Does anyone know for sure if you can some how fit a 3 inch aftermarket catback onto a STOCK downpipe. I believe the stock downpipe is 2.5 inches. I have a 3" catback and have recently lost my job and have no money to buy a downpipe

A couple people have told me its possible without getting any leaks Id just like to know how. I really appreciate it, and sorry if this is a n00b question.

 

I bolted my old SRS to the stock downpipe, just made sure it was nice and snug with the stock donut gasket.

 

it can be done cuz i did the same thing when i first got the car

 

thanks for the input guys. But Im 99% sure that theres no gasket on my DP. Do you think that if I got a replacement the fitment would be better?

 

http://www.jscspeed.com/catalog/Suba...u_WRX_STI.html
or
http://www.rallysportdirect.com/shop...er-p-3911.html

here's an idea of the part you need. I'm not necessarily recommending that you buy from them, just giving you the idea that this need has been addressed with a part designed for your situation.

btw, don't 1/2 a$$ it, just either do this part or bite the bullet and mod the downpipe section to a full 3" (get rid of the bottleneck). downside to that is you wouldn't be able to put on your stock cat-back in the future...whereas if you get this part, you would.

{In case you ever worried about putting that back on (e.g. sell the car or really worried about smog)}

p.s. if you have a stock downpipe, it used a "donut flange" to connect to the stock cat-back. there is the half circle looking gasket that is used.

don't let someone convince you that using the gasket and RTV mated to the new flat-flange cat-back work...i tried it--what a waste of time. just get it done right the 1st time.

 

Awesome thanks so much Cheston. I really appreciate it, $35 aint too bad so I'll just do that rather than waste my time and risk having a huge leak again lol.

EDIT- after reading about both of those, they boths say that they are 3" downpipe to stock catback adapters. Does it matter if mine situation is the other way around?

 

ive run an hks hipower 3" and a blitz nurspec touring 3" and both bolted up to my stock dp, no gasket

 

Damn, maybe Ill try bolting it up first. We'll see.

 

I think the way it is is that the stock downpipe is 3" but with the doughnut gasket it gets narrowed to 2.5" or something like that for the stock catback. So when you put your 3" catback on you just take out the doughnut gasket and put a normal 3" exhaust gasket in there. I have a 3" exhaust on my 02 that bolted up so you should have no problems