New diesels emit almost no fumes
Shock as new test proves new diesel engines emit almost no NOx at allA new series of independent tests show that the modern fleet of diesel engines emits almost none of the poisonous Oxides of Nitrogen (NOx) that were at the heart of the Dieselgate scandal.
Diesel combustion has been the automotive whipping boy of Europe, with sales of new diesel cars dropping from more than half the market to less than a third since 2015 and several German cities ordering to ban older diesel engines, causing many brands to axe diesels altogether.
Yet it turns out car-makers were right when they insisted they could clean their diesel engines up, with premium manufacturers leading the way.
With exhaust gas recirculation (SCR) and urea injection, the Mercedes-Benz C 220d led the way in the independent tests, emitting no NOx at all during an on-road test.
While the C 220d emitted zero micrograms of NOx per kilometre, the BMW 520d proved the Benz figure was no fluke by emitting just 1mg/km on the same test.
The legal (Euro 6d Temp) limit for NOx emissions is 168mg/km, and it was the failure to meet this limit that lead the Volkswagen Group down the path to the Dieselgate scandal.
It also lead Daimler, Opel and PSA (Peugeot and Citroen) towards “thermal switches” to shut off their emissions cleaning at cold and hot temperatures.
Conducted by the German car club ADAC under RDE (real driving emissions) on public roads, the test involved 13 models including cars from Audi, Honda, Citroen, Kia, Opel, Peugeot, Volvo and Volkswagen.
The cleanest of the small cars was the Opel Astra, whose 1.6-litre four-cylinder turbo-diesel matched the BMW 520d by emitting just a single microgram of NOx per kilometre.
The Volkswagen Golf trailed not far behind, having come from the disgrace of Dieselgate and emitting thousands of times the legal limit to emitting just 14mg/km, or 12 times less than it’s allowed to.
Some of the cars tested emitted lower levels of NOx than equivalent petrol-powered models, which came as a shock to ADAC.
A Bosch study early last year showed that on-road NOx emissions could be slashed to well below the legal level, but that was met with skepticism, given that the world’s biggest automotive supplier was at the heart of the Dieselgate scandal.
NOx is a classified poison; with the World Health Organisation insisting it is involved in deaths from heart disease, dementia, asthma, lung disease and many others.
Even the worst of the ADAC-tested cars, the Honda Civic 1.6-DTEC, easily slid beneath the accepted legal limit, but will fail the next limit without major technical improvements.
It clocked 101mg/km, and the failure of its diesels in Europe has been cited as one of the key reasons for Honda closing its Swindon factory in England.
Even so, the Civic’s test result was almost double the next worst emitter, the Volvo XC60 D5 AWD with 56mg/km.The official RDE limit is 80mg/km for diesels (but 60mg/km for petrol-powered cars).
Honda’s Civic only passes it because, for now, the European Commission (EC) gave car-makers an allowance of 2.1 times the limit to account for “test equipment inaccuracies”. At least, that’s what the loophole says.
The issue for Honda, and others with older generation diesel engines, is that the allowance drops to 1.5 times from the start of next year, which will effectively lower the limit to 120mg/km.
Even that may not be the end of the emissions story, because the European Court of Justice ruled the EC weren’t allowed to deliver the leeway and that the 80mg/km official limit should be enforced even today.
Some of the standout figures in the ADAC test came from car-makers who were slammed for thermal switching, including Citroen, Peugeot, Opel and Mercedes-Benz.
One of the more impressive performances in the test was from Audi’s A8 50 TDI. Not only is the A8 far bigger and heavier than any other car on the test, but also it was the only car to have an engine with more than four cylinders. The biturbo V6 TDI posted just 15mg/km of NOx.
NOx emissions (mg/km)
Audi A8 50 TDI 15
BMW 520d Steptronic 5
BMW 520d Touring 1
BMW X2 xDrive 20d 23
Citroen Berlingo BlueHDI 130 7
Honda Civic 1.6-DTEC 101
Kia Ceed 1.6 CRDi 22
Mercedes-Benz A 180 d 40
Mercedes-Benz C 220 d 0
Opel Astra 1.6 D 1
Peugeot 308 SW BlueHDI 180 30
Volvo XC60 D5 AWD 56
Volkswagen Golf TDI SCR 14
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