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| Let me start by saying that I'm no expert on the diesel combustion process, but Ithink I can explain your question. For many years, the main concern of the EPA folks with regards to diesel emissions was NOx, or oxides of nitrogen. The first main way to attack this was by retarding the injection timing, hence the lower power output and increased fuel consumption. Now, cooled EGR is also used to reduce NOx, which increases parasitic loads on the cooling system and thus negatively affects fuel economy.
The latest push in diesel emissions is with regard to particulate matter, i.e. that black smoke that you see coming out the stack. This reduction in the new 2007 engines has been achieved primarily through the use of scrubbers and other particulate type traps in the exhaust/muffler system, along with the ultra-low sulfer fuel. It is with regards to particulates that I think they can say that the air in some cities will be dirtier going in than coming out. | |
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2007 Diesel engines - not going to be very good
