7tjNTc4[/video]
I promised photos ages ago on my original write-up - sorry it took so long. I'm constantly adjusting and revising the tail section, everything before that I am a fan of. Once I get it all set I'll do final installation of the tailpipe with a better exhaust tip and fewer transitions, then cut and vband it all. My goal is to retain a swappable tail section, since I get bored easily I'm still working out kinks with my switch to a full helmholtz chamber, but I had been asked for photos of my quarter wave resonated exhaust. This iteration rotated things downward so you can actually see it in pics. It's 33.25" long cancelling ~106.67 hz. The sloppy welds are ones I did, and I used non-stainless wire (oops). When I switch to a full helmholtz chamber it'll be slightly less peak cancellation, but it will cover a broader range (probably from 100hz to 120hz or so, all the worst resonant frequencies I've found in the FiST). The ultra quiet kills a lot of high frequencies so it *does* kill turbo impeller sounds (no whistling) but you can hear the wastegate just fine. I have driven this around next to overly sensitive Orange County police and only got attention due to blowoff sounds and some crackling.
Future exhaust plans:
- Adjust the exhaust hangers because at present the exhaust is "squeaky" when the car is cold
- Finish new t304 helmholtz chamber
- Chop it up and vband it (I'll probably vband the stock exhaust too for easier reinstallation).
- New rear section with an interesting sounding muffler. Maybe a vibrant muffler or a borla x1? I dunno, I'll probably try a few.
- Pay a fab welder to fix my crappy welds.
Here's how I figured out the length of the quarter wave resonator:
RPM w/ resonant drone 3200
Pulses per rev 2
Resonant frequency 106.6666667hz
107hz (easier than 106.6666667)
1210.11 (assumed 71 degrees f)
11.30943925 (speed of sound@71f)/(frequency)
2.827359813 (wave length/4 (feet))
33.92831776 (chamber length in inches)
Here's how I'm planning the size of my helmholtz chamber:
Frequency 106.67 hz
Port area 0.0381 meters = 1.5 inches
Port length 0.1016 meters = 4 inches
Velocity of sound@expected temp 343.4 m/s
Volume 9.97E-02 cu meters = 333.2521 c/i
I'm not 100% on the sizing of the helmholtz; I have the necessary dimensions, I just have to figure out how I am going to fit it in near the rear section
I'm playing with hydro-forming it but getting exact dimensions is not easy there. So far I've just ruptured a bunch of sheet metal balloons. If there are any enginerds that read this and my math/dimensions are obviously wrong, feel free to chime in.
