Renault is introducing a 2.2 dCi engine, equipped with a new-generation particulate filter, which complies with the new Euro IV exhaust emission standards, which come into force from 2005, and require better performance of various engine components including exhaust after-treatment systems.
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The new filter/catalytic converter, a ‘periodic regeneration’ type, works without any additive and the automatic regeneration is controlled by the fuel injection computer.
During the second quarter of 2003, Renault will begin selling a version of its Vel Satis 2.2 dCi equipped with a particulate filter and complying with the Euro IV fiscal incentive requirements.
To achieve this level of exhaust emissions, major work has been carried out on the engine’s internal combustion (injectors, pistons) but also by increasing the size of the exhaust post-treatment components: catalytic converter, EGR (exhaust gas recirculation) system and particulate filter.
The new exhaust emission standards applicable to new-build vehicles in 2005 call for the halving of emissions of particulates and oxides of nitrogen (NOx).
Renault developed its particulate filter system in collaboration with Engelhard, Ibiden and Eberspaecher. It consists of a structure which incorporates channels, laid out in such a way as to force the exhaust gas to pass over its surfaces. This substrate of porous material, made of silicon carbide, is covered with a catalytic coating. Sensors which check the temperature and the pressure within the particulate filter inform the fuel injection computer which controls the regeneration of the filter and is also responsible for self-diagnosis of the system.
A new catalytic converter and EGR bypass intercooling are the other components which contribute to meeting the new standard.
The particulate filter is installed in the exhaust run beneath the vehicle, in the place normally occupied by the catalytic converter.
The filter works on a two-phase principle. The first phase is trapping as the filter fills up with particulates.
The second phase, regeneration, involves the periodic burning-off, every 300 to 500km (200-300 miles) according to the way in which the vehicle is used, of the particulates which have accumulated in the filter. In the presence of oxygen, the regeneration through combustion of the particulates takes place naturally whenever the temperature of the exhaust gas exceeds 570°. The fuel injection computer, by altering the injection schedule, brings about this increase in temperature.
The oxidation catalyst, now of greater volume, is installed immediately downstream of the turbocharger exhaust. Its warm-up is faster and its larger size improves its efficiency.
The EGR system reduces NOx emissions from diesel engines. Controlled by the fuel injection computer, EGR recycles part of the exhaust gas back into the inlet manifold. Mixed with fresh incoming air, it improves combustion within the engine and reduces the formation of NOx.
