Downpipe size

[Kod]

If you have a 1 3/4 or 2 inch downpipe can you buy a 2 1 /2 or 3 inch downpipe and install? I have no idea if it can affect the process or not, thanks for any reply's.

 

[koafallenangel]

i actually have a 3" straight pipe l. it uses the stock 2" flange. If you can find one for sell as long as the stock flange size then itll work. it should be very cheap at the closes shop that can weld in your area if you get a pipe from there using your old flanges.

 

[Kod]

Was drawing a massive blank when thinking of this.. forgot stock is 2"...

Was hoping their was 3" downpipes out that could hook up to the stock t25 / catalytic

 

[Joethefallen23]

There's almost no reason to hook a 3" downpipe up to a (max when ported) 2.5" o2 housing only to have it neck back down into 2.25" at the cat. Most DPs eliminate the cat. RRE makes a DP that bolts up to the cat and is 2.5". That'd be your best bet.

 

[Kod]

Apex N1 Downpipe for 2G Eclipse | eBay

So that should work for my car then right?

All shops for just replacing flexpipe are saying 145 - 170$ total.

 

[99ECLIPSEGSXDSM]

There's almost no reason to hook a 3" downpipe up to a (max when ported) 2.5" o2 housing only to have it neck back down into 2.25" at the cat. Most DPs eliminate the cat. RRE makes a DP that bolts up to the cat and is 2.5". That'd be your best bet.

RRE is 2.5 coming off the o2 until the flex. After that its 3" including the cat or test pipe you choose. Besides that I agree there's no point in bolting up a a bigger Downpipe with the stock cat. Save up and buy them both so you only have to mess with it once and be done.

 

[DSM4LIFE-AWD]

At first I ran a 3" catback with big success holding 15psi without creeping and nothing. Than I deleted the cat and run a 3" downpipe, say hello to boost creep cause it come with it with a stock turbo and manifold.

 

[Kirkamus]

Personally i just got my Srs downpipe and Altered it to fit my stock Cat which wasnt to hard ill take some pics of it when I get my turbo back from Extremepsi.


Just use a cutter to cut the flange and weld the flange at your desired length.

Can be done at both downpipe and catback portions of the pipe.

 

[Joethefallen23]

RRE is 2.5 coming off the o2 until the flex. After that its 3" including the cat or test pipe you choose. Besides that I agree there's no point in bolting up a a bigger Downpipe with the stock cat. Save up and buy them both so you only have to mess with it once and be done.

You're right. I totally forgot about that. Is there even a full 2.5" downpipe available for these cars then?

Either way OP, grab yourself a Megan DP and SRS catback for less than $450 and be done with it. If you need to keep a cat for emissions purposes. Pick up a high flow cat for cheap. Do it right and do it once. Using such a large DP with the stock 2&1/4" pipe is likely to hurt performance. When the exhaust hits the larger pipe, it will expand and cool. It then has to try and force it's way back down into a far smaller pipe. Your back pressure will be through the roof and spool will likely be effective. Frankly, I could just be talking out of my ass. I'm no thermodynamics genius, but when it comes to exhaust, you want to start from the back and move forward. Want to put a 3" catback on the stock DP and cat? Go crazy. The opposite in this case just doesn't work.

If they don't sniff the cars, grab a cat look a like and run an o2 sim. You can build one for less than $25 or so. I pass with flying colors every time. Even left the old o2 sensor in and ran a fake loom into the car for appearances. They have those SS cat test pipes for like $60 on eBay.

 

[jed344]

I have a true 3in down pipe bolted to my 2.5 PR o2 housing with a 38mm Tial on it. But most o2 housing are 2.5in anyway unless you are running a bigger turbo with a 3in Vband.