quick cat question

[theksmith]

I have an 01 cherokee with the larger round cat. I want to replace it wth an oval or small round one just so that I can run a full width belly pan (dpg).

From reading this board, it seems that most people think little of "free-flow" cats and think that a modern cat without too many miles flows just fine. So is something like this all I need (supposed "high flow":

http://cgi.ebay.com/ebaymotors/2-5-...33629QQitemZ8023931695QQrdZ1QQsspagenameZWDVW

or be better off with a more name brand:

http://cgi.ebay.com/ebaymotors/5300...ewItemQQcategoryZ33629QQitemZ8025467482QQrdZ1

or can I get something that will work and be cheaper at local autozone/checker/pep boys?

or... do some of you think that the $150+ "high flow" cats really are worth it?

P.S. above all I don't want to worry about check engine light coming on becuase of o2 sensor getting unexpected signals from a cat that's not really working as good as the stock.

Sorry for the long post.. just tyring to be clear on what I'm looking for, Thanks!!

 

[theksmith]

Nobody??

 

[lilredwagn]

That second one there (magnaflow) looks good. Looks a lot like the one I have. Including the lack of O2 bung.

It says OBDII compliant, but there is no indication that the cat has a bung, and in fact the guy links to another auction with bungs.

Carsound/magnaflow does now offer that cat with the bung, so maybe check their website and match up the part number. Then contact the seller, just to double-check.

I thought I could get someone to weld in a bung on mine, but 3 fricken places I tried wouldn't do it, so now I just drive around with a check engine light. Save yourself the hassle and get the right part number.

And yes, the "high flow" cat added absolutely zero performance gain, but if you need it for clearance, go for it.

 

[theksmith]

Thanks for the reply!

I ended up with the magnaflow 91006, from ebay for $53.75, free ship:

http://cgi.ebay.com/ebaymotors/Magn...33629QQitemZ8027063884QQrdZ1QQsspagenameZWDVW

According to magnaflow's site, the size will clear my skid, and it is recomended for up to a 4.2L engine. I crawled under my xj... apparently the 2001 does not have air injection, nor an o2 sensor on or after the main cat. I guess there is only a sensor or sensors before/after the pre-cat on this year. If anyone is looking at this and your model has the o2 on the cat, then you need magnaflow model 91036.

 

[Silent]

Ok, do the high flows help anything at all? And maybe I am not following to good. Why would the check engine light come on if you have the right one for your make/yr of your veh. Just curious.

Thanks,
Silent

 

[partsbill]

Ok, do the high flows help anything at all? And maybe I am not following to good. Why would the check engine light come on if you have the right one for your make/yr of your veh. Just curious.

Thanks,
Silent

Probably due to either 1 of the 4 oxygen sensors or even the gas cap

 

[Silent]

Ok, do high flows do anything besides cause chk light to come on?? LOL

Thanks,
Silent

 

[lilredwagn]

Ok, do the high flows help anything at all? And maybe I am not following to good. Why would the check engine light come on if you have the right one for your make/yr of your veh. Just curious.

Thanks,
Silent

If that was directed at me - I have a '96 and I am *supposed* to have an O2 sensor in the cat. My check engine light comes on because I *don't*, because none of the commercial places around here will weld in a bung for me, and I don't have a buddy with a welder.

I could probably find someone if I looked hard enough, but it wasn't worth my time, and now, after hanging loose around the driveshaft for a couple years, I've gone and shredded the O2 wires and connectors, so at this point it would be even more involved to fix than finding someone to weld a nut into my cat.

As a side note, if you short out the +5v feed to the O2 sensor, it will blow the ASD fuse, and the jeep will suddenly die and not start again. (crank ok, no fuel or spark though)

Performance wise, the high flow cat (and 2.5" exhaust with magnaflow muffler) made no noticable difference in performance (though the mike leach header made a significant difference) I couldn't tell you whether the high-flow cat changes the exhaust tone at all.

 

[theksmith]

if you want to cheat you could probably add a resistor of the right value between the o2 sensor lead and ground. But what size resistor to give the right "fake" reading I don't know... search google maybe!

 

[Cjmartz2k]

Is there rear (cat) O2 sensor really an O2 sensor, or is it just sensing heat from the cat telling you wether or not it's there and or glowing bright red? That's how they are over here, and as long as it's in the exhuast stream, it doesn't complain. As soon as you let it dangle in the free air though, it starts throwing a code.

 

[bdtsr]

My '98 MIL/Check engine light stays on with the message "Catalytic Convertor Efficiency Below Specified Limits". This is due to the cat having some internal material removed. I plan on replacing it at some point. NJ uses the computer for '98 and newer vehicles and allows two sensors to be "Not Ready". Clear the ECU with the scanner, drive 10 miles, go through inspection. Works every time.

 

[Cjmartz2k]

Well I guess that answers that question--mine's a '98 also.

 

[mattmankow]

Just to throw in a wrench. Kristoffers' idea with the resistor wouldn't work. The rear O2 is supposed to chage values just like the front ones, albeit at a slower rate.
On my Y2k with the cats in the manifolds, I don't have an O2 after the rear cat. Technically you could gut the rear cat without throwing a mil.

 

[theksmith]

Just to throw in a wrench. Kristoffers' idea with the resistor wouldn't work. The rear O2 is supposed to chage values just like the front ones, albeit at a slower rate.
On my Y2k with the cats in the manifolds, I don't have an O2 after the rear cat. Technically you could gut the rear cat without throwing a mil.

I have an 01, I believe our 00 and 01 years are the only ones with the pre-cats? Can we change to performance headers, or are the precats in the header?

 

[majic_tech]

I have an 01, I believe our 00 and 01 years are the only ones with the pre-cats? Can we change to performance headers, or are the precats in the header?

The only one that will be a mil concern is the monitored cat....the one with o2 sensors on both sides, and theres no way to "fool" the computer into thinking theres one there (only a fool would try it) So I wouldnt recommend trying it. Get a magnaflow and go on to some more legal mods. Rather than messing with your emissions system.

 

[majic_tech]

My '98 MIL/Check engine light stays on with the message "Catalytic Convertor Efficiency Below Specified Limits". This is due to the cat having some internal material removed. I plan on replacing it at some point. NJ uses the computer for '98 and newer vehicles and allows two sensors to be "Not Ready". Clear the ECU with the scanner, drive 10 miles, go through inspection. Works every time.

your e test guys must all be hopped up on dope ...........I dare you to try that here.....works 0% of the time ......I believe you meant to say 2 emissions monitors not met.... And I'm not a naxja spokesperson but I would think this kind of cheating the system would be highly discouraged here, considering the system is designed to protect the environment ......... If you dont mind breathing noxious fumes, get a plastic bag and put it over your head or perhaps lock yourself in a sealed garage and keep them to yourself.....the rest of us may not enjoy filthy air in our lungs..........while Im at it might I suggest you use a condom each and every time we dont need anymore people around here with no consideration for others ....yea Earth first will f*** up the other planets later right?

 

[streetpirate]

your e test guys must all be hopped up on dope ...........I dare you to try that here.....works 0% of the time ......I believe you meant to say 2 emissions monitors not met.... And I'm not a naxja spokesperson but I would think this kind of cheating the system would be highly discouraged here, considering the system is designed to protect the environment ......... If you dont mind breathing noxious fumes, get a plastic bag and put it over your head or perhaps lock yourself in a sealed garage and keep them to yourself.....the rest of us may not enjoy filthy air in our lungs..........while Im at it might I suggest you use a condom each and every time we dont need anymore people around here with no consideration for others ....yea Earth first will f*** up the other planets later right?

How about we pull our proverbial heads out of our proverbial @$$es and figure out that air pollution is mainly caused by the 99% of cars on the road not driven by enthusiasts. The percentage of vehicles on the road that are required by law to pass emissions testing and are owned by enthusiasts is very small. you should be able to register your car as a non-commuter and keep it street legal and not have to go through deq. so by all means lets cheat those bastards trying to stick their noses up our tailpipes.

 

[majic_tech]

How about we pull our proverbial heads out of our proverbial @$$es and figure out that air pollution is mainly caused by the 99% of cars on the road not driven by enthusiasts. The percentage of vehicles on the road that are required by law to pass emissions testing and are owned by enthusiasts is very small. you should be able to register your car as a non-commuter and keep it street legal and not have to go through deq. so by all means lets cheat those bastards trying to stick their noses up our tailpipes.

Lets be honest here dude the pollution is caused by people who cheat the system and those who neglect thier cars .....enthusiast or not, we are all responsible.......but at least you admitted to having your proverbial head in your proverbial a$$

 

[ZomBrady]

Lets be honest here dude the pollution is caused by people who cheat the system and those who neglect thier cars .....enthusiast or not, we are all responsible.......but at least you admitted to having your proverbial head in your proverbial a$$

Wow, you are too right.

If you really want to talk hypocritical, I'm an environmental engineerring student, and I'm running a puched out cat right now. In my defense though, I melted it right when tuition was due and and also have a family of four to consider when figuring repair costs into our budget.

On a lighter note though, my XJ is a 1996 with a stroker and my check engine light still hasn't come on. . . . Still can't figure that one out.

 

[majic_tech]

Im not talking hypocritical do I need to post my emissions sheet to prove that? Its not that hard to get an xj clean as a whistle without cheating or losing power..........