Im looking into branch resonators for my exhaust. The drone at highway speeds is about 90hz and I calculated that I could use a 37" pipe parallel to the exhaust pipe but am wondering how I could calculate a shorter, bigger resonator to save space?

Also, I can't find the pieces for a cap on the resonator. Where can I find odd exhaust pipes? This isnt really something that anyone sells.

 

A larger diameter pipe should allow you to shorten your wavelength, and thus your pipe.

That said, this is an extremely difficult thing to accurately produce. Understand that if you are not DEAD on, you will not be able to cancel the resonating frequency and even risk creating another.

 

I don't think he will create another more like move the rpm range that the drone exists. But yeah larger diameter will make a bigger difference. I would just cut a circle out of sheet metal for the cap, or maybe add a flange and add a circle of steel plate three bolt holes. Something common and easy to find gaskets for.

 

I was thinking a flange connection. I talked to my welding mechanic. He said that a band clamp would allow me to remove it easily and trim it off.

I was afraid of creating another frequency but that doesnt seem like it would happen that easily. There are a lot of people who have done these and they all say there is a huge difference, both decibel drop and the cancellation of that resonance. No mention of another added noise. I did the math right and confirmed it with an app on my phone. Its closer to 100 hz.

Thinking about the concept of an IAR I could do a butterfly valve design but Im not sure how to do that. They sell those for the tailpipe. Maybe I can use that.

I didnt think about sheet metal though. That would work.

 

Sounds as though you have it figured out.

 

Yeah, take a look at my other post. I did a write up. I was just a little worried that I was missing something. But this thing works great. Better than I imagined.