I need a 60-63mm (stock sized) test pipe or HFC today.

installed a test pipe on my S2000 yesterday because my catalytic converter innards had become detached and rattled really badly.

It must be a 70mm because it sounds so tingy with the stock exhaust.
I picked up a INVIDIA TP from a fellow S2000 owner to try. the inner diameter was just over 2.5", but I guess the standard is to measure outer diameter.

Is the bottleneck effect of turbulence the reason for the shit sound?

 

Can't help today but you have a standard 63.5mm (AKA 2.5") piece of pipe. Pipe diamater is inside diameter.

Sounds crappy because it's a test pipe. Probably smells too.

-- Chuck