(the cover of West Virginia University final report)

 The VW's emissions scandal is casting dark clouds over the future of diesel engines. The nitrogen oxides  (NOx) problem, i.e., the problem known as off-cycle NOx emissions, which was smoldering in Europe, home of diesel engines, has caught fire in the United States.

 In general, NOx measurements taken during emissions testing using pre-defined test conditions can vary in real-world conditions depending on driving conditions and driver skills. This off-cycle problem reportedly surfaced in emissions from diesel vehicles when Euro 6 (Europe's latest emissions standards) was introduced in Europe in 2014. But it came as a shock to the world when it was discovered that the deviations in NOx measurements in VW vehicles resulted not from variable testing conditions alone but from deception by VW, one of the prominent OEMs in the world vying for the number one spot.

 The NOx emissions levels of VW vehicles powered by 2.0-liter diesel engines，which were measured during on-road tests by the International Council for Clean Transportation (ICCT) and West Virginia University (WVU) in the United States, were unusually high. They were so high, in fact, that they couldn't be explained simply as an off-cycle problem. The tests revealed that the deviation resulted from the use of a "defeat device."

 This report focuses on what has been disclosed and how and why it happened.

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Volkswagen Group Diesel Emissions Crisis (LMC Automotive)