“And so the car will not pass the test sometime in the future? When the engine wears a bit — design to test margin?”
Please see CFR on ‘useful life’.
So, all of the VW customers will probably have a problem passing emissions as their cars get a few miles on them?
How long have VW been tweaking the engines to pass? It would be interesting to see if cars are indeed failing. Those cars might be reaching the 100K miles limit.
One thing that is always lacking when someone designs a test is real test world results. It is never exactly clear if there is too much margin or not enough. It is usually a statistically educated guess. Worst of all, the test designers will probably not go back and check the real world results to determine if there is too much margin. Too much margin means unnecessary cost.
Also, I am not defending VW but more importantly questioning the test itself. How often have we seen the government mandate something that doesn't make sense but people continue doing it because the “government says we must.”
Ethanol is a good example. I predict that Obamacare will be another.