The environmental friendliness of modern diesel engines is greatly overratedJanuary 28, 2020
Automotive brands and trade associations insist that modern diesel engines on paper and in practice are currently very clean and thus can help reduce CO2 emissions.
However, problems and doubts about diesel emissions continue to arise. Not a week goes by without negative news. Previously, Volkswagen, due to which a diesel scandal with fraudulent software began in 2015, received a fine of about 135 million euros in Canada. A week earlier, the brand paid more than 28 million euros in Poland. In both cases, fines arose due to diesel engines.
Last Thursday, RDW announced that the Jeep Grand Cherokee and Suzuki Vitara should be checked by dealers to solve the problem of excessive emissions of nitric oxide (NOx). If this fails, RDW will begin the process of recalling the European OTTS.
However, car brands and trade associations insist that modern diesel engines, especially those that meet the latest European emission standard, are clean. This is confirmed by a recent study by the independent non-profit organization Transport & Environment, conducted by the British engineering company Ricardo, which revealed that the so-called particle filter in the exhaust system of diesel cars causes significantly more harmful particulate emissions during the cleaning process.
A diesel particulate filter (DPF) has been mandatory for diesel engines since 2013. Combined with increasingly stringent emission standards such as Euro 6d temperature, this has ensured that modern diesel engines that comply with this standard do indeed emit significantly less NOx. This applies both to laboratory conditions and to public roads. CO2 emissions from diesel engines were already lower than from gasoline cars.
The big “but”, however, is associated with the release of particulate matter (PM). The filter needs to be cleaned from time to time. This is regulated by the machine itself by burning PM by regeneration. According to the researchers, up to 1,848 times more particulate matter is released during this process, and ultimately, the legal limit of PM emissions per kilometer was exceeded between 32 and 115 percent during DPF regeneration. If you include the most harmful ultrafine particles (about 10 nanometers), then the emissions will be 11-184% higher.
With test cars, the Nissan Qashqai and Opel Astra, a cleaning process occurs approximately every 420 kilometers. During the test, cleaning was carried out at a distance of 15 kilometers, which becomes a risk if this process begins directly in the city. Particulate matter emissions also continued to increase during the first half hour after purification. Although PM emissions exceeded limits during DPF regeneration, total emissions remained within normal limits. NOx emissions, which also increased significantly during the refining process (an average of 133% for Nissan), also remained within the legal limit.
Analysts estimate that there are 1.3 billion cleaning sessions every year for 45 million diesel cars with such particle filters in the EU. The fact that these and other modern diesel cars have OTTS, despite the (temporary) excess of PM emissions, is due to a gap in globally agreed light-weight test procedures (WLTP). Many reports say that if DPF regeneration occurs during an emission test, then the emission standard does not need to be applied.
Given the test results and the sharp increase in PM emissions during the cleaning process, Transport & Environment recommends that policy makers do not mark temporary Euro6d diesel engines as “clean”. In addition, despite favorable NOx and CO2 emissions, such diesels should not be eligible for subsidies on purchase. Finally, no exceptions should be made for these vehicles in environmental zones.
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