I work with diesel engines maintenance, and I doubt that they use a hidden urea (AdBlue) device to cheat the tests.tok-tokkie wrote:This claim in today's Guardian sounds preposterous to me but I would like to hear informed reaction:http://www.theguardian.com/business/201 ... chael-hornThe devices are thought to work by injecting more urea – an exhaust fluid – into the car when it is being tested. This limits nitrogen oxide emissions to a fraction of their usual level. The car detects it is being tested because devices such as the anti-collision systems have to be turned off when it is in the laboratory. The extra urea is not injected into the car when it is on the road because it would quickly run out.
Where would that urea be stored & why has it not been picked up in all these years?
IMHO, they use different calibration for EGR valve.
https://en.wikipedia.org/wiki/Exhaust_gas_recirculation
In order to pass the emissions test, the engine calibration software leaves the EGR valve more open and, as a side effect, the engine efficiency is decreased.