This is all very fascinating, but also very over my head! I found a post detailing some reasons why this technology never made it to production; apparently such an engine is always running rather close to its limits and could more or less self destruct if there was a small problem with air/fuel ratio and timing. https://www.yellowbullet.com/threads/smokey-yunicks-hot-vapo...
Sidenote, I don't know why the forum software makes you hit "See More" to see the whole post. Here are filters for uBlock Origin:
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