need new cat...

need advice

now, i know this has been discussed time and time again....but for the most part i dont really remember the verdict...(probably cuz it didnt affect me at the time

i have a 96 4.0 HO XJ, auto, and i think the cat is going bad (heavy duty rattle at idle and most low end speeds ( i dont hear it on the highway)
it is NOT the heat shield...and a mechanic buddy of mine thought it was the guts of the cat rattled loose

my 3 options:

1) buy new OEM cat

2) buy aftermarket hi-flow cat

3) hollow out existing cat

are the hi flow cats worth the $?? which brand is best? ($/performance)

im eventually going to do a cat back exhaust....so the more performance i can get out of it, the better

thanks!!

CaptTrev
Member #255

Being '96 and OBD II.......

You really should use one certified for use on OBD II vehicles, and most are not certified for use. Carsound on line has them and well priced. The OEM ones on these later Jeeps are the same ones used on Grand's 5.2's so will flow plenty. And, make sure to keep your cat. These engine systems are designed for proper backpressure and the help for the environment is not so bad a thing either.

If not also upgrading the precat system, just replace the muffler with a better one of same pipe size. Upgrading the size of the exhaust pipe following the cat will have no effect whatsoever except to your wallet...reguardless what people may say. Is just not physically possible-

I had a random technology cat on my '95. When I destroyed it and got a '96 I found that the aftermarket cat products for the OBDII is slim. Random technology makes one, but they had also told me that they were getting mixed reviews; I believe the second O2 sensor is not heated properly. Listen to Judd and get an OEM cat that is OBD II certified. I have heard of terrible performance on XJ's with the cat removed.

If you get a new cat make sure that it has the bung on it or you can get one w/ out & have one welded just after. I run a Borla header w/ a custom 2 1/2" exhaust after the header collector w/ a high flow cat & DynoMax muffler on my '97 & it runs GREAT.

cat

try truckperformance.com.
I just got a high flow cat from them for 68.00, Carsound and it was on sale. I do have an 88' but it's worth looking into.

What would the effects of running without a cat or with a hollowed out one be on my 89? Will I lose low end, what will it sound like with a cherrybomb? What are the effects on the enviroment?

It takes a lot to loose low end. Just look at the piece from the CAT to the header, not exactly bent mandrel tubing and also the Dia isn't very big. With that, it sounds cool, louder but on the free way, can't really notice a difference.

I am able to start out in 2nd gear again, so I actually increased the torque a bit. My CAT was PLUG UP, like someone stuff a banana in my tailpipe,

Keep the cat

I say again, gotta keep the cat. There are many good reasons for this, and is NOT terribly hard to loose low end on these 4.0's- just talk to Rusty at Rusty's. I spoke with him when deciding whether or not to order his 2.5" catback system. He said even with a full 2.5" system (which is what i made for my '98) that as long as the cat is retained most low end torque will still be there. He said when they tried it without the cat, lost all low end.

Had better get used to emissions stuff on vehicles. It is here to stay, and is way better designed now than used to be even if it does cost sometimes to keep it in good working order.

The guts came loose inside my CAT a couple years ago. I didn't feel like spending the money for a new one, so I spend $6 on a piece of pipe the same length. I haven't noticed any performance differences one way or the other. It is a little louder without the CAT, but power and gas mileage are the same. I kept the old CAT and throw it in once a year for the emissions inspection. The guts are loose, but evidently it still reduces the emissions or they are low enough without it that it passes.

I actually just had my cat replaced today at the dealer. I also have a 96 and it is still covered under the federal emissions warranty (80k or 8 years). You should look into that if your jeep is in that range. It cost me $0 =)