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.

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The influence of fatty acid methyl esters (FAME) and hydrotreated vegetable oil (HVO) diesel blends on the exhaust emissions from a passenger car was examined. The impact of FAME for the cold urban phase (UDC) was increased CO and HC emissions, probably due to blend physical properties promoting incomplete combustion. The HVO blend caused the lowest CO and HC emissions for the UDC. NOx emissions did not change significantly with the fuel used, however the UDC was characterized by lower NOx emission for FAME blends. Particle emissions were highest with standard diesel. Emissions of carbonyl compounds increased as fuel biodiesel content increased, especially during the UDC. HVO in diesel fuel decreased carbonyl emissions. Formaldehyde and acetaldehyde were the most abundant carbonyl compounds in the exhaust gas. Total particle-bound PAH emissions were variable, the emission of heavier PAHs increased with blend biodiesel content. The HVO blend increased emission of lighter PAHs. Nitro-PAHs were identified only during the UDC and not for all blends; the highest emissions were measured for pure diesel. The results showed that emission of nitro-PAHs may be decreased to a greater extent by using biodiesel than using a HVO blend.

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This paper summarises the 6th International Exhaust Emissions Symposium (IEES) held in June 2018 and attempts a synthesis of the main arguments of the event in the context of emission control and affiliated considerations relating to the environmental performance of vehicles. Among the drivers influencing vehicular powertrain development, the field of vehicular exhaust emissions is experiencing wide-ranging and rapid changes. New emission regulations such as Euro 6d and new test methods (RDE and WLTP) are the main challenges for the automotive industry caused by political, socioeconomic and technical factors. Air quality is very high on the political agenda, and pressure remains to limit and reduce greenhouse gas emissions from the road transport sector. In addition to limits becoming increasingly stringent, the list of parameters subject to legal limits is slowly expanding-and, most importantly, these limits must be met under a wide range of conditions. A range of strategies are available to overcome these difficulties, which was explored during the 6th International Exhaust Emissions Symposium (IEES) hosted at BOSMAL in June 2018. This paper reports and summarises the topics of the 6th IEES and attempts a synthesis on the current status of the field of IC engines, hybrid powertrains and electric vehicles and what the coming years may hold for the automotive and fuel industries and other allied fields.

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