Originally Posted by theaveng
(sigh). I truly don't understand. Why do people have such a hard time grasping the "diesels are cleaner now" concept? Diesel engineers aren't just sitting on their butts doing nothing. They are improving the engines to make them cleaner. TO ANSWER YOU: Ya know how our insights produce high NOx levels (via lean burn) and the catalyst traps & neutralizes it?
Well. That's what the diesels do as well. That's why even though ULEV qualification requires them to output very little NOx and very little PMs, the modern TDI cars received the rating from California's Air Resource Board.
Another major change is the fuel itself. Diesel only has 15ppm of sulfur, which makes it cleaner than gasoline (50ppm).
The cost of NOx capture has always been prohibitive, Honda managed with their excessive material cost and low power engine with no profit margin. It's these aftertreatments that are pushing Europe back to petrol for the smaller cars as they simply can't hide the cost on non premium vehicle so a large difference in price is appearing between petrol and diesel models of the same car.
It's not how diesel do it anyway, for EU6 they are injecting urea into the exhaust not capturing it. As your in the states I'll forgive your understanding of diesels as here in Europe they are turning out to be total pains to run and own. They have a multitude of complex expensive parts. DPFs that frequently clog and can not regen, injectors and high pressure pumps that fail and dual mass flywheel that fail.
The low pressure EGR systems that rely on post DPF gas are even introducing valves in the exhaust to increase back pressure to promote exhaust gas recirculation to the combustion chamber, all these thing are also impacting the efficiency of the engine.
I agree they are getting cleaner, not really like a good petrol though as that now enters an exciting period of development.