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Old 03-02-2012, 03:23 PM   #8 (permalink)
Diesel_Dave
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Quote:
Originally Posted by MetroMPG View Post
The description "clean" implies the task of dealing with emissions is complete! Things are as good as they need to be! Might as well call them "MISSION ACCOMPLISHED!" diesels.
Well, in one sense that's close to being true (not counting CO2). North American and European diesel emissions regulations started in the late 80's & early 90's. The regulations are typically announced ~5-10 years or so ahead of time in order to give manufacturers time to develop the technology. The last phase-in in North America wraped up in 2010. EuroIV will roll out in 2014 (almost in production now). While many of the other parts of the world are catching up, I haven't heard any rumors of any further tightning of the emissions standards in North America & Europe (and I work in diesel R&D). Keep in mind that if you compare these latest regs with the original ones (around 1990), the emissions levels are around 50-60 times less. Yes, that's 50-60 times (not percent). We're talking about pollutant levels that used to be measured in the thousands of parts per million (ppm), that are now measured in the single digits. If you're still using an internal combustion engine, there literally isn't much more that can be done to make them much cleaner. Depending on where you're driving, you really are looking at the tailpipe emissions being almost as clean as the ambient air.

CO2 regualtions are, of course, still tightening, but that's a topic for another thread.

I do get your point, however, that nothing's is truly and completely "clean"--including humans--which put out CO2 & methane

Just as an FYI, the term "clean diesel" can mean different things to different people, however, my understanding is that the first origin came with the advent of the ultra-low sulphur diesel fuel (ULSD), which came in 2007 in the US. Previously, everybody ran low sulfur diesel which had <500 ppm sulphur. ULSD has <15 ppm sulpher. While that change did result in a reduction in sulpher dioxide emissions directly, the big change was that it allowed the manufactures to use various forms of aftertreatment with catalysts. Suphur poisons catalysts and can also form sulphuric acid in aftertreatment. So removing the suphur from the fuel enabled the use of diesel particulate filters (DPFs), diesel oxidation catalysts (DOCs), selectic catalytic reduction (SCR), and lean NOx adsorbers. The use of those devices has brought down the emissions by at least an order of magnitude. Of course they've also reduced the fuel efficiencies of the engine and increased the cost substantially. I was just reading an article in Diesel Power magazine about diesels being sold in 1/2 ton pickups in the US. The diesel exhaust/aftertreatment system cost more than the total cost of the gasoline engine & transmission combined.
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Last edited by Diesel_Dave; 03-02-2012 at 05:14 PM..
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