Greenrod wrote:Frank_Butcher wrote: There have been many questions about the application of the urea solution in test mode, and why they can't do it all the time. The answer generally seems to be that it would mean carrying a urea tank that would need to be refilled.
What's interesting is that many diesel cars today (including mine) already carry a urea tank (branded AdBlue). By the same principle it lowers emissions and hence creates compelling metrics for company car drivers and eco lovers. I once had to refill the tank with the car threatening to deactivate itself within 300 miles.
I'm not sure of the discrepancy - perhaps it's the volume of the urea solution being applied or that smaller vehicles would be unable to carry such a tank ? Certainly Merc C Class and BMW 3 Series upwards carry the AdBlue tank so if they're worried about anything, it would have to be about smaller cars or excessive amounts being used in test mode.
(Just checked and the Passat also carries an AdBlue tank).
Thanks Frank - good info.
It will be interesting to see how it all pans out.
The discrepancy as I understood it was that the software could pick up when it was being tested due to the predictability of the test and behaved itself accordingly. When it knew it wasn't being tested, it didnt always activate the urea additive and so emissions were not controlled as they should be, and as when tested.
The reason for doing this apparently was to increase fuel economy.
I'm not well up on the blue motion system other than its a possibility that if some cars don't carry an ad blue tank they may just inject more fuel under certain conditions which in turn raises the combustion temperature causing the soot to be burnt off by way of particulate filter regeneration.
Which is also terrible for fuel economy....