Gutted out Cat info

[nfo184]

i own a 95 grand cherokee v8 and want to gut out the cat converter....is this hard? also will it sound louder or deeper??? or get bettter flow??

[neon_rt]

LOL. You may not get very many answers.
...I am going to commit a federal crime... will it make my Jeep sound louder or deeper....?
I don't think anyone here is willing to admit they shunned Federal emission law to make their exhaust sound different.
CATCO makes low restriction /high performance Cats for $80-$125 and a local muffler shop can put it in for you. If you want more power/different sound alter the exhaust after the CAT where it is legal for you to do so.

[legalfee]

Right, I agree. Not only are there legal implications (that's a capitol offense in California right?) in removing the cat converter it would change the back pressure that the system is setup for. Also that's where the rear O2 sensor goes. SJ

[dksob81]

well 2 things, 1. I doubt you will hear much change from gutting the cat. 2. You will not gain any horse power, you will actually lose some lil ponies, because by gutting the cat you actually cause excessive backpressure, which causes more restriction hence the loss of the ponies.

I agree with neon get a high flow cat, and a catback exhaust system, flowmaster makes a great system not much louder then stock but ALOT deeper sound. You don't have to worry about the O2 Sensor on the cat, because your jeep did not have it on the cat, thats post 95 models (96 and later).

[mikieem]

Ok, a "friend" of mine tried this when he was in school. He threw on a 40series flowmaster and about a month later, the cat started rattling, so he decided to gut it, didn't have time to finish so he just threw on a straight pipe for the time. Now that made a big difference to the point where he threw a new cat on because it was too loud without it. So I would highly recomend not doing it, putting on a 40 series is good enough

[BenBB]

Yea i put a 40 series on my '96, and about 2 months later, the cat started rattling, usually when i was just ideling, does anyone know why that happens and/or a way to fix it without gutting the cat? Thanks.

[neon_rt]

It could be that the exhaust system it vibrating against something b/c the muffler doesn't fit well. I would check the whole system for clearance and hanger problems before blaming the cat. If it is the Cat, just have it replaced with a High Flow one and call it good.
Interest thing about Jeep exhaust systems, they have a 2 1/2" inlet at the cat and a 2 1/4" outlet. That is one of the reasons the OEM cat is so expensive, it is non-standard. You can potentially put on a Catco 2 1/2" in/out and upgrade to a full 2 1/2" exhaust system.
A Catback system using the stock Cat is worth 5-6hp at the wheels (seen it on a dyno test). I would think that a Cat upgrade might give you 4hp more for a total of 10hp.

[YtseJam454]

Originally Posted by dksob81

well 2 things, 1. I doubt you will hear much change from gutting the cat. 2. You will not gain any horse power, you will actually lose some lil ponies, because by gutting the cat you actually cause excessive backpressure, which causes more restriction hence the loss of the ponies.

What the devil are you talking about? Gutting his catalytic converter will Decrease backpressure in the exhaust and will certainly make it louder. Do I recommend doing it? No As far as the guy who asked about the catalyst substrate breaking loose and rattling around inside, generally that is caused by excessive hydrocarbons entering the cat (ie cylinder misfire) and causing the substrate to break apart or even melt like in the event of a lean mis condition. If you want to make your exhaust sound cooler just go with an aftermarket muffler. Aside from the fact that the Cat does hamper some performance it really is a great invention that helps us all live longer and healthier.

[dksob81]

Originally Posted by YtseJam454

What the devil are you talking about? Gutting his catalytic converter will Decrease backpressure in the exhaust and will certainly make it louder. Do I recommend doing it? No As far as the guy who asked about the catalyst substrate breaking loose and rattling around inside, generally that is caused by excessive hydrocarbons entering the cat (ie cylinder misfire) and causing the substrate to break apart or even melt like in the event of a lean mis condition. If you want to make your exhaust sound cooler just go with an aftermarket muffler. Aside from the fact that the Cat does hamper some performance it really is a great invention that helps us all live longer and healthier.

Have you ever dyno tested a vehicle with with a cat then the same vehicle without the cat. You lose horsepower. Watch horsepower TV, watch mythbusters, they have all done it, you loose horse power when you put a straight pipe on. And all because the cat stopped backpressure from trying to re-enter the engine. The cat act like a 1way valve (but not so much) it helps restrict the exhaust from flowing back to the engine, because engine exhaust isn't constant it flows in spurts, from each cylinder. I've done this test myself, I know.

Gutting the cat will decrease restriction, not backpressure.

[Ron68]

I just replaced the cat on my 97 - PITA. The 2 1/2" inlet was a snap. I used a cutoff wheel, but the clamp on the muffler inlet distorted the muffler so bad that in order to save replacing the muffler, I had to make four parallel cuts and use a rented tailpipe expansion tool to get the 2 1/4" cat outlet to go into the muffler inlet. Using the tool along with some "percussion engineering" allowed me to get the cat installed far enough into the muffler so I had no leaks.

Yes, I did break the law a few years ago when I got the "death rattle" in the cat in my 87 Cherokee. To save a few bucks, I took out the cat and used a pipe to beat out the insides. I reinstalled the empty cat and drove it for over a year, and astonishingly, I even passed an emissions test. I did get caught the next year with a failed test and I had to replace it. I can't say if I noticed any reduction of power or any other adverse effects, and when I sold the 87 a few years later with 328,000 miles, it was still running great.

(If any law enforcement types are reading this, I of course, made the whole thing up...)

[dksob81]

Originally Posted by Ron68

I just replaced the cat on my 97 - PITA. The 2 1/2" inlet was a snap. I used a cutoff wheel, but the clamp on the muffler inlet distorted the muffler so bad that in order to save replacing the muffler, I had to make four parallel cuts and use a rented tailpipe expansion tool to get the 2 1/4" cat outlet to go into the muffler inlet. Using the tool along with some "percussion engineering" allowed me to get the cat installed far enough into the muffler so I had no leaks.

Yes, I did break the law a few years ago when I got the "death rattle" in the cat in my 87 Cherokee. To save a few bucks, I took out the cat and used a pipe to beat out the insides. I reinstalled the empty cat and drove it for over a year, and astonishingly, I even passed an emissions test. I did get caught the next year with a failed test and I had to replace it. I can't say if I noticed any reduction of power or any other adverse effects, and when I sold the 87 a few years later with 328,000 miles, it was still running great.

(If any law enforcement types are reading this, I of course, made the whole thing up...)

Well it wouldn't be enough power to even notice, a horse or 2. I think when HP TV did it on a nova, they got about a 4HP loss using a stright pipe. You would never really notice it, but heck if your gonna lose 1/2 a horse then it's not really worth the risk.

[nfo184]

ok 1. to get it right......if u have a boosted civic and take out the cat u will get more hp...maybe not on our cars or on a oem stock car but yea it can help....but thanks for the inffo...i'll get a hi flow since most people seem to have a problem with the oem cats after they do a cat back install....this way i wont ruin my new exhuast with the crappy stuff breaking in the cat....and emissions smissions...its ob1 and i live in ny

[Integra4200]

I jus bought a 96 jeep grand cherokee laredo, with the 5.2. we had to replace the cat. my dad went to the local parts store and bought a jones muffler. there supposed to be the same design as magnaflow but half the price. we put that on with a magnaflow cat. and it sounds great.

[motocip]

I gutted the cat on my 1996 5.2 GC. I did it because the internals were rattling around and I did not want to spend the money on a new one. Just grabbed a steel rod and rammed it through, it all came out. I have 152,000 miles on my Jeep and have put about 7,000 since gutting the converter. I cannot say whether or not I gained or lost anything power wise, but I will say my mileage has not changed and my check engine light never came on. You can definitetly tell my exhaust is richer smelling though. I went with a Dynomax cat back system I got from summit. It was a good deal at around $100.00. My jeep sounds pretty good, I like some tone to my exhaust. I don't claim to be an expert on the matter and I don't recommend doing it for power gain reasons. Send the converter police, I'M GUILTY!!

[YtseJam454]

Originally Posted by dksob81

Have you ever dyno tested a vehicle with with a cat then the same vehicle without the cat. You lose horsepower. Watch horsepower TV, watch mythbusters, they have all done it, you loose horse power when you put a straight pipe on. And all because the cat stopped backpressure from trying to re-enter the engine. The cat act like a 1way valve (but not so much) it helps restrict the exhaust from flowing back to the engine, because engine exhaust isn't constant it flows in spurts, from each cylinder. I've done this test myself, I know.

Gutting the cat will decrease restriction, not backpressure.

Actually yes we do Dyno test vehicles all the time. We also flow test all of our engine modifications baselining our results. And you said in your original post that it increases backpressure by removing the cat. Install an exhaust backpressure gauge in your 02 bung with and without the cat then tell me you still believe that. Would you say 2 psi or higher in the exhaust is considered hi back pressure? As far as HP gains and loss this would strictly be dependent on engine design, camshaft profile, timing, tuning etc. Just popping your exhaust off and putting a fart can on there will decrease mileage and overall street economy but that isn't what you are saying here is it....?