Gassers may put out as much (or more) PM as diesels

[Winnipeger]

According to testing done by the University of Minnesota's combustion particle scientists, modern gasoline cars may put out just as much particulate matter as diesels. Could have some interesting implications down the road...

http://www.healthyhome.com/files/Documents/Gasoline cars may need particulate filters.pdf

 

[Sip'n Diesel]

no big surprise there

 

[TurbinePower]

Since the U.S. highway vehicle fleet burns about three times more gasoline than diesel, and since gasoline vehicles are now proven to emit substantial amounts of PM and "toxics," the current exclusive regulatory crackdown on diesel vehicle PM doesn't quite hit the clean-air bull's-eye, scientific studies indicate.

Can we get an NSDT on that one? Diesel driving folks have been saying for years, even decades, that just because you can't see a gas car's smoke doesn't mean it isn't killing you.

 

[chewy]

I have seen many a hybrids with sooty exhaust pipes. But the new PDF TDI should be spotless.

I just used the EPA web site to dig up some interesting data on how the Jetta TDI compares to gasoline cars emissions wise. The Jetta TDI gets an EPA Air pollution rating of 6. The vast majority of all gasoline cars also get a 6.

But there is a decent amount of gasoline powered cars that get less than 6.

All of the "heavy duty" pickups get 2 or 1, most work vans (like the Ford Econoline) get 3. Basically the millions of the heavy duty pickups with gas or diesel pollute way more than the Jetta TDI. Yet the EPA ignores that. Do they really care about our lungs?

Also the following gassers in non CARB states get less than 6 as well (they get 3)

Dodge/Chrysler with 2.7 liter V6, and 4.7 liter V8, Lexus SC 430, and surprisingly the Scion XD does so as well.

This poorly researched/worded quote from Consumer Reports got me started.

New exhaust-system treatments, such as soot traps and catalytic converters, along with newly mandated ultra-low sulfur diesel fuel, make those diesels clean. But they're still less so than gasoline engines.

http://www.consumerreports.org/cro/cars/past-road-test/chevrolet-malibu-hybrid-vs-volkswagen-jetta-tdi/overview/malibu-hybrid-vs-jetta-tdi-ov.htm

The Saturn hybrid in the article also gets a 6 from the EPA, even in CARB states. So the quote is really misleading.

 

[RabbitGTI]

I remember reading an article about particles from combustion in cars. IIRC gas exhaust particles are less than 1 micron and can be inhaled deeply into the lungs. Diesel particles are larger, similar in size to dust and pollen and mostly expelled from the lungs. Don't know if that is true, can't remember the source.

 

[wxman]

Based on a number of studies I've seen, the PM from gasoline engines in typically normally distributed around 10 - 30 nanometers (nm) particle aerodynamic diameter, and diesel is typically normally distributed around 80 - 100 nm. Kittleson (the lead author of the University of Minnesota study) says that emissions of extremely small particles (3 nm - 10 nm) makes up the largest category for gasoline PM (i.e., greatest numbers).

Here's a graphic (from Environmental and Health Impact from Modern Cars, Ecotraffic (Sweden)) depicting the relative particle numbers of a gas and a diesel (w/DPF) Peugeot in respective particle size bins...

Particle numbers in particle size bins of two identical cars (Peugeot 307 - one with a 80 kW 1.6 liter gasoline engine (SI-P); the other with a 80 kW 2.0 liter HDi FAP diesel engine with CR injection and particulate filter (CI-CR/DPF)):

Particle size distribution for the Peugeot cars in US06

​

 

[TDIMeister]

One thing to add is that there is still plenty of debate about whether particulate quantity or mass is the most important parameter. A large number of small particles has no correspondence in total mass to a smaller number of larger particle distribution. From a toxicology standpoint, which is more relevant -- quantity inhaled into the body or mass? -- is, I believe, still mostly an open question.

For our purposes we just need to be aware that when we see graphs like that which wxman posted above, that we interpret it with an appropriate understanding that there is another side to the story. Also, I must comment that the comparison of PM emissions of a gasser engine against a DPF-equipped Diesel naturally puts the latter in a particularly beneficial light. Since the number of DPF-equipped Diesels globally is dwarfed by the cumulative number of non-DPF equipped Diesels that are operating, it would be enlightening to readers to see the distribution for one example.

 

[wxman]

TDIMeister - acknowledged.

The reason I posted the graphic was to illustrate that DPF is very effective across the entire particle size spectrum. I've seen many comments on various message boards/blogs that even diesel engines with DPF have much higher levels of nanoparticles than equivalent gas engines (i.e., DPF only filters out relatively large particles). This in conjunction with many other study results I've seen shows that is clearly not the case.

 

[rodneyh1]

Based on a number of studies I've seen, the PM from gasoline engines in typically normally distributed around 10 - 30 nanometers (nm) particle aerodynamic diameter, and diesel is typically normally distributed around 80 - 100 nm. Kittleson (the lead author of the University of Minnesota study) says that emissions of extremely small particles (3 nm - 10 nm) makes up the largest category for gasoline PM (i.e., greatest numbers).

I think you mean lognormal distribution.

http://en.wikipedia.org/wiki/Log-normal_distribution

Found some data from Kittleson (pg 22) that has VW TDI with diesel and biodiesel. Both distributions are lognormal I believe.

http://www.aqmd.gov/TAO/Ultrafine_Presentations/Session1_1_Kittleson.pdf