After the “Dieselgate” Volkswagen, “Renaultgate”? that is not there. It does not prevent. The Directorate-general for competition, consumption and repression of fraud (DGCCRF) has indeed transmitted to the public prosecutor of Nanterre, the findings of its investigation on diesel Renault. This is what has been announced Michel Sapin, the minister of the Economy Wednesday night. Renault could, therefore, have to answer before the justice of irregularities in the clean-up of its diesel engines. Of course, the investigation does not relate to the firm’s habs. The impact for the image of the builder of Boulogne-Billancourt, do not risk less to be devastating. Even if Renault has reaffirmed it a s soon as it “complies with the French legislation and european”.
The bare minimum
so What is the problem that is worth so much a reproach to Renault? In fact, like Opel, Fiat or Mercedes on some of its models, Renault is happy with the bare minimum in terms of clean-up, while respecting the letter of the texts of regulations (Euro 6). But, at the same time, the manufacturer plays on the grey area of the text, engaging in practices deemed to be misleading, as the “window heat”. what is It? This window thermal is simply curbing as a function of temperature and of the hygrometry of the air efficiency filters that trap the NOx (oxides of nitrogen), including the dangerous nitrogen oxides (NO2), which attack the respiratory tract. It is precisely this that blamed the French car maker to the Royal Commission, which built on the preliminary findings of the tests of the UTAC CERAM performed in real conditions of traffic.
Gaspar Gascon Abellan, head of engineering at Renault, pointed out that the NOx trap system is an inseparable part of the EGR (for Exhaust Gas Recirculation). This circuit lowers the combustion temperature by re-injecting the exhaust gas into the engine. simply. Yes, but here it is: “alone, the EGR reduces the source of 85% of NOx. But, when the ambient air is too cold or too hot or too wet, there is a phenomenon of opening of the soot deposits that seal off and block the EGR valve”, explains the specialist Renault. “sometimes serious consequences on the longevity of the engine.”
Setup of the driver software
To prevent this, Renault has logically set up the pilot software, in order to limit the rate of recirculation of exhaust gas when the air is out of the range of temperatures defined (between 17 and 35 degrees). But the catch is that, in western Europe and particularly in France, it is rarely to 17 degrees, and this, for several months. The system does simply not during a good part of the year. Unfortunate. It is the ambiguity ! But this is not a fraud, per se. Because the legislature has provided an exemption clause in the eu regulation 715/2007. This text does state “the use of defeat devices that reduce the effectiveness of emissions control systems,” but provides that “this prohibition does not apply when the need for the device is justified in terms of protecting the engine.”
window is minimized, the stronger are obviously the emissions of NOx in real world conditions of driving. Renault, but also Fiat, Opel and Mercedes are hiding behind the need for this. They simply need to demonstrate that their diesel engines could not withstand the operation full-time of these remediation systems to ensure that they are allowed to reduce the effectiveness of a temporary basis. And the turn is played, legally and transparently…. At least in the face of the authorities, if not to the public.
Another problem: the optimization of the adjustment of the diesel engine for the cold start. Here, too, the majority of manufacturers are satisfied with the bare minimum and see that the engine is never started hot during the cycle standardized certification test. So, it treats the emissions during the cycle, even at the sacrifice outside. However, T&E finds precisely that, if the emissions are compliant to the standard motor cold, it will explode when it is started up to hot…
PSA is a lot much better
Then, squaring the circle? No. Because there are overall two processing pathways of NOx. The NOx trap as at Renault, discusses intermittently pollutants through a filter to build, with all the disadvantages resulting therefrom. Not very effective. There is another solution. It is the continuous processing, a lot more sophisticated, through a catalyst for selective reduction (so called SCR in English). But this solution remains far and away the most expensive, a few hundred euros. Therefore, it is understandable that Renault, which sells mostly cars, entry-not (too) expensive, has chosen a system that is less expensive.
PSA is doing a lot better in all the tests, because he has rightly decided to equip its latest Blue-HDi of the famous SCR system,, which is reduced by chemical reaction of the nitrogen oxides directly into the exhaust. A process that dépollue much better, over a wider range. Being a pioneer, PSA has already been extended to its range. A wise choice. But most difficult for the motorist. Because it requires an injection of’“Ad Blue”, a liquid containing 75% urea which converts the oxides of nitrogen… nitrogen and water, harmless. For an additional tank (17 litres at PSA), to fill in regularly.
Renault has he made the wrong choice ten years ago? Yes in terms of actual effectiveness. No, because, for less, the NOx trap is enough to pass the famous certification test in force. Gaspar Gascon Abellan confirms, however, that the next generation of diesel engines of Renault will benefit from the SCR. This will be needed to pass future Euro standards 6.2, which will come into force in a year. And this, as much as the cycles of probate of europe will be then be cured to better adhere to actual usage on the road.