The Backus engine shares the pre-compressor piston with this design, but this engine also has the pre-pre-compressor piston (with different geometry) and also t

The Backus engine shares the pre-compressor piston with this design, but this engine also has the pre-pre-compressor piston (with different geometry) and also the low-pressure power piston. It seems to still be novel, despite sharing characteristics with previous designs.