BenRNBP

A few recent threads have got me thinking on this - with the different diameter bore components (fanimold, cat, cat-back) do they all have the same doughnut/flange sizes just with different bore tubing ? I know from a gas flow point of view it'll do funny things if you have narrow, to big to narrow again but will they bolt together in pretty much any order ? e.g. get 70mm cat with OEM cat-back, or a J's manifold + 70mm cat + OEM cat back ?

I think I know the answer but have never been 100% sure about the interchangableness of the parts.

Mr-T

This may not help you 100%, but to my knowledge all the flanges are similar sizes (Close enough to bolt on to the other). But as you mention, you will have all sorts happen with the gas flow.

Chuck S

There's a lot of science, experience, and (I suspect) blue smoke and mirrors involved here. Honda engineered the stock exhaust system for a smooth flow.

I've been told by several folks that jumping immediately from the under-60mm header to something line a 70mm exhaust has some negative effect on mid-range torque. Some say it's better to scale up the diameters to say a 63mm cat followed by a 70mm exhaust. I've neither the time nor money for dyno testing the various combinations though. I do know that my current system butt-dynos much better than stock. Sometimes perception is reality. Sometimes not. A 70mm exhaust is about 160% or more of the header.

Stock header ---> Berk 63mm high flow cat ---> Invidia 70mm dual "cat back" exhaust. Intake in the K&N FIPK. Car will get a Honda tune as soon as my laptop comes back from repair -- "someone" spilled beer on the keyboard.

-- Chuck

E4RTH WORM JIM

63.5mm I found to be the most powerful.