exhaust piping size

[mizjif]

Hey i got a '91 hatch and im doin cat back exhaust minus the cat and was wonderin what the recomended size of piping is for max. hp increase without goin to big or small and wut kind of hp gains i may get out of larger piping, no cats, and a higher flow muffler???

any help would be awesome

 

[Tom]

2.5 is the largest for a natural aspirated car, hp gains depend on other mods done to car and condition the motor is in.

 

[Si_Racer13]

if your engine is stock stay with a 2 1/4... if you plan on swapping to a B series, or building the engine go with a 2 1/2

 

[mizjif]

thnx guys
2.25 it is
...the b series engine will come in year-year and a half so i'll just do wuts best for my d series for now...