Catalytic converter or straight pipe

Keith1138

Keith1138

Well-Known Member
Joined
Nov 18, 2015
Location
Harrisburg NC
My catalytic converter is completely toast. My jeep Cherokee has two catalytic converters right below the headers. My question is would my vehicle suffer if I straight pipe it. If I did that what about the down stream o2 sensors. Also any good shops in the concord/charrolotte area that would straight pipe or replace the converters for a fair price?

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It'll run just fine. The downstream oxygen sensor will trip an efficiency code due to it's voltage signal mimicking the upstream one.
Some people buy an old school anti-fouler and place it in the downstream bung.
Then you'll need to find a station that'll pass it.

Or just buy a $80 Magnaflow universal cat like I did for my wife's ZJ.
 
Are you asking about removing the two cats in the header or the third downstream? The computer needs the two in the header, but doesn't know the difference if the downstream is there or not. That being said, I would replace the downstream with a universal fit cat. I had one done in my old xj and it was only like $50 more than a straight pipe.
 
LBarr2002 said:
Are you asking about removing the two cats in the header or the third downstream? The computer needs the two in the header, but doesn't know the difference if the downstream is there or not. That being said, I would replace the downstream with a universal fit cat. I had one done in my old xj and it was only like $50 more than a straight pipe.
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Removing the two top cats. Or replacing them.

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FYI in NC I had a hard time finding a shop that was willing to overlook NC laws and touch my Ga tagged Jeep (no emissions laws) because there was no cats. I eventually had to turn to the good people on NC4x4 to recommend a shop that was willing to do off the books work on a “rock crawler rig”.

Hope that helps you save a few wasted phone calls to phone book listings
 
I think I'm leaning towards to replacing both completely. That way I don't have to worry about inspections

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Just bought a set of direct replacment pacesetter cats and y pipe for my 04 tahoe, fit good and priced well.

I called muffler masters in kannapolis and they said they wouldn't even touch it.. Different time I called before about my 88 suburban and explained that the P.O. cut off the cats and i wanted a new system from the manifold back with new cats. He again said they wouldn't touch it and when I questioned him he hung up, lol.
 
No respectable shop will straight pipe it, as that is a EPA violation section blah blah. I'd say throw a universal in it and gut the two upstream or leave them or install a direct fit catalytic system (order online, save a lot over walk in at parts store). Direct fit will be "easy" to install (read: every bolt snaps on removal but you may get lucky. At least the xj is set up with through bolts to the manifold, but it's studs at the down pipe, which you could hack off the flanges and use a coupler if they break)

Non-foulers work on some years (02 and under typically, as the ECU didn't have enough processing power to assess voltage and frequency and time delay) but not others due to the detection algorithm in the ECU. There is another non-hardware solution. I'll send you a pm with it.
 
Keith Odom said:
I think I'm leaning towards to replacing both completely. That way I don't have to worry about inspections

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I debated on this for a long time in my zj! I ended up cutting cats throwing a thrush welded under it and ran pipe all way out single past trans and dumped it down! It wouldn't pass inspection in va bc was catalytic exhaust system, so I welded front axle and made it a trailer queen... lol prolly not much help but that's my experience!
 
Also, with it being a 96+model, there's not a shop in the state that can get it passed if the light is on***.


***Excluding those willing to risk fines, more fines, prison, fines, loss of inspection license, as well as more fines, and did I mention prison? Also they would need specialized inspection equipment to make it pass a standard obd test. All for $20 inspection revenue? Nah..
 
I decided that the raw gas smell coming out of the tail pipe wasn't worth losing 3 horsepower. It's terrible if you try to go around a drive through with no cats...
 
a_kelley said:
No respectable shop will straight pipe it, as that is a EPA violation section blah blah. I'd say throw a universal in it and gut the two upstream or leave them or install a direct fit catalytic system (order online, save a lot over walk in at parts store). Direct fit will be "easy" to install (read: every bolt snaps on removal but you may get lucky. At least the xj is set up with through bolts to the manifold, but it's studs at the down pipe, which you could hack off the flanges and use a coupler if they break)

Non-foulers work on some years (02 and under typically, as the ECU didn't have enough processing power to assess voltage and frequency and time delay) but not others due to the detection algorithm in the ECU. There is another non-hardware solution. I'll send you a pm with it.
Click to expand...
For some reason mine doesn't have the tri-angle bolt plate. It is just a solid piece all the way down to the converter right before the muffler. That's why I'm looking for a shop. It it did have the bolt plate I would change it my self. With a custom fit y piece.

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What about deleting the upper cats and installing a downstream high flow cat? I wonder if that would pass inspection?
 
If the downstream sensor is after the second converter, just change the downstream converter out. Sawzall either side of it and put a converter in that is sized for the pipe and longer than the original. I'll do it for you if you want to bring it to rutherfordton.
 
a_kelley said:
If the downstream sensor is after the second converter, just change the downstream converter out. Sawzall either side of it and put a converter in that is sized for the pipe and longer than the original. I'll do it for you if you want to bring it to rutherfordton.
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Thanks for the offer but both down stream sensors are after the first two cats before the two pipes conjoin leading to the other cat and muffler.

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ckruzer said:
What about deleting the upper cats and installing a downstream high flow cat? I wonder if that would pass inspection?
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Not likely. If the emissions equipment book calls for 3 converters, and you have 1, it fails visual inspection.

You would also have to find a way to delete the two downstream O2 sensors, again, if the book calls for 4, and you have 3, fail.

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