[JackMcCornack]

Roger that, Mech, and looking at the 6-stroke as a steam engine I'd guess it has 10% efficiency...but since the first four strokes convert, say, 30% of the combustion energy into work, if strokes 5 and 6 can extract 10% of the 70% left over, that's another 7% to add to the 30% efficiency, total 37%. In concept.

There's some extra heat energy in the combustion exhaust; if there were two exhaust ports (one for stroke #4, one for stroke #6) the combustion exhaust could be heat-exchanged to preheat the injection water (600f, maybe?) you could get a 1500 psi hit right off the starting blocks--a brief but significant boost to BMEP.