Stock turbo / downpipe question

[MarcVIII]

I've done a search and couldn't find anything on this.

Anyways I was wondering if you could install a 3" turbo back exhaust all the way through the muffler on a currently stock car. Does the 3" downpipe bolt right up to the stock turbo or would I need a reducing flange? Will this car pass e-check most likely, as I am due? Would turning boost down (maybe to 0 or 1psi) help e-check or would stock setting be best? I am ordering a high flow cat (3" of course). Will this setup (dp, high flow cat, piping, muffler [all 3"]) be rather loud and require a resonator or not?

I have most the parts for upgrades from this go fast recipe site below and fitting this exhaust would complete everything to stage 2.

Go Faster Page

 

[not_boostworthy]

The 3" downpipe (depending on the make) should bolt directly to your O2 housing without modification. I had to dent my 3" downpipe a little at the bolts to make room for the nuts to go on. As far as passing emissions you probably won't have an issue if you buy a QUALITY 3" cat. I'm sure you already know that an "Ebay Hi-Flow Cat" is nothing more than a test pipe and will most likely not do any good for your emissions test. As for a resonator, I like the exhaust note of a good 3" exhaust with or without a resonator, but if your worried about emissions and noise and such, I would recommend putting on a resonator. Good luck!

 

[hewhoisknot]

I have bolted on 2 3"exhausts on 14bs and never had a problem. The nuts did require a crowsfoot to go on though because of the narrower positions of the studs on the 14b o2 housing. And yes u should be able to still pass emissions. My buddy had a full 3" no cat and still passed his emissions. But if your really worried about not passing put on really tiny wheels on your car, because if the car is too low to go on the rollers they can't do the test. That's what happened to me and i got a waiver good for 2 years.

BUN

 

[95blackGsTurbo]

Good advise about the crow's foot. That is what I had to do the first time I put a 3" downpipe on. But as for you MarcVIII I would HIGHLY recommend a 2 1/2'' downpipe. I had a 2g before my 92 Tsi Awd, hence my name, and I put a full 3" exhaust on it and I downgraded to a 2 1/2'' downpipe because I was having big issues with boost spike. Would set the MBC at 15 and it would spike at about 18 for at least a couple thousand rpm's before it settled back down which took a while too. I felt NO performance loss betwen the 3" and 2 1/2'' downpipe. Kept the 3" catback with cutted ebay cat. Even with all of the mods I had you still couldn't tell on a stock T25. Just a suggestion but a highly recommended one if you want to save the life of your turbo.

 

[MarcVIII]

I was looking at getting a CATCO cat and weld on an O2 bung and one of these downpipes

2.75" inlet / 3" out long

3" through

What do you guys think?

 

[MarcVIII]

I went with an OBX cat and a Megan Racing dp (top one).

 

[FrankNstein]

3" Pacesetter downpipe bolted up no problem. 3" Catco universal was easy, just cut the flange off my 3" cat-back and used band type clamps. Muffler has a 5" tip, not overly loud, but deep sound for a 4 cylinder. Never had the emissions checked. If your car is stone stock, you should install a less restrictive intake, gotta get air in before you can get air out.
E.

 

[scottsee]

I had one hell of a time installing my 2g 3in Megan Racing DP onto my o2 housing. insted of denting the DP for the nuts to fit onto the o2 studs, I just took off my o2 housing and drilled the o2 studs out and replaced them with the smaller bolt/nut combo that came in the package.

Oh, and the only way to really help with the restriction in our induction system is to replace our Karman MAF with a GM MAFT. the 2g MAF accounts for almost 77% of the intake pressure loss, Airbox is only around 15-20%

 

[MarcVIII]

As for intake I have an CAI filter and UICP. I was looking into make an intake from the maf casue it looks relatively straight. So I should be getting air in rather nicely. The MR dp i bought was allegedyly already crowed to 2.75", so it looked easy to get to those bolts. I have lift too, so not a huge problem.

The thing is I am adding a cat to this system, which would require it to either cut the SS MR dp and reflange it or relocated the O2 sensor, which i was thinking would be cutting and extending wires. The problem in that was I am unsure whether cutting O2 semsor wires and extending them will atler the reading that the sensor will give. The sensor measures on a spectrum, right? Will extending the length of the wires effect O2 Sensor reading (not wideband BTW)?

 

[tighty]

Oh, and the only way to really help with the restriction in our induction system is to replace our Karman MAF with a GM MAFT. the 2g MAF accounts for almost 77% of the intake pressure loss, Airbox is only around 15-20%

Just curious...but where did you get this info?

 

[97EclipseGS-T]

With the stock 02 housing, you should be alset. The only problem occurs when you go to a evo 3 housing. I had to make the screw holes on the downpipe into an oval shape to get the o2 housing to fit. They are a tad wider. As for deciding on what to get, if you have a stock car, turbo, and plan to keep it that way and you just want a little more power, 2.5 is def. enough. All the variables depend on whether or not you plan on the future to make some serious hp. I went with a 2.75 to a 3 inch, because I eventually went with a bored out t-28 on a bored out evo 3 housing. Hope this was useful.