The Institute for Internal Combustion Engines and Thermodynamics, Graz University of Technology, has presented several applications of its 2-stroke LPDI (low pressure direct injection) technology in the previous years ([1], [2], [3]). In order to improve the competitiveness of the 2-stroke LPDI technology, an air cooled 50cm3 scooter application has been developed.
All previous applications have been liquid cooled. This air cooled application demonstrates the EURO 4 (2017) ability of the technology and shows that the 2S-LPDI technology can also be applied to low cost air-cooled engines. Hence, the complete scooter and moped fleet can be equipped with this technology in order to fulfil both the emission standards and the COP (conformity of production) requirements of Euro 4 emission stage. The paper presents the Euro 4 Scooter results and describes the efficient conversion process of the existing carburetor engine to the LPDI version. Euro 4 results can be achieved with conventional exhaust system architecture known from the present Euro 2 applications. Costs can be even reduced by omitting the secondary air system and choosing a cheaper catalyst - 100 cpsi instead of 200 cpsi. Therewith the costs for the basic engine (hardware) are on the same level as or even lower than for actual Euro 2 engines. A special engine development is NOT required, which leads to a simple modification of existing models.
To be able to apply the LPDI technology to air cooled engines, a special heat protection for the fuel injector, located in the cylinder, has been developed. This solution allows stabilizing the temperature of the fuel injector tip below 100°C and therefore it lies below the component limit of 125°C.