Cerlist Diesel

The other two-stroke

- Jim Allen

Four-stroke diesels have long been the norm. Two-strokes? Sure, we all remember the “Screamin’ Jimmys” of years past… sometimes even fondly... and those legendary Uniflow GM diesels pretty much define the American memory of the twostroke diesel. Few remember another twostroke diesel that mounted a challenge in the American market.

Europe embraced the diesel engine much earlier than North America. Because of high fuel taxes, Europeans demanded higher fuel economy and developed diesel technology for their commercial fleets and passenger cars. One of the more important figures in that process was Professor Doctor Hans List (1896-1996), an Austrian engineer, scientist and internal combustion engine theorist.

In 1948, Dr. List started the Institute for Combustion Engines in Graz, Austria, the Austrian acronym being “AVL.” They are still in business and responsible for many high-tech advances in combustion engine technology. In the early days, List was a proponent of loop scavenging, a method whereby the engine breathed through ports and didn’t have valves at all. The father of this idea was Adolph Schnuerle, who conceived it in 1926. Loop scavenged engines can be designed for any fuel and many of the best gasoline two-strokes are loop-scavenged. They are high revvers and were considered very efficient in their day because they don’t have the major internal frictional horsepower losses of an engine with a conventional valvetrain.