I have a 2000 jeep cherokee classic with the 4.0. And I was thinking about cutting the second cat off that’s connected to the headers.

Would this boost power or not make enough backpressure? I think there is a set of cats off off the exhaust manifold.

 

Do you have a aftermarket muffler and tail pipe?
Cause that does not look quite stock to me.
My rear cat has flanges on both ends.

 

I have a flow master super 44. And I wanted to cut that cat off to install a muffler cutout in its place. Just to have a very loud Jeep when I’m with the boys.

 

I lost mine on the highway and now have a cheap muffler only after the split cats. It's a little louder than stock and sets a catylist efficiency code after a long high speed run.

 

On which Jeep?
Cause there is no O2 sensor after my rear cat so wondering how that is possible.

 

That is a resonator, mine also fell off (2000 with cali emission) and when I got new exhaust put on left it off. Its a little louder now but that's it.

 

Yea mine is gone too but no 02 issues so I'm guessing his is caused by another reason.

 

I kinda of figured that but what do I know. LOL
Plus he has XJ's and WJ's so I was wondering if a WJ is set up different.

 

nevermind...lol

 

I don't know about a Federal WJ but a Federal '00 XJ has an O2 sensor after the rear cat. Being that it is the only cat on the Jeep.
'00's can be either in an XJ. Federal or CA. All '01's are CA Emissions.

 

That's dumb. It's also possibly going to ROB you of power. Exhaust systems are just that - systems. They are designed to work together.

 

Sumthin' ain't right, Ralph. The sensor after the cat is just to tell the 'puter how your cat is feeling today. It doesn't have anything to do with the operation of the engine. (Californian packages are different.) See my sticky on that topic on the top of the XJ forum.

You need to look again. You should have at least one O2 sensor ahead of the cat somewhere.

 

I know that.
I am talking about how Dave said he threw a catylist efficiency code not running a rear cat.
And he makes sound like he has the dual cat setup.
As you pointed out the downstream O2 sensor just deals with cat efficiency.
On an '00 or '01 XJ with CA Emissions I don't see how that is possible cause there is no O2 sensor after the rear cat.
So the rear cat can't tell the computer it is not "feeling well" today. LOL.

 

That is not a cat...its called a resonator for what that is worth...I don't know if there is anything in it...There are 2 cat s in a 00 /01 but they are side by side up in the exhaust manifold. There are 2 because of the shape of the exh collectors..the first one cat's cyls 1-2-3 and the 2nd one cat's 4-5-6.They both then join into 1 collector at the crossover pipe. Each cat has a pre and post o2 sensor so the computer can change the fuel mix in 1-2-3 separate from 4-5-6. Then both cats have their own output o2 sensor to monitor each cat..All this is done in the "exhaust manifold"assembly before it joins the crossover pipe at the transmission bell housing

 

Know that too.
But every time I call it a resonator I get corrected. LOL.
In a Federal Emissions '00 the upstream O2 sensor is in the intermediate/down pipe.
Since there is only 2.
Jeep calls one part a resonator and the other a cat in one of their parts illustrations.
And even though it looks different in the illustration they look the same with an O2 sensor behind it.
I know this cause I stole the wiring harness and computer from an '00 Federal Emissions Jeep out of the boneyard.
Might try something someday. LOL.

Doesn't help that auto stores call it a cat too.

https://www.napaonline.com/en/p/EXC1...ndex=Universal

This is the walker replacement for my '00 with CA Emissions. Best I can tell what you would use for a Federal '00 too.
There is a bung hole that is plugged on mine.
Weird thing is look up the exhaust diagrams at Walker.
The first is a CA Emissions with a build date after 1/20/00.
Even Walker calls it a cat.
The second is a Federal Emissions with the same build date.
Notice how there is no part number for the cat in the Federal Emissions one.


Now I agree with you but just all this weird info that seems to contradict each other.
Done a lot of research on this over the years. MLOL.