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.

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.

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 10 nm on-board systems can be ready for introduction in future regulations.

Vehicular ammonia emissions are currently unregulated, even though ammonia is harmful for a variety of reasons, and the gas is classed as toxic. Ammonia emissions represent a serious threat to air quality, particularly in urban settings; an ammonia emissions limit may be introduced in future legislation. Production of ammonia within the cylinder has long been known to be very limited. However, having reached its light-off temperature, a three-way catalyst can produce substantial quantities of ammonia through various reaction pathways. Production of ammonia is symptomatic of overly reducing conditions within the three-way catalyst (TWC), and depends somewhat upon the particular precious metals used. Emission is markedly higher during periods where demand for engine power is higher, when the engine will be operating under open-loop conditions. The air-to-fuel ratio, cylinder temperature and rate of availability of carbon monoxide and nitrogen monoxide all correlate to varying degrees with ammonia production. In addition to a literature review, this study presents ammonia emissions data from three European passenger cars, using three different fuels, with varying physicochemical characteristics and carbon:hydrogen ratios, namely gasoline, LPG and CNG. All vehicles were tested on BOSMAL's chassis dynamometer over the New European Driving Cycle, with undiluted ammonia quantified directly at tailpipe. Both cycle mean emission factors and second-by-second data are presented. The results indicate a degree of correlation between ammonia emission and demand for engine power, for example upon commencing acceleration and following gear shifts. Emission over the entire driving cycle was found to vary depending on the fuel used, and between the three vehicles used in this study. One vehicle emitted 93 % more ammonia when operating on gasoline than on CNG; the other vehicle emitted 2 % more ammonia when running on LPG than on gasoline. A simple numerical correction implied that the lower carbon:hydrogen ratio was at least partially responsible for the minimal ammonia emissions observed when running on this fuel.