gutting a cat
 

I want to gut my cat on my 2005 it has 3 of um. Will it hurt anything? what about the sensors on um?

Down fall is emissions and poor performance. you will also end up with a check engine light (CEL)

so i should just leave um? its a 2.3 i allready put a straight flow glasspack on it. so maby just headers huh?

I don't take apart my TV and reconnect wires trying to get better picture quality right? Why - because I don't understand how it works.

I suggest you use this analogy with your truck as well. Don't modify what you don't understand.

^^Nicely put, Turb'z.

the only purpose for the cats is emissions, if you dont have to pass emissions tests (we dont in alabama) then gut the hell out of them. they are extremly restrictive and you will notice a big difference without them, but you will most likely get a check engine light because the only purpose of the rear o2 sensor is to check to see if the cats are working. but if the check engine light bothers you too bad just take the instrument panel out and take out that bulb haha. most shops that can reprogram the computer can remove the code that trips the sensor without the cats so it doesnt come on again, although im not sure how much that costs

WOW, where you getting your information?
When they first started putting cats on, a couple of the car mags did some testing to see how much power they robbed and what would happen if you ran with out cats.
One test was with a Camaro, (car of the time), they ran this on the drag strip with and without the cat, the result was a better e.t. with the cat.
The other test was real world on another GM product that ran a tank of fuel out, with and without cats, results there were like the Camaro. Better mileage with the cat.
Now that was probably close to 40 years ago and I would bet that today's technology has improved the cats to where removal actually hurts performance.
Before you jump in and gut or remove your cat, do a little searching and a lot of reading on the subject. Stay away sites that deal solely with emissions.
Aside from the Federal regulation banning the removing cats, there doesn't seem to be much sense in it. Cats are near free flow unless they are plugged. Open the rest of the exhaust up to the diameter of the pipe between the cats and throw the stock muffler.

Ray

all i know is that when i took my cat out i picked up close to 2 mpg, i think it was about 1.7 or so, and i noticed a bit more power, both low end and high end, i ended up puting a magnaflow highflow cat on it because i didnt like the sound of the 4 banger with that little restriction, after i put that on i lost a little power and a little gas mileage but it was still better than stock but still not as good as it was without the cat (if could do it again i would have just put in a glasspack or another muffler instead of a cat), so i am getting my information from personal experience,and as far as a cat being being nearly freeflowing you have apparently never looked inside of one, even a new one is extremely restrictive, my 2000 2.5L only had 1 cat on it so i would figure you would pick up more if you took out the 3 that you have. oh and by the way mine didnt trip the check engine light but i cant say it wont on yours. if you ran the car at the track with the cat then took it off and ran it right after you did (as they probably did in the test) it probably will run better without it. but if you cleared the computer after you took it off drove it about 10 miles so the computer can relearn the system it would run faster and get better mileage. you should clear the computer after any mod you do no matter how small because the computer is expecting everything to be there as it was from the factory. it will eventually relearn the system on its own but it will do it much faster if you clear the computer. in case you didnt know you can clear the computer by leaving the battery disconnected for about 20 minutes but i always leave it disconnected for about 30 to make sure. also if you gut the cats you should also free up the intake side some also because if you have the factory intake and a more free flowing exhuast you could have too little back pressure which can hurt performance but if you open up the intake side it will correct this.

Re: gutting a cat
 

From my experience, I would just leave the cats alone. Factory tune is to make a vehicle run efficient. From the headers back to the cat, just leave it, change out the muffler if you'd like. The back pressure is there for a reason. Like when you cough, if you just have a dry cough, it hurts your throat, but when you actually cough something up, it's not to bad. When I gutted my cat in my other truck, it gave me worse gas mileage and that was it.

Re: gutting a cat
 

Put a high flow cat on it, call it good. It is a federal law that you must have a cat that is not tampered with. Emissions testing or not. Also in my experience you don't gain anything by taking it off. That can differ depending on the vehicle but that's my experience. I've never seen any real good reason to take off a cat. Also the CEL will come on and your truck will run poorly in newer vehicles. The 02 sensors located in your cats can also tell you when there is a problem with your engine, removing them doesn't allow you to . Just my .02 cents

Re: gutting a cat
 

I got a cherry bomb universal cat for an Accord i had that the previous owner removed. it was basically a straight through design. I didnt notice any change in performance or mpg.

Re: gutting a cat
 

you might lose mpg.
i know when i straight piped my old truck i went from 18 to 12.

Re: gutting a cat
 

Not sure I believe this as it is hard for me to understand how taking off something after the entire combustion process will do anything to help mpg. And how much exhaust do you think you are actually putting off for the cat to actually not flow the exhaust through quick enough? I feel our trucks do not put off too much to get "stuck" in the cats. Of course I am no way any where near an expert in this, just using what seems logical to me.

Re: gutting a cat
 

If his catalyst was seriously plugged from running incorrectably rich then yes it could be a restriction, but in proper working form removing a catalyst will not help you gain mileage.

Re: gutting a cat
 

as far as our trucks not putting out enough exhaust to get "stuck" in the cat, have you ever taken one apart and looked inside it? they are extremly restrictive. have you ever wondered why a cat has to have a heat shield, get under your truck after you drive it and the exhaust is still hot, the cat is a hell of alot hotter than the rest, from a thermodynamic point of view this means that the cat is taking alot of engery out of the system, in this case it is kenetic energy that the cat is taking out of the system slowing down the gas and creating more pressure of the engine side. and yes the engine does need some backpressure but the cat gives it more backpressure than it needs. and no mine wasnt stopped up when i took it out. i was running in with no cat for a while and decided to put a magnaflow highflow cat in because i didnt like the sound of it. when i put on the highflow cat my mpg went down but they were still higher than it was stock.