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Performance Exhaust Research

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J6G1Z:
I suspect the HRC exhaust design favors a high RPM track bike.

Think I would try for long slender primaries to maintain velocity that merge as seamlessly as possible into the collector. I like the reverse megaphone design. http://victorylibrary.com/brit/mega-c.htm

I'm not much of a BMW fan, but found this interesting: http://bmwmotorcycletech.info/InExTuning.htm

J.

Dynachuck:
I used 1-1/4" OD stainless tubing for my headpipe,  but installed an integral torque cones in the flanges roughly equal to the stock ID (.875). then at the collector, I went to 1.75 OD, then to a werkes exhaust can. (which has a reverse cone shaped perf tube inside.) I was amazed at the difference to the pipe i had before which was a roached out stock header with a mechanical baffle. Note that i have an open air box and foam Uni filter.  this thing pull hard now. may people think that 1-1/4" head pipe is too big for a stock bike but the torque cones seem to make up for that and it does still have nice top end.
I got all of my material from cone engineering, (180's, straight pipe and collector) but making it this way was a lot more work than i thought.  (every change in direction requires two welds and a pie section) next time I'll use a tubing bender.

smcohio:


I do agree that the hrc pipe is a little too open of a design for a road pipe that needs to utilize the full rpm range.  As stated in the link that you attached about reverse megaphones they are designed to increase velocity at the exit of the pipe which is a great thing to have at that point. I wish that my father in law was  in this forum because he has a great conversation about the science of a reverse megaphone. If you are ever on advrider i recommend having a conversation with markk53, be prepared because one question will turn into a 3 day conversation haha. As dynachuck was saying about torque cones you need to keep the back pressure and heat contained to a certain point in the pipe to maintain your low end torque range and then after that speed it back up on the exit with a reverse megaphone design. And lastly the final pipe will be mandrel bent so very little weld sections.

J6G1Z:

--- Quote from: smcohio on May 20, 2018, 07:20:32 pm --- ...I wish that my father in law was in this forum because he has a great conversation about the science of a reverse megaphone....
--- End quote ---

Please feel free to invite him over if he has an interest.

Thanks
J.

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