An Historical Overview of Stratified Scavenged Two-Stroke Engines - 1901 through 2003

The Two stroke engines have been around for more than a century and have survived so far, primarily in portable applications. From the beginning, two-stroke engines have suffered from poor fuel economy and high fuel emissions compared to the larger, heavier, but more efficient four stroke designs. Over the last 100 years many innovative ideas have been designed and patented with the intent of improving these two critical shortcomings. Stringent emission regulations introduced in the last two decades have now provided an impetus to revive, revise, and apply technologies to meet these new requirements. With this in mind, many engineers and scientists throughout the world have researched stratified scavenging and injection to make low cost two-stroke engines that will compete with the four-stroke engines. An attempt has been made in this paper to chronologically present the evolution and implementation of stratified scavenging and injection applicable to small portable two-stroke engines. A brief overview of designs dated from 1901 through 2003 have been described with Figures.