Aftermarket cats

G

GudaXJ

NAXJA Forum User
Location
Richmond, Va
I'm about to redo my exhaust. I've searched and have got a whole bunch of info on different mufflers but not too much on high flow cats. I've read about magna flow and gibsons. I saw one on quadratec by random technology for $269, and that seemed a little steep. In the end i'm looking for deep idle with a little to medium growl. I hate noise makers! I'm basically looking for input on different cats and even mufflers. I was told two glass packs would give me reallly deep sound but not too loud, but all the glass pack jeeps i've heard seemed a little ricey at hight rpms. Can anyone suggest a good quality high flow cat and muffler combo?
 
Oh and its a 98 4.0...
I was just at rusty's website and they don't recommend the flowmaster 40 series? I've been reading otherwise someone fill me in...

Thanks in advance!
 
It's just taste in sound. They think you should run a quieter muffler with a I6. They are probably right on even a decently modded 4.0. It's all subjective though. I have a dynomax cat back, catco hi-flow cat, and borla header on my 4.6L and it sounds bad ass.
 
I have not done my XJ yet but on my YJ I did a new system using a pacesetter header, a carsound cat off of ebay and a 40 series flowmaster all in 2.25 and it sounded great. There is no reason to pay so much for a cat check out ebay for some. I plan on doing the same to my xj in the future but useing a different header this time.


http://cgi.ebay.com/2-25-Magnaflow-...ryZ33629QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
 
OK guys, I am probably gonna get a ton of flack for this one. All of these companies that are selling you a "high flow" cat aren't really selling you one that is any different from a "standard" cat. If you have ever seen the insides of the convertors they all have the smae substrate construction. The honeycomb is exactly the same. Eastern catalytic has come out with a true high flow cat, but they are only in universal applications as far as I know. They did not make a direct fit the last time I looked into them. The reason that they say that there cat is a high flow is the substrate construction. Intead of having 4000 small holesfor the gasses to pas through, it only has 400 holes of a greater diameter for the gas to pass through. The numbers are academic and not actual, but from what I have seen this is the only true high flow cat.
The reason that you may not want a 40 series Flowmaster is because it can get kind of obnoxious in around town driving. I know because I have one. On the highway it is no big deal at all. I might suggest a Flowmaser Super 40 or even 50 series for a daily driver.
 
Next year my XJ will be to old to have an exhaust inspection.

Can you run without a cat and just pipe it straight to muffler.?????

PS. its 4.0 as well.
 
I got my new cat from fulllinexhaust.com, it was a magnaflow that bolted right up. Between that and the dynomax ultraflo muffler the Jeep sounds pretty good. It only costed like $60-70, so I couldn't complain compared to random technologies. But you do have to remember that random technologies is supposed to be stainless where mine is aluminized.
 
Magna flow makes a kick ass exhaust plus on their website you can hear it, click on the wrangler with the 4.0. I bought one plus the random tech. cat plenty of power plus low toned sound.
 
scrape. Of course you can run it without a cat. Though it is illegal to tamper with emissions systems on rigs I doubt you would run into any trouble unless some rogue cop gives your XJ's exhaust a visual inspection. I know plenty of people here in CA that do not run a cat. Those of us blessed to live where the land is green air and water are clean in Humboldt Co. California (Northern California) do not have smog checks. We only have to smog the vehicle during a sale. I really do feel for all those so-cal people who have to deal with smog all the time. My XJ since its only one owner has never has to pass smog here in CA since it was bought new at the dealer 20 years ago.
 
I am kinda confused about all this high flow/delete my cat talk. On a 190-200hp application like the 4.0 a stock replacement cat will work just fine. How much hp you gonna lose? Maybe 5 hp a the rear wheels if you got a air intake header and cat-back. I remember seeing a good build up in hot rod a few years back where they ran a 350hp 350 and put some no name 2.5 inch cats behind it. They lost seven hp at the flywheel.

Dont forget there are many laws about removing or replacing a cat converter, like you cant walk up to a shop with high flow cats and have them installed there. The shop must provide the converters.

Cats got a bad name because the old lead pellet design ones had horrible airflow, the brick design used today flows much better, and the stock jeep converter is very wide, that shows it offers plenty of surface area to improve flow. It looks to have twice the surface area of the 2.5 inch summit cats I have sitting in the garage.
 
Flip94ta said:
Dont forget there are many laws about removing or replacing a cat converter, like you cant walk up to a shop with high flow cats and have them installed there. The shop must provide the converters.
Click to expand...

Ah....baloney? At least that's not even remotely true in the last two states I lived in (Utah and New Mexico).

I really like my Magnaflow, I replaced my cat along with the muffler and tailpipe at the same time, so I couldn't tell you what made the most difference. I mail ordered the cat and had a local shop do the welding for me, as well as all of the disposal of the old crud. They simply sell the old cats anyway, so it's great for them.
 
I am not sure if it varies by state but in the three places I've lived its been quite illegal to replace a working cat, bring your own cats, or sell used cats.

As for high flow cats do some searching on the net, its be proven that "high-flow" units are often just rebranded.
 
Last edited:
Flip94ta said:
I am not sure if it varies by state but in the three places I've lived its been quite illegal to replace a working cat, bring your own cats, or sell used cats.

As for high flow cats do some searching on the net, its be proven that "high-flow" units are often just rebranded.
Click to expand...

IIRC, the vehicle has to be more than 5 (?) years old and have oer 60K miles before the cat can be changed. That's pretty easy for most XJ owners.

My cat is a true 2.5" opening and exit, there is a wire screen on the upstream side, and the plates are arranged horizontally such that you can see approximately 50% daylight when looking through it. That's pretty high-flow in my book.
 
If someone has the time maybe they can check out the laws.

It all depends on surface area, I have a 2.5 inch summit cat that probably has 30-40% less surface area than the factory cat. I think the factory cat is the last thing to change out of the factory system. It seems the manifold and muffler would yeild much more of a power gain. I'd like to see someone dyno an XJ with and without the factory cat. I bet its about 3rwhp difference.
 
Flip94ta said:
If someone has the time maybe they can check out the laws.
Click to expand...
I'm sure it will depend on where you live, but in my area, you cannot replace it unless 5 years since manufacture of the cat has passed, or it has functioned for over 90,000 kms, or 50,000 miles. Since our laws specify that in order to pass inspection a vehicle must have all original equipment or replacements, you cannot run catless here. Shops will remove, sell and install cats, OEM or aftermarket, but if your vehicle was originally equipped with one, its illegal to remove it. Also, without getting too environmentalist here, its much better for emissions, and you lose hardly any horses, so just run one...
 
Last year I bought a high flow cat that was truely high flow from the perspective of looking through it. little to no obstruction.

I bought one just a few months ago that looked like stock. The difference is that the site I bought it from listed cats based on displacement of engine. So I bought one for a 6L engine. Yes it cost more but you buy them based on in/out diam. It fit fine and I would guess it is higher flow because it is built for a higher displacement pump!
 
You must log in or register to reply here.

Similar threads

M
Looking for aftermarket keyless entry ('95 XJ Country)
Replies
4
Views
322
Unclewolverine
U
C
Seeking Tuning Advice for Gen 1 SVT Raptor Shocks on a Jeep XJ
Replies
1
Views
323
Evan03
E
P
Help! Ticking, Misfire, Bucking, Loss of power, and Sadness
Replies
15
Views
394
phantomboda
P
W
May regret using Rotella in my '96 XJ
Replies
11
Views
1K
75SV1
7
T
Another Cooling Issue Thread - 99 Cherokee 4.0
Replies
18
Views
841
Black1990jeep
B
Back
Top