In the 1970s, what I wanted was the Amanté. It is very similar:
_____
renault_megane_dci -- If there is a running engine based on this principle, it's kept pretty well under wraps.
OTOH I don't know if you can trust an animated GIF for the timing information. I just noticed the compression cylinder doesn't show an exhaust valve.
The complete design has a compressed air-hybrid mode where there is a big air tank available to the interconnect passage. It can be fed from the compression side, or used to drive one side or the other in air mode.
They also talk about an intercooler in the interconnect passage. While I can see a tank, it's hard to imagine an intercooler that could withstand the peak cylinder pressure/volume. Maybe a carbon fiber tank with aluminum fins strapped to it and a shrouded cooling fan?