autogyro wrote:Effective cylinder filling is to a great extent reliant on valve overlap and duration, which cannot be completely duplicated with both ports/valves in one unit.
I would heartily disagree. I have extensively studied single, bifurcated, axial/radial flow rotary valves for high speed 4-stroke racing engines. And I have a US patent (#5,052,349) on just such a design. Coincidently(?), it is very similar to the Ilmor/Bishop F1 design, and my patent predates theirs by several years. But my patent was only valid in the US, so maybe that's why the Ilmor/Bishop development work was all conducted in Europe. http://www.google.com/patents?id=TT8gAA ... q=&f=false
I never built a running engine using the design (due to lack of money), but I did lots of flow bench and modeling work with it. What I found was that my single rotary valve had far superior port-time characteristics (due to the more aggressive opening and closing flow areas possible with a fixed speed rotary valve versus a less aggressive cam-driven, reciprocating poppet valve flow), higher mean flow coefficients, better scavenging characteristics, much greater max flow areas possible with a single rotary valve port versus the typical 4-valve poppet head, and less "short circuiting" of intake/exhaust flows during timing overlap due to the tangential, swirling intake flow vectors inherent in the axial/radial porting geometry of the rotary valve. The rapid opening/closing effect of the rotary valve also produced a more intense intake/exhaust flow acoustic signature, which resulted in more power from intake/exhaust manifold tuning.
My rotary valve design also had no valvetrain operating frequency limit, like a poppet valve system has. And it also resulted in a much more compact cylinder head package than a poppet valve/spring/camshaft system. So it had lots of promise for a racing engine application, like in F1. But alas, I didn't have the money to pursue its development. And my patents have now since expired, so anyone is free to use it. And you will have my blessing to do so.
I spent way more money on it than I should have. And in the end, I got nothing from all of my years of effort and tens-of-thousands of dollars spent, except heartache. But honestly, I'd probably do it all over again, because at the time it made me feel that I had a purpose in life.