Exhaust Question WRX

[Archie]

I have read that that stock pipeing, 2.5 inch is sufficient for up to say 300 hp. With this in mind and an AP on the car stage 2, if i go with stock sti tbe w/o cats i should be fine right?

[Honest_Bob]

You mean just a stock sti catback? Lots of people have done that. Only thing you have to be carefull of is that the sti catback has a donut flange. You've got a few options.

1) Buy a downpipe with a donut flange. Fits the stock sti catback and your good to go. It severely limits your choice on aftermarket catbacks should you decide to go with one in the future.

2) Buy a downpipe with the normal 3" flat flange and have someone modify the stock sti catback and have a 3" flat flange put on it. Best idea if you deffinitly know that your going to upgrade to an aftermarket exhaust in the future.

But if your going to spend the money on purchasing a sti catback and having to pay someone to put the flat flange on it your gettting close to the cost of what a brand new ebay catback is gonna cost you. There are a few good catbacks on ebay that I believe can be had for around $300.

So for $175 you pickup an HKS catless downpipe, and another $300 for an ebay special catback your looking at roughly $475 for an entire 3" exhaust. I'm willing to bet you could probably go even cheaper if you were to check out the classifieds section of Nasioc.

Now if quiet is your goal then you can disregaurd that. The sti exhaust is gonna be a good deal unless you can find a Greddy SP2 or Maddad whisper used.

[Archie]

but what i want to do is get something a little lower toned, not as loud as the 3 inch tbe i have now. I figured that the stock piping of the sti catback and a regular 3 inch downpipe would keep it a little more mellow or close to stock sound.

[JET02WRX]

Originally Posted by Archie

I have read that that stock pipeing, 2.5 inch is sufficient for up to say 300 hp. With this in mind and an AP on the car stage 2, if i go with stock sti tbe w/o cats i should be fine right?

Can you clarify if you have an aftermarket turbo back exhaust, or currently have a stock exhaust? If you have an aftermarket downpipe, you have to find out if it has a donut flange that will accept the sti catback.

[Archie]

Originally Posted by JET02WRX

Can you clarify if you have an aftermarket turbo back exhaust, or currently have a stock exhaust? If you have an aftermarket downpipe, you have to find out if it has a donut flange that will accept the sti catback.

aftermarket dp, id just get it expaneded so any flange would work, i just want the exhaust quieter

[05slvrwgn]

I connected an Invidia 3inch DP with a flat flange to my stock cat-back with a donut gasket. i took the spring bolts out and used the supplied springless bolts. Just crank them som' bitch's down(the bolts). I didnt have any leaks. I drove like that for about a month before getting an Invidia cat-back to match.

i wouldnt not recommend the hks downpipe. it has a similar to stock flat plate against the wastegate that will cause turbulence and fluttering.