Why Detroit Diesel’s two-stroke engine was called Screaming Jimmy – Jalopnik

One of the most important contributions in the history of propulsion technology came from a 19th century engineer named Rudolf Diesel. Although his idea was patented in the 1890s, it wouldn’t be until the 1930s that the first diesel-powered car made its first trek from Indianapolis to New York City.

Today, modern diesel engines continue to outsell gasoline in heavy-duty trucks because of their towing and fuel economy advantages. However, this would not be the case without the events of the 1930s, which were a pivotal time in the US. Automakers like GM launched diesel-focused divisions, refining and experimenting with this new alternative power plant. One of the achievements of GM’s Detroit Diesel Corporation would be a two-stroke engine, affectionately and accurately nicknamed “Screaming Jimmy.”

Because of its two-stroke configuration (where the engine fires once for every other crankshaft rotation) versus a four-stroke engine (which fires once for every other crankshaft rotation), the Screaming Jimmy sounded like it was revving twice as much as it actually was, and produced a higher pitched note. According to some accounts, industry professionals working with these engines even grew tired of the constant, rapid whine coming from the machines. The distinctive scream was also exacerbated by the Roots blower, which was used to direct exhaust gas away from the cylinder.

Detroit Diesel’s two-stroke design proved itself under the hood of the 1938 GM 719 Coach, a 165 hp bus. The following year, the Screaming Jimmy was offered in several variants and available in several GMC trucks, with horsepower ranging from 65 to 165.

This two-stroke design offers some advantages over the four-stroke configuration. Theoretically, the two-stroke engine could produce twice as much power because the power stroke occurs more frequently (each crankshaft revolution). It also offers the benefit of fewer moving parts, which means fewer points of failure and less weight. In addition, the two-stroke manages heat better than the four-stroke.

Because of these advantages, although you won’t find two-stroke diesels in many cars anymore, you will find them in industrial applications such as huge generators or large ships. Just look at the gigantic ship The Ever Give, which is powered by a 79,500 hp diesel engine that is bigger than most houses. And you guessed it: it’s a two-stroke.

One of the main problems is that the design uses a mixture of oil and fuel for combustion. This creates quite a bit of dirty black smoke. A two-stroke engine might use a quart of oil every 600 miles, all of which would be released into the air as smoke.

Today, apart from a few specialized vehicles, most cars and trucks feature a four-stroke design because they can run without releasing as many harmful emissions into the air. In addition, they operate more efficiently, which improves fuel consumption and transport overhead costs. Unfortunately for fans of the iconic Screaming Jimmy, these modern four-stroke diesels lack that unique sonic signature. At least two-strokes have managed to live on elsewhere and have become the dominant performance engines in motorcycle racing.