Foyle wrote:[....]DI 2-stroke should be the standard for high performance and low cost with good efficiency. It also has more relevance to a world that wants hybrids and range-extenders.
Very good post foyle!
Yes DI 2 Strokes would have been really an interesting way to go. DI and forced scavenging are the (in these times easy) tools to avoid burning oil and outputting unburnt fuel.
One power cycle per cylinder and rev leads to lower rpm at comparable power, and there is no need for the valve train. Both will result in better mechanical efficiency.
Also for a small range extender, with a more or less stationary operating point (constant rpm and max load) a 2 Stroke DI makes much more sense than the Audi approach with a wankel, which is inherently inefficient due to huge surface heat losses.
THAT would have been really a step forward in many aspects, not the least being costs.