no catalytic converter

The Shocker · **Posted:** Fri Aug 31, 2007 12:34 am

my cat was going out so instead of replacing it I took the hot knife and cut it out and welded a straight pipe in its place, I already have a magnaflow 0 restriction exaust and my question is that if i dont have the cat does it compromise my mpg or horsepower because ive heard that some vehicles require some back presure to achieve optimum power and so far i have not felt any loss of power

myjeepwalks · **Posted:** Fri Aug 31, 2007 1:23 am

The Shocker wrote:

my cat was going out so instead of replacing it I took the hot knife and cut it out and welded a straight pipe in its place, I already have a magnaflow 0 restriction exaust and my question is that if i dont have the cat does it compromise my mpg or horsepower because ive heard that some vehicles require some back presure to achieve optimum power and so far i have not felt any loss of power

Dont let the tree huggers know you did that. :lol:

I dont about AZ but here in NJ that's like a $2500 fine. :shock:

tommudd · **Posted:** Fri Aug 31, 2007 7:34 am

What year do you have? I know some had like 3 of them , mine has two just wondering and yes its a big fine if they catch you but if not.... how does it drive can you tell a difference? Does it seem that it has a loss of power?

scoobysnax · **Posted:** Fri Aug 31, 2007 9:10 am

I’ve heard of people cutting their muffler off and leaving the cat on but not the other way around. I think I remember reading in the manual that if the cat is malfunctioning it can affect the engine performance and could cause damage to the engine. I’m sure someone else will be able to offer a better (and correct) answer.

tommudd · **Posted:** Fri Aug 31, 2007 9:46 am

I was confused as mine has two cats one on each side so removing one would be kind of upsetting the system for sure????

WoodysKJ · **Posted:** Fri Aug 31, 2007 10:08 am

you will be sending your O2 sensors into orbit.

There by confusing your PCM and throwing all you engine chemistries out of wack. Not to mention if you get caught. The Tree Huggers and their long arm of the law will clobber ya.

Good luck. Hope all that is worth it.

Next time ask on here before doing a dumb thing like that. Your engine and PCM will like it better.

tjkj2002 · **Posted:** Fri Aug 31, 2007 10:13 am

Some of the early KJ's have 3 cats,the newer ones have 2.WoodysKJ is right about the 02 sensors going wack and messing up the PCM unless you get the 02 sensor foolers from Jegs.And it is a $2500 Fedrel fine for removing a cat.You will not see any performance gains from removing it,it may actually get worse.Hope your state doesn't have emisions or inspections.

Signcutter21 · **Posted:** Fri Aug 31, 2007 11:03 am

AZ doesn't have inspections, at least in the rural counties. Those in Phoenix I thought had to pass an emmisions test. When I had my muffler installed, the guy told me that the only way they could legally take it out was if it was bent/ beat up. Time to break out the BFH. LOL.

With everything being computer driven in the new cars, I wouldn't mess around with pulling it off.

detroit_doc · **Posted:** Fri Aug 31, 2007 12:22 pm

WoodysKJ wrote:

you will be sending your O2 sensors into orbit.

There by confusing your PCM and throwing all you engine chemistries out of wack. ...

Nope.

Most vehicles have two O2 sensors. One is upstream of the cats that is used during closed loop operation in conjuntion with the MAP/MAF, IAT, TSP, etc to help determine injector duty cycle (fueling requirements). The other O2 sensor is downstream of the cat and is soley used to determine how well the cat is performing.

You may throw a code and have your check engine light come on because your cat is not performing as it should (mainly because it's sitting in a pile in your garage). But it will not affect the fuel air mixture or hurt your engine in any way. You can fool your computer into thinking the cat is still there by using an electronic O2 simulator or simply by using a couple of anti-foulers (available at your local parts store) to pull the downstream O2 sensor partially out of the exhaust stream. The later is what a lot of S2000 and WRX guys do when they pull their cats and it works very well. I have never had any luck with electronic O2 simulators. They never seem to work.

That being said, if you are not doing it for performance, then you are stinking up the atmosphere for absolutely no reason. Go to a junkyard and get yourself a cat.

myjeepwalks · **Posted:** Fri Aug 31, 2007 1:03 pm

Or you can just get a high flow cat from summit for like a $100 or so. If you state/county doesn't require emission inspections i'd say the hell with it and leave it. The down stream o2 sensors dont have anything to do with preformance. They just monitor the cats. If the cat is missing it will probably throw a check engine light. The upstream o2 sensors are the ones that will affect perfromance.

sleeve84028 · **Posted:** Fri Aug 31, 2007 2:14 pm

I thought the Chrysler computers were learning computers... Meaning, it'll learn that the Catalyist isn't there and throw the engine into LIMP mode.

Having an O2 sensor go bad is one thing, but removing the catalytic convertor is entirely something else. Something else being I wouldn't be bragging about it

detroit_doc · **Posted:** Fri Aug 31, 2007 3:49 pm

sleeve84028 wrote:

I thought the Chrysler computers were learning computers... Meaning, it'll learn that the Catalyist isn't there and throw the engine into LIMP mode.

Having an O2 sensor go bad is one thing, but removing the catalytic convertor is entirely something else. Something else being I wouldn't be bragging about it

All modern engine managment systems "learn" to some degree. They are always trying to adjust the fuel/air mixture leaner and add ignition timing. The leaner the air-fuel mixture is, and the more ignition advance that can be run, results in better power and fuel economy. The computer keeps leaning and advancing ignition until a knock event occurs. This helps determine the most optimized a/f mixture and ignition timing for a particular condition. It stores off these optimized values for the next time you experience that same set of variables (throttle position, load, intake air temperature, MAP/MAF, O2 sensor reading, etc). This allows your vehicle to adjust for things like fuel quality, atmospheric differences, and to save them off so that the next time you drive it uses those settings instead.

That learning capability has nothing to do with emissions controls. It will not go into limp mode due to a percieved emission controls problem. It will eventually throw a code and turn on the check engine light.

I agree that the OP should replace his cat. It's one thing to take it off a 700 horsepower 4 cylinder WRX. There is no good reason not to run one on a liberty.

Neatus · **Posted:** Fri Aug 31, 2007 4:07 pm

Signcutter21 wrote:

AZ doesn't have inspections, at least in the rural counties. Those in Phoenix I thought had to pass an emmisions test.

Yes, you have to pass an emissions test/inspection in the Phoenix area but the laws are more loose in the outlying areas. Just an inspection with out an emissions test.

Quote:

Nope.

Most vehicles have two O2 sensors. One is upstream of the cats that is used during closed loop operation in conjuntion with the MAP/MAF, IAT, TSP, etc to help determine injector duty cycle (fueling requirements). The other O2 sensor is downstream of the cat and is soley used to determine how well the cat is performing.

I believe my KJ has 6 O2 sensors! :shock:

Someone correct me if I am wrong

Jeepjeepster · **Posted:** Fri Aug 31, 2007 7:05 pm

It has four Neatus. One before each cat and one after each cat. You have two cats.

Neatus · **Posted:** Fri Aug 31, 2007 7:08 pm

Jeepjeepster wrote:

It has four Neatus. One before each cat and one after each cat. You have two cats.

Whew...Thanks, the thought of buying six is scary. So don't some KJs have more than two cats? Does that mean they have six?

Jeepjeepster · **Posted:** Fri Aug 31, 2007 9:55 pm

The early libertys had 3 like tjkj said but I would not believe they had 6 02sensors.

Im not 100% sure but I would guess they switched from 3 to 2 cats when they changed trannys.

McMoney · **Posted:** Fri Aug 31, 2007 10:56 pm

I believe my CRD only has one cat....well it had one cat :wink:

FastTRX · **Posted:** Sat Sep 01, 2007 12:51 pm

My 02' has three...one off each side of the headers and then one about a foot before my muffler. I believe only the front 2 have o2 sensors. I had people tell me I needed to get rid of my cats but I never justified a reason to. It's a liberty, not a sports car. Don't think it will make much difference in sound or performance.

Jeepjeepster · **Posted:** Sat Sep 01, 2007 1:43 pm

I cant believe that many people want to take the cats off. I just do not see a point other then to pollute.

tjkj2002 · **Posted:** Sat Sep 01, 2007 2:42 pm

Jeepjeepster wrote:

I cant believe that many people want to take the cats off. I just do not see a point other then to pollute.

It's not that it will polute more,it will unless you reprogram the PCM to run without the O2 sensors.Me and buddy got a '86 Suburban to pass emissions in California with a 454(had a 350 in it),headers(that's it,no more exhaust),and a Holley 750cfm double pump that was stamped "not for use in California".Granted we had to pay off the tester for the visual inspection but passed sniffer test with flying colors,it's more about how you maintain a vehicle.A better maintained vehicle will pollute less even without cats,if it is setup right to.

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