RB exhaust diams

[Roy]

IS there any real difference in the exhaust diameters of say an RB20 exhaust v RB25/26? I understand my HKS Hyper exhaust is 80mm, would it be fair to assuem that most aftermarket cat back GTR exhausts are also 80mm, or are they typically a bit bigger, say 90mm?

[MerlinTheHapyPig]

my rb20det has a 3.5inch exhaust (89mm). general rule with turbos & exhausts, the bigger the better, coz u don't need backpressure.

most aftermarket ones i've seen tend to range from 3.0 inch to 4.0 inch.

[R31Nismoid]

i got a 3"... but i need a 3.5" or a 4" really with the power im making.

I can kinda feel it slowing later in the rev range

250rwkw is ok for 3"... you'll need bigger than 3"

easy power and response to be gained.