I've heard that if I gut my cat the interior diameter will be TOO LARGE and slow down the exhaust velocity? What do you guys think? I was going to get a high flow cat, but they seem rather expensive, and a lot of people complain about them clogging up in just a few months.

If it is okay to gut a cat then, I will take anyone's glogged 2.5" off his/her hands real cheap.

 

bump

 

The inside diameter of the cat is too large. It works kind of like a resonator and causes a loss of performance. Best thing to do is get a test pipe. I had one custom made by cutting off the flanges for the bolts off my cat, and welding a 2" pipe in between them. That way it bolts in and out without being welded to my headers and exhaust in case I ever need a cat again. Best $20 upgrade ever.

 

I've heard that test pipes are way too loud. If I don't gut out a cat I'll replace it with a resonator. I can't use the flanges from my current cat anyway because I'm moving up to 2.5". Thanks for the reply.


[Modified by fredtoast, 4:57 PM 4/3/2003]

 

No problem. My testpipe is hooked to a DC-Sports 4-1 header and Tanabe Racing Medallion.......it's a little loud, but still sounds good.

 

The reason a gutted cat will disrupt flow is that what you are left with is not designed for flow. It's either a box with lots of crap hanging on all over the place, or at best a large empty chamber that will create turbulence and reduce gas velolcity.

The only way to go is a test pipe if you really want to improve your system flow. Even if you are increasing the size of your system you can make one from parts at Pep Boys or any muffler shop for $20, like the previous post said.

If you have a well designed muffler you shouldn;t be much louder than you are now.

FWIW, there are very few things you can do to a car with a hammer and chisel that result in real performance gains!

 

Thanks for the reply, but come to Tennesse sometime and I'll show you a few things about weight reduction. Most sheet metal is optional around here.




[Modified by fredtoast, 10:51 AM 4/8/2003]

 

OK, you got me on that one!

Hammer and chisel is a good way to "add lightness"....

 

Test pipes aren't that loud. I've got one with a JDM 4-1 and it didn't make a noticeable difference. You probably already have a resonator so you shouldn't need a second one. One thing I did think about doing instead of getting a test pipe if you already have a 2.5" burnt out cat sitting around is to gut the cat and get some sort of aluminum or steel tubing with a 2.5" OD and shove it in the cat. The piping shouldn't move and it's nice because the cat already has the flanges. And the flow of air will be smoothed out. It would also pass a visual inspection too.

s

 

I cut the flanges off of my stock cat and welded them to a pipe. That way the test pipe bolts in and out.

 

Also, Florida isn't very bad with visual inspections. We get away with alot of ****.

 

i agreee with you