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Before you begin

Post by Admin on Sat Mar 28, 2015 9:42 pm

First you need to know what the RPM spread is between gears. Sheet 4 of my Excel file can help you with that. I know how to look at the return wave combined graph and see what the beginning and end RPM is of a pipes powerband. I hope I successfully conveyed that info on my pages at
What happens if the pipe powerband is too wide? You won't have to be as exacting with gear changers but then again the supercharging effect of the pipe will be lowered. What happens if it's too short? You will have poor acceleration at the beginning or the end of that gears RPM spread. One of my pipe designs (while I was still trying to figure this all out) caused  the engine to not have enough power to keep accelerating when I upshifted to 4th gear (the highest gear on this bike). That made 4th gear practically useless to me.
The powerband is determined by how long the baffle return wave is. A longer wave makes a wider powerband. You can make the wave longer by making the cone gradually get steeper angled. The first 40mm can be a slight 4 degrees. The longer you make the wave, the lower the peak strength of the wave is. There's only so much power in the reflected wave and by stretching it out you lower its peak. Imagine a pyramid of modeling clay. If you widen the base then the peak will have to be lowered to maintain four flat sides.

To give a bit of background on my experiences- I started out using the 2 Stroke Wizard software to make my first pipe for my 60cc motorized bicycle. That pipe was a disaster and I thought then that no one really knew this topic in depth and so I set out to fill the gap. Then I started a year long brainstorm figuring out what exactly was happening inside the pipe and engine and eventually designing my Excel file ECcalc to help me with my own designs. I have no experience with the software from MOTA or IWT so I can't answer questions regarding those. My recent experience designing the pipe for my Suzuki AX100 confirms that my software is right on target.

Last edited by Admin on Sat Mar 28, 2015 9:44 pm; edited 1 time in total (Reason for editing : spelling)


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Join date : 2015-03-28
Age : 61
Location : Asuncion, Paraguay

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