Bluetec diesels now 50-state legal

Is being just like a traditional gas vehicle good? No, of course not.

That emission rating is the dirtiest allowed. Anything worse and sales are forbidden.

In other words, Prius is on the opposite end of the clean spectrum.

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I think this is good progress.

Diesel requires significantly less refinement than gasoline (energy savings there), is more energy-dense than gasoline (more miles out of a gallon) and has a much higher flashpoint than gasoline (safety).

The technical hurdles surrounding it's sooty nature will naturally be solved incrementally. Using a relatively harmless, abundant compound like urea to neutralize a relatively harmful product like Nox is a step in the right direction, quite elegant too.


Wonder if they'll run on biodiesel?

 

That is not true. Modern refineries must perform many additional hydrotreating steps to straight-run diesel to remove sulfur. Additionally, vacuum distillation of residuum from the fractionating tower is quite energy-intensive, more so than isomerization and catalytic reforming of naphtha's to derive octane blends and reduce benzenes

I covered all that in my thread how oil refineries work.

 

As John mentioned, those diesels are the dirtiest vehicles allowed under T2B5. Depending on the particular emissions, the min-spec T2B5 Mercedes with urea injection still pumps out PM, NMOG's upwards of 10-100 times that of a comparable gasoline motor

The NOx is't turned into "harmless" water and nitrogen as Road and Track suggested, that is suspect. True it is significantly reduced, but not eliminated

 

That's a very good question... since biodiesel actually increases the level of NOx.

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Not only that, the very high pressures involved with common rail injection will usually rule out any use of a "bio" diesel. Older mechanical rotary injection is usually ok with it though. Most biodiesels require a cosolvent like methyl ether ketone, which can bugger the DPF and other components.

Even a fuel not intended for onroad use, such as the Military JP-8, will result in short common rail component life. JP-8 is more to ease logistical issues than be good for a motor, it's far more suited for turbofan operation. JP-8 more-or-less replaces the DFA (Diesel Fuel - Arctic) spec for cold weather operation, so that also saves logistical issues

One thing about urea injection, how much ammonia is released during cold weather operation? Most of the modern diesels STINK in very cold weather, they are eye-watering if you're stuck behind one at a red light -20 C and colder