Smokey Yunick’s Hot Steam Engine | Internal combustion engine

Popular mechanics; Courtesy of RacingOne (Smokey), Letectví, internetarchivebookimages (Schematics)

If you are at all interested in NASCAR folklore, you’ve no doubt heard of Smokey Yunick. He was a stock car racing team leader, builder, owner, racer, engineer, engine builder and car designer, but above all an engineering genius. Yunick shook up stock car racing in the 1960s with his bold—often obviously off the beaten path—interpretations of the rules and regulations governing car configuration. However, when he wasn’t giving NASCAR officials headaches during technical inspections, he was also determined to play with the road cars.

yunick smoky
Smokey Yunick

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One of his projects was the hot steam engine. According to its name, it would vaporize the fuel mixture before squirting it into the cylinder head. Yunick had discovered that vaporizing the fuel mixture would lead to higher thermal efficiency, taking energy that is normally wasted as heat in the exhaust and cooling system and harnessing it instead to add power. Rather than rebuild a complete engine himself, Smokey opted to modify the Pontiac Fiero’s 2.5-liter four-cylinder engine. From the factory it wasn’t a fire-eater, spitting out a paltry 90 horsepower and 125 pound-feet of torque, launching the four-wheel rocket to 60 mph in about 12 seconds.

Meanwhile, the same engine modified with Smokey’s hot steam technology could produce 250 hp and 250 lb-ft of torque. If that wasn’t already impressive, the engine churned out those numbers while sipping fuel at a steady rate of just 50 mpg. It also didn’t need a catalytic converter, burning almost all the gas that entered the cylinder head.

May 18, 1986 May 23, 1986 pontiac fiero gt
Pontiac Fiero GT

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So what made these numbers possible? Conventional four-stroke engines are only able to use 25% of the fuel’s potential energy to produce power. The remaining 75 is lost through the exhaust system or transferred as heat to the radiator and other cooling systems. However, Yunick’s hot steam engine harnessed this otherwise wasted heat and used it to vaporize the incoming fuel mixture at over 450 degrees Fahrenheit.

The process of recovering this thermal energy began with a heat exchanger located under the carburetor. This used hot engine coolant (no, the irony is not lost on us) to warm the air-fuel mixture to 200 degrees. After the initial warm-up, this mixture was then directed to a turbine (Smokey called it a “homogenizer”, but it was actually a kind of turbocharger), which sent the mixture through an intake manifold where it has reached its final burning temperature. .

The engine operated at these extremely high temperatures while using a super lean air-fuel ratio, defying the laws of conventional internal combustion. Simply put, all engines need air, fuel, and sparks to run smoothly. A lean air-fuel ratio contains more air than fuel, while a rich ratio contains more fuel than air. Ideally, engines should be in the golden loop zone between rich and lean, where they produce optimum efficiency and power.

scan of thornton rutter h 1922 modern engines

Scan of Thornton Rutter, H. (1922) Modern Motors

By now you’re probably wondering why the hot steam engine never caught on, especially with those crazy efficiency and horsepower numbers. It is said that the astronomical temperatures required for the concept to work required advanced metallurgies that would have been too expensive for a production car. Hot steam engines also ran very close to their breaking point, meaning any minor issues like improper air-fuel ratio or temperature would cause the engine to fail instantly.

Perhaps modern technology and engineering could fix some of these fatal flaws.

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