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During the late 1980’s and early 1990’s the two-stroke-cycle engine was an extremely popular and highly publicized automotive powertrain technology globally. Active development programs existed at many OEMs during that period, including GM, where the author was involved, and production seemed eminent. Autoweek stated on the cover of its March 12, 1990 issue, “Revolution for the millennium or Wankel of the ‘90s?” This paper covers the new technologies that led to the generation of so much excitement in the industry and press, the advantages and disadvantages of the engine concept, R&D tools developed at that time that are still in use today, and various engine concepts pursued in the industry. The story is not only interesting from engineering and technology perspectives but illustrates how innovations in certain subsystems become enablers to revive a system technology by eliminating issues that prevented it from making it to production in the past.

Spark-ignition direct-injection technology existed since about 1930 for the primary purpose to give multifuel capability over what the compression-ignited diesel engine could provide. In subsequent decades development of multifuel engines continued both as higher-compression-ratio “spark-ignited diesel” and moderate-compressionratio stratified-charge engines. Global events in the 1960-1970’s, namely the oil embargo, oil-supply crises, and the passage of the U.S. Clean Air Act intensified interest in such engines. The military and large commercial fleet operators were particularly focused on efficiency and multifuel capability over concerns for fuel supplies. Automobile manufacturers were focused on gasoline-fueled efficiency and the potential to reduce engine-out legislated NOx emissions with the stratified-charged combustion systems.