Why don't people just punch out the "screens" inside the OEM cats instead of buying high flow cats/test pipes? Is there a disadvantage to this? Will it resonate as bad as test pipes?

 

If you look inside the OEM catalytic converter, there is more stuff than just screens. You can take the time to gut the catalytic converter, or spend $200 on test pipes. Its your choice.

 

check it out.

to be honest, an OEM wants to spend the least money as possible, and there is so many things you can do to your car that is not illegal. such as a cat-back exhaust. x-pipe or y-pipe. everyone thinks x-pipe is illegal. but as long as it has a carb e.o.# it's ok.(california only) as far as cats. personally i think it would be best to go out and buy a high flow cat. cuz no matter what you do or how you look at it. when it comes time to smog your car, guess whats gonna happen.. yup, your gonna fail smog. and yup as soon as your o2 sensor starts getting all those weird readings sent to the ecu, yup your gonna trip your check engine light. and that is not all. your car will then begin to run rich or lean depending on what Lambda reads. if it runs rich, your car will get a nasty smell. if it runs lean, your damaging your engine. so, just go and get your high flow cats. so that way, you can pass smog, be street legal, and not damage your engine.

 

Just be a man and get test pipes. So there might be a little rasp and it's not street legal. What are you a saint? More power overall.

 

there's very little you can do to keep your car legal, so go crazy. but I know your question was not to keep your car legal, but it's just a thought.

 

many people have rattle problems after gutting the inside of the stock cat. There are screens, platinum beebee's among other sorts of cleansing material. On top of it not being that easy to gut inside of the cat. Also, your gutting a pair of $1000 cats that you may need in the future to re-sell the car. Easy enough to find, but to replace new would be outrages. Moral of the story, if you want performance, buy performance parts, dont make stock something it isn't.

 

initially I just bought a used set of OE cats for $50, gutted them out myself, and keep my OE cats in storage...gutting the OE cats didn't take long, but was a PITA. Make sure to where some kind of filter/mask b/c you won't want to breathe in all of the dust. (I bought a 1/2" drill bit about 18" long to do the job)

you could probably just gut the bottom portion of the cat out, and that would result in something very similar to a HFC...not as noisy/smelly/raspy.

 

The reason I bought test pipes instead of gutting my OE cats was that the inside diameter of the pipes is 2" instead of 2.5". With test pipes, a y-pipe, and a resonator delete, my exhaust is straight 2.5" all the way to the muffler.

 

OEM cats are heavy as fu*k compared to aftermarket HFC or TP...it's not just added hp, but also weight savings.

 

I did something similar. I bought a pair of gutted OEM cats. No issues, no negative noise, and no idea if it helped or not. lol However, the car does sound as I was hoping (more pronounced without any noise that could be classified as RICEY).

You can probably find them on Ebay or the classifieds cheap. Mine came with some other stuff I bought from another member, but it was cheap (close to $60 shipped).