And importantly, how easy will it be to get AdBlue when you run out? And how long will it last? I'd hate to run out of the stuff in the middle of the desert, or a snowstorm.

Cervus,
Or how about running out of AdBlue in crawling urban/suburban traffic during hot summer months.
_One possibility would be for them to have a large enough tank of this AdBlue. Every 10,000 miles, you go in for a tuneup anyway. A container with enough to 11,000 or 12,000 would be enough. That way, with your tuneup, you will get a refill of AdBlue, and maybe an oil/filter or tranny fluid change too.
_
___As engines themselves become cleaner and more efficient, the amount of AdBlue needed will likely decrease. There might be a point that Adlue will not be needed for NOX.

Not that a Mercedes owner is likely to hit up the local quick change oil station for their tune up needs but I could see this being a problem for any "average" vehicle equipped with such a solution.

.......That must be an awfully large tank.?.....

Thomas, have you read somewhere how much of this urea is used, say in a mile, or as a percentage of diesel use? I have not read anywhere how much of this stuff is used. Could be a quart every mile, or possibly as little as a tablespoon every thousand miles. I just dont know. But I have to give the Mercedes engineers the benefit of the doubt that they have designed its storage, and use, to be somewhat bearable, if not just a slight nuicance. My thought is that it could be something like every 8-10k miles. That gives them the right to determine service intervals to replenish this stuff, while also maintaining other aspects of the cars maintenance. Maybe some sort of "red carpet" maintenance offering disguised to allow them to check this urea system out. My thoughts are that this will be taken out of the shade tree mechanics hands and be only offered as a dealer service. May not be an entirely bad thing. Lets see how this develops.

Note that the 6cylinder CDI missed Nox by .01, 4 & 5 cyls should be there.

"If a four or five cylinder could make the NOx standard then we'll probably be seeing a diesel Wrangler, PT Cruiser, and Caliber/Compass/Patriot in the near future."

I thought the whole point of pushing clean diesel is to have a new "premium" (and hopefully profittable) product for the market.

If automakers really believe that adding diesel to every line of cars will generate enough sales to boost the bottomline, I'm sure it would have been done so much sooner. Jeep Liberty CRD only sold about 10,000(?) units or so, over who knows how many years. To me, that means adding "diesel" to model "X" doesn't mean it will always sell.

I know emissions is always used as the main reason why there isn't more diesels being sold, but in the end, the sad truth is that fuel economy and emissions are not really the top reasons why people buy cars.

If Customer X happened to want a BMW 5-series, he/she would not care if Toyota/Lexus Hybrid, Passat TDI, or E320 BlueTec get better mileage. Tourag is probably a very capable SUV, but even offering a diesel version really didn't help when the market is pack full of so many competative choices.

What DC is doing here is really just spicing up the image of clean diesel marketing it only in the premium market. If it really does take off, we would more likely see a Chrysler 300 with BlueTEC, rather a low-margain vehicle like the PT Cruiser, or Calibre.

Except that diesel engines can run off SVO or biodiesel, which is hugely more economically / agriculturally / CO2 balance viable than gasoline or ethanol.

That's by far the biggest advantage of the diesel engine.

AdBlue is a 35% aequeous solution of high purity synthetic urea (aka not urine). A precursor step in the catalytic chain converts the harmless urea into the active component, ammonia.

The additive consumption rate is approx. 3-4% of the fuel flow. Here in Europe, where SCR has already been adopted widely by HDV manufacturers and a distribution infrastructure now exists, the additive cost per US gallon (~$2.50) is about half that of diesel fuel (~$5).

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EPA has expressed several reservations regarding the introduction of SCR in the US:

- nationwide availability of AdBlue additive. One idea is to store the urea in powder form and refill only the distilled water. The correct concentration would have to be maintained by a tamper-proof automated system. MB claims the SCR system for its passenger cars would be frugal enough to permit the distribution of (presumably imorted) AdBlue via its US dealerships only. Note that there are currently no plans to introduce the SCR variant in the EU, as emissions regs here can still be met with less expensive equipment.

- tamper-proof detection of low and empty AdBlue and volume by the OBD and, associated emergency operations mode. Burnt decades ago by unscrupulous US carmakers, EPA continues to assume the entire industry is full of crooks looking to undermine its clean air regulations. CARB is even more paranoid. By contrast, European regulators have accepted available sensor technology for measuring fluid level and urea concentration as adequate.

- anti-freeze protection for the AdBlue tank (the noral solution ices up at -11 deg C, i.e. 12 deg F).

- the reliable light-off temperature of the SCR catalyst package is around 250 deg C, i.e. 480 deg F. HDV engines are operated at high load most of the time, but even so, the NEDC used in vehicle certification permits higher exhaust temperatures than the equivalent US test procedures.

- even if the required gas temperature can be reliably sustained, the NOx conversion rate is currently limited to around 85% because of the open control loop and the need to avoid excess ammonia from entering the atmosphere. Once sufficiently fast and reliable NOx sensors become available, the conversion rate can be increased to 90-95% using closed loop control logic.

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There are several alternatives to SCR technology, but they do present serious challenges of their own:

- NOx adsorbers do not require any additive and can operate using lower exhaust temperatures. However, the application effort requried for transparently alternating between the lean and slightly rich fuel mixtures required for adsorber technology is very high. Worse, the catalyst material is highly susceptible to sulphur poisoning. Even with ULSD (15ppm) and 10ppm diesel becoming available in the US and EU, respectively, between now and 2010, NOx adsorbers still require periodic sulphur purging. This requires exhaust temperatures of 650 deg C (1200 deg F) to be maintained for extended periods of time in a component located relatively far from the engine due to its bulk. Catalyst performance is permanently reduced to some extent after each sulphur purge cycle.

- HCCI largely avoids NOx production by eliminating combustion flames. Instead, the pre-mixed fuel ignites simultaneously throughout the chamber at the same time in a near-isochoric flash. Controlling this reliably, especially during load transients, is hard. When using diesel fuel (gasoil or similar), high charge motion, high-pressure fuel injection, high levels of cooled EGR, in-cylinder pressure sensors and powerful engine control logic are all required in addition to a variable gemoetry turbocharger. However, given the already advanced state of modern turbodiesel technology, the incremental cost would still be far lower than that for the lean-burn NOx exhaust gas aftertreatments described above.

Unfortunately, diesel HCCI only works when the engine is sufficiently hot and operating in part load (6-8 bar BMEP and <~15kW/liter of four-stroke displacement, <~3500 RPM). Above a certain load level, combustion noise becomes unacceptable. Besides, EGR levels cannot be as high at elevated loads, leading to NOx levels comparable to those produced in conventional combustion. The state of the art dictates that any HCCI-capable engine must operate using conventional combustion during warm-up, extended idling and at high load - and switch between combustion modes transparently wrt torque, emissions and noise levels.

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Does all this mean that diesel engines are doomed to go extinct? No, but it is likely that the ever-more stringent emissions regulations will raise the economic threshold for diesel engines to MDVs, or at least large LDVs like full-size SUVs and pick-up trucks. This applies especially in the US, where diesel LDVs are exotic vehicles and gasoline electric hybrids are the fastest-growing market segmen.

By contrast, HDVs will continue to operate on diesel - many observers believe EPA will have little choice but to permit SCR systems for this vehicle class in the next few years. This would trigger the establishment of a distribution infrastructure for AdBlue at truck stops in the US.

We're neurotic about particulates and NOx when CO2 is arguably the biggest problem. Diesels trump spark ignition engines in this regards. Why don't our myopic fed/state agencies get this?

-mt

The problem is – particles have an atmospheric lifetime of hours to days (depending on size). CO2 has an atmospheric lifetime of decades. We need to start addressing CO2 emissions sooner rather than later.

Rafael:
Good to hear from you again.
Some additional comments. Due to unbelievable ignorance of US driving public, EPA and CARB are rightfully concerned about proper operation of SCR equipment in private LDV. Even for highly controlled HDV, there are some concerns. Couple of years ago HDV diesel engine manufacturers settled EPA suit (for record in EPA history multi billion dollar penalty) for programming on-board computers to move gradually to higher power/lower fuel consumption mode with elevated emissions as a consequence.

I do believe that SCR will be widely used in US on HDV as robust and proven technology, unlike NOx absorbers. BTW, there is one interesting twist. Synthetic urea is very energy demanding chemical, and according to calculations from the point of view of energy/cost it is more advantageous to use NOx absorber and waste some diesel fuel in afterburner to eliminate O2 presence in exhaust during periods of absorber’s regeneration, then use urea all the time. This equation is tipped to urea advantage in EU due to overpricing of diesel fuel.

As I mentioned before, NOx absorber is emerging technology, and hopefully will be developed to tolerate current sulfur levels in gasoline. Otherwise it will be another 10B$ to upgrade refineries to ultralow-sulfur gasoline…

In GDI engine with CVT (like in Prius), regeneration of NOx absorber could be easily and cheaply accomplished, unlike in diesel engine.

Slipping of urea with consequent unpleasant smell is emerging problem. This summer I have pleasure to spend one week in Vienna, and then in New-York. Air in NY is clean, which I can’t say about Vienna. Quite noticeably diesel cars to blame. I could only imagine some of them will smell pee in addition…

I live in Portugal where diesel cars are everywhere.
Believe it or not, the pratical result of using that type of engine is low quality of life and air.
The air smells awfull, it burns your eyes and throat,(you can't ride a bike near a diesel car) there are walls completly black because of soot, but the most noticed problem is the way people are using them. People using gasoline cars usually get very good mileage because gasoline is expensive so they drive more carefully with better planing. Those driving gasoil cars, generally use it in a very diferent way (gasoil is much cheaper than gasoline)so they don't care if they polute or are not driving eficiently.
Gasoline engines are not so eficient but there´s no reason for it. They can run on hydrogen,ethanol, natural gas and could be as eficient (but they have to use very high octane rating fuel to avoid knocking)so the best way to use gasoline is HCCI combustion.
Low octane gasoline (wich is cheap and can be obtained from biomass) is the best fuel for full and partial load operations in real HCCI engine(HCCI diesel engine is not a real HCCI engine because it has a stratified and heterogeneous charge and is very expensive).
So i think diesel cars should disapear and be replaced by fuel eficient and clean real HCCI engines fueled by low cetane and low octane fuels (fischer-Tropsch gasoline for example).
Why should we have to buy particulate filters,nox depurators and very expensive engines when HCCI is clean, eficient and cheap.