Euro 6 is reducing NOx, but diesels still underperforming
While homologation testing takes place in a laboratory, Emissions Analytics uses a Portable Emissions Measuring System (PEMS), which analyses the content of the exhaust gases over a standardised on-road route.
Euro 6 set much stricter limits for nitrogen oxides (NOx) emissions from diesel vehicles, from 0.18g/km to 0.08g/km, but did not move the limit for petrols, which is 0.06g/km. NOx has been proven to cause respiratory problems in humans.
Emissions Analytics said the systems used to meet Euro 6, most commonly selective catalytic reduction (using a urea-based solution) or lean NOx trap after-treatment technology, was proving effective. Four vehicles have already met the 0.08g/km limit during the on-road testing, whereas only one of the Euro 5 compliant vehicles met the 0.18g/km limit during PEMS testing.
The average NOx emissions for Euro 6 vehicles is still high, at 0.340g/km – more than four times the limit, but a 54% reduction on the 0.736g/km averaged by Euro 5 models. Emissions Analytics added that the issue was much less for petrol vehicles, which are on average 24% below the 0.06g/km limit, but 22% did not meet this requirement.
Emissions Analytics recently launched an online database of its results on its website, aimed at helping the industry and businesses to get a clear picture of real-world exhaust content. This will be updated in real-time as new results are gathered.