Andyjo Posted June 8, 2006 Share Posted June 8, 2006 So, i'm getting a WRX exhaust for my OBS... which has a set of 2" borla headers coming from the block.. my question is if i want to go from 2" to 2.25", can i just made an adapter flange? I drew it up in solidworks... would this really mess w/ the flow? or would it work? Bending a pipe shouldn't be that hard If i just have a chamfer on the hole... to the correct size.. that would work, right? Link to comment Share on other sites More sharing options...
Subarutex Posted June 8, 2006 Share Posted June 8, 2006 Do it. IT won't be a problem at all. I had 2.5" welded directly to my stock EA82 header. No flange or nothing, and it was just crudely crunched down around the smaller header pipe and welded. Noticable power gains (mid to high rpm ranges) and a killer burly sound. Link to comment Share on other sites More sharing options...
Andyjo Posted June 8, 2006 Author Share Posted June 8, 2006 sounds good! Now i just need to get some 1/2" plate (left all my scrap at school ) and have the CNC Plasma Cutter guy have a go at it I'm not sure if they can do the angle like that... but i could just have the prototype guys try it out Link to comment Share on other sites More sharing options...
BoostedBalls Posted June 8, 2006 Share Posted June 8, 2006 what part is 2" and what part is 2.25"? If you are going from an exhaust port to a larger pipe, you don't need anything fancy. The step will actually help air flow in some cases. Going from a larger port to a smaller header pipe- yeah, you will need a gentle step of some sort. I would just drill out the center with a 2" holesaw and then chamfer one side with a carbide bit. That's what I do and it works. Link to comment Share on other sites More sharing options...
88HatchMonster Posted June 8, 2006 Share Posted June 8, 2006 Am I reading something wrong? 2" to 2 1/4" muffler pipe? Why can't you just use a two dollar step-down piece from the auto parts store? Link to comment Share on other sites More sharing options...
Andyjo Posted June 9, 2006 Author Share Posted June 9, 2006 They make step down pieces?... wierd I'm going from a 2" header, to a 2.25" rest of the exhaust (cats etc..) and... i can do it for free at work, whereas it would cost $$ to buy a step down i have to make an adapter from the ej22 header to the downpipe intake of the wrx exhaust. Link to comment Share on other sites More sharing options...
88HatchMonster Posted June 9, 2006 Share Posted June 9, 2006 The difference between 2" and 2 1/4" is so minimal that I could see even overlapping the pipes slightly and simply welding all the way around. Or you could snip 6-8 quarter inch deep notches in either pipe and either flare it out or scrunch it down over the other pipe. It need not be an exact science, especially if you have a mig welder handy. Doesn't mean you have to butcher it, but I don't think you need to be cutting parts on a CNC machine... Just K.I.S.S. on this one. You're gonna have the most trouble snaking the two pipes together where they will meet and not interfere with anything else under the car. There's nothing you can really engineer to solve that problem you just gotta go in and start cutting bending and welding. And yeah, they have every kind of step down/step up hardware you can imagine. They also have prebent pieces for cheap too. Usually when I'm building an exhaust I pull out all their angles and lay it out on the floor in the store, and then buy some extra pieces that I think I might need as well. Then I just return what I don't use. Get a bunch of clamps and hangers too. I weld everything up, but use clamps to clamp on the rubber hangers. *Edit: OK I guess I see the reason for the adapter flange, so you can bolt to the headers instead of welding the whole thing together... I would take the flange that's bolted up to the header right now and just saw it off from the rest of the pipe and grind it flat, then just weld 2 1/4" to that, and there's your adapter. Link to comment Share on other sites More sharing options...
seanski06 Posted June 11, 2006 Share Posted June 11, 2006 what are you going to do about your cats and o2 sensors? are there no problems with mixing it up...or are you going to do something to make the sensor's think they are working also....those step down pipes at a napa are a good alternative...although when i tried using them it wasnt quite long enough for my need....i had a local shop make a custom pipe/sleeve so i could connect my cats to my resonator pipe after i cut off both flanges due to rust..throw some clamps on it and works like a charm...no leaks, flow problems? haha i wouldnt be confident enough to tell ya it works good.... for one i hardly race my car at high rpm's and i only did it to gain my low end torque back from when the flanges seperated..i could only make it up hills in 3rd when my cats and resonator seperated like an inch apart..i never thought that a break like that would make a huge difference g/l with the exhaust and give me details when your finished http://community.webshots.com/photo/548832254/2187839410053449880XtVJYO incase the above picture doesnt work Link to comment Share on other sites More sharing options...
Andyjo Posted June 12, 2006 Author Share Posted June 12, 2006 I'm going form a set of Borla single port EJ22 headers, to a 03' WRX exhaust.. so it still has a cat, and o2 sensors... at least 1 sensor... not sure how many... i guess i'll find out on friday! Here's the exhaust Looks like 1 Cat, and 1 sensor... where as my OBS has 2 cats, and 2 sensors.. i guess i'll have to figure out something.... any ideas anyone? Link to comment Share on other sites More sharing options...
seanski06 Posted June 13, 2006 Share Posted June 13, 2006 I'm going form a set of Borla single port EJ22 headers, to a 03' WRX exhaust.. so it still has a cat, and o2 sensors... at least 1 sensor... not sure how many... i guess i'll find out on friday! Here's the exhaust Looks like 1 Cat, and 1 sensor... where as my OBS has 2 cats, and 2 sensors.. i guess i'll have to figure out something.... any ideas anyone? i think theres ways to ground out the wires or something ..so that the sensor thinks its working....i know my one buddy did it to his ram when he decided to install smokestacks out the back of the bed ha Link to comment Share on other sites More sharing options...
Beegeer Posted June 13, 2006 Share Posted June 13, 2006 2.2ohm resistor, heard this can work. i think theres ways to ground out the wires or something ..so that the sensor thinks its working....i know my one buddy did it to his ram when he decided to install smokestacks out the back of the bed ha Link to comment Share on other sites More sharing options...
mikeshoup Posted June 13, 2006 Share Posted June 13, 2006 It looks like the O2 sensor bung is after the cat. You'd want to have an O2 sensor before the cat. That would be the one to tell the car if its running rich/lean. The second O2 sensor goes after the cat, and is so the computer can compare the two readings and determine if your cat is in working order. If you get one O2 sensor before the cat, hook it up to the computer, and ground out the second O2 sensor. Computer will think your cat is in 100% working order. Probably the reason you only have the one O2 sensor from the WRX exhaust, is I think the primary O2 sensor is on the uppipe (or maybe downpipe) of the WRX. Link to comment Share on other sites More sharing options...
Andyjo Posted June 13, 2006 Author Share Posted June 13, 2006 It looks like the O2 sensor bung is after the cat. You'd want to have an O2 sensor before the cat. That would be the one to tell the car if its running rich/lean. The second O2 sensor goes after the cat, and is so the computer can compare the two readings and determine if your cat is in working order. If you get one O2 sensor before the cat, hook it up to the computer, and ground out the second O2 sensor. Computer will think your cat is in 100% working order. Probably the reason you only have the one O2 sensor from the WRX exhaust, is I think the primary O2 sensor is on the uppipe (or maybe downpipe) of the WRX. Could i just ground out the one? soo.. take the existing sensor i have, put it in that hole (as to plug the hole), and ground it out? and just ground out the 2nd one as well ? And by grounding out.. you mean taking the leadin wire of the sensor, and just slap it to ground? so there's no resistance? seems like stuff would short out... or did i read that completely wrong? only problem i have is that i don't feel like poping a new hole in front of the cat & threading it... or whatever i'd have to do to get a sensor there... Link to comment Share on other sites More sharing options...
mikeshoup Posted June 14, 2006 Share Posted June 14, 2006 Could i just ground out the one?soo.. take the existing sensor i have, put it in that hole (as to plug the hole), and ground it out? and just ground out the 2nd one as well ? And by grounding out.. you mean taking the leadin wire of the sensor, and just slap it to ground? so there's no resistance? seems like stuff would short out... or did i read that completely wrong? only problem i have is that i don't feel like poping a new hole in front of the cat & threading it... or whatever i'd have to do to get a sensor there... Scratch that, I don't know enough about what to tell you. Regardless, you need to get a bung for the O2 sensor put in BEFORE the cats. If your car was equipped originally with one O2 sensor, then just plug the second hole. If you car was equipped originally with two O2 sensors, then just plug 'em both in. What I was saying is if that O2 sensor bung is indeed before the cat, then you'd need to find a way to trick the computer into thinking that the second O2 sensor was plugged in, when it isn't. Thus, no reason to put in a second one. Again, this is only if the exhaust you're getting has the O2 sensor before the cat. Link to comment Share on other sites More sharing options...
Andyjo Posted June 14, 2006 Author Share Posted June 14, 2006 an exhaust shop can just slap one of those in, right? i'd like to stay away from shops like that.. but i dunno if i have the knowhow to get one of those in Link to comment Share on other sites More sharing options...
Andyjo Posted June 15, 2006 Author Share Posted June 15, 2006 Just got it, and checked, it looks like it'll just bolt up to the back end of my front cat! meaning no fabbin' up a new tube w/ sensors & stuff woohoo!! Link to comment Share on other sites More sharing options...
seanski06 Posted June 16, 2006 Share Posted June 16, 2006 ???...so now wait u have both o2 sensors plugged in...however there plugged into a wrx cat not instead of the impreza one....and it still works fine no cel? for some stupid reason i always thought that if its not the matching cats as the factory specific ones then it wouldnt work haha be really it is just a filter also let me know if u lost any low end torque going up hills from the bigger exhaust Link to comment Share on other sites More sharing options...
Andyjo Posted June 16, 2006 Author Share Posted June 16, 2006 Well.. i'll let you know how it works tomorrow.. it's on.. a few small leaks in the front end (i didn't feel like sealing it properly... ) SOOO... the WRX exhaust is about... 3" shorter than the OBS exhaust, causing a little trouble with the hangers... the rear end hangs almost perfectly when it's not hooked into the EJ22 pipes, but you've got to bring the wrx pipes forward to hook them to the 2"ers, and that's what messes with the hangers etc... as for going from 2" -> 2.25" , all i did was drill some new holes in the wrx cat flange there, and bolt it straight to the back end of my front cat. and yes, i threw my 2nd o2 sensor into the wrx cat. It seems to run fine (backing it out of the garage...) it's pretty loud, but i'm going to blame the leaks in the flange connections for that... other than that, it's wicked bassy, almost sounds like a wrx or something Link to comment Share on other sites More sharing options...
seanski06 Posted June 17, 2006 Share Posted June 17, 2006 let me know after a week or so...how u like it....it may become droning in like 3rd gear....or u'll feel like an A- Hole when going through town... and let me know about ur low end torque thanks -sean also i made my skid plate i'll have to get ya some pictures...i think we were discussing this earlier Link to comment Share on other sites More sharing options...
Andyjo Posted June 18, 2006 Author Share Posted June 18, 2006 Alright... well.. after fighting w/ the system for a whole night.. the other day, i got ahold of a friends welder. SO, to make it fit properly, i took out the middle cat section, and chopped off the flange (w/ a little bit of pipe still on it), cleaned that pipe section up, bolted that part to the back end of the front cat, then i went in & bolted in the mid-cat section to the swivle/moving joint thing. THen i used our floor jack to bring that pipe up to the proper height (as to be alligned w/ the flange pipe part), then i just tacked it together from there. It was about 1/4"-3/16" away.. so i had to do alot of filling w/ the welder. (it varied... because i can't cut straight w/ a sawzall ) but anyhow, after i mig'd it together, i took our die grinder, and cleaned up the inside pipe section, then the outside... threw some high temp block paint on it, and then threw it back on the car, with some copper rtv + gaskets, etc... It doesn't sound as stupid as is did before! wierd..... but yeah.. it doesn't do any droning or anything... only when engine braking really... It seems to have a bit more pep when scooting around town, haven't gotten onto the highway yet. As for low-end torque.. i don't think it's lost any really... i was towing my trailer back front the barn, and noticed no difference... and yeah, send me some pics of that skid plate Link to comment Share on other sites More sharing options...
Andyjo Posted June 18, 2006 Author Share Posted June 18, 2006 Twin tip muffler tips look HOTT on the impreza Link to comment Share on other sites More sharing options...
seanski06 Posted June 19, 2006 Share Posted June 19, 2006 haha i actually changed my mind with the skidplate it works, but i wanna do something a little more different...im gonna make another template one out of thin aluminum then have it made again...i show ya pics of the new one...when its finished Link to comment Share on other sites More sharing options...
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