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Right now I have a cat back exhaust, now thursday i'm gonna buy me headers, so i was thinking of getting a pipe to replace the catalyc converter, but this guy was telling me that if i remove the cat. there will be no back preassure and eventually would cause long term damage to the engine, is this true or would the engine be fine if i remove the cat?

 
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Not True.

If you remove stock Cat.
Illegal.
You won't pass emission.
Also Check engine light will be on.

I have Race header and car smells.

 
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I'll just put the old cat back on when the emmisions test comes, i dont think the check engine light will be on because there is a plug for the oxygen censor, how bad does your car smell?

 
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yeah and you will prolly get pulled over...dont do it...itll be REALLY louder

 
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the car smell = exhaust fumes. running the car with no cat = hi flowing... thus creating more pollution while giving the car "better performance". thats why it smells, but its not that bad of a smell.

check engine light/malfunction indicator lamp WILL be on if you run a straight pipe and catless. i bought the megan hi flow cat test pipe which is the downpipe after the header and replaces the cat. i plugged in my o2 sensor into that, malfunction lamp still on. only way to get rid of that indicator lamp is by o2 simulator.

ask that guy "how would it effect the engine in long terms?"

 
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im pretty sure youll lose torque if you remove the cat.. so i wouldnt do it. it wouldnt cause any harm to the engine though

 
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i was wondering.... if the o2 simulator is in thhere which turns off the CEL... then does that mean it would be able to pass emission check... cause all they do is plug into the ODB2 connector which reads the 02 sensor... but if u have the simulator then it should be fine.. wouldnt it??

 
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my homie removed his cat out of his civic and when he drives its loud as hell and it spews out black smoke...u'll get caught easy...he got caught on the 2nd day without it on cuz cops saw taht and gave him a fixer

 
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i have been driving without a cat for 2 years now and no black smoke and not as loud as hell....

 
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does this even make that big of a difference to be risking tickets and **** as well as polluting the **** out of the air?

 
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well... for me i still got the resonator in there so it still sound like a really soft aftermarket exhaust.. not loud at all.. no mod thats costs $100 or more that only gives u 1 or 2hp is worth it... u would be spending a sheit load of cash just to gain 10hp even at that... but to me that just means that much more closer to a higher hp... but i got my cat removed for free... even if it only does give 1/2hp or 1 hp it still wasnt anything outta pocket for me.. IMO

 
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no way 10hp no ****in way

 
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will u lose torque if u remove the cat?? even if u have the same stock piping??

 
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ahem... i didnt say 10hp from removing cat if thats what ur refering too

 
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i dont see how giving your exhaust better flow will decrease torque/horsepower works =\ and im pretty sure backpressue doesnt play that much of an important role either..

i have the megan hi flow test pipe which replaces the cat converter along with a downpipe. its 2.5" thick i believe and serves a purpose: hi flow, better performance giving quicker throttle response, cant really claim hp or torque gains, but im assuming 1hp+.

as for pollution, sounds... im running mine with oem exhaust so its still quiet and does not spew out any black smoke at all. matter of fact, no smoke is visable during the daytime unless i just started up my car to warm it up, after few minutes, no sign of smoke. BUT you can smell the exhaust fumes. by having my stock exhaust on, im pretty sure it would fool the cop if he were to smell any fumes.

 
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I'd say do not remove it. You will never pass emissions test. The sniffer will pluck you out with ease. If you still want better flowing exhaust and to remain legal, I'd recommend going Random Technology. They utilize all of the factory O2 sensors to prevent CELs. They can be used with any SHORTY header that would mount up to the stock downpipe. It is a direct fit and works well~

http://www.dezod.com/pd_random.cfm

 
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hey dezod.. by putting a o2 sim on the sesor to get rid of the CEL... would the ecu also think that the gases being put out from the cat are correct... considering that emissions connects to the obd2 connector that reads the sensors u would think it would work.. i know they dont stick the reader thing in the exhaust like my truck.. so wat u think????

 
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ive got apexi gt spec catback, hp racing header, and megan hiflow cat and its louder than freaken hell

 
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we have a cat??????? lol

 
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quick question,

right now I have a DC Header, OBX Hi-flow cat, and DC Sport TCS. with this on I wont pass emission right??? so if I replace it with random or stock cat, I will pass emission??? let me know

 
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if u have a cat on i always thought u would pass emissions... i dont have a cat so i definitely wont pass

 
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I've considered it now and my conclusion is that it simply isn't worth the hassle of switching it when testing and than getting caught once in a while with it for minimal performance...The engine is 1.7 4 cyl, and if you remove the cat you can't squeeze out that much diff. in HP or torque anyhow.

 
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This is a good question. Glad someone is asking it. The answer depends upon where the SIM is placed. Prior to the cat or after the cat (since our car has 2). The emissions on the vehicle would probably be way off if in either spot. The Sim always makes the mixture be STOICH from my understanding. Let it be known, first off that I am not an expert in 02 sims, I do not use them, nor condone them, nor even like them. It just sends a phony signal to the ECU that emissions are A-OK. Even if it is super Rich or Lean. The probabilty for havoc is there, I just do not see the benfit outweighing the consequences.

As an experiment, I relocated one of the O2 sensors (the one normally below the header) to RIGHT BEFORE THE CAT on the new downpipe. The car threw CELS (delayed sensor reading from bank 1 sensor 1 & too rich bank 1 sensor 1). The sensor had a hard time reading and re-calibarting the mixture so my EGT's and A/F's were all over the board and real spuratic. The car would run UBER rich and suck *** for performance. I put it as close as I can get it to where it is nornally and BAM.....Everything stablizied. Think this was just from relocating. Imagine what eliminating would do?


GOD DAMN OBD2................I WANT OBD1 or OBD0 back!

 
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okay.. but i know the first sensor thats nearest to the head checks the a/f mixture.. but from my understanding the second o2 sensor reads the effectiveness of the cat.. which is where the sim would be put because its throwing the CEL.. correct me if im wrong.. i also did an experiment where i tried running the second o2 off the pipe and also removing it entirely..it doesnt affect my performance but it sure does throw a light??.. any thought or tests u could run

 
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Correct, the second one determines the effectivness of the catalyzation process. So you tried using it with the test pipe and it still threw a light because the test pipe doesn't catalyize the mixture. Just acts as a resonator. Try a Random Tech Hi-Flow cat. They work well. I am running it on my 2.5" downpipe. We welded in 2 O2 bungs for the sensors.

 
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Good questions.
about time someone responsed to this guy

 
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You guys are a bunch of idiots!!! If you take your cat off you are going to lose your bottom end power!! We are talking about a 1.7l 4 cyl. here!! They need back pressure!!! And to top it all off, removing the cat isnt going to give you any horsepower at all!!! You will lose HP!!! If you want to drive a fast car, then your first step is to sell your all show no go Honda!!!!!

 
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why does everyone diss the civic when u guys drive one and bought one ur self... if ur gonna do that then why did u buy it **end rant** as for the removing cat and back pressure and stuff.... yea u loose alot of bottom end but gain high end.... basically makes daily driving suck but better for racing situations

 
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i dont really think its dissing our cars, its just being realistic. our cars are economy cars that arent meant to go fast. theyre meant to get from point a to point b, and get good mpg. thats it.

 
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i know our cars are economy cars.. but hey.. we got people out there that want to up the ante a little and yet get turned down... i mean.. if someone wants to do womething to there car and it only adds 2hp....let them do it.. but lets say they do 5 things to the car that yields 2 hp a piece.. the that ups the ante at least 10 hp... this is just an example so i dont wanna be flamed for it... but i just gotta say lighten up a little... isnt that we are all here for.,.. to help each other out and not shut everyone down