Cat or no Cat

[JeepXJ_90]

I got a 1990 XJ 4.0 bad cat on it, should i cut it out and run a staight pipe to the flowmaster or should i put a high flow cat on there?

[GSequoia]

Run a cat, there is absolutly no reason not to.

[shortxjdoug]

high flow

[Slo-Sho]

If there are emmisions laws in your state then I would recommend replacing the converter. If there are no laws as such, and you are going for maximum power then you will need about a 3' section of 2.25" straight pipe available from any muffler shop for about $10.

[JeepXJ_90]

there are no emsion laws for vehicles produced before 96

[GSequoia]

Once again, there is no reason not to run a cat.

You will not get better power from removing a cat. Modern cats flow well, partiuclarly the high flow ones.

There is no reason not to run a cat.

[JeepXJ_90]

so what kinda high flow cat should i get?

[GSequoia]

I assume from your handle your XJ is a 1990 model, yes?

If so let price decide for you, get the most economical one you can find. One of the nice things about a Renix system is that it is not very picky about certain parts, the cat is one of them, a standard universal (cheap!) model works fine.

[shortxjdoug]

i have a magnaflow cat into a flowmaster 40 and i am extremely pleased with the setup. i have bashed both on the rocks and they are built like damn skidplates, the magnaflow is also a lot smaller than a stock HO cat so it tucks away really nicely

[XJoshua]

It makes no difference whats so ever. Ive ran catless for awhile and all I got was heat build up in the muffler instead of the cat. No extra butt dyno power, well unless your cat is poorly clogged like mine then going catless and swapping in a new cat will make a worlds of difference. I probally gained 20HP back and had no more overheating issues.

[aparke4]

x2 on the magnaflow 54 bucks shipped to my door... i had to replace my banged up random tech! :flamemad: :tear:

[Flip94ta]

Yes please run a cat, our children will thank you.

I bought two 2.5 inch cats from summit and they seemed like good units.

[JJacobs]

Federal law, not state. If it came with a catalytic converter from the factory it must always have one. That'd cover all gas powered vehicles currently on the road, by the way.

[jmaxj]

Federal law, not state. If it came with a catalytic converter from the factory it must always have one. That'd cover all gas powered vehicles currently on the road, by the way.
that's a good enough reason for me not to run one:D

[Harlee&Tahoe]

Run a cat!
I just bought a Ultrafit Catalytic converter, direct fit, 2.5in. high flow for $87.95
Looks good, small, and will bolt right in.
Haven't installed yet waiting for pacesetter headers to arrive before I install cat though. Don't want burn out cat because ex. man. is cracked and O2 sensor is running engine rich.
Just bought whole exhaust, header, head tube, cat, and Dynomax catback. All 2.5in. for $540.66

[pabloconrad]

that's a good enough reason for me not to run one:D

x200

[XJoshua]

Can we make a sticky on this. I see this issue on every forum Im a member of. I dunno I really dont care what you run, but we need to just make a all enlightening post and hope people read it.

As far as things to include. Difference in CFM, Power, Noise with a specific muffler, videos, sound clips, everything to try and start a revolution of ending the to cat or not to cat questions...

[pabloconrad]

Can we make a sticky on this. I see this issue on every forum Im a member of. I dunno I really dont care what you run, but we need to just make a all enlightening post and hope people read it.

As far as things to include. Difference in CFM, Power, Noise with a specific muffler, videos, sound clips, everything to try and start a revolution of ending the to cat or not to cat questions...

[dallas xjs]

http://i13.tinypic.com/2yxpsmh.jpg

[Beej]

Can we make a sticky on this. I see this issue on every forum Im a member of. I dunno I really dont care what you run, but we need to just make a all enlightening post and hope people read it.

As far as things to include. Difference in CFM, Power, Noise with a specific muffler, videos, sound clips, everything to try and start a revolution of ending the to cat or not to cat questions... Personally, I think its completely unnecessary. A few minutes of research pretty much anywhere shows that there is no significant difference to performance by running a cat as opposed to not running a cat. You will only see negligible performance differences in numbers, not enough to make a real world difference.

The difference is in the emissions; they are significantly lower when running a cat.

You want the greenies off our backs? Run a damn cat and tell everyone else you know to run one too...

Can't this bloody thread be locked now?

[dallas xjs]

http://i13.tinypic.com/2yxpsmh.jpg

[shortxjdoug]

http://i13.tinypic.com/2yxpsmh.jpg

damn! and i paid 150 for mine..........i wonder if is comparable to a magnaflow?

[GreenbeltXJ]

ive been roasted before on this but i still don't run a cat, on any of my vehicles. oh and i love the above picture, i crack up every time i see it.

[NighthawkXJ]

I know there is "no noticable difference" between running one and not in the eyes of those that know. However, my wife (goddess of the check book and legendary penny puller) would have you know otherwise. I cleaned my cat out after a weekend on the trail, and did not have the money to fix right that second, so i just took it out, cleaned out all the smashed up stuff, and reinstalled on the go.

I instantly lost 5 mpg and alot of power. I got home broke from the extended gas budget and ordered an all stainless 2.5 inch cat shown on the auction here:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=003&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=130037408763&rd=1,1

I am still waiting for my new exhaust manifold to come in. And for those wondering, yes the manifold was leaking before the cat messed up, so it is the same problems before cat issues as after, cat blame the mpg problem on the manifold. Once all the parts come in, (this week i hope) then i will replace the manifold, cat and muffler(with a flowmaster 40) and have a 2.5 inch tail pipe made and then all the joints welded.

the noise was not the problem for me, and im used to running old junk, so the deal with emmisions did not bother me alot, but the powerloss and mpg going in the shitter was enough for me to scream stop.

[shortxjdoug]

it runs like poopoo without a cat, even if there is no downstream O2 in the cat............... nuff said

[Harlee&Tahoe]

I only paid like 80-90 for my 2.5in Dir fit bolt in to make any repairs easier later. not a whole weld in the sys. E-Bay

[MrShoeBoy]

The 4.6L stroker in my 91 XJ doesnt seem to care that the cat is missing. Been running it that way for over 2 years now and has no performance issues. It passes the sniffer test with flying colors. As long as you keep up with maintence on the motor like oil changes, air and fuel filters, keep all the vacume lines in good shape, and change spark plugs and wires every so often the motor will run clean. Its when its neglected that it doesnt work. My dads car has 250k on the LT1 and he has been running no cats for almost 4 years now and has yet to have an issue with passing emissions. Its all about maintence, not if you have a cat installed.

AARON

[GreenbeltXJ]

The 4.6L stroker in my 91 XJ doesnt seem to care that the cat is missing. Been running it that way for over 2 years now and has no performance issues. It passes the sniffer test with flying colors. As long as you keep up with maintence on the motor like oil changes, air and fuel filters, keep all the vacume lines in good shape, and change spark plugs and wires every so often the motor will run clean. Its when its neglected that it doesnt work. My dads car has 250k on the LT1 and he has been running no cats for almost 4 years now and has yet to have an issue with passing emissions. Its all about maintence, not if you have a cat installed.

AARON


.........nuff said

[Beej]

The 4.6L stroker in my 91 XJ doesnt seem to care that the cat is missing. Been running it that way for over 2 years now and has no performance issues. It passes the sniffer test with flying colors. As long as you keep up with maintence on the motor like oil changes, air and fuel filters, keep all the vacume lines in good shape, and change spark plugs and wires every so often the motor will run clean. Its when its neglected that it doesnt work. My dads car has 250k on the LT1 and he has been running no cats for almost 4 years now and has yet to have an issue with passing emissions. Its all about maintence, not if you have a cat installed.

AARON Assuming your location is accurate, you live in Mecklenburg county, which is one of NC's required emissions inspection counties according to the NCDOT website.

You might pass a sniff test, but how did you pass the visual inspection required on vehicles manufactured after 1981? Do you have a hollowed out cat or something? And if you do, did you know that under NC law, you are committing a Class 1 felony for falsifying your inspection?

[jeepnuts311]

i dunno about fuel injected vehicles, but on my AMC360 powered '84 grand wagoneer i hacked the exhaust system off about 1" after the cat and my gas mileage plummeted into the 6mpg range.

-Tim

[streetpirate]

my mileage stayed the same with the exhaust dumping out just before the cat, and i noticed a very slight if unoticeable loss in low end, and more pull above 3k.

it doesnt hurt anything to run a quality cat.

[peeweexj]

I run with not cat, and won't run with one until I live in a state with inspections. It saved me money, sounds better, and I have no cat to get hung up or rattle.
I'm not concerned with the pollutants I put out, but more with things like illegals jumping over the borders and killing americans, not my exhaust killing them.

[jeepnuts311]

I'm not concerned with the pollutants I put out, but more with things like illegals jumping over the borders and killing americans, not my exhaust killing them.

ignorant quote of the day.

-Tim

[peeweexj]

What do you have to say? Just trying to rack up posts?

[JJacobs]

I.. uh.. know people who have hollowed out a converter so it looks functional. And I was told that a cammed, header'd Renix 4.0 wouldn't pass emissions that way without a vacuum leak.

[BBeach]

I run with not cat, and won't run with one until I live in a state with inspections. It saved me money, sounds better, and I have no cat to get hung up or rattle.
I'm not concerned with the pollutants I put out, but more with things like illegals jumping over the borders and killing americans, not my exhaust killing them. You should be concerned about both. :lecture:

[mavinwy]

Mine had a plugged cat when I got it. We wanted to insure that was the problem before spending major$$$, so we threw a test pipe on since the rest of the exhaust was a 2.5" (behind the cat) with a flowmaster.

I now get 23 mpg on average, and have gotten as high as 26 on the highway. Before I could not do better than 13-14. The sound is a little louder, but for 10MPG I can live with it.

I'll likely crawl under in the spring and put a high flow cat on, but right off there are other projects to do that do not involve crawling around in the cold :) We don't have inspections here, so it'll wait.

It'll definately be a high flow cat though....... The gas mileage is enough of a proof to me that a non-high flow would not be worthe the few $$$$ saved.

Jim

[hizzo3]

i replaced the cat on my 2.5 with a 3inch cat from magnaflo. i then ran a 3 inch section the rest of the way. butt dyno felt that around the 3k mark up there was a boost, all the rest seemed the same

[Darky]

I run with not cat, and won't run with one until I live in a state with inspections. It saved me money, sounds better, and I have no cat to get hung up or rattle.
I'm not concerned with the pollutants I put out, but more with things like illegals jumping over the borders and killing americans, not my exhaust killing them.
"They took our jobs!"

[WB9YZU]

It seems to me there are a number of posts which are just wrong.

1st of all. If your vehicle came with a catalitic convertor, you are required to replace it when it goes bad. You may not bypass it, you may not remove it, you may not hollow it out. Since it is a Federal law, it applies to all 50. There is no age limit to this.

It is not relevant that a certain State or other does not check emissions. The Federal regulations take precidence.

So, based on that alone, the original poster is required to replace the convertor. That I am aware, NAXJA can adopt no other view of this and the moderator should close the thread since NAXJA does not support illegal activities.

Besides... these things work. Anyone old enough to remember the old leaded days realizes that the combinination of unleaded fuel and catalitic convertors has resulted in better air even though the number of vehicles on the road has increased.

For those who say it will get "hung up", my muffler takes all the abuse since it is near the breakover point and not protected. The Cat on the other hand seems to get protected by the crossmember nicely.

Cost...don't give me that! Surly if you can afford to put on a lift, you can make sure your vehicle is in emission compliance.

Ron

[Slo-Sho]

Do racing associations such as NASCAR, IHRA, NHRA, or any other sanctioned racing body mandate the use of Catalytic converters? This is a legitimate question, not trying to be a wise guy.

[WB9YZU]

Do racing associations such as NASCAR, IHRA, NHRA, or any other sanctioned racing body mandate the use of Catalytic converters? This is a legitimate question, not trying to be a wise guy.

No. The EPA exempts engines that are used exclusivly for competition.

If you use your vehicle as dual purpose, road and race, the mormal EPA restrictions apply to the modification of the emission system.

This may help, though it is written for MC/ATV use.
http://www.epa.gov/otaq/regs/nonroad/2002/f02045.pdf

Ron

[Dzl DV8]

I can say when my cat clogged, I R&Red it with a piece of straight pipe. Instant performance gain.
When the CATGO cat arrived and I put it on I noticed no difference.


when was the last time you heard about someone being cited for not running a cat?

With an altered MAP, FPR and injectors haven't I broke the same federal law?

Never lock a thread for exploring alternative ideas, just stay on topic!!!

And no, I didn't search...

[XJoshua]

Unfortunately I agree with Ron. These threads are everywhere, and bugging the hell out of me. $50 from SummitRacing gets you a universal DynoMax Catalyst Converter.

But! Many cities dont enforce any laws about being emission tested before being registered. I have yet to see any enforcement officer pull over someone with a loud exhaust and check to see if they have a cat installed nor even look at the distance your tires are poking out of the fender wells.

I for one am all for preserving the air quality and earth its self, but just run a cheap cat and recycle the old one at a metals shop so you get money for the metal inside of it, or sell it to a crack addict so he can do that and buy himself a 8 ball and everyone is happy.

Putting this tread in the FAQ wont solve anything either, because no one ever looks in there enough or uses the search for this. JUST USE A CATALYST CONVERTER.

If you are stricktly TRACK or OFF-ROAD then go straight pipe of be nice and run a CATALYST CONVERTER...

[seanyb505]

I have a 97, about two years ago my cat went bad. i wasnt about to fork over what local shops were asking for catalytic converters so i found a place which would replace the cat with a straight pipe. i had a straight through muffler installed at the same time. he said to get a trick sensor to prevent the check engine light coming on. i put off getting the sensor, and the check engine light never came on! my mileage went up about 2 mpg, and there was a noticable power gain. this could have been due to the bad cat, but my jeep has never run better.

[montanaman]

It seems to me there are a number of posts which are just wrong.

1st of all. If your vehicle came with a catalitic convertor, you are required to replace it when it goes bad. You may not bypass it, you may not remove it, you may not hollow it out. Since it is a Federal law, it applies to all 50. There is no age limit to this.

It is not relevant that a certain State or other does not check emissions. The Federal regulations take precidence.

So, based on that alone, the original poster is required to replace the convertor. That I am aware, NAXJA can adopt no other view of this and the moderator should close the thread since NAXJA does not support illegal activities.

Besides... these things work. Anyone old enough to remember the old leaded days realizes that the combinination of unleaded fuel and catalitic convertors has resulted in better air even though the number of vehicles on the road has increased.

For those who say it will get "hung up", my muffler takes all the abuse since it is near the breakover point and not protected. The Cat on the other hand seems to get protected by the crossmember nicely.

Cost...don't give me that! Surly if you can afford to put on a lift, you can make sure your vehicle is in emission compliance.

Ron

I Agree 100% !!

[jeepster09]

Ever since we got rid of the cat the dog is a lot happier!
:doh: