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With the introduction of gasoline particulate filters (GPFs), the particle number (PN) emissions of gasoline direct-injection (GDI) vehicles are below the European regulatory limit of 6 × 1011 p/km under certification conditions. Nevertheless, concerns have been raised regarding emission levels at the boundaries of ambient and driving conditions of the real-driving emissions (RDE) regulation. A Euro 6d-Temp GDI vehicle with a GPF was tested on the road and in the laboratory with cycles simulating congested urban traffic, dynamic driving, and towing a trailer uphill at 85% of maximum payload. The ambient temperatures covered a range from −30 to 50 °C. The solid PN emissions were 10 times lower than the PN limit under most conditions and temperatures. Only dynamic driving that regenerated the filter passively, and for the next cycle resulted in relatively high emissions although they were still below the limit. The results of this study confirmed the effectiveness of GPFs in controlling PN emissions under a wide range of conditions.

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<div class="section abstract"><div class="htmlview paragraph">The implementation of emission standards has brought significant reductions in vehicle emissions in the EU, but road transport is still a major source of air pollution. Future emission standards will aim at making road vehicles as clean as possible under a wide range of driving conditions and throughout their complete lifetime. The current paper presents the methodology followed by the Consortium for ultra LOw Vehicle Emissions (CLOVE) to support the preparation of the Euro 7 proposal.</div><div class="htmlview paragraph">As a first step, the emission performance of the latest-technology vehicles under various driving conditions was evaluated. Towards this direction, an emissions database was developed, containing data from a wide range of tests, both within and beyond the current RDE boundaries. The results revealed that harsh accelerations, extreme ambient temperatures, very short trips (particularly at urban conditions), DPF regeneration and uphill driving, or combination of those conditions, can result to high emissions. Next, suitable technology packages to address such high emissions were defined and evaluated, using simulation models. On top of this analysis, additional elements were assessed, namely on-board emissions monitoring, additional species to be regulated and instrumentation for future on-road emission testing.</div><div class="htmlview paragraph">The overall analysis revealed that existing state-of-the-art emission control technologies can achieve very low emission levels, but not under all driving conditions. Thus, additional improvements and potential new technologies are needed to bring ultra-low emissions. These technologies include larger exhaust aftertreatment devices, optimized engine and aftertreatment thermal management (mainly during cold-start) and further penetration of electrification. Particularly the latter is heavily enforced by the CO₂-related measures and can strongly support the limitation of pollutant emissions, as well.</div></div>

Gaseous emissions of modern Euro 6d vehicles, when tested within real driving emissions (RDE) boundaries, are, in most cases, at low levels. There are concerns, though, about their emission performance when tested at or above the boundaries of ambient and driving conditions requirements of RDE regulations. In this study, a Euro 6d-Temp gasoline direct injection (GDI) vehicle with three-way catalyst and gasoline particulate filter was tested on the road and in a laboratory at temperatures ranging between −30 °C and 50 °C, with cycles simulating urban congested traffic, uphill driving while towing a trailer at 85% of the vehicle’s maximum payload, and dynamic driving. The vehicle respected the Euro 6 emission limits, even though they were not applicable to the specific cycles, which were outside of the RDE environmental and trip boundary conditions. Most of the emissions were produced during cold starts and at low ambient temperatures. Heavy traffic, dynamic driving, and high payload were found to increase emissions depending on the pollutant. Even though this car was one of the lowest emitting cars found in the literature, the proposed future Euro 7 limits will require a further decrease in cold start emissions in order to ensure low emission levels under most ambient and driving conditions, particularly in urban environments. Nevertheless, motorway emissions will also have to be controlled well.

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