Hi.
I want to make a new 2 - 1 system for my bike. My plan is to use 38 - 39mm pipes (because 2V monsters are not found of to big pipes?? ), I'm going to have the Y-section placed were the original X-section are, so the pipes are same lenght as original. The Y-section will have 38 - 39mm inlets, and cone from 43mm to 50mm on the outlet. Or do you guys think differently? All ends up in a Coffman Shorty Exhaust Muffler.

Do you see any flaws in my idea? Cant find a lot about the subject on the big old interweb....

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Okay, after posting this thread I stubled into this site http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/
Here they linked to several sites and I found out reading here that exhaust is extreemly simple and complicated at the same time....
Reading here http://www.eng-tips.com/viewthread.cfm?qid=104735 made me wana cry and regret starting to think about building my own system.
But reading here http://www.ducati.ms/forums/57-supersport/81269-my-2-into-1-exhaust-project-8.html (isnt this guy restricting flow alot??) made me want to try again....

I´ll read the posts you gave later, but for your info, here´s another one:

http://www.ducatimonsterforum.org/index.php?topic=55255.0