I was just wanting to post this in the Peak Econobox thread about the
Scuderi Cycle engine.
It had separated compression and power cylinders with a reservoir in between. Easy Peasy gas/compressed air hybrid. But they spun their wheels in the development process trying to make a proprietary inline four. The same thing that killed Elio.
Anyways, if they'd done the development work on an air-cooled boxer four....