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Most of the development work on rotary valve engines was done by Roland Cross in the 1930's. His sytem is very similar to that which Ilmor are using except in the valve oil sealing arrangements. The Cross valve ran in single cylinder form in the TT in the late thirties, and a small generating set for aircraft using a Cross engine passed a Ministry of Supply (now Ministry of defence) 150 hour type approval test in 1945. Esso later collaborated with Cross in the Abingdon Cross engine in the 1960's(?), so that type of rotary valve development is not new at all. The reason poppet valve are still used is just economics and the sort of interest displayed by Renault. Cross was running 13:1 + compression ratios on 75 octane fuel before WW2. Perhaps that is the real benifit of the rotary valve, and maybe it will be needed in today's climate? Anyone knew what happened to the Coates rotary valve engine. I saw this running in V8 form some years back.
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