View Full Version : cutting my catalytic converter off???

06-13-2005, 11:41 PM
has anyone ever experienced problems in their truck specifically a 98 gmc or chevrolet when cut off the catalytic converter to have a louder exhaust system?? ive heard ppl say your check engine light will come on but they have replaced the oxygen sensors and the light went off. should i cut my cat or not ?? i was going to cut my cat and put flowmasters on it , i wanted to do this b/c i know my flowmasters will be louder without the cat on my truck!!! what do yall think?????????????????????/ :huh: :huh: :huh:

06-13-2005, 11:45 PM
any replies??

06-13-2005, 11:50 PM
I think you will find that you wont like it. It wont sound like you think it will. If you are trying to get true duel exhaust it wont sound or flow like it should. Those vortec engines require a certain amount of backpressure to perform at their best. Yes you can cut them off weld in new plugs for your oxygen sensors. But the OBDII computer system can be tricky. Call flowmaster direct and ask them they will be very helpful.


06-14-2005, 12:12 AM
I drilled mine out a few years ago on a tacoma I had and shortly there after the engine light came on and stayed on. I could not figure out how to trick the O2 sensor. Bought another one and it came on again a few months later. Took a hit when I tried to sell it. I aslo called around the junk yards and was told more than once that they could no longer sell them???

Called toyota and they wanted 1200 to install it. Save your self some money and leave it be.

06-14-2005, 12:14 AM
well i know a way to make it sound real good which is running a 3'' pipe off my exhaust mainfold into a f40 series flowmaster (1 inlet dual outlet) and 2 1/2" pipe out the backside with 4'' by 20 inch long tips, and i had a buddy that researched it as far as the sound part and it sounds awesome !!! im just worried about the part that says if i cut my cat things will start screwin up on my truck ~ duramax do u think it will mess up anything in my truck???????????????????

06-14-2005, 12:48 AM
Save your money and the police will be all over you too.

06-14-2005, 04:41 AM
Struttin, what happens when you cut your cats is that it sends faulty readings to your computer. Your o2 sensors read the exhaust temp then relays to the computer how rich or lean to make the engine run. You can by o2 simulators to get the computer not to throw the code that gives you the check engine light. It's all up to you and what you want. I would leave the cats or cut holes in them and gut them them weld the holes back up. That way you still have your cats for emission purposes if you have to get emission testing done. You have to have cats on certain models. There are complete systems out there that sound awesome. Just do some research. Any more questions just ask. I will be more than glad to try to answer.


06-14-2005, 09:26 AM
Its a Federal offence to tamper with any emission control device, whether you live in a county that requires emissions or not. You risk substantial fines if you are caught. OBD 11 vehicles use oxygen sensors in front of and behind the convertors to monitor convertor performance. Thats why you will see check engine lights if you remove or disable the convertor.

06-14-2005, 09:35 AM
You beat me to it badger.

06-14-2005, 09:52 AM
what about older trucks that were not made with catalytic converters???? im thinking about cutting it but im still not sure!!!

06-14-2005, 10:44 AM
IMO, the sound is not worth the trouble you might have.

06-14-2005, 10:51 AM
i've been down both roads...get the true dual exhaust and keep your cats. you will like it a lot more. i would much rather have loud BUT CLEAN sounding exhaust than somethin that just screams

06-14-2005, 11:29 AM
well all i can say is if you heard this guys gmc with a flow on it no cat 3''pipe in and 2 1/2'' pipe out you would want to cut that cat haha man this is such a datgum hard decision ...what about gutting my cat????

06-14-2005, 11:33 AM
you have to think though....

once you cut your cat off you are losing back pressure...

this results in loss of power, and worse gas mileage...

if you put on true duals (2 mufflers...2 sets of pipe, 2 cats) you will gain horsepower, and get better gas mileage...not to mention it won't sound like a hot rod it will sound like a TRUCK.

06-14-2005, 11:37 AM
well maybe i will put 2 12'' glass pax and turn them around backwards

06-14-2005, 12:16 PM
yea i've heard of that bein done...if you put water in em when they heat up they'll bust and you'll shoot flames out of the tailpipes...but you didn't hear it from me :bounce:

06-14-2005, 01:47 PM
ow i already knew about that ..we would heat them up and back them up into the river landin' anyhow im just gonna cut my cats cause i know a boy that knows how to do it rite!!! so i recon we will see what happens

the HEED!
06-14-2005, 01:50 PM
emissions without converters on your vehicle

06-14-2005, 01:54 PM
what u mean cant pass???? u forget i live in statesboro,ga i CAN do what i want ppl that preach about emissions control are just a bunch of tree leaf green freaks :banana: :banana: :banana: ::ke: ::ke: ::ke: :smash: :smash: :smash: :crazy: :crazy: :mad:

Perry Hayes
06-14-2005, 05:27 PM
Why don't you just run straight headers then.You will be the loudest truck in town.

Perry Hayes
06-14-2005, 05:29 PM
Why don't you run straight headers then,you will have the loudest truck in town.

06-14-2005, 05:29 PM
what u mean cant pass???? u forget i live in statesboro,ga i CAN do what i want ppl that preach about emissions control are just a bunch of tree leaf green freaks :banana: :banana: :banana: ::ke: ::ke: ::ke: :smash: :smash: :smash: :crazy: :crazy: :mad:

It's still a federal crime to remove them and you could be fined or go to jail for doing so.

06-14-2005, 05:47 PM
im scared!!!!!!!!!!!!! :eek:

Eddy M.
06-14-2005, 06:07 PM
agree with badger it's aginst the law to cut them off---get a flowmaster set with the cats mounted--my 8.1L chevy has dual flowmasters with dual cats and roar when you step on it

06-14-2005, 07:11 PM
AAhh, just put on the headers and then run some galvanized fence pipe straight out the back......that fix'er.

short stop
06-14-2005, 09:20 PM
IT MIGHT BE POSTED --I didnt read em 'all ----not real lejit but you can cut a hole in cadi , pull out the guts and weld the cadi back toghter ---you got to know how to use a torch and a welder . you can do this without ever taking it off the truck . If you live in the EMISSION CONTROL ZONE ------- IT WILL NOT PASS ---SS

06-15-2005, 12:13 AM
Its :offtopic: but i like all the hunters to have loud exhaust,it trains the deer and turkeys to listen for the pipes but they never hear me coming :shoot:

06-15-2005, 07:21 AM
bull---that's what i was gonna say....i love my exhaust, but i hate having to creep up the dirt road at the crack of dawn tryin to be quiet...

not to mention it makes my parents ALWAYS know when i'm late cause they hear me pull in everytime and i could NEVER sneak out cause as soon as i crank the dang thing up they would wake up...oh well- guess that's the price we pay.

06-15-2005, 11:25 AM
im scared!!!!!!!!!!!!! :eek:


FYI, EPA already has a few "roadside sniffers" in operation in the Metro area that will sample the tailpipe emissions of your vehicle while sitting at a redlight. People are getting letters in the mail instructing them to take their vehicles for emissions tests if the sniffer dtects excessive emissions.
This is a pilot program in Georgia that I learned about just a few weeks ago. I don't know where they are located or how many there are, but we were told about it at the last emissions inspector training class.

So go ahead, take a chance :smash:

I must admit, I have become sensitive to some of the vehicles on the road that choke me & make my eyes burn when I'm stuck behind them on a 2 lane road..........


06-15-2005, 01:01 PM
i wont have to worry about that i live in statesboro,ga so everybody rides around with no cats , ow and think about all the old model trucks around here that have no cats

06-15-2005, 01:14 PM
struttinsouther- sounds like you had your mind made up before ya ever asked us what we thought :huh: ::ke:

06-15-2005, 05:47 PM
ure right brad patt i recon im a just gonna take my chances :( :confused: :confused: we will see what happens?? same with tint law i havent got pulled over yet??? and i have 5% on my gmc all the way around with a 5%strip on my windshield that is 17 '' long!!! takin my chances sooner or later ill prolly get slammed with a fine who knows!!

06-16-2005, 01:31 PM
I see you have your mind made up but before I bought my 99 z71 with a 5.3 someone cut the cats off and had obnoxiously loud flows on it. I put quieter flows on it, but it is still loud and exhaust work now will cost a fortune to get it back right. The older trucks you keep mentioning will perform better to an extent IF THE NEED IS THERE for the lack of exhaust restrictions. As someone said, just run you some headers and galvanized pipe out the back, heck cut em off under the cab. It'll sound gooooodddddd.......

06-16-2005, 10:35 PM
it will sound like a TRUCK.
And just what, exactly, does a TRUCK sound like?

The Snakeman

06-20-2005, 11:38 AM
The US Supreme Court ruled that state tint laws are unconstitutional b/c they are not all universal.

So if you get a ticket for Tint. Get you a good lawyer that likes to fight, and not cop a plea,and fight it in court.

Cat. Converter Law is federal so it is constitutional.