i searched in the R forum and didn't find exactly what i needed. also, some of the info was contradictory.

please help me out with these questions! the exhaust would initially be mated with the oem header/cat until i can put on a jdm 4-1/carsound.

- what is the difference between the usdm and jdm exhausts? is the difference simply the length of the b-pipe or the overall inner diameter of the piping?
- i've looked about and found the inner diameter to be about 60mm, or 2.375". are there any restrictions/bottlenecks similar to the oem exhaust?
- what is the weight of the mugen b-pipe + can versus the oem?

no need to comment on the build quality, price, sound, and/or comparison to other exhausts.

 

I believe the JDM exhaust is longer and it has a different style tip.

 

"JDM" Mugen exhaust has longer b-pipe to accommodate shorter "JDM" cat.

"USDM" Mugen exhaust has b-pipe that's same length as "USDM" ITR b-pipe.

B-pipe piping dimater & muffler piping diamter are same between "JDM" & "USDM".

The only "bottle neck" is at the "twinloop" part of the muffler. I believe they are narrower then 60mm where it curves to form the loop.

Weight difference between a Mugen exhaust & a stock exhaust is negligible.

If you want an exhaust for the track, probably Fujitsubo RM-01 (that Chris N) has is a better choice. (RM-01 is very streetable from what I hear.)