gutting cat. - Toyota Nation Forum : Toyota Car and Truck Forums

victor91mr2 · 02-24-2005, 11:04 PM

has anyone gutted their cat., if so how did you go about doing so. i want to gut my cat because i dont really want to spend 300$ on a downpipe. thanks

T3vzGfeF · 02-24-2005, 11:15 PM

well my friend and i used a heavy duty pry bar and a hammer to gutt out my cat, until we saw a crack in the middle part of the cat...so then i ordered a test pipe on ebay...it replaces the stock cat...

check it out--> http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

S92GT · 02-25-2005, 12:26 AM

humm, what all does this do for performance, where are the gains on the powerband, where can you feel it the most?

vtsuckah · 02-25-2005, 05:48 AM

It's not worthe the time and effort, not to mention your car will reak of sour ass.

Pineapple · 02-25-2005, 08:39 AM

A gutted cat will acturally hurt power.
If you look at the thing closely, it got bigger size then your exhaust pipe. With the stuff inside, it got same x-section area as the pipe so exhaust flow with same velocity and pressure. Removing the ceramic inside the cat will increase x-section area. When gas go from a small x-section to large, it slow down, then it need to squeeze down again to exit the gutted cat into small pipe. The expansion and compression require energy which increase back pressure and reduce exhaust velocity.
Either buy a highflow cat or replace it with a pipe.

vtsuckah · 02-25-2005, 09:11 AM

Pineapple is right, there is no gains from doing so. I could go into the whole thermodynamic explanation, but pineapple's will do.

S92GT · 02-25-2005, 10:06 AM

I didn't mean gutting it, I meant the test pipe, getting rid of the cat all the way, how much is that?

Pineapple · 02-25-2005, 10:20 AM

A few pnoy. Cat are not that restrictive. Get a 3S-GE header, stock one are good. That'll remove your stock cat. You can put one back after the header or leave it that way.

Quote:

Originally Posted by vtsuckah

Pineapple is right, there is no gains from doing so. I could go into the whole thermodynamic explanation, but pineapple's will do.

I've forgotten all already.

S92GT · 02-25-2005, 12:08 PM

well, rockin' a 5s I can use all the HP available

vtsuckah · 02-25-2005, 12:15 PM

haha still not enough to make a diff. A header and cams will give you the most bang for your buck.

Pineapple · 02-25-2005, 02:52 PM

Quote:

Originally Posted by S92GT

well, rockin' a 5s I can use all the HP available

You don't really want to free flow everything. 5S is about torque, not HP. Get a 4-2-1 header. 3S-GE one will do, even stock one is 4-2-1.

T3vzGfeF · 02-25-2005, 04:50 PM

well i have a video clip of my exhaust with the test pipe revving it up...but i need a host...

victor91mr2 · 02-25-2005, 11:28 PM

you all may think that there is no hp gains but when you think about it,
back- pressure isnt exactly what you want with a turbo system(3SGTE not 3SGE). That cat. is completely plugged, its like a sponge. Also this is an "In-expensive" way to free my exhaust of any restrictions wich was the goal to begin with, with this mod i may lose some torque(minimal), but my spool time and repsonsiveness with be enhanced. Its not like im gutting the cat while using factory exhaust, im using the 3in APEXi N1.

karugs · 02-25-2005, 11:50 PM

I thought you were going to slice your pet cat up

MR-355-5sfTe · 02-26-2005, 03:00 AM

Quote:

not to mention your car will reak of sour ass.

I'm glad someone mentioned the smell! my rx7 had a gutted cat, and it smelled like sulfur... aka "sour ass".... but it made that rotary scream.... once I get my 5sfe turbo engine installed I will be running 2 1\2" from the turbo to the tips.... no restrictions, and minimal bends....