The physics behind the Volkswagen diesel scandal

Guinnessy writes: Volkswagen recently admitted that it equipped diesel cars with "defeat devices" that belch 40 times the EPA standard on nitrogen oxides. Yet despite the mass of coverage, details on exactly how the devices cheated on emissions tests, and why diesels expel such gases have been sketchy. Physics Today's Charles Day takes a look (http://scitation.aip.org/content/aip/magazine/physicstoday/news/the-dayside/digging-into-diesels-a-dayside-post ) at how diesel engines work, and why its clear its not just a lone software engineer who came up with the cheat. "...software is impotent without hardware. To recognize when a car was being tested and not driven, the defeat device required data from a range of sensors—sensors that a noncheating car might not need.... Whereas it's conceivable that a single software engineer, directed by a single manager, could have secretly written and uploaded the code that ran the defeat device, installing its associated hardware would require a larger and more diverse team of conspirators," he says.