The story begins in 2012 when the Center for Alternative Fuels Engines Emissions (CAFEE), at the West Virginia University, was contracted by the International Council on Clean Transportation (ICCT) to perform some real world emissions testing on diesel cars.
The ICCT is a non-profit group based in Europe and at the time was trying to pressure European regulators to improve their NOx (oxides of nitrogen) emissions standards to, at least, those in the place in the US. The organisation wanted to some real-world numbers to back up its argument.
For the paper, the five-person team, including Dr Gregory J Thompson and Daniel Carder, drove the vehicles "under typical United States driving conditions" on urban, highway and rural routes along the west coast, and measured the cars' outputs via a portable emissions measurement system.
The team also tested two of the vehicles using standardised test cycles under lab conditions.
Both Volkswagen's were powered by the same 2.0-litre four-cylinder turbo-diesel engine. One Volkswagen and the BMW, powered by a 3.0-litre turbocharged straight-six diesel, both used a urea-based AdBlue selective catalytic reduction system. The other Volkswagen was fitted with lean NOx trap.
The Volkswagen with the NOx trap exceeded the permitted US emissions standard by between 15 to 35 times, while the AdBlue-equipped Volkswagen did so by 5 to 20 times. The BMW X5 had average NOx emissions that were at or below the required standard.
Carder told the IEEE Spectrum that "we presented this [report] in a public forum in San Diego, in the spring of 2014". Although the findings were missed by much of the media, the United States Environmental Protection Agency (EPA) was in attendance.
After the report was released, the EPA began going through the necessary procedures, testing, and protocols before confronting and forcing a confession out of Volkswagen.
It’s not the first time that Carder and the University of West Virginia have been involved in exposing emissions testing violations. In 1998, Carder and his university colleagues helped to expose the use of similar defeat devices by Caterpillar and Cummins in their heavy-duty diesel engines.
The CAFEE report funded by the ICCT can be read in its entirety here.