2000 civic dx header install

[dopey32570]

Hey All,

Was looking at upgrading my 2000 civic dx with some performance 4 2 1 headers and just had a couple of questions. I know that on the dx the catalytic converter is attached to the stock header. If I just remove the catalytic converter altogether what would be the harm if any besides the legal aspect of it which I'm not really worried about because there are no smog restrictions where I live. Just curious if it would mess with the computer or be super loud or something like that. Also is it possible to go straight from the headers to an aftermarket cat-back exhaust or do I need like a test pipe or something in between? Any help anyone could provide would be greatly appreciated. Thanx!

[B16EJ1]

Yes you could remove the cat but since the 00 Civic is OBD II there is a problem since there is no Cat for the second o2 sensor. The CEL will be on unless you find an o2 sensoer simulator. A test pipe will still not work cause the sensor in the cat is supposed to read the converted exhasut gasses which the pipe does not do.

[SilverY2KCivic]

CEL means you'll be doing WORSE performance wise than you should be by adding the header, since a CEL throws the ECU to run the motor in "limp home" mode which seriously hurts performance and fuel economy.

[97civichx]

I would say to buy an aftermarket high flow cat converter because then the sensor would read right and they dont have as much restriction as the stock ones do

[dopey32570]

ok..was looking at the header some more and called the guy just to make sure I had all info. The header has 2 o2 sensors...(one on the bottom of the header itself and another on the bottom of the downpipe) so looks like the o2 sensor problem would be all set. My next question would be would this downpipe then connect straight to the catback exhaust or do I need another piece of piping to connect it all together? Thanx for the replies!!

[B16EJ1]

It will connect to the exhaust but even though the header has 2 o2 sensor holes the code will still be thrown and the CEL will still go on because like I said before, the 2nd o2 sensor reads coverted gasses. We installed a test pipe on my friends 00 Si and the CEL code came on for that reason. Took that shit straight back to the shop. Get a high flow cat or if you think I'm FOS try it anyway.

[dopey32570]

ahh didn't think about that..thanx for the warning...thats why i'm posting...tryin to get all the info so i don't get burned after i buy everything...thanx again!! Also one more thing and i might be retarded for asking but oh well....if i do end up getting the high flow cat which i probably will...where does it end up going if the headers connect straight to the catback??

[B16EJ1]

You'd have to get an exhaust shop to cut a section of the exhaust out for your cat. It doesn't cost much.

[dopey32570]

Does anyone know where I can get an O2 sensor simulator and about how much they cost?...also would 2.50" exhaust piping be too big for my ride? I only have an apex intake and then would be adding the headers and exhaust..thanx

[B16EJ1]

o2 sensor simulator? I have no idea. I've heard a couple people on here say they had one. IMO 2.5 in is too big, especially for the minimal flow of the D16Y7. I'd go 2.25.

[hondaconcepts]

Well I just want to thank you all.. your conversation reassured a lot of questions i thought i had the answers to. I too am going to run a header on a D series engine. The plan is to like you said... run a B series header with a High flow CAT. Answer me this though.. on an EX where is the #1 bung for the O2 sensor? end of the header section or front of the CAT. section? I am seeing a lot of headers out there.. even ones advertised for B series engines that have 2 bungs #1 in, top of the header #2 bottom of the header. I am assumeing this is a JDM header. If thats the case one will need to be plugged to move the #2 O2 to the rear of the CAT. Any help is greatly appreciated. Thanks