ok i want to kno wat size piping most of u guys recommend for the B18C.
Its an NA application. ITR cams and manifold. looking to make anywhere between 180-200whp

2.25
2.36
2.5

 

2.5 prolly

 

2.5" for 180-200 whp

 

ok thanks for the replys guys, im leaning towards the 2.5" full piping now.

im thinkin about gettin apexi WS2 muffler, but they come in 60/80mm.

what are the advantages or disavantages of having a larger/smaller muffler inlet size from ur exhaust piping??

 

If there is a large change from your exhaust piping to the inlet on your muffler it will cause a bottleneck in the air flow and create backpressure which is the opposite of what you want to do, for example:
2.5" exhaust piping
2" muffler inlet
To maximize power try to make the exhaust setup as free-flowing as possible the larger the diameter of piping, the more HP capacity for the exhaust system (within normal limitations of course.. nothing over 3" really.)