A Swedish examination of Volkswagen’s diesel emissions fix has called into question claims the recalls do not compromise vehicle performance.
Teknikens Värld, a publication famous for its dramatic “moose test” dynamic assessment, tested 10 different vehicles pre and post-fix, finding most of them experienced a loss in engine output.
Its website says “it is clear to us that in many cases the driveability of the cars has worsened dramatically. It is not the same car as before the fix”.
Volkswagen’s Swedish arm said it was surprised by the result. Its Australian arm is on the record saying the recalls do not affect vehicle performance.
“In approving the update, the type approval authorities in Europe conducted a review and certified that following the update the fuel consumption figures and CO2 emissions originally listed by the manufacturer were confirmed,” Volkswagen Australia said.
“They further certified that previous engine performance, maximum torque and previous noise emissions remain unchanged.”
Owners of Volkswagen Group models affected by the diesel emissions scandal have been reluctant to commit to the recall in a range of markets including Australia, where less than a quarter of owners affected by the issue have submitted cars for software updates.
For 2.0-litre diesel engines, the recall involves nothing more than a software upgrade, while the smaller 1.6-litre units also receive a new filter for the air intake.
Teknikens Värld subjected 10 Volkswagen Group models from Volkswagen, Skoda and Audi to before-and-after tests examining power and torque levels along with fuel consumption.
Results were varied, with a few of the cars actually gaining power following the recall, though the increases were accompanied by additional fuel use.
Vehicles with the 1.6-litre engine performed best after the recall (and fitment of an airflow filter - which the 2.0 litre engine does not receive), but each still showed a reduction in torque.
Teknikens Värld says most of the tested vehicles lost both power and torque, while higher engine speeds were required to reach the peak torque figure.
Citing a Passat Alltrack (all-wheel-drive wagon) as an example, Teknikens Värld claimed the vehicle is now 9kW and 10Nm poorer following the recall, and that its fuel consumption increased by four per cent. Further, peak torque previously available between 1500-2300rpm now arrives at 1900rpm.
Teknikens Värld sent their test results to Professor Ingemar Denbratt of the Chalmers University of Technology.
“Based on the measurements it seems torque has been reduced at lower rpms,” Professor Denbratt said.
“There may be several reasons for this. The goal has been reducing CO2 emissions and to achieve that you can either increase exhaust gas recirculation (EGR) or postpone the time of injection or a combination of these. But to be certain as to what has been done more information is needed, such as a complete torque curve, fuel consumption, CO2 emissions and exhaust temperature records.”
More than 228,000 vehicles are on the diesel emissions recall list in Sweden, while in Australia, the number is around 80,000.