Exhaust Pipe Diameter?

**NaturallySmashed** · 03-10-2015

Hello I'm getting mixed results on the diameter size of the exhaust pipe for a 2003 grand prix gt. I'm cutting the cat out and and clamping it back on.. just need to know if I need the 2.5 inch band clamps or 2.25.. anyone know? Thanks.

**blueguy** · 03-10-2015

stock downpipe is 2.25"

**Scottydoggs** · 03-10-2015

but the pipes not really round, so clamping maybe a issue. most get it welded in.

**NaturallySmashed** · 03-10-2015

Thanks for the 2.25.

I'm gutting the cat and taping/clamping it back on for a couple of months until buying a new cat is feasible. Then I will be getting new bolts, gaskets, and cat/ pipe. Seasonal work for me so just trying to keep the money I have until the spring. I'll reply to this thread if it seals properly and the band clamps/tape that I used. Trust me I don't want to use the clamps but for this purpose it's only costing me about 20 dollars to get me through a couple months.. I really don't even care if it makes noise, I just want it to run right so I don't feel like being on the road is dangerous lol

**Scottydoggs** · 03-10-2015

in that case drop the whole down pipe, take a grinder to the top of the cat and cut out a square area, then gut it, then have the plate you cut out welded back on. inspection cant see the top of the cat so they have no clue, then leave it that way if you like.

if the check engine light comes on have it tuned out. if medford is long island, theres a few guys out there who can tune the code out.

or you can try a o2 emulator. cause a gutted cat is no cat. and that sometimes will cause the code to come up.

**NaturallySmashed** · 03-10-2015

That could be a good idea. I actually have an o2 spacer on already from when the cat started to throw the p0420 code lol Now it's just clogged up. Who tunes out here? Guys in shops or guys on the forum?