wvumtnbkr PowerDork
3/10/23 8:55 p.m.

So, on my 3.9 gm v6 swapped rx8, I have a full stainless exhaust ending in the stock rx8 muffler.


For the most part, it sounds great!  However, at almost exactly 3000 rpm, it sounds like the exhaust is falling off and SUPER raspy.


I'm thinking I can add a resonator or 2.


The question is...


1 resonator on each leg before the 2 banks merge?   Or 1 resonator after the merge?


Obviously, 1 is cheaper and easier.  However, I want to solve this issue once and for all.  I don't want to redo it.


So, learn me exhaust resonators on a raspy 60 degree v6.


Thank you!

DirtyBird222 PowerDork
3/10/23 11:25 p.m.

I would run a axle back system with a helmholtz resonator to kill that drone. There's a ton of science behind it like figuring out the exact frequency you want to cancel out which correlates to how big or the shape of the helmholtz resonator is. 

PLM makes them for the 3.6 Camaros. I'm sure you could fab these on to your current exhaust. https://privatelabelmfg.com/collections/exhaust-headers/products/plm-axle-back-muffler-delete-chevy-camaro-2-0l-3-6l-v6-2016-2021-stainless-steel-dual-tips?_pos=3&_sid=256089ead&_ss=r&variant=40947124404362

APR Sells an inline version


I just bought this system for my S2000 to cancel out that 3000k rpm drone I was getting from the other cat back system I had, even with a helmholtz and a 1/4 wave tube. 

DirtyBird222 PowerDork
3/10/23 11:33 p.m.

You could download an app that could pick up the frequency of the drone, plug that information into this site to figure out the size that you would need and have one dabbed up. I personally would try an off the shelf option first. http://www.mh-audio.nl/Acoustics/HHReso.html


Also nameless performance makes a bunch of axleback stuff for Subarus with them built in if you want to try and repurpose one of theirs. 

VolvoHeretic Dork
3/11/23 5:50 p.m.

When your exhaust hits that drone sound, does it mean that's the peak scavenging RPM of your exhaust?

67LS1 Reader
3/11/23 7:42 p.m.

The OP mentioned "Rasp" not "Drone" so a Helmholtz tube probably isn't the solution.

Personally, I'd use two resonators as far forward as possible. And the longest body lengths I could fit.

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