So I have a 2004 Subaru impreza 2.5 n/a and I was wondering if taking off all the pipes, mufflers etc up until the catalytic converter  would mess up my car at all with back pressure and such until i get a new pipe on there.

I'm not up on the technical parts, but a friend of mine had a straight piped  1995 Impreza. Sounded mean but was a slug on acceleration.

 

I think the general rule is that you gain a little bit on top speed (Which is usually asking for speeding tickets, arrest and accidents) but lose the low end power. These cars usually don't need much modification. An aftermarket (fart can) muffler will give you sound if you want it. More power usually means motor swap. Guys on Nasioc have documented a few EZ30 swaps into Imprezas. I'm not a fan of turbos 0 NA = reliable and simple. So if ever I wanted more power, that's how i'd do it.

 

"There's no replacement for displacement."

I assume you mean just for a few weeks?

 

I doubt there would be any permanent damage - but I have no experience doing it.

 

from what i've read, generally speaking, you want a smooth, equal-size internal path to propagate the pressure pulses - it aids in cylinder scavenging and helps with low rpm power. Changes to larger/smaller diameters or odd shapes can cause issues.

Edited January 18, 201610 yr by 1 Lucky Texan

If you dont mind bleeding ears, and excessive noise tickets, i dont see an issue. Your engine wont like not having much back pressure, but for a short time it "shouldnt" do any damage.

 

For the cost of a muffler, some flex pipe, and a few clamps, you can redneck engineer an exhaust that will keep the local po-po and your ears happy. On the plus side, you can re-use the muffler when you get a proper system installed.

 

Your other choice is to hit up the impreza forums and buy a take off from someone who installed a catback system

Well as others have said, you won't gain any additional performance that you will notice. It may sound "cool" for about the first 5 minutes with the loud exhaust, then the sound becomes noise, and will drive you crazy. Don't bother turning on your car sound system, you won't be able to hear much.

 

Cops apt to pull you over for the loud pipe, imo, not worth getting a ticket.

It seems it would still run ok, maybe throwing p0420 if it isn't happy with things back there after the rear o2, though right on, I would imagine it would be loud. I know how loud my old rusty soobs seem when small holes get in the exhaust near the back.