You may be right about that. I've been reading over on a porsche forum where a guy has been using this approach over a long period of time with not much success (he may finally get there, haven't finished reading all 9 pages) but I think where he's failing is that he was using 1.25" pipe on his 2.5" exhaust

If you look at the motordyne exhaust, it uses a very short branch but is quite large. From people that switched from FI to motordyne (boost lee i think), the drone is less compared to FI.

I would guess that the volume of the side branches is a big factor.

the motordyne utilizes Helmholtz "resonators" (excuse the term if that's incorrect) where as what this thread is focused on are the 1/4 side pipe resonators. Two very different approaches. THe Helmholtz works on volume, the side pipe works on length. From what I understand, the Helmholtz style covers a greater range, but they're harder for the DIY'er or local shop to build, because you have to have the different size pipes vs canisters for the effect.

If I'm mistaken, anyone, please correct me. THis is still all very new to me, as I just learned about this last night!

I have no clue if youre rightt, or wrong, but it has to have something to do with the volume anyway, maybe? The longer the pipe you branch off, the more volume there is inside. I dont know, I didnt do physics after high school, but it seems to me just thinking with my beer brain that the volume has as much to do with it as anything. Even if the "tuned to 1/4 wavelength, bouncing sound waves back to cancel out others" makes for good resoning.

It's not about volume. It's the length that matters. You tune it by changing the length. The pulse wave hits the end of the capped tube and bounces back into the exhaust pipe. What you want, is that pulse wave to hit the other pulse wave coming down the exhaust at the right time to cancel out the drone. The problem is that you can only tune it for a narrow rpm range.

so, Beemerkid, did you ever finish this? What were your results? I went to a couple of muffler shops, one refused to even try, one was willing but wasn't sure the Injen exhaust was really metal (haha) to weld properly... Going to two others for quotes, but still no success in getting the work done...

I got mine done today... I couldn't be happier. I had a local muffler shop weld in a pair of 26" long capped pipes upstream of my mufflers, and they go out on the back side and up over the cans... You can't see them at all from behind the car, and it basically eliminated all of the problem areas. I can drive through my neighborhood or at cruising speed and I have no droning at all between idle up to about 5k rpm. Up there it does come back some, but I'm rarely at that rpm for more than a few seconds, and I don't mind the loudness when I'm at WOT, it was just the cruising speeds that were killing me!

I did quieten down the entire system, but that's ok, it still has the deep rumble that I like, just not at neighbor waking volumes...

https://c5.staticflickr.com/6/5666/3...2143a195_b.jpg

https://c4.staticflickr.com/6/5664/3...da030f15_b.jpg

I'm selfish and want it a little louder on the outside and quiet on the inside. :)
Overall though, not having to deal with a headache after every long drive is nice. :)

that's pretty much what I have now... whereas before, it was louder inside than out!

Great to hear, or should I say not hear.....

Since adding in the supercharger and having Seb work his magic the 2-2.7K rpm range has gotten really loud when under load. When my wife is with me I stay out of that range by staying in a lower gear. I might have to give this a try as it does get quite loud while cruising below 80.

Thanks for letting us know that this works. ROLL RIDE!!!!!

BTW: Did the shop use 304 stainless?

I don't get it...we spend good $$ on a exhaust and then have to modify it to be useable:mad:

10 years ago I wouldn't have a problem with the drone. :)

I have full motordyne shockwave on my car with the ART test pipes and I have ZERO drone and all full quality exhaust. Well worth the money. Hemholtz design is even on the test pipes.

Yeah, this was the next option for me. To switch to motordyne but the side branch option is a lot cheaper with the exhaust I already had.

If I could do it again, I would do motordyne. Nothing wrong with FI. Its on the list if I have extra funds.

I went with aluminized because 304 would have cost 3x's the price and at that price point, I would have just gone with one of the other exhausts that already has the helmholtz, like the ARK grip.