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I understand what Carlos is saying. But The DMX is an example of a motor that makes great power with very small transfer passages. The cccr is a factor to consider, but I also agree with pipe-ster. We can work with quite a variety of things and make them work. In testing various combination for CP industries, we have had a chance to test many cccr setups. Fortunately, we've been able to get satisfactory results out of each cccr we have worked with. As the bore gets larger, the cccr is very hard to get down to the lower ranges. But it doesn't seem to matter; we have some setups that are good as any on the dyno and in the field, that are on the highest end of the cccr range.


As to transfer volume: consider how little time the transfers are full open. And then compare the size of them to the passages. You will find that the volume of the passage does not need to be much larger than the window for the window to be the limitation of the flow. And if the passage was as small as the flow size of the window, the window is still the limiting factor for most of the transfer-open cycle, since the window is closed to some degree at all but BDC.

Fun discussion, but not as critical as some would think, imho.


i just looked at some cylinders that run good and i see a what nate is saying about the transfer window size.
 
I just spent the last couple hours reading a thread on PS about crankcase compression ratios.(Brain hurts alittle) Awesome read if anyone is interested and beleive some of the members here contrubuted to the thread.



http://www.planetsand.com/forums/ubbthreads.php/topics/322/1



I know the next time I have my motor out I will be giving this a shot and see what mine measures out to. It's amazing how technical our simple 2 stokes can be.



Maybe we can get some discussion around it going here?
what happened to this post?
 
been working on a engine with cccr of 1.6:1 and thats with a 4mm spacer under the cylinder. ran fine when it was a stock motor. gonna double check all my calculations again to be sure theyre correct but does 1.6:1 seem alittle off to you guys ? its a reed valve engine with boyesen ports that stay open 360* but the main intake port is only open 196*. seems like it should be open longer
 
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