With all of the benefits, High comp ratio, over-expansion of exhaust gas, it still suffers with some fundamental geometric limitations; namely combustion chamber shape and intricate inlet/exhaust ports. With liquid fuel, crevice losses will likely be very high, surface area to volume ratio (and therefore heat rejection) will be high and practical efficiency will be lower than expected.
The design seems to make the assumption that at the higher compression ratios, the fuel is not prone to knock; anyone can draw a PV diagram for a spark ignition engine that offers greater efficiency than diesel; but practically its unlikely to be acheivable.
Nice idea regarding atkinson cycle operation though - a longer exhaust stroke than compression stroke; although this doesnt look variable. It\'d be interesting to see whether the motor will still suffer with the low speed/power density issues conventional atkinson cycle motors suffer with. (or even more conventional engines with aggressive VVT that are given the name atkinson engines like the prius)
always an interesting read. I\'ve got some genuine japanese books written by the lead designer at Mazda, they consider many different rotary lobe designs, and summise well why the 3side rotor, 2-lobe design was chosen, ill see if i can dig them out.