Vehicles of the booming class of 50 cm3 two stroke scooters typically need an oxidation catalyst to fulfill the actual emission regulations. In contrast to most other motorized road vehicles, however, their catalysts and exhaust emissions do not undergo durability requirements. Furthermore, the air to fuel ratio may easily be changed and is often tuned to rich to achieve good drivability. The hydrocarbon emissions of this vehicles class is becoming relevant compared to the decreasing emissions of passenger cars and, since most of these scooters are used in urban areas, contribute remarkably to local air quality problems. Out of this, six 50 cm3 two stroke scooters were tested during their first 1000 km. A test sequence, consisting of the legislative test, the urban part of the WMTC (World harmonized motor-cycle test cycle) and some constant velocities, was repeated several times during the first 1000 km. Even though the vehicles were loaded to bring them from the shop to the laboratory, thus no single kilometer was driven by the user before the first test, 4 of 6 vehicles failed the legislative test from the beginning! Another vehicle failed it after 40 km mileage. At several constant loads the catalyst efficiency was determined by comparing the pre- and after catalyst exhaust-gas concentrations. The efficiencies considering hydrocarbons vary in a wide range from 10 to 80 %. At high loadpoints some catalysts even show a negative CO efficiency, i.e. the CO concentration after the catalyst is higher than before. This seems to be caused by partly oxidizing hydrocarbons. The observed catalyst ageing over the first 1000 km is smaller than expected.
Catalyst behaviour and emissions of 50 ccm two stroke scooters over the first 1000 km
Katalysatorverhalten und Emissionen von 50 cm<sup>3</sup>-Zweitaktmotorrollern während der ersten 1000 km
incl. COST 346 - Final Conference, Transport and Air Pollution, International Symposium, 14 ; 164-169
2005
6 Seiten, 5 Bilder, 1 Tabelle, 8 Quellen
Aufsatz (Konferenz)
Englisch
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