Under European regulations, a defeat device is described as "any element of design which senses temperature, vehicle speed, engine speed (RPM), transmission gear, manifold vacuum or any other parameter for the purpose of activating, modulating, delaying or deactivating the operation of any part of the emission control system, that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal vehicle operation and use."
To date, the VW Group has only confirmed that the software was used during emissions tests in the USA (a process called FTP75), where cars must achieve lower levels of NOx emissions than in Europe, and that around 11 million vehicles worldwide are fitted with the cheat software, including almost 1.2m in the UK.
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VW claims that the delay in establishing whether it also cheated European tests is a result of the scale and complexity of the EA189 engine production cycle. The single EA189 code incorporates three different cubic capacities and multiple power outputs - and the powerplant has also been paired with three different manual gearboxes and three specs of DSG dual-clutch transmissions. It was also fitted across four brands - VW, Audi, Seat and Skoda - and most cars were modified every model year.
The spokesman added: "Only EA189 engines show a significant difference between cycle test results and on-road results. Whether and how this software really interacts is part of internal and external investigations. We are working at full speed to implement technical measures to eliminate these deviations. That’s why these questions are based on speculation."
A VW spokesman has previously declined to speculate on how much effect the 'defeat device' could have had on NEDC results. In 2009 Europe’s NOx regulations were not as strict as those imposed in the USA, when legal limits were set at 70 milligrams/km, a drop of 90% compared to the limits that had previously been in place. That has led to suggestions affected cars would not have needed to activate the cheat software during European testing because it would not have been required to pass the tests. In 2009 the EU5 emissions limit for NOx was 180mg/km.
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