Real world emissions tests gain consistency

Search for a reliable real-world emissions test protocol began in 2015

Published: September 9, 2017, 10:20 PM
Updated: September 13, 2017, 5:30 AM

Groupe PSA emisssions testing

car exhaust

With more and more companies caught in the diesel emissions-cheating scandal, the push is on to create reliable real-world testing, instead of the laboratory testing that is currently the norm.

The search for a reliable real-world emissions test protocol began in 2015, as first Volkswagen and then others such as Chrysler, Nissan and Renault, were found to include a program on their vehicle onboard computers that could sense when the vehicle was being tested on a dynamometer an switch on full emissions controls, but would then shut them off when the vehicle was back on the road in order to not impact the power delivery so desired by many drivers.

VW 3-litre TDI V-6

So, companies began to look at new emissions testing, preferably on real roads so that software wouldn’t be able to tell if the vehicle was being tested, and so that consumers would have a more realistic and attainable fuel economy rating on which to base their purchases.

The latest from Groupe PSA (Peugeot, Citroën, DS Automobiles, Opel and Vauxhall) and partners T&E, FNE and Bureau Veritas seems to be the best yet, with highly reproducible results and a margin of error of just 3% (up or down – a swing of six).

After performing some 430 tests on 60 vehicles, over 18 months, the group came up with a few observations about their tests. The average combined fuel economy of the more than 1,000 vehicles was just 5.8 L/100 km, which is itself more than 1.74 L/100km worse than the published ratings on new car window stickers.

Audi Q7 2008 diesel

The tests also found that the difference in economy between laboratory and real world was virtually equal for diesel (2.4 L/100 km higher) and gasoline (2.5) but when you consider the higher economy ratings for gasoline, the different as a percentage is much worse for diesel (53%) than it is for gasoline (42%)

“These real-driving tests show that it is perfectly possible to achieve CO2 emissions and fuel consumption figures almost identical to those obtained by drivers on the road,” said Greg Archer, Director of Clean Vehicles at Transport & Environment. “But real-driving tests are only part of the solution to the emission cheating scandal. The upcoming EU decisions on how and who approves cars for sale will be key to ensuring the system of testing and approving cars is independent and rigorously enforced.”

Testing also affirmed some long-held beliefs, such as that diesel vehicles are more fuel efficient than their gasoline counterparts (by 1.5 L/100 km, combined), that manual trasmissioned vehicles are more economical than their automatic kin (by just four tenths of a percent.)

“The protocol has proven to be extremely reliable for real-world fuel consumption tests,” concluded Philippe Lanternier, Executive Vice-President, Corporate and Business Development at Bureau Veritas. “We are confident this extensive experiment can be successfully replicated to effectively measuring NOx emissions. This new step will contribute to further increase the reliability of automotive tests and measurements.”