Exhaust Conversion (LX/DX/CX/HX to EX) (96-00 Civic)
 

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My header was really close to touching the tranny mount bracing so i took the lower midpipe off the header and grinded a bit of the brace down a bit so it will clear, that way i dont have to worry about any rattling noises. it might have been ok but i wasnt taking a chance. your header might fit better so this might not pertain to your swap/upgrade.

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Now your header is firmly mounted to the head.... now if you dont care about mother nature of being legal then you COULD simply bolt the header up to your stock DX midpipe BUT YOU WILL HAVE A CEL LIGHT, IT WILL BE ILLEGAL AND WILL NOT PASS SMOG TESTS OR EVEN VISUAL INSPECTION. AND IF YOU DO NOT USE SOME KIND OF O2 ELIMINATOR IT WILL PUT YOUR CAR IN LIMP MODE WHICH WILL KILL YOUR PERFORMANCE AND BE A TOTAL WASTE.... needless to say go the extra mile and be nice to mother earth and keep the car legal!




Now that your going to keep your car legal and emission friendly lets continue....

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Put the new gasket on the rear of the header and bolt the catalytic converter to the header. i did not use the factory spring bolts because I HATE THEM!!!!!! ive always had issues with them so i bolted it solid.

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O YA if your reusing your DX mid pipe be sure to cut it down close to the length of the converter.
OR if your upgrading your cat back exhaust with a EX cat back exhaust then youll be able to simply bolt the converter up and your done with all the hard work!

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I was cheap and modified my DX piping to fit my EX header system... biggest problem NO ONE SELLS THIS FLANGE!!!!!!!! but i was lucky enough that my local muffler shop had some ones old rusted off flange laying around the scrap pile and he just gave it to me. so i wire brushed it on the bench so i could weld to it... ya my welds sucked but i was in a hurry to get done and figured i could always just buy a cat back system later on for the mid pipe since i still want to keep my stock muffler.
anyways i welded a exhaust adapter to the old flange and then sliped it onto the stock piping, gave it afew tach welds with it on the car THEN i got lazy and instead of pulling the whole mid pipe off to weld it solid i just went back to autozone to return the O2 socket set and pick up a few simple clamps. then i just clamped the adaptor to the stock piping..... so far no leaks so no need to remove the whole mid pipe off the car and weld it solid.

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now that your piping is all bolted up your golden! only thing to do now is plug in the O2 extenders and plug them into your O2 sensors.
some simple routing the wires free from moving parts and heat sources.
Also when i installed my extender wires they pluged into the senors with ease BUT when pluging them into the engine harness they where a PITA!!!!!! took alot of force to get them plugged in and i had to use a pair of pliers to get the plugs the rest of the 1/4inch in together. after i got them all plugged in firmly i fired up the motor and so far free from CEL troubles. tho i have not had a chance to drive the car yet. i quite for the night. but if it has not came on yet then im pretty sure it wont come on later.
and no leaks so far.
and i used all new OEM gaskets. new gasket ring on the convter and head/header, and donute gasket on the header/cat.

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AND NOW YOU HAVE A NICE LOOKING, EASY BREATHING EXHAUST...

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FINALLY Be sure to re-torque the bolts at the head and midway flange after you use it once and let it cool down all the way.
END..........

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My header was really close to touching the tranny mount bracing so i took the lower midpipe off the header and grinded a bit of the brace down a bit so it will clear, that way i dont have to worry about any rattling noises. it might have been ok but i wasnt taking a chance. your header might fit better so this might not pertain to your swap/upgrade.

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Now your header is firmly mounted to the head.... now if you dont care about mother nature of being legal then you COULD simply bolt the header up to your stock DX midpipe BUT YOU WILL HAVE A CEL LIGHT, IT WILL BE ILLEGAL AND WILL NOT PASS SMOG TESTS OR EVEN VISUAL INSPECTION. AND IF YOU DO NOT USE SOME KIND OF O2 ELIMINATOR IT WILL PUT YOUR CAR IN LIMP MODE WHICH WILL KILL YOUR PERFORMANCE AND BE A TOTAL WASTE.... needless to say go the extra mile and be nice to mother earth and keep the car legal!




Now that your going to keep your car legal and emission friendly lets continue....

Attachment 22191


Put the new gasket on the rear of the header and bolt the catalytic converter to the header. i did not use the factory spring bolts because I HATE THEM!!!!!! ive always had issues with them so i bolted it solid.

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O YA if your reusing your DX mid pipe be sure to cut it down close to the length of the converter.
OR if your upgrading your cat back exhaust with a EX cat back exhaust then youll be able to simply bolt the converter up and your done with all the hard work!

Attachment 22194



I was cheap and modified my DX piping to fit my EX header system... biggest problem NO ONE SELLS THIS FLANGE!!!!!!!! but i was lucky enough that my local muffler shop had some ones old rusted off flange laying around the scrap pile and he just gave it to me. so i wire brushed it on the bench so i could weld to it... ya my welds sucked but i was in a hurry to get done and figured i could always just buy a cat back system later on for the mid pipe since i still want to keep my stock muffler.
anyways i welded a exhaust adapter to the old flange and then sliped it onto the stock piping, gave it afew tach welds with it on the car THEN i got lazy and instead of pulling the whole mid pipe off to weld it solid i just went back to autozone to return the O2 socket set and pick up a few simple clamps. then i just clamped the adaptor to the stock piping..... so far no leaks so no need to remove the whole mid pipe off the car and weld it solid.

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now that your piping is all bolted up your golden! only thing to do now is plug in the O2 extenders and plug them into your O2 sensors.
some simple routing the wires free from moving parts and heat sources.
Also when i installed my extender wires they pluged into the senors with ease BUT when pluging them into the engine harness they where a PITA!!!!!! took alot of force to get them plugged in and i had to use a pair of pliers to get the plugs the rest of the 1/4inch in together. after i got them all plugged in firmly i fired up the motor and so far free from CEL troubles. tho i have not had a chance to drive the car yet. i quite for the night. but if it has not came on yet then im pretty sure it wont come on later.
and no leaks so far.
and i used all new OEM gaskets. new gasket ring on the convter and head/header, and donute gasket on the header/cat.

Attachment 22199

AND NOW YOU HAVE A NICE LOOKING, EASY BREATHING EXHAUST...

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FINALLY Be sure to re-torque the bolts at the head and midway flange after you use it once and let it cool down all the way.
END..........

this is a great detailed write up
i'm gonna add it to the DIY I made right away

you may want to add to the end of the DIY about re-torquing the bolts at the head and midway flange after you use it once and let it cool down all the way

o ya THANKS. i almost forgot that...

ok... today took it for a drive and still no CEL light so that is great!!!!!! only downfall is i have a pinhole leak somewhere (most likely my mounting flange or weld to the flange or maybe on the clamp... its only a pinhole and only noticable at higher rpms. just a chance i took with modifying the dx midpipe... o well ill fix it!

not sure if its just me or not but it does feel better on the butt dyno ;)

i just have to pull the car back out in the shop and torque everything back down again and remove the midpipe to just weld it all solid.... ill probably do that friday since im off work.

Ok I know I asked about the o2 wire extentions already but... Did you use the extentions for both the o2 sensors or just the one located on the cat? If you did both o2 sensors then why, is there a reason for this? My header has 2 o2 bungs. I was going to plug the back one and use the bung located on the first header tube for the the first 02. If I did this I would only need the longer o2 extention right?

i put them in the proper EX position... the primary in the heades rear and the one on the ex cat. i didnt want to put it in the front since well the sensor mounting in front is ugly anyays. ;)
so i used the long one for the rear cat sensor and the short one for the rear header sensor.

Ok that what I figured you did. I will try extending only the o2 sensor on the cat and see if that works. I am trying to be as cheap as possible with this swap, but I want to do it right the first time. I will post up my swap as well once I get to. It will be a few weeks though as I am saving money to get a cat back made at the same it. Thanks bass once again.

no problem. good luck with the swap. its definatly not hard.. and as long as you use decent parts it should bolt up pretty easily.

Yeah I know I have done a few IHE in my time. I got my header in. I went with the ebay one so we will see. As far as quality it looks good, nice clean welds and good bends. The only thing I have picked out so far with the get what you for header is, it is painted grey not ceramic coated. I left a bad review about that. We will see if it fits ok. I am bidding on a magnaflow cat rigt now :) Could you get some pics of your wire extention and how you routed it? Also what size nuts are needed for the studs on the head? Thanks.

um... not sure on the side of the nuts... i just took one of the header bolts with me since one of them came out anyways... but if you simply pull one nut and take it to your hardware store and match em up ;)

its not to difficult. took me awhile to find the right thread pitch but i found it finally and they actually had enough.... tho i bought to many. but i figured it keep em all since its not that much money.... but they were like 50cents each. but well worth not using the old rusty ugly nuts!!!!!!!

and the wire extenders are not hard to route at all... simply route the wires away from any moving parts or hot parts. i can mine up and over the motor and right under the distributor... and the wires where just long enough to reach the stock wire mounting points on the front of the block.

id take a picture of them BUT with the black wire loom it blends in to well and you cannt really see them ;)
ill get some larger pictures uploaded and post links up for ya...
just give me another min to upload them larger.

http://i40.photobucket.com/albums/e2...exhaust057.jpg

just look for the 2 shiny black wire looms right under the distributor... ;) give them a bit to get dirty and match every other wire loom under the dash.LOL of course i also used some black electrical tape around both ends of the wire extenders just so it looks alot better and blends in like its really suposed to be there! :)

Cool thanks for the pic. I just wanted to see if you ran the wires under engine or over it. I did want to run then under due to the chances of damage. Oh yeah and I found a three bolt flange on ebay so the exhaust shop can make my cat back removable. I just did a search for a 3 bolt flange. Here is the link if anyone wants it http://cgi.ebay.com/ebaymotors/ws/eB...3A11&viewitem=

jw if you can use the flange from the upper header to the lower header turn pipe from the stock y7 one or if that flang would fit onto an EX stock cat converter? ..

cuz im doing the same setup with an EX header to cat. converter but i got a ctr mid pipe .. the flange on the ctr pip is too big for the stock EX cat converter .. so im jw if i can reuse that flange on the y7 on to the ctr midpipe since flange are hard to come by ..

hum. you know i never checked the flange on the dx turn header pipe. i never even thought about it. im not positive if its the same size or not but it looks like it might work.

ill have to try that when i remove my midpipe to weld it solid. but it looks like it should work.
i just havent had the desire to work on the civic lately.... my trucks taken priority with my moding funds lately.... i just bought some bullet mufflers for it today. gotta make this truck rumble.

lol .. well let us know how it goes when you DO do it .. cuz if it does fit .. i jus might weld that flange onto the ctr mid pipe save me trouble of chopping up that ctr mid pipe

or better yet ill jus try it myself when i do take off that y7 exhaust header/cat .. and ill let yall know

you got a picture of this CTR mid pipe? im curious to know what ya mean...

well i say it just looks like any regular mid pipe .. the piping is a little larger/bigger .. so the flange on it is bigger than the stock ones on the y7/y8 so it wouldnt just bolt onto the ex cat. converter .. thats why i was wondering if the flange on that y7 would fit the ex cat. converter .. 3 bolt flanges and all .. cuz if it does then i can jus weld that flange onto the pipe i have ... but ill take pix of it tomomrrow or so .. its dark here already ..

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here's a pic of the mid pipe next to the ex cat. converter .. it looks like it would fit but the flange is a little wider on the pipe so it wouldnt fit ..

well hard to tell exactly how much its off BUT if the bolt holes are just slightly wider simply drill/grind the holes a bit larger. doesnt look like its off to much.... if in doubt of sealing use a high temp flat gasket also between the 2 flanges.

yea its not that off but yea i could try that .. i just picked up an after market header and bolt it onto my DX piping w/out the cat .. ran fine and all wit the CEL ofcourse .. jus wanted to do some test runs .. but ill be puttin the cat. converter on soon .. but ty for your inputs

well got mostly everything in . turns out the mid pipe is a little longer so ill be taking it to the muffler shop to have it shorten by a little and i picked up an gsr muffler too but gonna have to cut and weld that too so we'll see how it goes ..

but then i see what you mean bout them spring bolts .. kinda annoying as it doesnt completely seal my cat to the piping .. ill have to go find some nuts and bolts too ..

btw what shift linkage are you running? .. im using stock DX but then it keeps hittin the cat. converter .. i cant really go into 5th or reverse .. only by forcing a little can i get into those gears .. jw if your having that problem too

what kind of shifter do you have?

im using the stock dx linkage... i do have a ebay short shifter and it does feel like it hits something when its in gear but it only feels like it knocks it at certain rpms.

its nothing hard tho just a soft knock..... and it doesn't hit anything when i shift gears at all so its not that big of a deal for me. i was going to jack the car up and see whats actually hitting. but im waiting for a warmer temp outside.

My ebay shifter hits my stock HX piping a little. I can hear it rattling when in reverse. I would try removing the heat sheild or denting it to make some clearance. The EX LX HX and DX all use the same shifter linkage. How is your civic running with the headers and cat??

well so far running completely normal. exactly as planned ;)
but i havent driven it much lately.

i have a short shifter also .. and i checked it and its actually hittin the o2 sensor on the cat .. its just harder to get into 5th and reverse .. heat shield already taken off

ill try to get a pic of it later

what kind of short shifter?
you're either gonna have to get an exhaust shop to rotate the cat, or you're gonna need a better shifter.

you could always try to bend the exhaust alittle to..

all depends how the linkage is hitting. you cannt bend it very much so all depends how much its hitting...

or another thing to try is if its just hitting the sensor..... simply either get some smaller HARDENED bolts and washers to replace the header to cat flange.... and on the cat to midpipe use a drill or small ball grinder to open up the bolt holes in the midpipe.... then you can simply turn the cat alittle and hopefully the sensor will clear the linkages...



well actualy ya know what..... i just got thinking... i wonder if maybe i put my cat on upside down.... im not sure... if the cat was simply upside down.... maybe i screwed up. NEED TO FIND SOMEONE WITH A EX 5SPEED to look at there stock cat on the car.... i just thought the sensor would be on the top to keep it from posibly hiting road debri..

i think it was a buddy club short shifter .. had it for a while so not sure .. but i went to the exhaust shop to have it weld on and all so they bolt everything back up for me but i guess i can try to rotate it a little ..

but yea i had the sensor sitting up also .. since i think thats how everything else matched up .. but not sure .. my friend got an 5 speed ex .. ill have to ask him to check his for me ..

ya hit your friend up and see what it looks like stock.

I think you put yours on right bass. If im right the o2 on the ex cat should be at about 2-3 o-clock if viewing from the rear of the car.

this might be a funny reply, but i'm having a hard time finding some nuts. i went to home depot, and 3 other hardware stores. does anyone know a store that i could buy these from? i'd like to replace my worn ugly nuts. (haha i know i know)

well i bought mine from a local hardware store kinda farm store... try something like that or sullivan or how ever its spelled.... if they have them they will be in the little boxes drawers.

ok i'll try the local tractor supply, i totally forgot about that place. thanks dude. by the way, nice write up! funny thing, this is my first civic and i thought up the same thing because i don't want to pay for a stock manifold/cat for my LX. cost is 100 bucks less to just put a cheap header on with a generic cat. :)

i put my o2 sensor up on the top of the header and one in the cat...was fine for a few weeks now i'm getting a "bad cat" code...i'm going to move the sensor down to where you orig put yours down at the rear of the header, which hopefully will make a difference.
time will tell and i'll let ya know. nice write up by the way

Stop for a second and think about that...
if you're getting a code for a bad cat, how is putting the second O2 sensor in header, which is before the cat, going to get rid of the code? It's going to be reading a/f ratio levels before the cat so it's not going to be able to detect the cat and will still think the cat is bad.

what did you use to extend your wires?

i bought the extenders that he suggested in his first post to extend the o2 sensor wires. i'll re-check them to make sure one of the pins didn't push back some how after a few weeks.

well my harnesses where very tight connections that i had to use some pliers to get them fully snapped in. if you didnt fully snap the 2 ends together then it could have come apart alittle bit to not make connection.