Removing Cat Converter

[o0 XeRO G 0o]

lets just say (hypothetically speaking of course) that I wanted to take my cat converter out. How much of a sound and performance difference would i hypothetically gain? And what would be the fine if the police found out? any ideas?

[JiP]

A) I would gladly pay a ticket if a cop actually laid down on his stomach to look under my car and notice there was no cat, if he even knew what a cat was.

Good luck trying to unbolt it. I removed my cats, if your 7g is like mine you have 2, on is curved and is between the exhaust manifold and flex section this cat is the actual pipe that holds your O2 sensor which you need. The middle CAT is easy to replace with a straight pipe. To get them off though you'll need an angle grinder and grin the nut off the end and the cat will fall right off. Then take your cat, grind off the post where the screw is, and drill out that hole so that when inspection time comes, you can reinstall your cat in 2 seconds.

I have no cats on my car, my engine revs a tad faster, barely noticable, it doesnt do any real performance increase on the car unless you have a turbo I guess. And loudness well, if you have the propper gaskets and a fully welded testpipe you won't notice anything different. You'' drop about 50 lbs off your car if you remove both cats for you weight concious people

[redboy]

i gutted mine, so it looks like i still have one there, cept its empty. i got a little performance, not much, and a little more miles to the galon and sounds a bit louder. i dont have emmisions laws here so for now i dont have to worry about johnny law comin after me for that....

[o0 XeRO G 0o]

i dont think i have emission laws in ohio, but i'll have to check around. does that mean if there arent emaission laws, its ok to do this?

[JiP]

Its one of those things like downloading mp3s that you really cant get cought for. There is no way to see a car on the road and be like OMG HE HAS NO CATs! So it really doesnt matter. You only need it for the sniffer emmisions test and since you dont have any in your state, pull that sucker out, while your at it pull your EGR system crap that will give more in performance then your CAT will. My car came with no EGR system from factory so its cool.

[manybrews]

there really no benefit from removing it.
MAYBE 1 hp increase. so removing it really does nothing but pollute (and also cause a check engine light to illuminate).

[BEAST]

What is the EGR?

[JiP]

Removing it doesnt cause the ce light to come on Your second o2 readings are always going to be a little less then the first o2, and the second o2 voltage will directly follow the first o2 pattern just a few milivolts less, which the ecu thinks everything is fine.

The EGR valve I think may only be on cali spec cars, cause mine came from factory with a blockoff plate which is just a peice of metal that some jokers sell on ebay for $25 bucks which you can make for $2. Its on the side of the intake manifold, you might not even have it. And if you dont have a manual book like chiltons or something, dont bother doing anything to your car until you get one.

[o0 XeRO G 0o]

the only reason i would want to take the cats out is so i wouldnt have to pay for the high flow cats from rpw, and i could save a good deal of money while upgrading my exhaust. i just bought my muffler (apex'i) and i was wanting to get the piping upgraded to 2.5 inch. so i could just run 2.5 inch piping from the headers straight to the muffler right? sorry bout the questions, i dont know much about exhausts at all

[JiP]

Ye that would work...but you should do some more research, some people will upgrade there exhaust to 3" piping when there car is NA and they'll just lose power.

Your exhaust system is made so that there is backpressure which causes a "scavenging" effect. Its created so that the force actually sucks out the remaining gasses in your piston chamber during exhaust stroke due to the vaccum create. Upgrading to bigger piping will not always increase power because you'll lose the backpressure and on your next stroke you'll have some dead air remaining in your chamber giving you less power.

Unless you have a turbo then you can do whatever you want, your turbo will create the suction that you need to pull the left over gases and you want to get rid of the exhaust as fast as possible, so bigger piping is better in that case.

[o0 XeRO G 0o]

thanks for all the help... i'll look into it and let you guys know what i've decided later on

[manybrews]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>Removing it doesnt cause the ce light to come on Your second o2 readings are always going to be a little less then the first o2, and the second o2 voltage will directly follow the first o2 pattern just a few milivolts less, which the ecu thinks everything is fine.

.</div>
yes, it does. thats its job. the rear o2 does NOT follow the front, which is why its used for testing. after the cat has fired off, it should run a fairly constant 300 to 500 mv, with no fluctuation.
if they follow each other, thats when the ECM knows the cat. is dead.

[JiP]

If it wasnt clear the way I wrote it, I meant your O2 sensors have the same output when you have no CATs on your car, and the slight voltage drop in the 2nd 02 is enough that the ECU doesnt throw a code.

[redboy]

on alot of cars it does, but all of mine that i have gutted it out on, the check engie light never cam on. my galant has been gutted for like a year and the light hasnt comon yet for anything....

[sabzi5858]

btw, i won't get too involved on the topic, there's a lot of good info on it out there if you want to do the research, but: backpressure is never a good thing, you don't want it (in terms of power atleast) the exhaust gas scavenging effect (which you want to have) is what could be lost because of the change in size of exhuast pulses, high and low pressure areas, and distances

[manybrews]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>If it wasnt clear the way I wrote it, I meant your O2 sensors have the same output when you have no CATs on your car, and the slight voltage drop in the 2nd 02 is enough that the ECU doesnt throw a code.</div>
it sure will... if yours doesnt, theres something terribly wrong with your ECM and/or O2 sensors.

[JiP]

Well I've had my car long enough that I know how it works in its normal condition, I have a lot of graphs and sensor information for the car bone stock from my datalogger as well as after market gauges to backup the information. I had no change with removing the Cats. I have also helped friends remove CATs off their cars - 2 eclipse's and a civic and we removed the cats off all of them and never threw a ce light. I welded up the neccasry pipes for them, my welding is kinda shotty and we reused gaskets, there are defintly small air leaks in the exhaust piping maybe that contributes to the fact that the ECU thinks the exhuast is cleaner by the time it passes the second o2... I dont know. I dont know if its a fluke, but I have never had a problem and the people from msg board who suggested removing them to me havent had a problem on their dsms either.

If it works for you it works, if it dont, well it dont.

[96TEXASgalant]

I had my CAT removed when I went overseas and never put it back on. I also had straight 2.5" pipe installed and I definately noticed a difference in sound. I noticed I little more torque, but If I may offer my opinion and advice I would tell you not to remove it. If your planning on doing something drastic (ie. Turbo, ect.), do what you have to. But if your just trying to squeeze every little hp out of you car, you should invest your money elsewhere.

[peanotation]

noticed a difference in sound??? people a mile away would wake up when they heard me coming. its hard not to notice something when it slaps you in the face. when i took my cat off, it sounded like a god damn nascar. every car i ever drove by with a car alarm would go off. just idling at a light would make people a block away look in my direction. that shit was so loud, it made the car vibrate like there was no tommorow. i eventually put it back cause music couldn't be heard, and you couldn't talk to people, let alone talk on a cell phone.

[JiP]

Did you have gaskets on or an aftermarket mufler? I got a louder sound from a CAI then I did from removing my CAT. The only car we did that had an anoying sound to it was an eclipse with an aftermarket cherybomb type muffler, the muffler was anoying in the first place...removing the cat made it even worse.