Principle of operation
The 5-stroke concept engine utilises two fired cylinders (High Pressure - HP) operating on a conventional 4-stroke cycle which alternately exhaust
into a central expansion cylinder (Low Pressure - LP), whereupon the burnt gases perform further work. The LP cylinder decouples the expansion and
compression processes and enables the optimum expansion ratio to be selected independently of the compression ratio.
Sounds a bit like a triple expansion steam engine (well double expansion in this case)
That's a 50% increase in part count for a specific fuel efficiency no better than a CVCC Honda engine.