I had the factory JCW tuning kit installed on my 2012 MCSa right after I got it. I was very unhappy with the amount of drone from the exhaust. It wasn't that it was too loud, just a BAD drone from about 2500 to 3200 rpm. The amount of drone would change from time to time and at its worst, it would hurt my ears. I posted on the forum, searched the forum and the internet for a solution. The only one that seemed to always work was a side branch resonator. I did do a few muffler changes, to no avail, before I had the side branch resonator installed. I did not do the calculations presented, but just experimented with the resonator length. This did cost me a few extra bucks, but in the end was worth it. I started at 28" and ended up with 44",it still has a SMALL bit of resonance between 3200 and 3300 rpm, but is out of the "cruise" area and is very livable. I did find that the length of the exhaust pipe, before it splits into 2, before the muffler or tips does change the rpm at which it will drone. I ended up with a "one pipe" straight thru muffler. I think if I had kept the JCW muffler, I could have used a slightly shorter resonator pipe. I had the work done by Kenz Muffler in Oxnard, CA, they were very helpful and do very nice work. In the finished form the end of the resonator tube is supported by the exhaust pipe with the ability to move with expansion.

 

I've never seen anything like that before. How does it sound? It looks like the end of the resonator pipe is closed off, does that hinder performance at all?

 

It does not affect the exhaust sound except for the drone. It should not affect the performance in any way that I know of and I have not noticed any change in power.

I won't try to explain how it works here, (I am a lazy typist) just do a google search for "side branch resonator" and you will get some great explanations.

 

http://bit.ly/SgJpBX

Here's a link... All in good humor folks...

 

Do you have any audio clips of your setup? I'm very curious...

 

This is actually more common then people think. You mostly see it done on the intake side of things to tune the induction sound. If done properly it can actually create more hp, but this is 9/10's stuff. The resonator being post cats shouldn't have any negative effect, and I wonder if you play with it more you might be able to customize your tone.

Great work and a genius idea.

As a side note they use this same idea in F1 exhausts that use the coanda style exhaust exit. It's used to balance the hermonic frequencies to help improve flow. You can see it just above the collector.

 

old thread booster - was there ever pictures of this custom work posted up? Very curious.....

 

The first time I saw this was on my brothers M3. He's got a custom exhaust put on it. But I noticed when we were on the freeway, it was quiet with no drone . Good job! I had a pretty bad drone on my car and went with a vibrant resonator. completely Took it away. If it didn't work, this idea would have been a good one also.