Which catalytic converter with new exhaust?

Hi. I plan on ordering the exhaust system from Rusty's with a flowmaster. I will keep on my stock exhaust manifold but my catalytic converter is still stock. I don't know if I have to replace it or not? Will it effect the flow or the sound at all with the new exhaust system. If I do have to replace it could I just buy any cat, or should I be looking at a certain one. I'm trying to keep the cost down since I'm a little short on money. thanks for any help....

You shouldn't have to replace your stock cat unless it's bad. I've smashed two of the OEM style ones on the rocks. The third time I got the Carsound one and have been very happy with it. It is a hi-flow style and seemed to be a bit better constructed. I noticed a small improvement in power but its just a "seat of the pants" impression, no way to verify.

Either way, you can expect to pay between $80 to $100 for a new cat. And depending on the laws where you live, it may not be legal to remove your stock cat unless it's faulty and needs to be replaced.

Hope this helps!

Dave

I second that, no need to replace it unless its broken (even though I replaced mine when I did a header to tailpipe exhaust redo).
I belive that the part number for the 4.0 cat and the 8 cylinder found in the grand cherokees is the same, so flow shouldn't be an issue.
If you do decide to get a new cat, look at catco hi flow cats. They are tiny compared to stock, a little better made in my opinion, and are only about 60 dollars from summit racing.

You didn't mention what year your XJ is or the mileage, but if it's under 5 (8?) years old or 80,000 miles it's illegal to replace your OEM cat anyway, unless it has failed.

It's an 87 with 168,000 miles. The cat makes a rattling noise when idling and it's very annoying. how do you know when the cat is bad?

Mine is making that same rattling sound. Are the ones from Summit a universal, or made for an XJ?

lostcreek21 said:

It's an 87 with 168,000 miles. The cat makes a rattling noise when idling and it's very annoying. how do you know when the cat is bad?

Click to expand...

That's how you know

Summit offers both a universal fit and a direct fit. I have used their direct fit on an XJ and an MJ and I have another waiting to go into an MJ. They are a direct fit -- they include the square flange to bolt up to the header pipe. The universals have round pipe on both ends and you re-use the old flange and a short length of the pipe. Summit's are Catco brand.

In addition....

For someone who may be reading this owning a later XJ, the converter used on these is the same as on the ZJ 5.2 so am sure it is up to the flow-task. No need to replace it for additonal flow requirements.

Not in CA you cant!

If you live in CA and you need a cat on a 96 and up ANYTHING!!!
You must use a factory cat or a cat approved by CA for replacement..IE has a C.A.R.B exemption number....Its a plate welded to the side of the cat and shows that CA accepted this cat for use in the state of CA.

FYI= CA stands for: 1. California
2. CANT do ANYTHING

If you guessed 1, your wrong! :bunny: