Celica Forums General Discussion Exterior taking off the catalytic converter

if i take off my cat.. and run a test pipe and straight pipe my exhaust.. will i loose or gain HP? i kno i will lose back pressure so my bottom end will suck but will my ECU throw a CEL and mess up my whole overall performance?

Dunno about performance gains or losses, but I doubt your car will pass emissions, so if you have to get that done, do it and then take it off.

And it's illegal... To much kaka will spread out from your exhaust pipe.

yeah i know that but how about the CEL and will it perform like poop because of the CEL? i was going to get a pipe made from my header-back.

i Heard that you will gain some Hp if you take it off...But it's just what i heard...

Yeah, and I think it weighs a few too, so it might be good for a weight reduction.

it won't pass emisions..thats the whole reason for having it on there.

you will gain...this is a big reason many japanese cars have to be "de-tuned" to come into america. emissions tests hinder performance.

ok.. i know its illegal and it wont pass emission but i dont have to smog it anytime soon.. and im going to have it flanged so i can put it on whenever i want.. but the QUESTION that i have is.. will it throw the CEL and will it mess up my performance?

as long as you're o2 sensor stays in tact you should be fine.

i don't know if you cel will come on...but it shouldnt mess up your performance. should help it, actually.

no it wont but if you keep the cel on, and you get another engine problem, you'll never know because the light will already be on. You'll have to get your codes read.

I passed emissions with my kazuma exhaust on...

they didn't even hook up my car to a machine, just stuck something into the ODBII port and let me go on my way.

I haven't done this but - Your cel should come on - the second O2 sensor is there just to see if the cat is working. You would see a performance gain only IF the ecu doesn't try to tune the engine to run cleaner (probably leaner) because it has no cat!
edit - there was a post on here or ecelica on how to trick the ecu into thinking there is a cat when there isn't - if you can do that I think you would definatly see a gain!

I removed mine and the CEL came on but there havent been any noticable changes since it lit up. the increase is nice, I would rec. doing it.

highly unlikely

I agree. Shouldn't hurt your car at all. I wouldn't do it because I couldn't stand to see that cel on all the time. And I forget who said this before but yeah, if the cel light is already on and another problem arises, you wouldn't know about it. I say do it at your own risk.

wont the crap comin outta the exhaust turn ur bumper all black and nasty?

well.. i was planning on putting my stock exhaust but with a long tip a little that would stick out further than stock.. because when i had my N1 exhasut on, the tip came out further so it wont burn the bumper. I jsut want to try to get the most out of my stock muffler.

that should work, then. just hope the cel doesnt come on

the Check engine light will come on if you remove your cat off.

y dont you just buy a racing cat?

the cel "IS" going to come on!the best thing to do is dont replace the fat pipe that go didrectly on the header(the one with the divider)start your custom pipe after this pipe(you can both flange the stock cat and your test pipe so you can switch back later for emisions) and put back the two o2 sensors.you can do a search and find out about the device that mimics a perfect o2 sensor for obd2 systems. or check splitsecond.com.about the gains,awsome!all rpm band but esp above 6k,(upwards of 15 hp with a straight through canister at the back)loud though! you ever bolt your stock muffler off?its louder than that but heavy loud and if your bends are good with one long length of pipe with no welds it should be free of most of that ringing sound.
ps: since you would be having the exhaust down it will be a good idea to wrap your exhaust with 2"x1/8th thick exhaust wrap.helps with scavenging and reduce the the sound of pipe vibrations.takes some pics and let us know what your butt dyno feels(if you cant get it dynoed)

I guess "tune the engine to run cleaner" was the wrong way to put it but I thought the ecu would go into "limp home" mode if it didn't see any difference in O2 one and O2 two. I don't remember where I read that and I haven't actually done it, so you just might prove me wrong. In fact me and a lot of other people would be happy if you did! Post your results if you do it!

it shouldnt make your car "limp home". as as already noted earlier by someone else...your ecu will turn out, and this is ordinarily fine but you won't know if there is another problem should one arise.

Yepp...The gain shoud be 5-10 hp. But please, leave it on. There is allready enoug pollution.