Pet peeve: "clean diesel" greenwashing

[gone-ot]

...not if you "start" with geothermal steam!

[cfg83]

UFO -

Originally Posted by UFO

@Old Tele man -- No, Dave is correct. The VW diesels with DPF do not use the urea for NOx treatment.

It looks like 2012 VW TDIs will have the urea injection system (in place of the DPF?!?!?) :

2012 VW Passat 101: What you need to know

FUEL ECONOMY
2.5L 170-hp engine, 31 mpg highway and 573 miles/tank
3.6L 280-hp engine, 28 mpg highway and 518 miles/tank
2.0L TDI Clean Diesel, 43 mpg highway and 795 miles/tank
Figures are manufacturer estimates.
...
TDI CLEAN DIESEL: We know what you’re thinking. Diesel used to be smelly, loud and nasty, and as a result got a bad rap in the states thanks to big trucks and long-ago mistakes by automakers. It’s just not true anymore, so – get over it. Today’s diesel is clean, thanks to the fuel and engine technology that VW uses to help improve efficiency and boost performance.† Fact is, TDI Clean Diesel models are arguably better and more efficient than their gasoline-powered siblings. There’s also the feel-good angle: the 2012 VW Passat TDI meets BIN5/LEV2 emissions standards, courtesy of a computer-controlled injection system that sprays fuel directly into the combustion chamber. At high pressure, this helps to promote more complete combustion. In addition, Passat TDI models use a special catalyst and urea-injection system that reduces NOx emissions by up to 95 percent. Filled by a 4.9 gallon tank located inside the trunk, the injection system delivers a range of approximately 15,500 miles. Service is handled at your local VW dealership and is covered by the Passat model’s no-charge Carefree Maintenance Program.

CarloSW2

[gone-ot]

...to be honest, I don't recall if they were 2011 or 2012 VW models that I was walking through last year (?!?) but, I do know what a latrine smells like (re: Chu Lai, RVN), and of the two, I prefer the odor of diesel over piss.

[mechman600]

Originally Posted by cfg83

It looks like 2012 VW TDIs will have the urea injection system (in place of the DPF?!?!?

Not in place of the DPF, but IN ADDITION to the DPF. The DPF takes care of the particulates. The SCR takes care of the NOx.

I think SCR was inevitable for VW. There's only so much NOx that a NOx sponge can take care of. Future emission standards will require SCR in one form or another because of its effectiveness and simplicity.

[Diesel_Dave]

mechman is correct. A DPF is for particualtes, while SCR is for NOx.

Here's my attempt at a quick summary. Diesel emissions mainly come down to NOx and particulates (PM).

PM can be controlled somewhat by changes to the engine itself, but in order to meet modern on-highway regs, it's almost always necessary to have a DPF to clean up the PM after it comes out of the engine.

NOx can be controlled on-engine by using EGR, which can get the levels low, but only to a point. If EGR alone isn't good enough, then the NOx has to be taken care of in the tailpipe either by SCR or a NOx adsorber (aka lean NOx trap). The SCR is extremely effective (95%+ reduction in NOx), but it requires the use of urea, aka diesel exhaust fluid (DEF) and is more expensive and bulkier than a less-effective NOx adsorber.

Different configurations make sense for different applications with different regs. I've seen all the following (for current regs):

1) EGR & DPF
2) SCR only
3) SCR & DPF
4) EGR, SCR, & DPF
5) EGR, NOx adsorber, & DPF

I don't know of any vehicles out there that meet the 2010 North American emissions regs with option 2. I know there are some Euro5 applications that use option 2, but I doubt anybody will make it work for Euro6. Option 1 is getting very difficult to do as well. I think Navistar is the only one using this for 2010+.

Keep in mind that all of these give a different tradeoff between fuel economy, initial cost, & DEF usage. Fluctuating fuel and/or DEF prices also affect which option makes the most sense. For example, SCR gives better fuel economy than EGR, but requires DEF usage--so if fuel is "cheap" EGR may make sense, while high fuel prices make SCR more attractive.

[gone-ot]

...pretty soon, we'll be carrying more "additives" around than actual diesel fuel.

[ron]

ever wonder why they came up with urea usage in the first place.I wonder if it was to get rid of it,they do have too clean up the feed lots somehow. nah

[Diesel_Dave]

Originally Posted by ron

ever wonder why they came up with urea usage in the first place.I wonder if it was to get rid of it,they do have too clean up the feed lots somehow. nah

If I recall correctly, SCR (with urea) was used for emissions contol first on power plants. In order for the process to work ammonia is required and urea is the "best" way to make it available in a vehicle.
Selective catalytic reduction - Wikipedia, the free encyclopedia

[undata]

I've been operating a clean diesel for fifteen years. They have gotten even cleaner during that time. If you go out of your way to criticize small diesel technology, you are in league with a lot of dummies. A lot of gas-guzzling, pedal-stomping, SUV-driving dummies.

It's a red herring to talk about what happens when a diesel starts - that's obviously the weakest link, but it's not significant to the overall emissions footprint. It's how much and what kind of emissions per passenger mile.

[ron]

WoW whats with all the lambasting undata, follow the money D D gave a link. 1928-32 research on corn beetles in cow shi- the gov says clean it up. now you have extra chems lets find a use for them,why dont we just burn it .ask yourself what did they do with all the superfund cleanup site chems that had to be gotten rid of can you say vulcanus I, II .or lets just put 1gal in each fuel tanker load and call it an additive(top secrete) no no pump it back down the hole fracking anyone. I'll stop now