I gutted my cat today....but....
 

I decided to take off my cat and gut it today. One for better mpg and two for the 2 or 3hp it gives you, which by the way, you CAN feel. Ok got everything hollowed out and put it back on. But when I go past 3k RPM accelerating fast, it makes this weird like vibrating or buzzing sound. It used to always do this if I haven't cranked my car for about an hour or so and then stopped about 1 minute later after it warmed up. It always sounded like it was coming from the cat. But now it does it every time I hit around 2800 to 3000RPM's and then stopped at like 3,100 RPM. Anyone have a clue what this could be? I made sure and got all of the **** out of it including the insulation....

RE: I gutted my cat today....but....
 

There could be a little piece of something vibrating inside the cat, or it could just be the way the exhaust hits the inside of the "gutted" cat causing the exhaust to make a vibrating sound.

The best way is to either buy a "test pipe" or just put a straight piece of pipe in to replace the removed cat.

RE: I gutted my cat today....but....
 

yea that's what Im thinking. Im gonna go with a high flow cat though I think. It's legal and still has better flow. Know any good brands that have cats that just bolt right up rather than being welded and that are under 100 bucks?

RE: I gutted my cat today....but....
 

I saw Magnaflow cats on e-bay for under 100. Depending on your application some were ~ 50.

Vibrations and buzzes are pretty non-descript and hard to diagnose, but is it a rattle like one of your heat sheilds or is maybe the resonance of the extra sound vibating something on your car right there?

How much louder is it? The exhaust I mean.

RE: I gutted my cat today....but....
 

It's not THAT much louder...Plenty noticable but not like way to loud or anything. Im thinking it might be something rattling form something being loose or something I dunno. It's not the heat shields seeing how they are not there anymore lol.

RE: I gutted my cat today....but....
 

i still say the Random Technologies cats are well worth the 200-225 you pay for them. but i know how it is trying to save up for every part.[:@]

RE: I gutted my cat today....but....
 

gutting cat [sm=nono.gif]

RE: I gutted my cat today....but....
 

mine does the same thing and its my short shifter hitting the exhaust, only way it would rattle is if you missed some pieces, and why would you trash a perfectly good cat, you could have sold that to a recycler for like 40 bucks even if it was bad

RE: I gutted my cat today....but....
 

it is not likely...but there is a small chance that when you put the cat back on the exhaust moved...i know when they took mine off and put it back on my cat-back moved and then at certain times my exhaust was rattling against the frame of the car...it was an easy bend-fix...but as i said its probably not going to be that in your situation...p.s. if you think it is that...a place like meineke will pop it up on a lift and take a look at it for you...they put mine up and fixed it for free!!!:D