Pipe design for my modified Kawasak H1

[jeff kushner]

I'm hoping the Admin will see this since there doesn't appear to be a lot of traffic even though you have dedicated a lot of time to building this forum. Your work is commendable for all you've written on 2 stroke chamber design. I have been building high performance two strokes for 30+ years but this is my first foray into pipe design. I had a friend with the MOTA program run some numbers on a set of "fat" pipes and he told me that without tapered headers, they were next to useless....BUT, with tapered 44mm headers expanding to 55-58 over the course of 300mm or so, the power went through the roof when coupled to an engine with a exh duration of 200+ degrees.

Do you have any way to check this for me, or for the tools that I can verify it myself before I begin cutting up and re-welding these pipes? I need to remove the tapered headers from an old set of pipes and graft them to the "fat" pipes.


Thanks,
jeff

[Rx7man]

Hello.. sorry I'm of no help to you.. yet... but I figure we have a bit of a dust bowl in here.. no better way to fix that than to say hi

[Admin]

Mota is a more advanced program and so I would go with its suggestions. Please let us know the outcome

[Morehp]

44 mm header is WAY too big for 166 cc. You have to be careful what inputs you use on sim programs like Mota, you have to be realistic. Garbage in = garbage out. What is the window area of your exhaust port? What is the peak hp rpm?

[Rx7man]

48mm is a BIG header pipe on a 168cc... I would expect something more along the lines of 38mm tapering to 45 over 300...

also, a 200* exhaust duration (if it doesn't have any power valves, etc) is going to lose serious torque and it doesn't have a whole lot of displacement to make up for it... it would certainly scream at the top end though

and I agree that simulation programs are Garbage in, garbage out.

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