All,
Here's a site you can use to design your own tuned pipe. It's in German, but the pipe design part is in English:
http://www.kreidler-verein.de/reso.html
I used this to design a pipe, it ended up being slightly larger than my original design, but overall pretty similar. It can also be used to reverse-engineer existing pipes for use on Spree et al.
FYI: On the Spree, the exhaust port angle is 140 deg, transfer port 104 deg, exhaust port area is 225 mm^2. Use exhaust temp of 600K. The Spree tops out around 8000 RPM at just under 30 MPH, so you can either use that as the RPM or go higher/lower.
Expansion chamber / tuned exhaust design program
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Expansion chamber / tuned exhaust design program
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Buy air filters and gaskets here (Ebay): http://stores.ebay.com/noiseguysstore
Buy air filters and gaskets here (Amazon): www.amazon.com/shops/spreepower
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