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De-Cat with 2 O2 sensors

V

VinceYJ

NAXJA Forum User
Location
Canada
Okay my question is:
OBDII XJs have two O2 sensors..one on the downpipe right after the header and one after the cat. If I were to "straight pipe" my XJ by removing the cat would I mess up my computer with the reading from the last O2 sensor being off?
Anyone have any expirience with this?
Plz avoid the "it wont pass smog" argument as my smog-test is good for 2 years....
thanks!!!
 
Get an O2 simulator from summit for about $60. I went catless 2 years ago and plugged one of these in and have had zero trouble since.
 
Rev Den said:
Why?

No gains.

Rev
Click to expand...

The stock cat is a bit restrictive, and for those of us who would not like to spend $200 on a highflow cat, a straight pipe is the way to go.
 
like beating a dead horse - the 4.0 L will see no improvments with an open exhaust - also the stock cat is not restrictive especially on the newer models.

i went with a magnaflow hi flow cat 54 dollars to my door off ebay and 30 bucks to cut off old exhaust and weld in new cat

it is not a great cat but flows really well with my flowmaster 50 - for the sake of our air quality put on that cat - open exhaust is cool for a while i guess but gets old after a while - to each their own
 
What's wrong. I tried to buy the 49 state cat with the hopes of getting an exhaust shop to weld a bung in it for me so I could install it. Apparently it's against the law here in CA to do that so none of them would do it unless it was a CA OBDII cat. So I had to get rid of it and goin strait pipe.
 
I did it to mine becuase I had 190K on the stocker. It made a noticable difference, not the biggest in the world but I could for sure tell. I also really hated my nice new 4.6 sounding like a shop vac over 3000RPM. Now when cruising the highway at 3K it sounds like I am flying a crop duster LOL.

If you keep your junk tuned up they are still emisions friendly. My old Toyota passed smog in atlanta with a gutted cat and 160K on the clock. I am confidant my jeep would do the same but I don't live in smog state so it doesn't matter.
 
It will if you don't plug an 02 sim into the rear O2. Otherwise you will have a check engine light.
 
Dont worry, it will pass smog...into the atmosphere. Is it really worth it when you can get a high flow unit for less than the O2 eliminator?
 
Not in CA it isn't :hang:
 
You will gain a small amount at very high RPM and pump a ton of crap into the air for everone else to breath. Please don't do it.
 
BBeach said:
Is it really worth it when you can get a high flow unit for less than the O2 eliminator?
Click to expand...
haha nope not at all. If I didnt have to get that O2 eliminator thing then I'd do it..but the eliminator is $69USD and a magnaflow high-flow cat is $79.99CAN so it's really NOT worth it.
 
ok , since you didnt state what year it is we can only guess .
if it is a 96 then you can run without a cat as long as the o2 sensor is still there , because they are covered under a current recall for just that .
the oem programming in the pcm wouldnt recognise a failing cat conv. or turn on the check engine light .
however you are going to lose low end torque and throttle response , but it will do 70 to 110 like right now on the highway .
how do i know ? after my cat started rattling , i just gutted it ( due to $ problems at the time ) and drove it like that for about a year with no check engine light .
it just isnt worth it in the long run , sooner or later you will have to replace it anyway .
 
Don't waste 60 dollars on an o2 sim. Go to Autozone and buy a set of Sparkplug defoulers. I don't remember the threadpitch for the Jeep, but most are 17mm. Drill the center out with a 1/2" bit. Make sure not to knick the threads on the inside. Just screw the o2 sensor into the defouler, then into the pipe. It works :)
 
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Car is a Mitsu Evolution 8, but it works for everything I've done it on.
 
VinceYJ said:
haha nope not at all. If I didnt have to get that O2 eliminator thing then I'd do it..but the eliminator is $69USD and a magnaflow high-flow cat is $79.99CAN so it's really NOT worth it.
Click to expand...
I see them all over ebay for less than $69USD, idk what the exchange rate is to see how much more/less it is but come on now, for anotehr hour of work you can be legal and safer to the environment instead of putting on a straight pipe. I have no respect for that at all. :mad:
 
JohnR said:
Don't waste 60 dollars on an o2 sim. Go to Autozone and buy a set of Sparkplug defoulers. I don't remember the threadpitch for the Jeep, but most are 17mm. Drill the center out with a 1/2" bit. Make sure not to knick the threads on the inside. Just screw the o2 sensor into the defouler, then into the pipe. It works :)
Click to expand...

Nice!
 
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