Maybe those guys can answer this question: If you stick your head up your ass and jump, will you disappear?
When I was a kid there was a guy who lived about half a mile away who had a tractor powered by that style of engine and you could easily hear it at my house when he got it running. It was a hell of a lot louder than the engine in the video, it made kind of a "whump" sound when it fired. I don't recall what kind of fuel it used but it was quite the curiosity even back then (the 1960s). The exhaust stack, which pointed straight up, would blow a smoke ring every time it fired. I think he spent more time trying to get it started than he did using the tractor. The flywheels were just massive (and dangerous).