Nothing new about defeat devices

Revelations in mid-September 2015 that Volkswagen had installed software on almost 500,000 diesel engines designed to produce different results during emissions tests conducted by the US Environmental Protection Agency (EPA) than in real life applications has seen the OEM rapidly spiral into probably the greatest crisis in the company's history. On 22 September, the OEM then admitted that the same engine management software was used on 11 million engines worldwide.

The discrepancy between the stated and real life emissions lies in the cars' emissions of oxides of nitrogen (NOx), which were found to be 10 to 40 times higher in real life than in test conditions. The discrepancy was caused by a so-called defeat device, software that recognises that the vehicle is being tested and activates specific emissions controls. Once the tests have been completed, the software recognises that the test is over and deactivates the emissions restrictions, enabling the engine to deliver more torque and therefore more speed than when the restrictions were active.