DUH charges Zafira diesel emits up to 17x more NOx than permitted under certain conditions; Opel rebuts with its own testing
German environmental NGO Deutsche Umwelthilfe (DUH) (earlier post) has charged that an Opel Zafira 1.6 CDTi diesel (Euro 6b) emits up to 17 times more NOx under certain driving situations than permitted by the Euro 6 limit value. Dynamometer testing for DUH was conducted at the Bern University of Applied Sciences (Berner Fachhochschule).
In three tests under the NEDC cycle with rotating rear wheels, the Zafira emitted between 2 to 4 times more NOx than allowed, according to the test report released by DUH. In three additional tests under normal test conditions—and thus with non-rotating rear wheels—however, the NOx values were below the legal value limit of 80 mg/km in each case.
|Select raw NEDC test results. Source: DUH. Click to enlarge.|
The testers also observed that, with non-rotating rear wheels and with a continuous increase in the speed to 150 km/h (93 mph), NOx emissions increased abruptly and exceeded the measuring scale of the analysis instrument. The report suggested that such behavior could be explained by a shutdown of the AdBlue (urea) dosing unit. Similar behavior was not detectable when operated in the 4-wheel drive mode.
The measurement results show that the vehicle behaves differently when the dynamometer is operated in the 4- or 2-wheel drive mode. The measurements carried out show the following trend: The NOx emissions in the NEDC cycle depend on the test mode of 2WD/4WD. In the 2-wheel drive mode the vehicle met the NOx regulations. At low speeds, NOx emissions are not always identical, and are likely to depend on the activity or the storage effect of the SCR system. The behavior of the SCR system seems to be dependent on the test mode, since the NOx trends are different in the two test stand modes of operation.—Berner Fachhochschule
DUH has submitted the report to Germany’s KBA (Kraftfahrt-Bundesamt), Germany’s Federal Motor Transport Authority.
Opel response. In response, Opel “sharply” (scharf) rejected the DUH charges, asserting again that GM developed software has no features that detect whether the vehicle is undergoing an exhaust emissions test.
The results of the alleged Zafira test conducted by the German Environmental Relief (DUH) are not comprehendible. It is not fair that the German Environmental Relief makes assertions but did not disclose the alleged results, despite us asking for them on multiple occasions.—Opel statement
Opel engineers put a corresponding vehicle (a Zafira with a 1.6-liter Euro 6 diesel engine) on the test bench in the presence of TÜV Hessen and conducted and protocoled additional tests in accordance with the regulations both on a two-roller and a four-roller test bench. These results showed compliance with the legal limits both for testing on two-wheel or four-wheel setups.
This is the only result to be expected, as it has no influence on the emission systems whether or not the rear wheels are in motion. This means: The allegations are clearly false and unfounded.—Opel statement