# BBC article - Diesel cars: What's all the fuss about?



## skier (Oct 19, 2004)

Interesting read: http://www.bbc.com/news/business-34257424


----------



## Doug Huffman (Apr 25, 2015)

I would suggest, rather, that it is more Euro-trash hysterical hyperbole, and DO NOT take science/technology from media that profits from ignorance. Follow the money.


----------



## BlueC (Jan 13, 2007)

Doug Huffman said:


> I would suggest, rather, that it is more Euro-trash hysterical hyperbole, and DO NOT take science/technology from media that profits from ignorance. Follow the money.


I think this statement sums it up:



> But data from the Society of Motor Manufacturers and Traders (SMMT) shows that average CO2 emissions from diesel cars are only fractionally lower than those from petrol cars.
> *
> This is largely due to the fact that diesel cars tend to be bigger and heavier than petrol cars, so any advantages in efficiency are wiped out.*


That's a ridiculous statement. Just take the 328i and 328d wagon. Diesel adds 60lbs.

If 60lbs truly makes that big of an impact on emissions, I'd imagine we'd have more success with controlling pollution by encouraging lighter drivers.


----------



## Pierre Louis (Oct 23, 2011)

I can understand why UK citizens dislike diesel as much as this author. Trouble is, the only problem with diesel pollution is NOx, largely driven by the Los Angeles Valley politicians to help prevent smog that replaced the black smoke of Native Americans that historically existed in the "bowl effect" in the valley that settlers apparently found. If NOx regulations were allowed to be adapted to diesel emissions as a compromise that credits the improvements in many other parameters (HC, CO, small particulates, CO2, etc.) then we might have a more rational discussion. Well to wheel for diesel is still quite good compared to gasoline or to electric (remember, coal or gas is burned to produce electricity).

The fact remains that diesel, a round peg, has to still fit into the square hole of gasoline engine pollution standards. If NOx were allowed to be higher in diesel, the other pollutants created with resulting engineering compromises (EGR, etc.) would improve. I wish enough people would realize that the smallest particulates are not regulated in gasoline cars as they are with diesels.


----------



## Dean_S (Mar 31, 2015)

The article compares pollution performance of real world driving VS standardized testing conditions. In all fairness, if this is done, one has to also do the same for gasoline engines.

Turbocharged gas engines used to be [now?] open loop at wide open throttle [WOT] as the AF ration is then made very rich to prevent knocking at high manifold pressures. The O2 sensors are also not wide band and can't resolve O2 levels properly in these situations. Things have probably improved. I have more soot on the tail pipe of my Saab 9-5 Aero than my 535dx.

When a cold gasoline engine is started, you can smell a lot of fuel in the exhaust. When I start my diesel in the garage, I am not aware of any exhaust smells.

I think that the comment re weight was referring to larger vehicles with diesel engines, not the added weight of a diesel engine on any given model. Note the weight of a fuel DEF tank; not trivial.


----------



## robster10 (Oct 8, 2012)

Seen of a few European countries with similar reports. The problem is they look at 10-15 plus year old cars with the black smoke spewing out the pipe. Modern diesel are different. None of my friends new my car was a diesel since they all say & believe "all diesels spew out black smoke". Just like when I fill up still get people give me a second look & then the truck guys. I still get them waiting behind me at the pump & shouting out "the gas pumps are on the other side". I always reply back to them "so just trucks use diesel".


----------



## Pierre Louis (Oct 23, 2011)

Diesel pollution is traditionally measured inside the exhaust pipe. Even in older diesels spewing black soot, the visible particulates are relatively large and fall to the ground. They get organically processed by nature, not someone's lungs. Studies of these older diesels compared to gasoline engines when done in the ambient air have shown gassers to have higher small particulates. Its a bias, as was said, against diesels because of "black" smoke that ignores the invisible "smoke."

One way to tell the newer diesels are very clean is to look inside the exhaust pipe - you can see through to the metal. Look inside a hybrid gasser's exhaust and its black.

PL


----------



## wxmanCCM (Feb 17, 2010)

Pierre Louis said:


> ...The fact remains that diesel, a round peg, has to still fit into the square hole of gasoline engine pollution standards. If NOx were allowed to be higher in diesel, the other pollutants created with resulting engineering compromises (EGR, etc.) would improve. I wish enough people would realize that the smallest particulates are not regulated in gasoline cars as they are with diesels.


I completely agree!

GDI, which virtually every car manufacturer is switching to in petrol vehicles, has been shown to have particle number emissions that approach those of unfiltered diesels. So if the objective is really to reduce ambient PM levels, banning diesel cars in favor of what likely will be GDI cars would not only not help that metric, it would likely reverse any downward trend from effectively requiring filters on diesels.

Furthermore, a recent study conducted in London between January 2011 and January 2013 ("ClearfLo campaign") found that black carbon (BC) constituent of ambient PM in London averaged 0.7 micrograms/cubic meter, while the average total PM averaged 12 ug/m^3, or less than 6% of the total ambient PM load was BC (Bohnenstengel et al., "Meteorology, Air Quality, and Health in London." _Bulletin of the American Meteorological Society_, May 2015).

PM from (unfiltered) diesel cars averages about 68% BC, which means that diesels could account for no more than about 8.5% of the ambient PM in London, even assuming ALL BC comes from diesel exhaust. The study concluded that most of the BC came from residential wood burning since the levels peaked during the evening, not during rush-hour traffic. So the contribution of diesels to ambient PM loads was considerably less than the ~8%.

This study was conduced primarily BEFORE DPF was effectively required on diesel cars in Europe (i.e., before Euro 5b).

Also, the OP article mentions that NO2 can form secondary particulate matter, but so does VOC emissions from gasoline exhaust and gasoline vapor (secondary organic aerosols). Gasoline exhaust is about 68% organic carbon. The aforementioned study found that organic carbon was far and away the primary component of PM in London (>50%, much greater than BC). Why do these articles always point the finger at diesels for their air quality issues, especially ambient PM?


----------



## Pierre Louis (Oct 23, 2011)

wxmanCCM said:


> ...Why do these articles always point the finger at diesels for their air quality issues, especially ambient PM?


Its pure unadulterated bias. Prejudice, if you will. Our culture...

PL


----------



## wxmanCCM (Feb 17, 2010)

Another perplexing issue with the "Diesel vehicles are the single biggest contributor to these high levels of NO2" mantra is that even if the "Diesel cars break nitrogen oxide emission limits" (graphic in middle of page) is true, how were ALL AREAS of the U.S. able to meet the NO2 NAAQS (ambient air quality standard) by 1998 when the average emission rate of NOx from GASSERS in the 1990s was about 1.8 grams/mile according to EPA? 0.8 grams/km would be less than 1.3 grams/mile or one-half grams/mile LESS than what cars on average emitted in the U.S. in the 1990s.

Gasoline cars of course were essentially 100% of the passenger car population in the 1990s in the U.S. Only about 50% of the passenger cars in the UK are diesels. Is the traffic congestion really that much worse in London than it is in, for example, Los Angeles? And I find it hard to believe that London's dispersion characteristics are that much worse than Los Angeles'! 

This doesn't pass the "smell test" IMHO.


----------



## Dean_S (Mar 31, 2015)

http://www.nytimes.com/2015/09/19/business/volkswagen-is-ordered-to-recall-nearly-500000-vehicles-over-emissions-software.html?_r=0http://

This describes a problem with VW/Audi diesels.

The allegations cover roughly 482,000 diesel passenger cars sold in the United States since 2009.

http://www.nytimes.com/2015/09/19/b...00-vehicles-over-emissions-software.html?_r=0


----------



## Flyingman (Sep 13, 2009)

The Sh!t just hit the proverbial fan on this issue.

Hopefully BMW has played by the rules and we wont be seeing any recall, etc....:eeps:

My suspicion is given all of our emission system woes that indeed BMW is fully using the system as intended, unlike our friends at VW/Audi.

Competition can bring out the worst in folks, some times.


----------



## Cavi Mike (Apr 15, 2007)

VW just earned a bunch of respect in my book. No sarcasm.


----------



## Dean_S (Mar 31, 2015)

I am guessing here... what would be the motive? Reduce exhaust gas re-circulation to avoid carbon build up [CBU]?
If the motive was to avoid cost/complexity of DEF systems, and they cannot alter software to get emissions right without DEF, they are totally screwed.

I am under the impression that many current 4 cyl diesels do not have/need DEF systems. Is this true?

The fines should be staggering: willful and premeditated.


----------



## sixpot_simon (Sep 13, 2013)

Dean_S said:


> I am guessing here... what would be the motive?


My guess is either cold-start emissions, or running dirtier to increase power.


----------



## Cavi Mike (Apr 15, 2007)

Dean_S said:


> I am guessing here... what would be the motive?


To keep power output up, so the "US" and "CARB" engines can have the benefit of the "world" engines that everyone else gets.


----------



## Pierre Louis (Oct 23, 2011)

Dean_S said:


> I am guessing here... what would be the motive? Reduce exhaust gas re-circulation to avoid carbon build up [CBU]?
> If the motive was to avoid cost/complexity of DEF systems, and they cannot alter software to get emissions right without DEF, they are totally screwed.
> 
> I am under the impression that many current 4 cyl diesels do not have/need DEF systems. Is this true?
> ...


Dean, I noticed you live in Kansas and have a "2015 335d X-drive." Do you test prototypes for BMW? To the best of my knowledge there is no such vehicle sold by BMW in North America. I'd like one of those, please....

PL


----------



## Dean_S (Mar 31, 2015)

Pierre Louis said:


> Dean, I noticed you live in Kansas and have a "2015 335d X-drive." Do you test prototypes for BMW? To the best of my knowledge there is no such vehicle sold by BMW in North America. I'd like one of those, please....
> 
> PL


Sorry, its a typo, should be 535dx


----------



## alocksley (May 16, 2015)

BlueC said:


> ...If 60lbs truly makes that big of an impact on emissions, I'd imagine we'd have more success with controlling pollution by encouraging lighter drivers.


Hmmmm....I wonder if the solution to emissions then is to get everyone to lose weight?


----------

