Gutting the cats?
Thread Starter
Staging Lane
Joined: Dec 2002
Posts: 62
Likes: 0
From: Texas
Gutting the cats? Have a bad cat on the left side. Gonna go ahead and replace but until then going to just gut all of the cats. How would you guys or have you guys done this in the past? Can you gut all of them or should you just gut the pre-cats? Is is better to cut a square hole and rip everything out then weld back or just ram them out with a big screw driver? I've had this bad cat for a while now. Maybe 4 or so months. I just now got around to finally hooking the car up and finding out exactly what has been wrong with the car. What kind of damage does this cause to the engine?
TECH Fanatic
Joined: Jun 2003
Posts: 1,070
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From: Further South than Hell
Originally Posted by importkilla
Have a bad cat on the left side. Gonna go ahead and replace but until then going to just gut all of the cats. How would you guys or have you guys done this in the past? Can you gut all of them or should you just gut the pre-cats? Is is better to cut a square hole and rip everything out then weld back or just ram them out with a big screw driver? I've had this bad cat for a while now. Maybe 4 or so months. I just now got around to finally hooking the car up and finding out exactly what has been wrong with the car. What kind of damage does this cause to the engine?
Thread Starter
Staging Lane
Joined: Dec 2002
Posts: 62
Likes: 0
From: Texas
Yeah. The SES has been on. Still is. I'm just now getting to a point where I can actually work on it.
I've heard a bunch of crap about the O2 sensors and still to this day am getting mixed replies. Some say you can run without cats/gutted cats and the car will run fine but the sensors will keep the SES light on. Then others say the car will run like crap. I'll probably get the sims anyway. Can't hurt.
I've heard a bunch of crap about the O2 sensors and still to this day am getting mixed replies. Some say you can run without cats/gutted cats and the car will run fine but the sensors will keep the SES light on. Then others say the car will run like crap. I'll probably get the sims anyway. Can't hurt.
""I've heard a bunch of crap about the O2 sensors and still to this day am getting mixed replies. Some say you can run without cats/gutted cats and the car will run fine but the sensors will keep the SES light on. Then others say the car will run like crap. ""
long bar or screw driver drive out the guts,
reset pcm to turn off SES lite, which will return unless you delete codes with EDIT or add o2 simms,>>BUT SES lite being on will have NO effect as to engine running,lite is only to warn of emmisuns(yes I know this is miss spelled- if I knew how I would have spelled it rite-it is 1:00am and my speller has gone to bed >> do know about the lite )
long bar or screw driver drive out the guts,
reset pcm to turn off SES lite, which will return unless you delete codes with EDIT or add o2 simms,>>BUT SES lite being on will have NO effect as to engine running,lite is only to warn of emmisuns(yes I know this is miss spelled- if I knew how I would have spelled it rite-it is 1:00am and my speller has gone to bed >> do know about the lite )
Last edited by SS SLP2; Oct 26, 2003 at 01:11 AM.
Originally Posted by SS SLP2
""I've heard a bunch of crap about the O2 sensors and still to this day am getting mixed replies. Some say you can run without cats/gutted cats and the car will run fine but the sensors will keep the SES light on. Then others say the car will run like crap. ""
long bar or screw driver drive out the guts,
reset pcm to turn off SES lite, which will return unless you delete codes with EDIT or add o2 simms,>>BUT SES lite being on will have NO effect as to engine running,lite is only to warn of emmisuns(yes I know this is miss spelled- if I knew how I would have spelled it rite-it is 1:00am and my speller has gone to bed >> do know about the lite )
long bar or screw driver drive out the guts,
reset pcm to turn off SES lite, which will return unless you delete codes with EDIT or add o2 simms,>>BUT SES lite being on will have NO effect as to engine running,lite is only to warn of emmisuns(yes I know this is miss spelled- if I knew how I would have spelled it rite-it is 1:00am and my speller has gone to bed >> do know about the lite )
Exactly. The front O2 sensors are used for tuning the car, the rear O2s are used only to determine cat efficiency/operation. The computer reads the voltage of the rear O2s and the frequency at which that voltage changes and compares that to the front O2s to make sure that the numbers differ in the correct range...which therefore means that the cats are working correctly.
When I read this, I was at work standing next to an ASE Certified Mechanic who used to be an emmissions ****...um, er...I mean "technician"
...back in California. He said the same thing ^^^ TECH Fanatic
Joined: Jun 2003
Posts: 1,070
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From: Further South than Hell
HMM, Maybe I was misinformed about the O2 things. But here is what I heard: The gases passing through gutted cats run in a lot of disturbance and bounce off inside. This can cause some of the gases to flow back and give bad readings on the rear O2 (I think it was driver side). So tubes are better than gutting your cats.
I had gutted cats on my car for about 8 months before I finally got an ORY. I bought the 02 simms and my SES light went away and my car ran fine. There is no possible way for the exhaust to flow back up the pipe and disturb the 02 readings.
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What is wrong with the catalyst?
If you got a poor perform code doesn't mean the cat is bad.
You'd be better off going to L/T's & ORP or just an ORP set up.
If the cat was indeed bad, there is a 5/50,000 on them.
But not if their "gutted".
If you got a poor perform code doesn't mean the cat is bad.
You'd be better off going to L/T's & ORP or just an ORP set up.
If the cat was indeed bad, there is a 5/50,000 on them.
But not if their "gutted".
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Staging Lane
Joined: Dec 2002
Posts: 62
Likes: 0
From: Texas
Originally Posted by NightHawk
Exactly. The front O2 sensors are used for tuning the car, the rear O2s are used only to determine cat efficiency/operation. The computer reads the voltage of the rear O2s and the frequency at which that voltage changes and compares that to the front O2s to make sure that the numbers differ in the correct range...which therefore means that the cats are working correctly.
When I read this, I was at work standing next to an ASE Certified Mechanic who used to be an emmissions ****...um, er...I mean "technician" ...back in California. He said the same thing ^^^
When I read this, I was at work standing next to an ASE Certified Mechanic who used to be an emmissions ****...um, er...I mean "technician"
...back in California. He said the same thing ^^^So if I were to get O2 simulators, would I need them for all cats or just the front cats?
Listen to NightHawk. The rear O2's do not affect engine operation (via the PCM). Once the blower was installed on my '01 SS, my SES light was on ALL THE TIME and the code was for the rear O2 saying decreased cat efficiency. However, it had no effect on the tuning. This is with the cats still on. The Vortech just crams so much air and fuel in there that the rear O2's read it as something wrong.
Thread Starter
Staging Lane
Joined: Dec 2002
Posts: 62
Likes: 0
From: Texas
Damn TWS. I'm not too far from you bro. I'm in San Marcos. Anyway, I definitely understand the back cats can be cut/gutted and the sensors will always think something is up, but what it sounds like NightHawk is saying is not to mess with the front cats or the engine will run like doodoo. I hope I'm not sounding like and idiot here but damn, cats were so easy in the old days. 91 and 92 pickups. Cut'em, dump'em and run'em.
Last edited by importkilla; Oct 27, 2003 at 08:56 AM.
Originally Posted by importkilla
Damn TWS. I'm not too far from you bro. I'm in San Marcos. Anyway, I definitely understand the back cats can be cut/gutted and the sensors will always think something is up, but what it sounds like NightHawk is saying is not to mess with the front cats or the engine will run like doodoo. I hope I'm not sounding like and idiot here but damn, cats were so easy in the old days. 91 and 92 pickups. Cut'em, dump'em and run'em.
Anyway, you can still run gutted cats or just off-road pipes, and you don't need O2 sims. Just use LS1edit to turn off the test for the two rear O2 sensors. Yeah some speed shops have LS1edit and will do it for you, price may vary. Or you can get your own copy of LS1edit from www.carputing.com for $550. Sounds like a lot of money, but it's actually worth it for all the things you can do with it.
Just a quick question on gutting the cats.
I am thinking about doing that for the time being until I can afford LT Headers and a custom Y-pipe to support hi-flo cats. But in the mean time I want to gut them if there is any performance gains.
I have LS1 Edit with the shop that's been doing my tuning already. With them correcting the rear O2's, what kind of gains should I see or is there any?
I am thinking about doing that for the time being until I can afford LT Headers and a custom Y-pipe to support hi-flo cats. But in the mean time I want to gut them if there is any performance gains.
I have LS1 Edit with the shop that's been doing my tuning already. With them correcting the rear O2's, what kind of gains should I see or is there any?
Thread Starter
Staging Lane
Joined: Dec 2002
Posts: 62
Likes: 0
From: Texas
What I've gathered so far is only a few horses. I'm hearing anything from 5 - 15 hp. I really don't think you can get 15 from it though. I'm thinking around 5 or so extra horses. I haven't really tested the power upgrade yet but can definitely feel that the car runs a lot better being able to breath.
Originally Posted by importkilla
What I've gathered so far is only a few horses. I'm hearing anything from 5 - 15 hp. I really don't think you can get 15 from it though. I'm thinking around 5 or so extra horses. I haven't really tested the power upgrade yet but can definitely feel that the car runs a lot better being able to breath.
Cool. . . .how's the exhaust note from it now? Really raspy or does it sound alright? I've heard mixed feelings in regards to sound.
And as for 5 to 15, every little bit helps. Probably gain more driving. Wonder if it'll knock down at least a tenth of a second in the 1/4? Hmmm I'm not going to be able to purchase headers till probably this time next year hehe, so looking at cheap alternatives for the time being.
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
Likes: 3
From: Troy, AL
1. There are only two cats. One per side. There is no such thing as front and rear cats.
2. The rear O2 sensors have NOTHING to do with performance. The car will run NO different with the cats gutted whether you run O2 simms or not. The O2 simms are to keep the SES light off of your dash. Programming can also do this.
3. Gutting cats WILL NOT give your front O2 sensors (the only ones that have anything to do with performance) faulty readings.
Just use a big screwdriver or similar shaped tool (a little curvature or some hook on the end helps) to gut the cats. There's no need to cut them open.
2. The rear O2 sensors have NOTHING to do with performance. The car will run NO different with the cats gutted whether you run O2 simms or not. The O2 simms are to keep the SES light off of your dash. Programming can also do this.
3. Gutting cats WILL NOT give your front O2 sensors (the only ones that have anything to do with performance) faulty readings.
Just use a big screwdriver or similar shaped tool (a little curvature or some hook on the end helps) to gut the cats. There's no need to cut them open.
Launching!
Joined: Nov 2002
Posts: 257
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From: Fort Carson, CO
I ran mine with the cats gutted and through a cutout and it was loud as hell. Sounded pretty damn good at WOT too. Its going to be a bit raspy and a little bit higher pitched in the high RPMS. I love the way it sounds. As far as the SES light, i went ahead and got o2 Simms because i hate looking at the light and also if something else is wrong that uses the light you wouldn't know.