Gutted cat noise

johnyrr · **Posted:** Tue Feb 24, 2009 11:38 am

So My friend gutted his cat this past weekend and was wondering what difference in noise people expierianced. I would have thought there would have been a little more sound, at idle it appears no different and when you floor it it seems to make more of a whooshing air noise and thats all we can tell. No more power and not really any noticible power. I think I might take it apart to see if he left a small chunk of the cat still there and maybe it lodged itself in the pipe and might be restricting flow/noise or something as he expected more from this mod. :roll:

liberty2.8 · **Posted:** Tue Feb 24, 2009 12:28 pm

Not much difference in sound except maybe a little more turbo sound (whooshing air noise) as you described it. Was gonna take it to the muffler shop today for the straight pipe but everything is closed today for Mardi Gras :cry:

I'll try again tomorrow. BTW, did YOUR FRIEND remove all of the cat core or just punch a hole through it. Pieces could have dislodged and clogged the pipe. If I were your friend, I would leave the flange unbolted and run around to ensure all loose pieces were removed; might require some banging on outside surfaces to make it all come loose.

bdptp73 · **Posted:** Tue Feb 24, 2009 12:30 pm

The turbo tames most of the noise. Gutting the cat will only reduce a little back pressure and allow more of the turbo whine out. Your friend might only see a little gain in mileage and it might coast a little better but that would be just about it.

Jason

johnyrr · **Posted:** Tue Feb 24, 2009 12:50 pm

why yes MY friend gutted the whole thing or atleast though he did. He did mention that maybe it coasted easier. I know the turbo does alot to muffle sound. My friend gutted the cat on one of his TDI's and noticed more noise and thats why he wanted me to ask others on the forum what were thier thoughts from when thier friends did the same thing. I think he might do a straight pipe too but doesnt want to incur a hassle from dealer if it ever need to go in for a convertor or something he could fix. I just think the dealer would look at a straight pipe and hassle the heck out of you. The wife is driving the truck so he will have to check mileage when he can pry it out of her hands.

JeepinJarhead03 · **Posted:** Tue Feb 24, 2009 1:53 pm

i used to gut cat's at the shop for me and my bro's and friends vehicles, if they have a heat shield on top, it's pretty easy to take them off and cut the top with a cutting disc, gut it, and shim the piece back on with another wider piece of metal and jb weld for sealing, can't even see it as long as the exaust is intact

i guess if the dealer had to take the exaust down to do something they might say something

or.. they might not, could always just say you patched a hole lol

liberty2.8 · **Posted:** Tue Feb 24, 2009 2:15 pm

Quote:

He did mention that maybe it coasted easier

That was one thing I noticed was that there was no longer the exhaust brake effect after guts were gone. I initially thought there was a 2-3 MPG gain because Lie-O-Meter suggested 28-32 MPG on highway but hand calculations show contrary. Will report after averaging several tanks of fuel.

fastRob · **Posted:** Tue Feb 24, 2009 7:38 pm

Get the vocal chords first or the gutting is noisy......

Actually I noticed no improvement.
The greatest performance improvement was cleaning the Manifold Air Pressure (MAP) sensor.
I also did a 3" CAT back with 3" Magnaflow muff, 2 1/2" would have been fine. And yes the Jeep does roll better.
Greatest improvements are due to programming: Inmotion, Edge and foot discipline(Happy Feet Control).

JeepinJarhead03 · **Posted:** Tue Feb 24, 2009 7:53 pm

Quote:

Get the vocal chords first or the gutting is noisy......

haha yes, i resisted a comment similar to this, my first thought this morning was Duhh.. you'd be noisy if we gutted you too..

Ohhhh he means the cat converterrrrrr

Cowpie1 · **Posted:** Wed Feb 25, 2009 6:29 pm

I yanked the muffler from my '06 International truck with a Cummins ISX 15L and replaced with just a resonator. Even with twin stacks and under full pull, it isn't all that loud. Turn on the jake brake and the noise is a lot more.

I am going to just cut off the cat in my CRD and just run a straight pipe to a high flow muffler and out the back. Shouldn't really notice any difference in sound. It is true, the turbos tend to knock the noise level down a bit.

retmil46 · **Posted:** Wed Feb 25, 2009 9:57 pm

JeepinJarhead03 wrote:

Quote:

Get the vocal chords first or the gutting is noisy......

haha yes, i resisted a comment similar to this, my first thought this morning was Duhh.. you'd be noisy if we gutted you too..

Ohhhh he means the cat converterrrrrr

Actually, if they're already gutted, they shouldn't be making any noise at all. :twisted:

Gutted cat noise

Who is online