New Lexus RC F expected to feature Atkinson mode!...

Off topic, but may someone explain to me what is the difference between particles emitted by a diesel engine and DI petrol engine? From EURO 5 emission standard on (2009), a DI petrol engine must meet the same values as a diesel engine (0.005 g/km). So what will this 2016 EU regs measure, a particle count instead of particle mass? What is the difference?

 

Since the implementation of Euro 5b (September 2011), diesel vehicles have been required to meet a particle number limit (PN - 6X10^11 particles/km) in addition to the PM mass limit. That PN limit is generally considered to be a much more stringent limitation than PM mass.

Euro 6 is supposed to be implemented in September 2014 according to Dieselnet (Emission Standards: Europe: Cars and Light Trucks). Note that gasoline direct injection cars will be given a 3-year order-of-magnitude relaxation of the diesel PN limit to 6X10^12 particles/km (footnote "g" in the referenced table).

Apparently, Audi expects to meet the Euro 6 PN limit without a particle filter by using a combination of DI and PFI (Green Car Congress: Audi using supplementary port fuel injection to address particulates from gasoline direct injection). Note however in that GCC post...

 

Interesting that says in 2017 gasoline engines need to hit a standard 1/10th of the standard today. Is there any scientific evidence that today's levels are unsafe? The gasoline particulate limit is much lower than the current european fleet.

 

Yes, the proposed PN limit for DI gasoline from 2014-2017 is a factor of 10 higher than the diesel limit, but will then be reduced to the diesel limit in 2017 (as proposed).

I'm not sure what the ambient levels of PM are in European cities. However, there are at least four independent studies which show that gasoline PM has higher levels of poly-aromatic hydrocarbons (PAH - many of which are known or suspected carcinogens) than diesel PM. If diesels are effectively forced to use filters, it would seem prudent to effectively require them on GDI also.

By the way, several source-apportionment studies have shown that gasoline PM is a significantly larger source of ambient PM in the U.S. than previously expected. A very recent study (using a different approach from previous studies) shows that about half of PM2.5 comes from gasoline exhaust sources (Green Car Congress: Study finds light-duty gasoline vehicles responsible for about half of PM2.5 mass, 14% of PM10 in road tunnel).

 

I've been saying since 2002 that gasoline engines emit PMs/soot but was always told I was nuts. I'm glad at least EU regulators are acting to filter gasoline engines. Now the CARB and EPA need to do the same.

 

Probably not, they should have the samw required level out, they shouldn't require haphazardly the same pollution control devices. I just question where the number came from. It seems like they just arbitrarily cut the number by a factor of 10, while not justifying it. That is where my question came from.

Did you read the link? It says that the catylitic converter is releasing Pt and Pd. That may mean they need to invent a better catylitic converter, not to filter the cats disintigration. I live in austin, and we get blow over from houston's pollution during certain weather. The bulk that comes this far is unlikely the metals lost from the catylitic converters, but the pollution coming from the refineries.

 

Actually, I would say they apparently had to give GDI an order-of-magnitude leeway over what diesels have had to meet since 2011, for the first three years at least.

Don't you think gassers should meet the same PN limit as diesels?

 

I don't think those new diesels standards hit europe until the end of this year. They have been lower up until today in euro 5, haven't they? I know the euro 5 had a higher number suggested, but not implemented. Euro 5 puts out too many particulates and NOx to run in the US, while new euro 6 compliant equipment only needs to be slightly upgraded.

Yes I think they should have the same health limit. I don't know which particulates are less healthy. As mentioned that previous texas study showed the cat decays in gasoline cars, diesels here pre 2009, don't even get emissions tested, becasue their emissions are so full of particlutates they foul the testing equipment.

 

I guess I'm not following you AG. According to the dieselnet link I posted previously, Euro 5b was implemented in 2011 (September) which cut the PN limit to 6X10^11 particle/km. There's a footnote ("c") which says that all (diesel) models had to comply with Euro 5b by 01/2013. So as of right now, all new diesel vehicles in Europe have to meet the 6X10^11 particles/km standard.

I interpreted the Texas study differently than you, although I may be wrong. The way I interpreted it, the Pt, Pd and Rh particles are unique markers for gassers that were used to distinguish from other sources of PM (e.g., diesel), not that all PM from gassers is composed of those elements.

As I mentioned, some studies have shown that gasoline PM is enriched in particle-phase PAH (e.g., DOE's Gasoline/Diesel PM Split Study, http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2003/session9/2003_deer_fujita.pdf). So it doesn't appear that gasoline exhaust PM should be considered any less of a concern than diesel exhaust PM.

One more data point, the USEPA has re-evaluated the PM exhaust emission factors for gassers in its new mobile source emissions inventory model (MOVES), based on an extensive study it did in Kansas City. As a result, the average lifetime exhaust PM emission factor is now higher for gassers than for diesels (greet.es.anl.gov/files/vehicles-13 - Tables A2 and A3).

 

Ah I thought it wasn't hitting until 9/2014. If it hit a year ago, I stand corrected.

No diesels also have catylitic converters. It was about how much of the PM came from cars and trucks versus industrial sources. After being embarrased by having worse air pollution than LA, houston started going after point sources, but IMHO not fast enough. One of the worst has been BP's texas city refinery, which routinely ignored safety and pollution standards and just paid the small fines. Finally they sold that refinery to marathon, which has kept pollution under control.

If that is the case, I certainly think we should have the same standard. The question is this one arbitrarily tough, simply because diesel needs a filter, and it may not cost much more to hit the new standard.

You meant for new Diesels, for diesels on the road today the pm is much higher.

 

Yes, I should have specified 2014 model year.

 

I'm not familiar enough with gasoline engine three-way catalytic converters and diesel oxidation catalysts to know what precious metals are used respectively.

The reason it appears that combination is a unique marker for gasoline exhaust PM sources is that it says in the GCC post...

(last paragraph in first italicized section)


The full paper is available at Elemental Characterization of PM2.5 and PM10 Emitted from Light Duty Vehicles in the Washburn Tunnel of Houston, Texas: Release of Rhodium, Palladium, And Platinum - Environmental Science & Technology (ACS Publications) (ES&T papers are usually pay-walled).

 

"... nearly eliminating contributions from diesel-driven vehicles..."

This could be saying that they are differentiating between catalytic convertor vehicles and non-cat diesels, and the percent of the diesel fleet in the study with a cat was just small. This is just a view based on no knowledge of the material differences between gasoline and diesel cats.

 

That may be true, but it specifically states in the full paper...

(Page 54-55)


I haven't seen anything that specifically addresses diesel catalysts composition however.

If this study included PM emissions from diesels with oxy cats/DPFs/SCR, it would seem to be a rather egregious error since it's my recollection that diesel trucks have had at least oxy cats since at least 2003. The actual emissions collection in the tunnel was conducted a little over a year ago (Nov 2012 - Jan 2013). It would seem that a relatively high percentage of diesel vehicles currently on the road would have catalysts (Diesel Technology Forum estimates that 33% of the on-road diesel trucks are 2007 compliant (oxy cat/DPF); 11% are 2010-compliant (oxy cat/DPF/SCR)).

Source-apportionment studies are supposed to "apportion" pollutants, e.g., PM, to specific sources. It wouldn't seem that this study is accurately apportioning PM emissions to light-duty sources if a large percentage of diesel trucks also use similar material for their catalysts and are thus included in the LD PM calculations.

 

Diesel cats don't do reduction, so I guess they wouldn't have rhodium, just platinum and paladium. I guess they could tell by the amount of rhodium. The new diesels use SCR, the older ones just don't work on the NOx. I'm not sure of the specifics. The question is are these metals from the cats as dangerous as some of the other emissions. If so perhaps we should modify these cats for polluted cities, or add filters to capture these particulates.

 

Need to correct myself.

According to the full paper, the tunnel has been closed to heavy-duty traffic since 2008 for security reasons. Thus, no PM emissions from diesel trucks are included in the PM emission calculation so it would seem.

 

I've looked under old Volkswagen TDIs. They've had catalytic converters since the 80s (in order to convert NOx to N2 and O2 and pass emissions standards).

 

You sure it was a cat and not a resonator? The sulfur levels in diesel from those times would poison a cat.

 

The old diesel cats were two way. They turned carbon monoxide to carbon dioxide and hydrocarbons to water and carbon dioxide. Old diesels, pre the ultra low sulfer reduced NOx by EGR, but usually produced much higher levels than gasoline cars that did it in the cat. The sulfer from the diesel would poison the catalyst in attempting to remove the NOx. Now with lower sulfur in diesel, removed at the refinery, SCR removes the NOx. Removing the sulfur also greatly reduced the volume of particulates, allowing for the use of particulate filters that would last a reasonable period of time. Go to those '80s diesels and you have much lower control of both particulates and NOx, but the new diesel fuel reduces particulates in these old engines to lower levels than the old fuel they started to run with.

 

Good point.

Diesel had 500ppm from 1993 onward, which is comparable to the amount of sulfur in gasoline at the time. They would be able to use the same catalysts to neutralize NOx. The CARB rated these cars as LEV (low emission).