Motors: Watchdog labels emission tests faulty

The entire basis upon which our cars are tested and evaluated for emissions and fuel consumption has been called into question in the wake of the VW diesel scandal which broke last September.

The official tests, conducted in a laboratory so as to be repeatable across all models, have come under fire for being out of date, far from rigorous and unrepresentative of what happens in real cars on real roads.

Now, the International Council on Clean Transport (ICCT), one of the groups that first helped to unearth the VW cheating scandal, has come to a new and worrying conclusion – the data being used to set up the lab tests is wrong.

According to Dr Peter Mock, managing director of ICCT Europe, "about one-third of the widening gap between official and actual fuel consumption and CO2 emissions from European passenger vehicles stems from manufacturers systematically exploiting deficiencies in the rules governing preparatory tests. The study focused on the tests used to measure forces of inertia, friction, and aerodynamic resistance affecting a vehicle on the road. Collectively these forces are referred to as "road load". The tests, during which a vehicle is driven and then coasted  on a track, determine parameters required to set up a chassis dynamometer to simulate road load during a type-approval test. The road load coefficients greatly influence the official fuel consumption and CO2 emissions values. If the coefficients used to set up the type-approval test simulate too little road load, the vehicle will consume an artificially low volume of fuel for the test, and emit less CO2."

Road load

According to Dr Mock, the ICCT’s data has revealed that the “road load” in tests is being underestimated. Across 19 different car models whose data was checked against real-world readings, the under-estimation of the load varied from 0.7 per cent to 14.5 per cent, or an average of 7.2 per cent in the 19 vehicles tested.

“That figure explains one-third of the average gap between official and real-world CO2 values for new cars,” claims Dr Mock. “By contrast, the average impact on emissions and fuel consumption of differences between the official US road-load coefficients and the real-world data was only 1.8 per cent.

The study spotlights an important difference in the transparency of the EU and US regulations. While data is publicly available in the US, it is considered confidential business information in the EU. This makes it nearly impossible for independent parties to cross-check the official road load parameters of a vehicle.

“It also spotlights deficiencies in current EU vehicle testing procedures that should be remedied. The introduction of the worldwide harmonised light vehicles test procedure (WLTP) in 2017 should provide an improvement in this respect. But it is crucial to also providently regular compliance tests, subsequent to type-approvals and carried out by the authorities, in order to ensure the reliability of information on fuel consumption and emissions of new vehicles in the future.”

The further erosion of the veracity of official testing figures is causing car makers to scramble to catch up with public perception.

Ford has announced a new line-up of 2.0-litre and 1.5-litre diesel engines which will feature Selective Catalytic Reduction (SCR) technology, more commonly known as AdBlue urea injection. By squirting a solution of urea into the exhaust, emissions of nitrogen oxides can be slashed by as much as 90 per cent, and Ford has said that it will start rolling out the technology to replace its current Lean NoX Trap (LNT) technology, starting with its 2.0-litre models.

On-road tests

Meanwhile,

Peugeot

has issued another result in its ongoing “real world” economy testing, being carried out in conjunction with environmental pressure group Transport &

Environment

. The French car maker (along with its sister brands

Citroen

and DS) has begun a regime of on-road testing to estimate fuel economy and has just released the figures for the updated 2008 crossover.

By using a 96km course, made up of motorway, urban and country roads, and what Peugeot calls “a selection of professional and amateur drivers, not directly employed by Peugeot, to ensure the results are as accurate as possible”, it has estimated that both the 100hp and 120hp versions of the 2008 1.6 BlueHDI diesel model will return 54mpg (5.2-litres per 100km) on the road, as opposed to the official test result of 76mpg, or 3.7-litres per 100km.

Interestingly, the petrol versions of the 2008, using the new 1.2-litre PureTech unit, got closer in the real world to their claimed figures than did the diesels.

The 130hp version scored 39.8mpg as against 59mpg in the lab (7.0l/100km versus 4.8l/100km in the lab), which is in line with the diesels, but the lowly 82hp version recorded 44.8mpg on the road against 58mpg in the lab (6.3l/100km against 4.9l/100km) which is around the half the difference of the other models.