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The attention on emissions of two-wheelers has been poor in the past, but today in countries with a large two-wheeler population it gives a significant contribution to aggregate emissions. In this paper the results obtained on a fleet composed by 22 two-stroke motorcycles (including mopeds) are presented. Sixteen in-use mopeds and six 125 cm3 motorcycles have been tested over ECE 47 and ECE 40 driving cycles respectively. Regulated emissions (CO, HC, NOx), carbon dioxide, benzene and fuel consumption have been evaluated by fueling motorcycles with two different gasoline formulations. One gasoline was a commercial Italian leaded gasoline with 1% benzene content; the other was a lower benzene and aromatics content gasoline. Benzene emissions decreased according to benzene content of gasoline.

Within EPEFE the relationship between exhaust emissions of five 1996 heavy duty engines including advanced technologies and an eleven diesel fuel matrix has been investigated. The fuel matrix was designed to study the effects of decorrelated fuel properties (density, polyaromatics, cetane number, back-end volatility (T95)). The main programme consisted of engine testing on the 88/77 EEC test cycle at standard engine settings. The findings were quantified using regression equations and showed, that fuel effects varied in both magnitude and direction between the four emission components. Individual engines had different emission levels and responded differently to fuel properties, due to engine technology. Additional tests were conducted with selected fuels at adjusted engine settings and timing. The observed density effect on emissions can be compensated for and fully explained by physical interactions with the injection system.