Thread: Bought Borla 2.25 In/Out Mufflers...Will they be restrictive?

Bought some 40357 Pro XS Mufflers 2.25 in/out for my '99 GTP...

I feel like these will limit my upgrade-ability in the future/be to restrictive with all the mods I will be doing to the car...

Ported/Polished Heads
Port matched/Polished LIM
Ported/Polished blower
Headers
Cat Delete

Should I put the mufflers on and get a custom Cat-Back...will this limit me to 2.25 piping?

Just get a pre-assembled cat-back system?

Thanks yall!

Originally Posted by BillBoost37

2 x 2.25 = 4.5" of flow at the mufflers. You wont be restricted there. Now what you do from the Y forward..that's up to you.

not exactly

(pi*r^2)*2 gets you 7.94 sq inches of space (pi*1.125^2)*2

while 1 3" pipe(like your downpipe) has 7.06 sq inches

so it flows enough to outflow your downpipe but not as much as your simple math shows.

The biggest cat-back restriction is that the y pipe is more of a T pipe.