resonance problem
Thread Starter
Advanced
Joined: Jul 2019
Posts: 53
Likes: 2
From: begium
resonance problem
Good morning I have a very strong resonance problem in the car between 1600 rpm and 1800 rpm I removed the 3 catalysts and the silencers from my 1988 C4, for the first 2 small catalysts I cut above, removed the 2 cartridges and resoldered them, it's invisible. for the central catalyst I broke it into pieces, removed it all and reassembled it, invisible too. I mounted two rear exhausts by removing the grille with rock wool and enlarged the outlet edge on the 4 outlets. The Corvette will make a nice sound very well, but between 1600 and 1800rpm it resonates in the car so loudly that you can no longer speak or hear the radio. This is very annoying because the maximum occurs at the legal speed on the motorway in Belgium. I put ceramic insulation in the rear fenders and everywhere I knew in the bumper but it didn't change anything. If you have any ideas or suggestions, I'm all ears. THANKS
Melting Slicks
Joined: Feb 2019
Posts: 2,568
Likes: 568
From: Carterville Il
2024 C4 of the Year Finalist - Unmodified
Good morning I have a very strong resonance problem in the car between 1600 rpm and 1800 rpm I removed the 3 catalysts and the silencers from my 1988 C4, for the first 2 small catalysts I cut above, removed the 2 cartridges and resoldered them, it's invisible. for the central catalyst I broke it into pieces, removed it all and reassembled it, invisible too. I mounted two rear exhausts by removing the grille with rock wool and enlarged the outlet edge on the 4 outlets. The Corvette will make a nice sound very well, but between 1600 and 1800rpm it resonates in the car so loudly that you can no longer speak or hear the radio. This is very annoying because the maximum occurs at the legal speed on the motorway in Belgium. I put ceramic insulation in the rear fenders and everywhere I knew in the bumper but it didn't change anything. If you have any ideas or suggestions, I'm all ears. THANKS
Your issue is from hollowing out your mufflers......The factory mufflers were designed to have one side of the muffler blocked off. This prevents the dreaded drone. All the sound deading insulation won't help at all. You are going to have to put on new mufflers or just get a whole new exhaust system. Or try re-blocking one of the muffler outlets.....
Last edited by Rush91; Apr 12, 2024 at 09:46 AM.
Drifting
Joined: Sep 2022
Posts: 1,488
Likes: 395
From: Liberty, SC
2023 C4 of the Year Finalist - Unmodified
"The factory mufflers were designed to have one side of the muffler blocked off"
i have wondered about this. I suspect that my mufflers are OEM... at any rate, the right , more than the left, only has exhaust coming out of 1 of the 2 outlets. I was wondering if i needed to try to get a blockage out or not. Sounds like i can just let it alone.
i have wondered about this. I suspect that my mufflers are OEM... at any rate, the right , more than the left, only has exhaust coming out of 1 of the 2 outlets. I was wondering if i needed to try to get a blockage out or not. Sounds like i can just let it alone.
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
"The factory mufflers were designed to have one side of the muffler blocked off"
i have wondered about this. I suspect that my mufflers are OEM... at any rate, the right , more than the left, only has exhaust coming out of 1 of the 2 outlets. I was wondering if i needed to try to get a blockage out or not. Sounds like i can just let it alone.
i have wondered about this. I suspect that my mufflers are OEM... at any rate, the right , more than the left, only has exhaust coming out of 1 of the 2 outlets. I was wondering if i needed to try to get a blockage out or not. Sounds like i can just let it alone.
Instructor
Joined: Sep 2022
Posts: 209
Likes: 81
From: Dalbo, Minnesota
Search the internet for, “Helmholtz resonator exhaust”.
You can purchase resonators or fabricate your own one.
the resonator will cancel the drone at its design frequency. YouTube has before and after videos.
You can purchase resonators or fabricate your own one.
the resonator will cancel the drone at its design frequency. YouTube has before and after videos.
Pro
Joined: Jun 2018
Posts: 532
Likes: 104
Get quieter mufflers. You can also add cats back in to replace your bad ones, or a resonator in the center and that might help some, but the easiest solution is good (and by good I mean quiet) mufflers. That will eliminate your drone.
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