Benefits to having a catalytic converter???

[prljeep]

90 MJ 4.0L

Are there any benefits (besides environmental and legal) to having a catalytic converter?

Does it effect mpg, engine temperature, oil pressure, ??? in any way???

I do not have one currently (no emissions testing)- but need to replace some exhaust pieces and thought about putting one back on if it has any mechanical benefits.

TIA-prl

[Zoro]

I don't think it helps with engine temp and oil pressure too much but I was running with no exhaust from the cat back and besides the awesome noise the only thing I noticed was a shift in horsepower probably due to the lack of back-pressure. Mine's a 90XJ.

Forgot to add, I also had a big drop in gas mileage too.

[WobblesXJ]

I don't think it helps with engine temp and oil pressure too much but I was running with no exhaust from the cat back and besides the awesome noise the only thing I noticed was a shift in horsepower probably due to the lack of back-pressure. Mine's a 90XJ.

Forgot to add, I also had a big drop in gas mileage too.


Drop in milage with no exhaust?

[jayuu]

maybe you just were a little heavier on the pedal subconciously to hear the awesome exhaust notes.

[BIGSLVRXJ]

Drop in milage with no exhaust?
Yeah that doesn't sound right to me either. I had always heard that on pre-OBD-II vehicles it really just made the gas mileage and performance better, as long as there isn't a downstream 02 sensor.

[HaleYes]

Before I knew better, I removed my cat because it was rattling really bad. I had a significant drop in MPG after removing it. After the fact, I SPOBI'd and found the 4.0 needs a certain amount of back-pressure to be at optimum performance. What that pressure is, I don't reall. SPOBI it out if your interested. If I had to do it over, I would have found another cat and replaced it.

[yardape]

Just a thought from left field,.... how about installing a catalytic convertor on your Jeep because it will limit the amount of Nitrous Oxide and other pollutants you send into the atomosphere and its the right thing to do?

[prljeep]

Still pondering the question...

Can anyone else confirm an increase in mpg with a catalytic converter?

As for the "right thing to do"- I bought it without one and I guess if my local gov't was concerned about it- they would test vehicles. I'll blame it on the gov't. Maybe they should pay for me to upgrade back to OEM.

[langer1]

Still pondering the question...

Can anyone else confirm an increase in mpg with a catalytic converter?

As for the "right thing to do"- I bought it without one and I guess if my local gov't was concerned about it- they would test vehicles. I'll blame it on the gov't. Maybe they should pay for me to upgrade back to OEM.
They test thousands every year with road block setups.
The OSP will also check for it on a traffic stop, the fine is $250.00 if it's missing.

[WobblesXJ]

yeah I heard about it needing backpressure as well. The 4.0 is a low torque engine, especially the renix. And back pressure helps with low end torque.

I was just trying to clear up what he said for the others.

For the record I dont' have a cat, just a muffler that comes out the side and with 31's and 3.55 gears I get ~15mpg after correcting for larger tires. I was wondering why this was so much lower than other people's claims. Perhaps it's the less restrictive exhaust, eh?

[jeo]

Just a thought from left field,.... how about installing a catalytic convertor on your Jeep because it will limit the amount of Nitrous Oxide and other pollutants you send into the atomosphere and its the right thing to do?
"The right thing to do?" Why has no one flamed this guy? :lecture: Buy a pure electric car if you want to do the right thing, instead of running two large Jeeps.

[prljeep]

I was thinking the same thing....just didn't want to say it.

Maybe his are converted to running off like 16 car batteries and a solar panel on the roof...

[cal]

My mileage dropped when I hollowed out my cat, too.

I only did it cuz i crushed it on the trail. The next time I am tearing my exhaust off, I'll be putting a new cat back on.

[Comanchedude]

"The right thing to do?" Why has no one flamed this guy? :lecture: Buy a pure electric car if you want to do the right thing, instead of running two large Jeeps.

Well why not go a step further and ride a bicycle?.. Unless you can convert your Jeep to electric. oh then how to haul the ton of batteries??

yardape had a valid point ..If it’s a DD then is should have a cat
We can help is small steps to control the human destruction of the environment
And some day if not too late I hope we can run a clean burning fuel in our Jeeps. Until then we use converters on our rides.

Ok Flame away

[jeo]

Well why not go a step further and ride a bicycle?.. Unless you can convert your Jeep to electric. oh then how to haul the ton of batteries??

yardape had a valid point ..If it’s a DD then is should have a cat
We can help is small steps to control the human destruction of the environment
And some day if not too late I hope we can run a clean burning fuel in our Jeeps. Until then we use converters on our rides.

Ok Flame away

The main thing that bothered me in the original thing he wrote was "the right thing to do." He's got no right to judge what is right and wrong for me. And the fact that he owns not one, but two gas guzzling Jeeps with a "high flo cat" that probably don't do as well for emissions as stock ones. Sorry, I should never post stoned.... :smoker:

[WobblesXJ]

Yeah I'm in the process of redoing my exhaust and a cat is in the works. I don't consider myself a "greenie" but it doesn't hurt to put one on (other than my wallet, and they can be had cheap).

[majic_tech]

Im no greenie either, but I do think if your gonna live on earth or have offspring that will, then at least be responsible, its not a matter of selectivity bad enough air quality will eventually kill everything, even the plants that keep idiots stoned

[majic_tech]

The main thing that bothered me in the original thing he wrote was "the right thing to do." He's got no right to judge what is right and wrong for me. And the fact that he owns not one, but two gas guzzling Jeeps with a "high flo cat" that probably don't do as well for emissions as stock ones. Sorry, I should never post stoned.... :smoker:
see^

[jeo]

Im no greenie either, but I do think if your gonna live on earth or have offspring that will, then at least be responsible, its not a matter of selectivity bad enough air quality will eventually kill everything, even the plants that keep idiots stoned
no need for name calling. also no need for someone to tell me what is right for me to do. you make your decisions, don't lecture me on mine. also don't yap about air quality when you're not driving an economical vehicle. see my point?

[tekguy4]

battery or gas, pollution is still being created, battery wont make, charge or dispose of itself, maybe solar charger would work, but how long would that take to charge the battery packs long enough to get a decent trip mileage interval?

[Matthew Currie]

Back to the original post for a moment, I think that one other consequence of lower back pressure will be that the EGR will not work correctly. Now of course, since you can run an Renix XJ with no EGR at all and never notice, this may be inconsequential, and of course if you're deciding to ignore emission control a working EGR is a hard sell, but there it is. The EGR valves, at least on some Renix models, require back pressure to work.

[yardape]

Wow,... didn't know I had stirred something up. You can make all kinds of excuses but taking reasonable measures to limit the amount of emissions created by your vehicle is the right thing to do. No one said anything about driving battery operated cars. I am far from being a greeny. What I do consder myself is a responsible adult and citizen of the earth. With respect to my 2 gas guzzling vehicles, not that I need to defend myself, I haven't figured out yet how to drive two at a time so I could have a fleet of one hundred and it wouldn't make any difference. They get tuned on a regular basis and both have catalytic convertors so my kid and any of your future offspring don't have to live in air that smells like a toilet; causes cancer in rats and people; and contributes to golbal warming. Perhaps you're having such a visceral reaction to my suggestion because I'm right?

[jeo]

Wow,... didn't know I had stirred something up. You can make all kinds of excuses but taking reasonable measures to limit the amount of emissions created by your vehicle is the right thing to do. No one said anything about driving battery operated cars. I am far from being a greeny. What I do consder myself is a responsible adult and citizen of the earth. With respect to my 2 gas guzzling vehicles, not that I need to defend myself, I haven't figured out yet how to drive two at a time so I could have a fleet of one hundred and it wouldn't make any difference. They get tuned on a regular basis and both have catalytic convertors so my kid and any of your future offspring don't have to live in air that smells like a toilet; causes cancer in rats and people; and contributes to golbal warming. Perhaps you're having such a visceral reaction to my suggestion because I'm right?
The main thing that's bothering me is that you're telling me what is right and wrong, and you repeated that in this message. And if you're going to make comments about poor air quality, global warming and such, then you should really look at your choice of vehicle, not whether it has a catalytic converter on it or not. I'm not angry at all, I just feel that you should not impose your ethics on me by telling me what the right thing to do is when you're also driving vehicles which contribute to pollution much more than you need to. I hope this makes sense to you and you can see my point of view. I can see yours, but I disagree with it. Can we just agree to disagree and leave this be?

[SBrad001]

Drop in milage with no exhaust?

With the OBDII and OBDI ecms, the lack of a cat with send 'false' high O2 reading to the ecm, which compensates for the 'false' lean reading by dumping more fuel into the cylinders. . . . Someone can correct me if I'm wrong but that is how I understand it.

[SBrad001]

The main thing that's bothering me is that you're telling me what is right and wrong, and you repeated that in this message. And if you're going to make comments about poor air quality, global warming and such, then you should really look at your choice of vehicle, not whether it has a catalytic converter on it or not. I'm not angry at all, I just feel that you should not impose your ethics on me by telling me what the right thing to do is when you're also driving vehicles which contribute to pollution much more than you need to. I hope this makes sense to you and you can see my point of view. I can see yours, but I disagree with it. Can we just agree to disagree and leave this be?


Jeo, I probably shouldn't wade in on this, since I AM being hypocritical, but here goes. And please realize that I am not attacking you.

Anyway, the fact of the matter is that we are going to drive and live how we like, but that doesn't mean that we can't limit or use sensible habits to minimize our pollution in order to offset our choosen lifestyles. By simply have a cat on your Jeep you minimize that NOx emission of your vehicle by 50% or more. How can that be a bad thing?

We all benefits from having a cleaner environment to live, work, play, and eat from. If that wasn't the case, we would have never enacted the Clean Water and Clean Air Bills. Our quality of life has improved in the last forty years because of these things.

Good gawd, I sound like a tree hugger now. . . .

[yardape]

Jeo, I probably shouldn't wade in on this, since I AM being hypocritical, but here goes. And please realize that I am not attacking you.

Anyway, the fact of the matter is that we are going to drive and live how we like, but that doesn't mean that we can't limit or use sensible habits to minimize our pollution in order to offset our choosen lifestyles. By simply have a cat on your Jeep you minimize that NOx emission of your vehicle by 50% or more. How can that be a bad thing?

We all benefits from having a cleaner environment to live, work, play, and eat from. If that wasn't the case, we would have never enacted the Clean Water and Clean Air Bills. Our quality of life has improved in the last forty years because of these things.

Good gawd, I sound like a tree hugger now. . . .

Bingo. Put much more eloquently than I did. It takes a village,... and on that note I am finished.

[Nevada City Sparky]

The main thing that's bothering me is that you're telling me what is right and wrong, and you repeated that in this message.

As did a lot of other people. That's what happens when you act like an asshat: people tell you to do the right thing. Now, take it like a man and go buy that cat. Stop being an asshat.

[jeo]

As did a lot of other people. That's what happens when you act like an asshat: people tell you to do the right thing. Now, take it like a man and go buy that cat. Stop being an asshat.
Once again, name calling is not required in a decent conversation.
The fact is, I do have a catalytic converter on my Jeep, and always will because of provincial regulations. The issue is not that of the converter, it is someone else telling me what is right and wrong. You do what you want, I do what I want, just don't sit there and talk to me about the environment when you own a non-fuel economical vehicle.

[the_chief]

if your local government doesn't require it, then the complainers can write their congressman. If you guys want to save the world, go choke the guy selling crack at your local jr high, or the guys driving 3/4 ton deisels for no reason, or the people burning wood to stay warm on red alert pollution days or,,,,,etc...

[SBrad001]

Once again, name calling is not required in a decent conversation.
Point.

The issue is not that of the converter, it is someone else telling me what is right and wrong. You do what you want, I do what I want, just don't sit there and talk to me about the environment when you own a non-fuel economical vehicle.

Ok, this is were our opinions differ. It's not whether or not you are following state/federal/provincial regulations, it's about how our individual actions impact others. If I choose to go out in the deserts/mountains/etc and change my oil and dump it out on the ground, I probably won't get caught, but I will be affecting some else's experience and enjoyment if they come along and step in my oil. . . . Can I make everyone happy? No. I don't expect too either, but I can try to be respectful and considerate of the others that share my common environment. I believe that is reasonable and something I must strive to balance with my way living.

[5-90]

Why would a "high-flow" catalytic converter be harmful to emissions?

I've changed out two of my four (the other two haven't failed yet) with BBChevvy catalytic converters (they're listed in the catalogue as for BBC, 1 to an engine, with the same size pipe as I had under there) and my biennial smogs are still outstanding. The only reason I can think of that I'm still getting sent to "test only" stations all the time is because I embarrassed the acting director and the regional director of the ARB in public years ago (I asked incisive questions they couldn't answer, they faked their answers, and I proved them WRONG!) and they're still gunning for me.

My emissions test results are typically as low as or a shade lower than those for new cars, even with the modified exhaust (I figure it cost me about $125 each for the two exhaust systems - from the converter flange back.

PFP "Universal Fit" BBC converter - $80
Walker Turbo II muffler - $20
Misc pipe and clamps - $15
One weld per system - a beer each)

5-90

[prljeep]

Well- I started this now 2 page discussion- only wanting to get some technical insight into the benefits (other than environmental) of the catalytic converter.

I guess from the round about discussion- most people said that a clean catalytic converter should increase mpg? I don't care if it is a 1 mpg increase that will make it worth me installing it!

With this established- can I just pickup the generic cat at autozone/napa/murray's and still be ok...???

[langer1]

With this established- can I just pickup the generic cat at autozone/napa/murray's and still be ok...???
Yes that will be fine, your engine will run better and gas mileage will be about 3 mpg better also.
Also you never know in Ohio when your going to run into a roadside inspection station.

[Truk]

Also you never know in Ohio when your going to run into a roadside inspection station.

Different parts of the state may be different, as in if you are driving around Cinci or somewhere that has e-check they may check for this, but I have lived in central Ohio my whole life and have never been through a roadside inspection where they checked, or had a OHP officer or anyone else check on my converter. I don't drive it much anymore, but my '91 Mustang was my DD for about 10 years without one.

That said, my current DD (99 Cherokee) is keeping the converter when I replace the exhaust, since I figure e-check will start here at some point while I have it.

[ChuckD]

Why would a "high-flow" catalytic converter be harmful to emissions?

I've changed out two of my four (the other two haven't failed yet) with BBChevvy catalytic converters (they're listed in the catalogue as for BBC, 1 to an engine, with the same size pipe as I had under there) and my biennial smogs are still outstanding. The only reason I can think of that I'm still getting sent to "test only" stations all the time is because I embarrassed the acting director and the regional director of the ARB in public years ago (I asked incisive questions they couldn't answer, they faked their answers, and I proved them WRONG!) and they're still gunning for me.

My emissions test results are typically as low as or a shade lower than those for new cars, even with the modified exhaust (I figure it cost me about $125 each for the two exhaust systems - from the converter flange back.

PFP "Universal Fit" BBC converter - $80
Walker Turbo II muffler - $20
Misc pipe and clamps - $15
One weld per system - a beer each)

5-90


If it isn't too much trouble could you tell me where you purcahsed you CAT? I am needing one ASAP.

Thanks

[5-90]

Any parts house should be able to get it for you - but I think I'd gone to Pep Boys because I needed it in a hurry, and they had it on the shelf.

Measure the pipe going in and coming out, and get a converter with a "straight through the centre" setup. I'm fairly sure that's ALL converters anyhow, but I know how mufflers can get.

While you're at it, get a short section of the correct size pipe (2.25"? It's been a while...) and cut the flange off the old converter. Weld the pipe to the flange as a stub, because that bolt flange comes in REALLY handy sometimes...

5-90

[Matthew Currie]

Any parts house should be able to get it for you - but I think I'd gone to Pep Boys because I needed it in a hurry, and they had it on the shelf.

Measure the pipe going in and coming out, and get a converter with a "straight through the centre" setup. I'm fairly sure that's ALL converters anyhow, but I know how mufflers can get.

While you're at it, get a short section of the correct size pipe (2.25"? It's been a while...) and cut the flange off the old converter. Weld the pipe to the flange as a stub, because that bolt flange comes in REALLY handy sometimes...

5-90

I may be wrong but I think the 93 cat is flangeless. I know the 95 is. The 93 is not handy to look at now, but I have a recollection that it is a slip-on type.