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The European emission legislation for two-wheeler vehicles driven by engines of ≤ 50 cm₃ is continuously developing. One of the most important issues in the near future will be the finalization of the European Commission's proposals for future steps in the emissions regulations as well as the verification of the impacts of current standards on the market. To have a basis for the discussion about these topics, the Association for Emissions Control by Catalyst (AECC) with the Institute for Internal Combustion Engines and Thermodynamics of Graz University of Technology (IVT) carried out an extensive test program to show the actual emission situation of state-of-the-art mopeds including mass and number of particulate matter as well as unregulated gaseous components. One of the main goals of these tests was to measure exhaust emissions without any modifications to the engines of standard production vehicles available on the European market.

Looking at upcoming emission legislations for two-wheelers, it is quite obvious that the fulfilment of these targets will become one of the biggest challenges within the engine development process. The gradual harmonization of emission limits for two-wheelers with existing automotive standards will subsequently lead to new approaches regarding mixture preparation and exhaust gas aftertreatment. Referring to these future scenarios, a state-of-the-art in development of catalytic converters for two- or three-wheeler applications should be presented. After choosing a suitable test carrier, which has already been equipped with EFI components including an oxygen sensor for λ=1 operation mode, a basic injection system calibration was used to optimize the combustion process. Based on this setup, a variable exhaust system was manufactured to be able to integrate different catalyst configurations.

More and more stringent emission legislation is implemented in the world wide market of motorcycles leading to higher product costs. But not every market is ready for high technological levels. Therefore the main topic of interest is: “Will a small one cylinder motorbike engine need an electronic device for fuel metering or is it possible to use standard carburetors in combination with some smart but simple ideas, to fulfil EU III cold start emission regulations?” The described ideas deal with a novel secondary air supply, an improved cooling system and simple NOx reduction methods, always paying attention to the performance and driveability of the vehicle. After describing the prototype design of the engine modifications, the achievable results with their pros and cons are discussed. Online recorder measurements give interesting emission plots of HC, CO and NOx. The homologation measurement results point out the obtainable values of the limited emissions.