I just bought a 91 NSX in great shape but it has one annoying problem. At about 2700 RPM there is a very loud vibration from the engine/exhaust. It's only during acceleration and after a couple of min of warming up. The car has an RSR Cat back exhaust installed about 5 years ago. My guess is that the resonance is in the exhaust. Is this normal for RSR? Is the RSR exhaust broken? Can this be fixed without a new exhaust?
Exhaust resonance at 2700 RPM
- Thread starter mc-ca
- Start date
I cannot speak to the RSR since I have not had a problem ever with one, and only installed one last year.
You may have some clearance issues. Check where the cat goes over the "rod beam" (Aluminum brace below the engine shaped like a big "U") Depending on the exact position of the exhaust it could be close to this and the cat is rattling against it. If you have headers check the downpipe for #6 (front drivers side) cylinder and make sure it is not hitting the front motor mount brace on the front beam.
It is not clear to me what exactly the sound is,so it could be the actual exhaust, but usually it is a clearance problem, especially if it changes with temp. Also under acceleration, the drive train will rotate counterclockwise and has potential to make the clearance with the rod beam/cat change. (smaller)
HTH,
LarryB
[This message has been edited by Larry Bastanza (edited 05 February 2003).]
You may have some clearance issues. Check where the cat goes over the "rod beam" (Aluminum brace below the engine shaped like a big "U") Depending on the exact position of the exhaust it could be close to this and the cat is rattling against it. If you have headers check the downpipe for #6 (front drivers side) cylinder and make sure it is not hitting the front motor mount brace on the front beam.
It is not clear to me what exactly the sound is,so it could be the actual exhaust, but usually it is a clearance problem, especially if it changes with temp. Also under acceleration, the drive train will rotate counterclockwise and has potential to make the clearance with the rod beam/cat change. (smaller)
HTH,
LarryB
[This message has been edited by Larry Bastanza (edited 05 February 2003).]
I think it's the exhaust. I installed a Tubi and have a resonance at that rpm. There was none with the stock exhaust.
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keep the shiny side up
MikeC 01 #46
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keep the shiny side up
MikeC 01 #46
It may just be the characteristics of the exhaust.
However, you may want to take a look at the exhaust very carefully. Some RSR exhausts have blown a hole/crack through the muffler/canister. I have seen 2 personally with cracks. If it is blown, the exhaust gets louder and may lead to the "droning" that you mentioned. Just check it visually with a flashlight when the exhaust is cold. Use your hands and feel on the top side of the canister for cracks or holes.
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www.acrmotorsports.com / 949-929-8973
However, you may want to take a look at the exhaust very carefully. Some RSR exhausts have blown a hole/crack through the muffler/canister. I have seen 2 personally with cracks. If it is blown, the exhaust gets louder and may lead to the "droning" that you mentioned. Just check it visually with a flashlight when the exhaust is cold. Use your hands and feel on the top side of the canister for cracks or holes.
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www.acrmotorsports.com / 949-929-8973
I checked the clearance and everything looked fine. The headers and Catalytic converters are all stock. It is just the exhaust that is aftermarket. I think that I'll look for a used factory exhaust and see if that fixes the drone/resonance. There was a part of the big metal strap on the muffler case that was broken off and flapping around just after I bought the car. A local muffler shop welded it back on and the noise level dropped.
A quick follow up - ACR got it right. The exhaust was cracked, right in the center. It was easy to see when it was off the car. I put a stock exhaust on and all is quiet! It still makes that great vtec sound at 5000+ RPM but I think that is from the intake resonator.
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