Ways to reduce exhaust resonance?

G

Gary McCormick

True Classic
Since it now qualifies as an antique here in PA, I replaced the catalytic converter in a stock exhaust system with a straight "test pipe". There now is a very loud (and annoying) resonance in the exhaust system at about 2400 rpm.

Suggestions on how to reduce this noise are welcomed.

Gary McCormick
Carlisle, PA
'79 X
 
This is one way.

Try this link.

http://vibrantperformance.com/catal..._1111&osCsid=62172de9c50873f47d97cbaa72388ec9

Vibrant makes performance high flow Racing Cat's. I have one on my car. This is an all metal Stainless Steel unit that does not have a ceramic core, but one made of metal. You may have to get some adapters to meet the small 1 7/8" pipe diameter.

Take a look at my 2 1/2" unit on my custom installation for my 79 X.
P3050452.jpg


TonyK.

Grimsby Ontario Canada
 
Gary:

Changing pipe length, orifices, baffles, etc will all effect and or change resonance.

Cats do baffle exhaust and change resonance.

I do not know what kinda roads you drive on, but I rarely drive sub 3000 rpm, so this lower resonance would only be a blip on teh rev scale to me (yes, I do driove around one gear lower then I probably should), but to you, I must be right in your cruise range.....

If you drop down a gear to get teh revs up another 1000 rom, what happens to the resonance.

changing teh length or distance of the pipes in your exhause can move the resonance up pr down in teh rev range....
 
Don't work in a library.

The exhaust system on my car was custom built by me. I don't like resonance but the 2 1/4" system had it( resonance) with the Cat and 1 chambered muffler, so the second was added. The sound, now is nice, throaty and Free Flow from the 1 7/8" stock system. Here is a picture of the proto type with on muffler on the floor with stainless headers. The headers stayed but the second chambered muffler was added. The bottle resonator was removed.

FinalAssembly2.jpg


FinalAssembly3.jpg


TonyK.

Grimsby Ontario Canada.
 
Looks very well done...

Would love to hear what it sounds like. If you can, could you post a vid for us to hear?
 
As Kevin says, Gary...

... and ya might wanna see if the testpipe was installed securely and tight. I don't know if they used old or new flanges, slip fittings and clamps, or welded it in. Also look for any leaks.

If all is well.. you might wanna look at what TIP you have, and change it out, experimenting to change the tone, and POSSIBLY the point the system resonates at.

If it truly is 2400 rpm, like Kevin said, I'm only there for an instant and probably never cruise at less than 3000.

You can also consider reinstalling a CAT... Summit has a nice universal for less than 60 bucks!
 
Gary McCormick said:
Since it now qualifies as an antique here in PA, I replaced the catalytic converter in a stock exhaust system with a straight "test pipe". There now is a very loud (and annoying) resonance in the exhaust system at about 2400 rpm.

Suggestions on how to reduce this noise are welcomed.

Gary McCormick
Carlisle, PA
'79 X
Click to expand...

1979 Xs are my daily drivers, and every single one of them gets a test pipe in their stock exhaust system. They don't have any resonance, so I can only assume that you have another problem. Get it doing the noise while in nuetral, then start poking around to see what part the noise is coming from.
The advantages of the test pipe is greatly improved gas mileage & more power, so if it's only annoying at one engine speed just make it a habit to not drive that speed.
 
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