By now you certainly know that Volkswagen, AG of Germany has been caught fudging emissions test results for its cars with diesel engines. Engineers with the California Air Resources Board found during compliance testing that while VW cars with diesel engines passed the standard emissions tests, they failed when subjected to real-world driving tests.
What actually happened, according to the California Air Resources Board (CARB), is that VW's emissions computer failed to spray enough of a substance called diesel emissions fluid (DEF) into the exhaust stream to neutralize the oxides of nitrogen that are produced in all diesel engines.
The DEF, which is a mixture of the organic chemical urea and water, reacts in the catalytic converter to produce nitrogen and water, both of which are harmless and hugely abundant in the atmosphere.
DEF is used in a wide variety of diesel car and truck engines, and it's widely available and relatively cheap. However, Volkswagen, along with fellow German car makers Mercedes Benz and BMW, uses a proprietary version of DEF called AdBlue, which is somewhat more expensive.
The amount of AdBlue used by a car in normal use depends greatly on the type of car, the type of diesel engine and how the car is driven. On a Volkswagen, the usage appears to be about five gallons every 10,000 miles. A parts department representative in a Washington, D.C., area Volkswagen dealership told me that the price of a 2.5-gallon bottle is $10.70.
While neither the U.S. Environmental Protection Agency nor VW has released any details on what the EPA is calling a "Defeat Device," the engineers in California who did the actual testing were more forthcoming. The engineers developed a special test to see whether VW was reducing NOx emissions in real-world use and determined that emissions were only partially reduced at the beginning of the test.
Then CARB found that the DEF dosing of the exhaust stream became insufficient and eventually stopped. While it's referred to as a device, the software code that delivered the bogus results was actually introduced into the VW emission control software during an effort by CARB and VW to clean up diesel emissions beginning in early 2014. The software was able to determine when a car engine was undergoing emissions testing, at which point it used enough DEF. Otherwise it didn't.
It turns out that Volkswagen engineers were aware of this problem for at least a year, but whether they informed the company leadership remains a question.
The statement of Volkswagen CEO Martin Winterkorn announcing an internal investigation suggests he was not aware. His position is not surprising, and the fact that a group of engineers might take it upon themselves to create a way to fudge test results is certainly not unique to VW.
In fact, during the years when I've tested digital systems including performance-enhancing software code became so routine that I developed tests that were designed specifically not to look like tests.