just wondering whats the normal size(od) of most fmic hard pipes?

 

hi between 2 and half and 3 inches.

 

so is it 70mm , 76mm or 63mm?

 

70mm , 76mm

 

63mm for many.

 

unless your pushing big bhp i wouldnt of thought 76mm would be needed really?

 

Big BHP does not need 76 diameter which would be a step backwards.
What is the diameter of the turbo compressor outlet?
What is the diameter of the throttle body inlet? While you might want something bigger than 63 diameter you will be producing a hell of a lot of power before you increase the hard pipe size.

 

outlet is 50mm inlet is 76mm. t/b is 70 - i think