What is the diameter for JDM ITR B-pipe and USDM ITR B-pipe?

 

Just having some fun while I'm snowed in...

If you want the answers take a look in the FAQs, rather quick and simple.
Exhaust - Header - General
https://honda-tech.com/zerothread?id=274617 - Header Specs
https://honda-tech.com/zerothread?id=398081 - Header Pictures
https://honda-tech.com/zerothread?id=299254 - How To Remove Blue spots On SS Headers
https://honda-tech.com/zerothread?id=685213 - Header Material
https://honda-tech.com/zerothread?id=258919 - Ceramic
https://honda-tech.com/zerothread?id=667745 - Header For Larger Displacement
https://honda-tech.com/zerothread?id=670408 - A/F Ratio
https://honda-tech.com/zerothread?id=669461 - A/F Ratio
https://honda-tech.com/zerothread?id=659201 - DIY
https://honda-tech.com/zerothread?id=716001 - Collector Sizes
https://honda-tech.com/zerothread?id=669614 - Equal Lenght

Exhaust - Header - Brand Specific
https://honda-tech.com/zerothread?id=397165 - JDM ITR
https://honda-tech.com/zerothread?id=520794 - AN-R
https://honda-tech.com/zerothread?id=668226 - Comptech Race
https://honda-tech.com/zerothread?id=498302 - SMSP
https://honda-tech.com/zerothread?id=668728 - Bisimoto

Exhaust - Header - Bench Racing
http://bob123e.tripod.com/theg...x.htm - The Great Header Test Of 2001!
https://honda-tech.com/zerothread?id=700477 - The Great Header Test Of 2003!
https://honda-tech.com/zerothread?id=743633 - USDM ITR vs JDM ITR
https://honda-tech.com/zerothread?id=268638 - Hytech vs SMSP
https://honda-tech.com/zerothread?id=700815 - Hytech vs SMSP
https://honda-tech.com/zerothread?id=676724 - Greddy Vs JDM ITR
https://honda-tech.com/zerothread?id=700409 - Best Header?
https://honda-tech.com/zerothread?id=673277 - Best Header?
https://honda-tech.com/zerothread?id=557249 - Best Header?
https://honda-tech.com/zerothread?id=525194 - Best Header?
https://honda-tech.com/zerothread?id=176240 - Best Header?

 

The ITR has a dynamic variable diameter pipe for optimal backpressure compensation and therefore maximum horsepower extraction.
It is however not for maximum torque creation.

 

The Best Motoring Type R legend dvd said it is 57-58mm or 2 1/4 od.