It found that NOx emissions were highly dependent on whether the car was tested on a two- or a four-wheel chassis dynamometer – in which only the front wheels or all four wheels are turning respectively.

The car met the 80 mg/km NOx limit when it ran the official NEDC test cycle on the two-wheel chassis dynamometer. But in NEDC testing in which the rear wheels turned as well, the car exceeded the NOx limit by a factor of 2 to 4. Three tests were conducted.

DUH states that “the measurement results show that the vehicle performs differently when the test is done in two-wheel or in four-wheel mode”. “The behaviour of the SCR installation seems to depend on the test mode because the NOx profiles in the two modes are different.”

Axel Friedrich, international transport consultant for DUH, adds: “I do not have a normal, technically plausible explanation for the emissions behaviour of the Opel.”

DUH also quotes a GM statement: “The software developed by GM does not have features that identify whether a car is in an emission test cycle.”

DUH has handed over the testing results to the responsible German authority, Kraftfahrt Bundesamt (KBA), with an urgent request to re-test the vehicle.

T&E’s Greg Archer commented: “It is good to see more testing is done so that the full iceberg can emerge rather than just the tip – the VW diesel NOx scandal.”

“As DUH says, there is no plausible technical explanation for a huge emissions gap that depends on whether two or all four wheels of a car are turning.”

“We deserve nothing less than a full explanation of anomalous testing results, across all brands, for NOx as well as CO2 and fuel consumption, for diesel as well as petrol engines, and not just cars but vans too.”

“Governments should leave no stone unturned in their on-going investigations into vehicle emissions fraud. Only determined politicians will get to the bottom of this AutoGate.”

Note to Editors:

SCR stands for Selective Catalytic Reduction, a technology to reduce NOx which works by injecting a urea solution known as AdBlue in the exhaust, which helps break NOx down into harmless nitrogen and oxygen.

Documents:

DUH press release (EN): High nitrogen oxide emissions in tests on an Opel Zafira Diesel

https://www.duh.de/uploads/media/PR_High_nitrogen_oxide_emissions_Opel_Zafira_Diesel_231015.pdf

DUH test report: NOx emission measurement of a passenger car Opel Zafira Diesel, Euro 6b on the roller dynamometer

https://www.duh.de/uploads/media/DUH_test_report_nox_231015.pdf

DUH chronological list of measurements: NOx – emissions on chassis dynamometer

https://www.duh.de/uploads/media/B431_DUH_List_of_measurements.pdf

For more information, contact:

Greg Archer

Clean vehicles manager,

Transport & Environment

greg.archer@transportenvironment.org