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The small two-stroke engine represents a strategic typology of propulsion system for applications in which lightweight and high power density are required. However, the conventional two-stroke engine will not be compliant with forthcoming legislations about pollutant emissions and new solutions, such as electrification, are seriously taken into account by industry to overcome the two-stroke engine drawbacks. In this scenario, a promising way to allow the two-stroke engine to be competitive is represented by the use of direct injection systems, in order to overcome the long-standing issue of short circuiting fuel. The authors in previous studies developed a low-pressure direct injection (LPDI) system for a 300 cm3 two-stroke engine that was ensuring the same power output of the engine in carbureted configuration and raw pollutant emissions consistent with a four-stroke engine of similar performance.

High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical port timing combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor is the standard solution for small two-stroke engine equipment, due to the necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) on an existing 300 cm3 cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure.

High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical port timing combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor is the standard solution for small two-stroke engine equipment, due to the necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) on an existing 300 cm3 cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure.