Use of a PPS sensor in evaluating the impact of fuel efficiency improvement technologies on the particle emissions of a euro 5 diesel car

The effect of "Start & Stop" and "Gear Shift Indicator" - two widespread fuel saving technologies - on fuel consumption and particle emissions of a Euro 5 passenger car is evaluated in this paper. The vehicle was subjected to a series of different driving cycles, including the current (NEDC) and future (WLTC) cycles implemented in the European type approval procedure at cold and hot start condition and particle number was measured with an AVL Particle Counter. In addition, we have utilized two Pegasor Particle Sensor units positioned in different locations along the sampling line to assess the impact of the sampling location on the particle characteristics measured during highly transient events. The results showed that the particle number emission levels over the WLTC were comparable to the NEDC ones, whereas NO_x emissions were more than twofold higher. Both fuel saving technologies can lead to reduced fuel consumption and, subsequently CO ₂ emissions, in the order of 5%. However, their impact on particle emissions was not straightforward, as the impact of the DPF loading was found much more significant than the effect of these technologies. However, in several occasions, the frequent start and stops of the engine actually led to an increase in particle emissions over the baseline. On the other hand, the reduced engine speed imposed when the gear shift indicator was respected generally led to lower particle emissions. Transient impacts on particle emissions such as those resulted by the fuel saving technologies studied can be much better monitored with raw exhaust sampling than following the type approval sampling procedure. This recommendation tends to be forgotten in regular research works.