losing the cats

Shocker · February 22, 2006

So I'm considering cutting off the cats on my 04 silverado with the 5.3L engine. I was wondering if any of you guys have done it, I'm sure somebody has. I'd like to know how it sounds, if there would be any performance gain, and what I would have to do about the O2 sensors.

Thanks guys.

GTUSN2006 · February 22, 2006

Havent done it or experienced it on a truck, but have on a 02 Firebird. It was alot louder and deeper after the instal of long tube headers and removing the cats. You should think about the legality of it though, depending on where you live.

As far as the 02 sensors, u usually have to get 02 simulators that are like 100 bucks a pair, connects to the harness for the rear sensors and fools the computer.

One side note on removing the cats, the car i mentioned above has had problems with making the front o2 sensors go bad. And that is expensive. Also, the exhaust smell is now obnoxious. I like that smell at the race track, but everyday it is very annoying.

I think some companies make high flow cats, may be an in between option for you.

redvett · February 22, 2006

Why would you want to remove the cats??? The removal wont make enought difference to be noticed. Removal will cost you performance (without a tune) incabin noise and of course emissions too.

Shocker · February 23, 2006

Havent done it or experienced it on a truck, but have on a 02 Firebird. It was alot louder and deeper after the instal of long tube headers and removing the cats. You should think about the legality of it though, depending on where you live.

As far as the 02 sensors, u usually have to get 02 simulators that are like 100 bucks a pair, connects to the harness for the rear sensors and fools the computer.

One side note on removing the cats, the car i mentioned above has had problems with making the front o2 sensors go bad. And that is expensive. Also, the exhaust smell is now obnoxious. I like that smell at the race track, but everyday it is very annoying.

I think some companies make high flow cats, may be an in between option for you.

<{POST_SNAPBACK}>

Do you know how removal of the cats could cause the front o2 sensors to go bad? I don't understand why that would happen.

And redvett, my main goal here is noise. I want my truck prettymuch as loud as I can make it.

Mr. Smith · February 23, 2006

Havent done it or experienced it on a truck, but have on a 02 Firebird. It was alot louder and deeper after the instal of long tube headers and removing the cats. You should think about the legality of it though, depending on where you live.

As far as the 02 sensors, u usually have to get 02 simulators that are like 100 bucks a pair, connects to the harness for the rear sensors and fools the computer.

One side note on removing the cats, the car i mentioned above has had problems with making the front o2 sensors go bad. And that is expensive. Also, the exhaust smell is now obnoxious. I like that smell at the race track, but everyday it is very annoying.

I think some companies make high flow cats, may be an in between option for you.

<{POST_SNAPBACK}>

Do you know how removal of the cats could cause the front o2 sensors to go bad? I don't understand why that would happen.

And redvett, my main goal here is noise. I want my truck prettymuch as loud as I can make it.

<{POST_SNAPBACK}>

Now what is the point in making it loud to annoy others? Also removing the cats is illegal plain and simple.

SubUrban Legend · February 24, 2006

In a lot of states (like Ohio and Pennsylvania), it's illeagle to remove any polution control equipment. The state motor vehicle dept. will make you reinstall anything that was removed (when you are cought). This is especially true in any state with state inspections. Most states will allow replacement of the exhaust system with aftermarket performance systems from the cats back. The loud pipes will definitely draw the attention of the local peace officers. I have a '90 Surburban with a stock cat and no muffler, just a straight pipe to the rear. It has a nice low rumble on acceleration without being too loud.

Larry S.

99Silver6.0 · March 2, 2006

Havent done it or experienced it on a truck, but have on a 02 Firebird. It was alot louder and deeper after the instal of long tube headers and removing the cats. You should think about the legality of it though, depending on where you live.

As far as the 02 sensors, u usually have to get 02 simulators that are like 100 bucks a pair, connects to the harness for the rear sensors and fools the computer.

One side note on removing the cats, the car i mentioned above has had problems with making the front o2 sensors go bad. And that is expensive. Also, the exhaust smell is now obnoxious. I like that smell at the race track, but everyday it is very annoying.

I think some companies make high flow cats, may be an in between option for you.

<{POST_SNAPBACK}>

Do you know how removal of the cats could cause the front o2 sensors to go bad? I don't understand why that would happen.

And redvett, my main goal here is noise. I want my truck prettymuch as loud as I can make it.

<{POST_SNAPBACK}>

They wont make the front O2's go bad. Its just gonna piss off the rears until you turn them off. Youll throw cat efficiency and insufficeint activity codes. You wont notice anything down low. But you will gain a bit up top. Especially if you have a bigger cam and tune. Dont do it unless you can kill the rear O2's and tweak the tune a bit.

GTUSN2006 · March 2, 2006

Do you know how removal of the cats could cause the front o2 sensors to go bad? I don't understand why that would happen.

<{POST_SNAPBACK}>

I guess go bad is the wrong word, but they throw codes all the time. The rear O2 sensors aren't a problem sense they have been eliminated with a custom tune. And thinking the problem with the front ones is that with long tube headers they are moved farther back and take more time to get to temp, if you let the car warm up before you drive it it doesnt throw the codes.

But as everyone else has said, and I will say again, unless your goal here is to be "THAT GUY" who everyone else on the road thinks is a jack**, or you are going to completely mod that thing out for the strip or trail, save yourself the legal hassle that you will get sometime and just put some original series flowmasters on it.

redvett · March 3, 2006

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And redvett, my main goal here is noise. I want my truck prettymuch as loud as I can make it.

Your a perfect reason our legislators are going after laws to make aftermarket exhausts illegal. There are some states that have made it illegal to use any exhaust that isnt DOT approved. Keep it up and we all will be forced to be quiet as OEM vehicles are. :-0

99Silver6.0 · March 3, 2006

Do you know how removal of the cats could cause the front o2 sensors to go bad? I don't understand why that would happen.

<{POST_SNAPBACK}>

I guess go bad is the wrong word, but they throw codes all the time. The rear O2 sensors aren't a problem sense they have been eliminated with a custom tune. And thinking the problem with the front ones is that with long tube headers they are moved farther back and take more time to get to temp, if you let the car warm up before you drive it it doesnt throw the codes.

But as everyone else has said, and I will say again, unless your goal here is to be "THAT GUY" who everyone else on the road thinks is a jack**, or you are going to completely mod that thing out for the strip or trail, save yourself the legal hassle that you will get sometime and just put some original series flowmasters on it.

<{POST_SNAPBACK}>

Lot of guys are using Vette front O2's to solve heating problems. Seems to work. Uncoated headers usually cause that problem alot because they cant hold in enough temp.

Shocker · March 4, 2006

Well, thanks to all for the info and perspective. I've been wanting longtube headers and when I do that I'll get some high flow cats as well. Do you guys with longtubes on your trucks have problems with the o2s throwing codes? How much would the vette sensors run?

rockertype · July 26, 2006

I hollowed out the cats on my 94 Silverado 350 at 150K miles. The truck now has over 340K on it! That's right 340K! Never had a problem with an o2 sensor yet!

My 02' HD with the 8.1 doesn't seem to have the "rear" o2 sensors you guys are talking about. Just two in front of the cats, way in front. I wonder if any cat modifications would bother the two front sensors???

redvett · July 27, 2006

Your 94 is an OBD1 and your 02 is OBD2 two different operating systems and removing the cat will cause the SES to come on. Removing the car will produce little or no improvement in performance but will hurt fuel economy and driveability. The newer engines require a certain amount of backpressure.

Dans Denali · July 28, 2006

Why remove them? I drag race a 84 Mustang and have been on a dyno with and without cats and saw no difference. We also saw no difference with a K&N!!! And besides the car smells up the house and garage without cats.

Dan