Lets make this nice and simple.

I just got a custom single 2.5in exhaust made for my 1990 rx7 vert. It has no cats, resonators, or mufflers. Just like any rx7 with an exhaust leak, it is making that god awful bubble/farting noise at low rpms. So could the exhaust be so free that it is making the noise, or is it an exhaust leak for sure? I also cut that metal hose to the stock cat and didn't plug it back up. Could that be making the leaking noise? I would like to have one rx7 that doesn't have a leaky exhaust.

 

The split air pipe can be left alone. You'll just be pumping air out through it if your air pump is in place. But it won't make noise.

You could have exhaust leaks if your gaskets aren't the best, or you have some warped flanges. Or the sounds you hear could be from thin-walled tubing.

 

The exhaust shop guy put a new gasket on the header where it normally connects to the pre cat and the rest of the exhaust is welded together. The tubing is 2 1/2 in diameter and it is thick tubing.

 

Then it may not be leaking at all, and you're just hearing the annoying sounds associated with an NA that has a fully open exhaust. A presilencer/resonator does a great job of cleaning up the exhaust note. It certainly did when I went from a straight pipe to one on my NA.

 

+1 vote for possible warped flange. My 2.5" custom pipe was made using the original pre-cat flange, so it was welded RIGHT at the flange. This caused it to warp, so it never sealed. I took it to a friend (ex-midas worker ) and he removed the piece, heated it and beat it to submission. Upon reinstalling the pipe and gasket, he recommended I let him use muffler mud on the gasket. I was skeptical, but I let him do it, and it never leaked. Later on down the line, I replaced the clutch and I didn't reinstall the gasket with muffler mud, and it leaked. So my lesson learned - don't weld ON the flange, and if it's warped, it's done... unless you use muffler mud as you would rtv.

 

Well the next time I go to see the car I will check if the flange is leaking. I am planning on adding a resonator as well, so the problem will be fixed soon. Thanks guys!

 

Who makes this mud + where can I find it. Is that the exact name too?


I tried RTV... don't ask me why. + yeah it didn't work. It did, but only where it was super thick.

 

You can find it at any discount auto parts store like advance/autozone/oreilly/krager etc. I don't remember its exact name, but it's sold in a tube and looks like plumbers putty when it comes out. Hardens like cement when it cures.

I think it's also used for rednecks to patch holes in their mufflers...

 

It's Sodium Metasilicate. At the auto parts store, the box will say "Muffler repair paste".

The stuff actually isn't ghetto when you think about it. The water boils out of it at 212*F and it will not melt until 1500*F. It hardens into glass.