Thread: Downpipe Questions

I want to buy a downpipe for my Grand Prix GTP. I'd prefer a 3 inch one. Larger diameter = more flow as well as a slight tone difference in exhaust, I'd presume. However, I believe the rest of the system catback is 2.5 inches.

I'd be buying a catted weld in 3in pipe, and just bringing it to an exhaust shop. I know a place that'll weld it in for 30 bucks and the old cat. Do I need a reducer, or some kind of flange?

Basicially, I want a 3 inch downpipe, and I need to know what to bring to the shop so they can do the whole job without issues.

Originally Posted by Bio248

the catback is actually 2.25", just for your knowledge. it flows great up to 350+ whp though so just leave it. i agree that you should go 3", but youll need a reducer to mate to your stock catback.

Gotcha, was close. Wasn't planning on touching the catback, as I'm horrified of raspy sounding exhaust.

Is this the reducer I'll need? ZZ Performance

And if so, will it fit with the 3 inch downpipe with the cat? Then.. Will I need the 2.5in gasket option for the downpipe?

I'm sorry I'm so terribly clueless, but I want to get this right the first time.

One 3'' weld in with cat, front and rear gaskets, and an exhaust reducer with flange it is.

Thanks much!