HowStuffWorks "How an Atkinson Cycle Engine Works"
Animated Engines - Atkinson
I should have mentioned that the atkinson achieved 4 strokes with only 360 degrees of the crank due to some tricky connecting rods and linkages
But Mazda's skyactivD (2.2L diesel) lowered compression to a measelly 14:1, but improved FE. So wouldn't that suggest that there are diminishing returns for just bumping up compression ratio?