Quote:
Originally Posted by Duffman
Ding Ding Ding! And the government is not mandating SCR to get there, most manufacturers are using it but not all. Also I think that is the 2010 standard not 2007.
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It was a phase in between 2007 & 2010, so you're correct.
You're right about SCR, too. The standards don't mandate HOW any of the emissions get met--that's up to the manufacturers. In some cases the levels do imply a certain technology. For example, it's virtually impossible to go to 0.01 g/hp-hr of particulates without a DPF (or at least some form of aftertreatment--you just can't get engine-out PM that low).
SCR is for NOx control. You're right that not all manufacturers are going with it. For the manufacturers it's a matter of picking your poison. If you go with SCR you can let the NOx fly out of the engine (to get great FE), and let the SCR clean it up, however, then you're going to have to use a lot of DEF (diesel exhaust fluid), and you have to pay for the SCR system (both in initial cost and maintenance cost & DEF). The SCR alternative is running high amounts of EGR. That means crappy FE, but low NOx. EGR also has it's cost associated with it (initial, maintenance, & extra fuel). So it's a complicated issue, like I said--pick your poison.