Couple of questions about tweaking exhaust

Hey guys...I'm thinking about adding a couple of either high flow cats, or glasspacks to try to kill some of my interior resonance. Any suggestions or videos of flowmasters with glasspack used as resonators or something?

See, the thing is, this exhaust has an AMAZING exhaust note. Very loud, very deep, almost masculine in its nature. The problem is it's a bit too loud, and at a couple of spots in the rpm range i get REALLY BAD cabin resonance. I'm going to add a couple of flexpipes that should help a lot, but i think i need to do a little bit more than that. I'm really just fishing for ideas in your brains right now, i'm not going to do it until i have the car back together and on the road, that way i can tell whether fixing my broken motor mount has helped with the exhaust resonance.

thanks guys!
Ethan

I think if you're having cabin resonance issues, I wouldn't believe it's the exhaust, but rather the mounts (and possible lack of bushings) that are securing the exhaust. The vibrations from the headers and rest of the system are travelling through the mounts and into the frame.

One thing I learned awhile ago is that resonators are just another kind of muffler really. When I had my 84 300zx running a magnaflow muffler on the end, I installed a straight magnaflow muffler in the middle of the pipe and it helped with the high end rasping and some db levels.

I am running 2.5" duals all the way to my muffler. I had an H-pipe installed just after the high flow spun cats. I could not beleive the change in tone and loudness. Very driveable, sounds almost like a stock 2.5 with twice the HP.

thanks to all for your responses so far...i'm intrigued by the H pipe after the cats, that's very interesting!

Pat i think you may be right on this one, it probably has to do with the custom solid mounts i made to bolt the sucker up to the frame...is there something i can add to that to help insulate the mounts? i'll add pics later, but the basic idea is take a couple pieces of angle steel, cut out the 2 pipes worth of material, tack them on, then drill holes and use existing studs on frame to mount. Maybe a rubber disk or something would help?

You already have an X-ish pipe within your system. You want to add an H-pipe too?

Pat i think you may be right on this one, it probably has to do with the custom solid mounts i made to bolt the sucker up to the frame...is there something i can add to that to help insulate the mounts? i'll add pics later, but the basic idea is take a couple pieces of angle steel, cut out the 2 pipes worth of material, tack them on, then drill holes and use existing studs on frame to mount. Maybe a rubber disk or something would help?

Thing is not to mount the vibrating steel directly to the frame. If you no longer have the stock rubberband/hook setup, maybe you can get away with an eyebolt/rubberband setup. Make a band around your pipes and fashion a loop or a hook out of it, then pick up a set of exhaust hangers (rubber) and use those to suspend (isolate) the pipe from the frame. I used a modified setup like this on mine using the stock hangers and some brackets that I welded. No muss - no fuss.

i didn't really have the room to do that with dual 3's, which is why i went with the setup i did...maybe it's time to do some sound deadening? I'll take a look next time i'm under there, but i'd like to stick with the mounts i have, since they work quite well!

I was a bit irritated with cabin resonance in mine so I kept adding to the tips. Make sure your tips are past the back bumper... amazing difference!!

interesting...i may have to take a look at that!

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Pipes were originally 1" past where the bigger ones start, Then I added the bigger ones and it helped, then I stuffed another longer pipe inside that to just past bumper. Sounds great inside with no drumming. I was tired of building and wanting to drive in peace and quiet! Still Shrieks WOT!

I do have a 3" high flow cat, 3" Cherry Bomb about 27" and 3" single muffler I built with dual 2 1/4" out. Mine has more of a staccato sound!

so i extended my exhaust tips out a little past the bumper...i'll add pics and maybe video soon, but it definitely, DEFINITELY helped with interior resonance...i have something that touches and rattles occasionally, so i need to get back underneath the car and take a look around...but other than that everything is nice!

Glad I could help!