01 XJ Header/precat replacement

USMCGunrock said:
To NAXJA MEMBERS: SOOO SORRY i mentioned "Cat Replacements or straight pipe". I'm 110% for cats, like i did say that i didn't replace mine cuz it was still good. The main cat i will replace IF it was bad WITH A LEGAL CAT REPLACEMENT. Again...VERY SORRY IF I OFFENDED ANYBODY.
Click to expand...
You didn't offend anyone. As a whole, the club leadership and moderators like to just make sure that the regulation is known, so whenever we see someone mention it, we make sure to post that there are regulations prohibiting it. Some people, however, freak out at the mere hint of correction...

:cheers:
 
After some more thought I may just end up going with an aftermarket replacement for the precats as long as I can find some that are "high flow" and have decent bends. We don't currently have emissions testing in Colorado but I would like to keep it legal if they ever change that. So I'll probably just end up replacing the precats with a high flow version and get a high flow cat.
 
Anyone know if that Catco precat is supposed to be a higher flow version?
 
Thanks, I dropped Catco an email. I'll forward their response.
 
That stupid stock version is so restrictive, it's producing enough heat to cause vapor lock and throw cylinder miss-fire codes in the summer with my 4.9L stroker... course I'm sure it doesn't help that it's 11 years old, probably pretty clogged up.
 
I changed my bolts to 8mm hex cap bolts so I could use my big Allen keys with the rounded
ends on it, ground the elbow off to fit a socket. Turns an ordeal into a 2 min jobbie.

Must suck with your emissions testing you guys got down in the US. As long as we have a
cat it's fine. It just needs to be good enough for the size of motor its with.
 
No emissions testing in Colorado!!
 
I don't know how big an impact the cat makes on a late model with the precats, but on single cat rigs, there's hardly enough restriction to make much difference until you get into serious horsepower numbers.
 
From Catco:

Dear Sir,

The 2200 is a converter that would flow better then the OEM unit installed on the vehicle now. The reason is because the 2200 series uses a metallic substrate as opposed to the ceramic type used in the OEM on your vehicle. The wall thickness is thinner on the metallic 2200 converter then on the OEM converter. This thickness affects how the exhaust gas flows through the converter. Also the 2200 uses a 200 cells per square inch substrate as opposed to the 400 cell used in the OEM cat. Again this would cause the exhaust gas to flow faster through the 2200 cat.


Bill Kaminski
 
Awesome! Thanks for the post Scienceguy!
 
Thanks for the follow-up...

Man, the items I 'need' to buy to add to my XJ just keep adding $$$ up... Header, Motor-Mounts to prevent cracking, Pre-Cats and exhaust to aid in the flow.
 
Redsnake said:
Thanks for the follow-up...

Man, the items I 'need' to buy to add to my XJ just keep adding $$$ up... Header, Motor-Mounts to prevent cracking, Pre-Cats and exhaust to aid in the flow.
Click to expand...

I was thinking the same thing. There’s no end to it. But I also like not having a car payment.
 
J. (Just) E. (Empty) E. (Every) P. (Pocket) lol

Redsnake said:
Thanks for the follow-up...

Man, the items I 'need' to buy to add to my XJ just keep adding $$$ up... Header, Motor-Mounts to prevent cracking, Pre-Cats and exhaust to aid in the flow.
Click to expand...
 
With a stock engine, or even close to stock, you won't be flowing high enough to worry about the little gain you get through a better cat. If your stock ones are functioning, your money would be better spent elsewhere. Shelbyluvv tested his car that runs an 11.46 quarter, and he found only 0.1 second difference between cat and no cat. If his car, putting well over 300 hp to the ground sees that little difference, chances are, our XJs won't see any difference. Do a good cat back, better intake, put some money into the heads, a cam, etc. Hell, regearing makes a huge difference in performance.
 
I'm looking to replace my precats because they are 11 years old, probably pretty clogged and they produce enough heat in the summer that they cause vapor lock and cylinder miss-fires. Which is apparently a common problem even on stock 4.0s.
 
I think Darky makes a valid point; although, I would rather see a true comparison between the OE cats vs. the Catco cats from a performance standpoint. Even though the performance gain might be minimal, the difference could still be measurable. The Catco by itself might not be huge, but the combination of modifying the entire exhaust system might make a more overall difference.

I agree with Darky in that sometimes we spend money in areas having little significance while overshadowing the areas of greater significance. Upgrading to a better cam for example might yield a more measurable gain than paying $250 bucks for a fancy air intake that probably performs nearly the same as stock. From that perceptive, the idea that “money would be better spent elsewhere” has some validity to it.

Personally, I think it about priority. Prioritize your spending to give you the best outcome. In my case, I’m redoing my entire exhaust, so why not pay the extra money and go with the Catco? Then again, I don't have any car payments, so I don't mind spending a few hundred each month for upgrades and keeping my vehicles in good working order.
 
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