I bought a generic "OEM style" catalytic converter off of ebay that me and my father installed ourselves. After about 1000 miles, I am getting this throaty growl coming from the exhaust whenever I hit 5k RPM and above. It also seems like its a bit down on power when it makes this noise.

When I let it idle in my driveway after hearing this, it stalled out once, and had to crank a few times to get started again. I can't seem to get it to make this noise at all when cold. I got a compression test done a week ago and the numbers were mid range, "ok" the technician told me. He did say I had quite a few exhaust leaks and that the rear O2 sensor is showing "no flow". Before I had the compression test I replaced the coils, wires and plugs as well.

It kind of sounds cool but I get this feeling like maybe the cat is blocked already and that noise is coming from exhaust coming out the front of the cat. By the way it has a Borla muffler on it.

 

Sounds like you've already killed a cheap cat.

 

I am assuming having this clogged cat (if that's what it is) is doing terrible things to the engine? Since, I don't want to drop a grand on an OEM cat, can anyone recommend something that will give me similar noise levels? I bought the car with a midpipe on it of unknown brand and that was WAY too loud for my tastes, and my neighbors ears. That's why I dropped $300 on a knock off cat from ebay.

 

Get a davesport cat and have it welded in to your midpipe, or in place of the ebay cat. That is if you want a cat. If not, check out the BHR midpipe. You can get that with a davesport cat as well.

 

Leave the cat too long on your car will eventually kill your motor as well....stop driving it before you swap it out...

 

did you fix the exhaust leaks?

 

I'm going to the muffler shop to have them fix the exhaust leak and look at the cat and see what shape it's in. I'll update soon.

 

Muffler shop fixed the exhaust leak. I was missing a bolt between the header and cat. It doesn't smell now, but I'm still getting the grumbley rhythmic roaring sound above 5k rpm. I seem to only be able to do it in second and third gear. Probably 4th but I don't want to be going that fast on the roads around here.

As a side note, the muffler shop guy thought I had an aftermarket header. He thought so because the header had no heat wrapping around it. It might very well be aftermarket, considering when I bought it, it had the racing midpipe and borla exhaust. Does anyone know if the stock header had heat wrapping around it?

 

No.

 

I tried to get the sound on video. Didn't have a lot of road to film on. :*(