How's it going guys? I'm just about ready to schedule an appointment for a cat-back exhaust system on my 2004 Civic DX. I have one quick question, however. The shop I go to makes their own mandrel bent piping and I was wondering what diameter I should use for the entire piping. I'm hoping to purchase an Apexi universal muffler (budget pending) for the system. Any pros/cons with this muffler in terms of sound? Any insight on mufflers/pipe diameter is greatly appreciated. Take it easy!

 

if you want the most flow go 2.5". But i would go 2.25". And if you are wanting the universal n1 apexi the only thing i can say is that it is kinda raspy other then that it sounds great. But others say there not raspy. On a stock piping with a universal n1 its not raspy but 2.5" its raspy. 2.25 seems to sound the best and all around good size.