I am thinking of what diameter tubing use in my SS exhaust. Is 2.5" an overkill if I don't want to modify anything apart from exhaust (sport cats later on) and K&N filter? I intend to use Magnaflow mufflers and despite various inlet/outlet sizes most of them have 2.5" core. I don't know too much about exhaust, but wonder what difference it'll make if I use 2.25" piping if the muffling part is 2.5" anyway.

 

michal, I installed a 2 1/2' Magnaflo x-pipe just after the cats and 2 1/2" Magnaflow mufflers. Next week 2 1/2" pipe will go from x-pipe to mufflers. Hi-flo cats will eventually complete the exhaust. I too was inclined to stay with the stock 2 1/4" pipe but plan to perform an ECU tune and the S/C re-geared plus a port and polish. My point is: You now say you won't perform future mods, but as they say...Never say never. A blown (S/C or turbo) engine benefits from free flowing exhaust. Even if you ultimately never go beyond exhaust, your STR will love ya for giving it a bigger straw to breath out of.

 

2.5" pipe you'll be getting next week is inside or outside diameter?
I measured my pipes and it turned out it's only 2.15" outside and only 2" inside! Even 2.25" would be and increase

 

Get that extra 1/4" boys, she will like it

 

I'm guessing the tubing is 2 1/2 outside diameter?, otherwise there is a noticeable visual difference.

 

In this case, ID will be about 2.36". Still good for about 460hp.