Exhaust questions

[Nayr747]

So I might have some money to get an exhaust or something else but I have a couple questions.

1: I am looking at Magnaflow and Catco 3" cats. I found some on ebay for $50-$60 but you need to get the o2 bung welded on. http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW These are a lot less than at Slowboy etc so I was just wondering if they're not as good somehow. Also how long does the cat need to be for a N1 cat-back? And (very newbish Q) do you need to weld flanges on the cat or what? RRE's pictures have flanges on the cats but Slowboy's Magnaflow pics dont.

2: I am looking at the N1 dp or something similar. I can get it off ebay for $215 but if anyone knows a better dp let me know. So I need to know what dp/o2 housing I need. I have the t-25 but I will soon be getting the evoIII16g or t3/t4. Should I stick with the stock o2 and just port it or get a different one (Evo or other)? And which dp will I need for these?

If I need to search better just let me know.

[Gsx_hooptie]

You're asking good questions.

1) Magnaflow and catco are good. You have to weld the o2 bung on those if you want to use your existing o2 sensor, just as you would for cats ordered from major vendors, they don't do that for you (well, maybe if you called and asked ). How long the cat needs to be depends on the specific downpipe and cat-back it's being mated to, from what I understand. Mine is exactly 20" for an n1 catback and RRE downpipe. I don't remember how long the stock cat is. The flanges on the cat are welded on by some vendors and included in the price, but not others. RRE weld them in-house for a total of 150. SBR sells you the cat without welded flanges for 125. SBR probably would weld them on for you if you called, for a little extra of course.

Either buy the whole setup at once from a specific vendor, as kevin suggests, or buy the separate dp and catback so as to measure the length you'll need for your cat. Then weld the flanges onto the cat to match that length.

2) The N1 dp is pretty good. It eliminates the cat you were talking about above. That saves money and hassle. If you want to keep a high flow cat, get a "short" downpipe. The benefit of the short style is getting to swap out a hf cat and a test pipe, depending on your mood er whatever. Short pipes are made by some vendors and Midas, no large name brand I know of. Not apexi.

General consensus is to keep the o2 housing you have until you upgrade the turbo to a point you'd need a larger one. For an evo 16g, you probably don't need to do more than port your existing housing. With a larger setup, skip the evo housing step and move directly to a custom o2 setup. Stock and custom o2 housings will match to normal exhaust. The o2 housing that causes problems is the evo, because of a slightly different angle to the dp.

Buy a three inch dp now, there's no trick to matching different dp's to different turbo setups. Just go big now, so you don't upgrade later. Usual stuff you've heard rambled off here before; mandral bent, good flex section, quality welding, logical exhaust pathway, made from stuff that won't rust.

Most exhaust systems meet these requirements, so don't forget to judge by price. An n1 system would be likely the best name brand setup. Custom made at a local shop would be the cheapest, other than you doing it yourself. Check out the vendors, most of their stuff is up to par.

Personally, I bought an Apexi N1 catback (3"), RRE evo flanged short downpipe with a RRE high flow cat. Bought the N1 used, got the custom stuff yesterday. Looks good, I'm happy with their work. Stuff was pricey though.

Taking the old exhaust off: Copious amounts of PB Blaster, remove the rear o2 sensor (22mm), then unbolt exhaust from hangers (14mm) as a single piece. When you're done, drag the whole thing out from the rear of the car, where it'll be easier work removing the exhaust pieces from one another if you want to salvage gaskets. Or don't, and recycle/toss your old exhaust and buy new gaskets. I haven't put my new stuff on yet, and I won't be starting the car for another couple months so there'll be no verdict about how it sounds.

Heh, getting rid of the old exhaust can be a chore. I called and no one wants it, even as scrap metal. No one will recycle it. Tried to leave it for the garbage truck to take it Maintainance to my complex called me to tell me that the garbage people wouldn't take it, that they were going to fine me if I didn't move it. To the dump it goes, unless anyone wants it for some bizzare reason.

[Nayr747]

Thanks for the great response. My only other question is boost creep. With the t-25 on there now I'm guessing I'll get some with a 3" exhaust. So I dont know which option is best: put just cat-back on for now, put the whole exhaust on and port just the o2 housing, turn down the boost, or wait until I get a new turbo.

For the cat, would it be smarter to get the cat with flanges already welded for en extra $100? If I got it welded afterwards I wouldn't know where to get the flanges (SBR?) and I hope I wouldn't measure it wrong somehow. But if it saved me money I would try.

You should keep your old exhaust incase you need to part your car out. Or at least keep it around for emergencies. I dont know but it seems like a waste to just dump it ya know.

[Gsx_hooptie]

I would port your existing o2 housing and leave it be until you upgrade past an evo 16g. I would do the full exhaust at once, since catback doesn't always mate nicely to the stock cat. The 3" exhaust will be good to go for any turbo, if and when you go larger than the evo, you can think about getting a larger o2 housing. It's easy to swap the o2 during a turbo install, anyway.

Originally Posted by Nayr747

For the cat, would it be smarter to get the cat with flanges already welded for en extra $100? If I got it welded afterwards I wouldn't know where to get the flanges (SBR?) and I hope I wouldn't measure it wrong somehow. But if it saved me money I would try.

I was in the same situation, and I pussied out and bought my cat with the flanges already done. SBR and RRE sell the flanges for 10-15 each, so 80 dollars total, plus the cost of welding. It would save about 50 bucks, the only problem in my case was that I was unsure about what size the cat was supposed to be. If you have the same setup I do, the cat is 20" give or take ~1/16." Measuring and welding that wrong would be bad.

After seeing my shiney new N1 and RRE stuff I have distain for my old exhaust Ideally I'd recycle it, but no one wants it. You're right that it would be smart to keep it at least until after I install the new stuff. Then it gets dumped.

[Nayr747]

I'll put it on all at once then and port the o2. Thanks for the help.

[kjewer1]

RRE DPs are the best thing going for the money IMHO. The N1 flex section was always weak, probably still is. The flex section is the most expensive component in the down pipe, so that is where most of the price difference comes from. But cheap skimpy flex sections usually dont last long. Prothane mounts may help...

[Nayr747]

Thanks for the advice. I'll look at that one too.

[Gsx_hooptie]

My stock dp had a flex section that allowed for quite a bit of wiggling, the RRE one is very stiff. It'll move if you make it, otherwise it's much more taut.

Damn it looks good, too