Smokey Yunick's Hot Vapor Engine: Genius Idea, Hazardous Reality

NASCAR innovator Smokey Yunick developed a Hot Vapor engine that heated and vaporized fuel to improve efficiency and power, transforming a Pontiac Fiero’s four-cylinder from under 100 hp and modest torque to about 250 hp and 250 lb-ft, with better fuel economy. The design relied on heating exhaust and cooling systems, a homogenizer, and ongoing pre-combustion vaporization. However, it operated on a fine line between detonation and full combustion, was highly sensitive to irregularities, posed major fire risks, and durability concerns, which prevented widespread adoption despite its potential. Modern research continues to explore waste-heat utilization in engines inspired by Yunick’s ideas.