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In order to asses the durability of DPF, a study has been performed in order to study the evolution of several taxis (Peugeot 607) and the performance of this after-treatment systems over 80,000 km mileage in hard urban driving conditions, which corresponds to the recommended mileage before the first DPF maintenance (this periodicity is applied on the first generation of DPF technology launched in 2000). More specifically, the following evaluations are being performed at regular intervals (around 20 000 km): Regulated gaseous pollutant emissions on NEDC cycle (New European Driving Cycle) Particulate emissions, by mass measurement on NEDC but also by particle number and size measurement with SMPS (Scanning Mobility Particle Sizer) technique on NEDC and on unconventional steady-state running points.

The use of Diesel engines has strongly increased during the last years and now represents 30% of the sales in Europe and up to 50% of the number of cars in circulation for some countries. This success is linked not only to the economical aspect of the use of such vehicles, but also to the recent technological improvements of these engines. The new technical solutions (high pressure direct injection, turbocharging…) have indeed allowed the increase of these engine performances while decreasing their fuel consumption, pollutant emissions and noise level. From an environmental point of view, Diesel engines are nevertheless penalized by their particulate and NOx emissions. The study and the treatment of the particulate, highly criticized for their potential impact on health, are the subject of numerous works of characterization and developments. PSA Peugeot-Citroën has recently launched its particulate filter technology on several types of vehicles.

New combustion processes like LTC (Low Temperature Combustion) that includes HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), PPCI (Partial Premixed Compression Ignition)… are promising ways to reduce simultaneously NOx and PM. Nevertheless, these combustion processes can be used only on a limited part of the engine load and speed map. Therefore, it appeared interesting to assess how the fuel, through its characteristics, could enhance the operating range in such combustion processes. That was the aim of an international consortium carried out by IFP and supported by numerous industrial companies. First a specific procedure has been developed to compare the different fuels on a early injection HCCI single cylinder engine. Then, using this procedure, a matrix of fuels having different cetane numbers (CN = 40-63), volatilities and chemical compositions has been tested.

Faced with the need to reduce greenhouse gas emissions, diesel engines present the advantage of having low CO₂ emission levels compared to spark-ignited engines. Nevertheless, diesel engines still suffer from the fact that they emit pollutants and, particularly nitrogen oxides (NOx) and particulates (PM). One of the most promising ways to meet this challenge is to reduce the compression ratio (CR). However a current limitation in reducing the diesel CR is cold start requirements. In this context, the fuel characteristics such as the cetane number, which represents ignition, and volatility could impact cold start. That is why a matrix of 8 fuels was tested. The cetane number ranges from 47.3 to 70.9 and the volatility, represented by the temperature necessary to distillate 5% of the product (T5%), ranges from 173 to 198°C. The engine tests were carried out at -25°C, on a common rail 4-cylinder diesel engine.