This paper examines the cold-start-up events of spark and compression ignition engines in the context of transient operation and emissions control. When the temperatures of the oil, coolant and engine block are equal or close to the ambient temperature, start-up can be difficult to achieve without significant excess levels of exhaust emissions and fuel consumption. In general, the lower the ambient temperature, the more significant these problems are. The physical processes responsible for this phenomenon are briefly discussed. Excess emission factors from a pool of Euro 4 and Euro 5 petrol vehicles and three Euro 5 diesel vehicles are presented, as tested over the Urban Drive Cycle at 24 °C and at −7 °C. A full modal emissions analysis was also conducted at 24 °C and at −7 °C on one petrol vehicle and one diesel vehicle over the New European Drive Cycle. The most problematic emissions are identified for both engine types, and recommendations are made to legislators regarding cold-start emissions.

No abstract

No abstract

No abstract

No abstract

No abstract

On-board portable emissions measurement systems (PEMS) are part of the type approval, in-service conformity, and market surveillance aspects of the European exhaust emissions regulation. Currently, only solid particles >23 nm are counted, but Europe will introduce a lower limit of 10 nm. In this study, we evaluated a 10-nm prototype portable system comparing it with laboratory systems measuring diesel, gasoline, and CNG (compressed natural gas) vehicles with emission levels ranging from approximately 2 × 1010 to 2 × 1012 #/km. The results showed that the on-board system differed from the laboratory 10-nm system on average for the tested driving cycles by less than approximately 10% at levels below 6 × 1011 #/km and by approximately 20% for high-emitting vehicles. The observed differences were similar to those observed in the evaluation of portable >23 nm particle counting systems, despite the relatively small size of the emitted particles (with geometric mean diameters <42 nm) and the additional challenges associated with sub-23 nm measurements. The latter included the presence of semivolatile sub-23 nm particles, the elevated concentration levels during cold start, and also the formation of sub-23 nm artefacts from the elastomers that are used to connect the tailpipe to the measurement devices. The main conclusion of the study is that >10 nm on-board systems can be ready for introduction in future regulations.

No abstract