Cat removal

I remember seeing a post a little while ago about removing the cat and just putting it back on when you get your emissions tested. I like this idea and now that its warm out I'd like to do it. I'm not sure how this works though. People who did it said they used a straight pipe, can someone explain this? Do I have to buy something specific to do this? Also is this gonna screw with my O2 sensor and flash the check engine light? Can someone just clarify this procedure so I know what to do? Thanks in advance.

depending on what car you have. you can bolt on a test pipe very easily. some test pipes have 1-2 inserts for your o2 sensor. if you have a header that doesn't have the o2 sensor insert on it. then you'll have to buy an extension and connect it to the test pipe. but most headers have it.

SIRII, i dont know what info you are reading but you gotta stop with all this.

on your del sol there is one O2 sensor before the cat on your exhuast manifold, if you remove your cat and put a test pipe in, basically a straight piece of piping, your car will be louder for one, and prolly start to have an odor from it. but make sure you put the cat back on before you get inspected, or else you will fail.

why do you think i said most headers have the o2 sensor on it.

OK, so how can I get one of these test pipes? Also what kind of gains can I expect? And is there anything bad that could happen?

just go to an exhaust place and ask for a piece of piping with a flange welded to it so it can be attached. the other way to do it is to just take out the cat from its housing.

the bad things that could happen are a cop finds out you dont have a cat and tickets you, which can be a sizeable $200 ticket. you could forget to put it back in and fail emissions as well as get a ticket. it will be louder, as well as smell differently because the toxic gasses arent being converted to something else. you will also be polluting a lot more, but you dont seem to mind that.

the gains will not be that spectacular, about the same as a header. if it were me i would just skip this mod and either invest in a hi-flow cat or focus on making the motor stronger in other areas.

and SIRII, i have to agree with crxlvr, you seem to have somethings backwards in what you are reading.

Originally posted by b16a3sol
and SIRII, i have to agree with crxlvr, you seem to have somethings backwards in what you are reading.

how do you figure?

first off sir, every header or manifold has an O2 sensor, so wow for you if you knew that.

id suggest just getting a high flow cat, such as the catco model, i have it and i noticed a gain with it, plus i cant be ticketed and it doesnt smell since there is no cat there.

Not every header has an o2 sensor bung. But yeah I suggest using a high flow cat instead.

they are supposed to tho, just cuz a company is worthless doesnt mean they shouldnt be there.

i've never got ticketed for having the test pipe

goto www.racingpipes.com they have different test pipes for different cars.

There's some nut here in Az with a black 88-91 hatch with a swap and i think he's either running strait header or a b-pipe, and that SOB is loud. At the illegals, i was standing right next to the car when he spanked this Firebird Trans Am. My hearing was messed up for 3-5 days.

www.testpipe.com also has a large selection of test pipes, they even got ones with a place to put your O2 sensor

Originally posted by SiRII
There's some nut here in Az with a black 88-91 hatch with a swap and i think he's either running strait header or a b-pipe, and that SOB is loud. At the illegals, i was standing right next to the car when he spanked this Firebird Trans Am. My hearing was messed up for 3-5 days.

where at in AZ? if you are talking about in tucson, the last time i was there it sucked ass. there were barely any good cars and hazardous seemed to be trying to take control of it. maybe you were lucky enough to see the supra owned by ryan woon with the biggest turbo he could fit into that engine bay hooked up. last i heard he ended up breaking 1000hp on his stock bottom end for around 1000mi before it blew up.

as for the straight pipe on that hatch, its not worth going deaf for an extra horsepower, especially when you are doing something illegal. dumping straight into the atmosphere will most likely rob power than give it, considering most engines like to utilize scavenging to get rid of excess exhaust still stuck in the cylinder.

is the Bomz racing high flow cat actually a high flow cat? or is it a pipe?

Don't go no cat unless your car is race only. I'd recommend a high flow cat but that's about it, if the car is a daily driven car. I remember reading about how the combs in the cat prevent back flow of "bad" exhaust gases from entering the engine shortening the life and possibly damaging the car. The O2 sensor, ECU, and the cat work together to make sure this problem doesn't happen (when a problem does arrive the O2 light kicks on and says maint. req.). the reason bad gases could get into your engine if you remove the cat is because the cat has chemicals in it to change the exhaust gases into less harmfal gases. So if you don't have a cat, you don't have any protection from harmful gases getting back into your engine. What would Ronald Reagan say about clean air acts if he heard you know...lol

But what about removing the cat on a turbo civic? Will you see more gains on a turbo car? It can't be as loud as a N/A civic. My Si was pretty loud with an Apexi N1 cat back, but after a turbo install, its not much louder than a stock exhaust. Plus I'm from Alabama (please, go easy on the redneck jokes) we don't even do emmision tests:bigthumb: . Plus, every other whitetrash Ferrari and 4x4 around here is running without the cats. So cops never really look at your exhaust. Would it be to my be to my benifit to go with a race pipe? One more thing. Does your check engine light come on or not if you have the second O2 sensor mounted back in the race pipe?

Oh! I didn't know about the Turbo...Sorry man! If you have a turbo I'd remove the cat, you'll free up some restricted horsepower. Because of the turbo forcing induction you don't have to worry about what I said before in my last reply. My friend did it to his 'Lude and got a pretty signif. power increase(if I had to take a guess i'd say 5-15 hp with removed cat on forced induction cars). Don't worry I won't diss Alabama, the highways have 75 mph speed limits, that's 20 mph faster than damn PA. It's only 55-65 where I live.

As for the second O2 sensor...I have no clue.

I think the original question was for a N/A car. I just sorta butted in, sorry. Thanks for going easy on Bama.

so any opinions on that Bomz high flow? ive never really heard of them.