CO and NO emissions

RalphVa

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I pulled together as much information as I could find to check CO and NO emissions for gas vs. diesel engines and to determine how much effect refinery emissions contribute.

Refinery emissions/mile are negligible compared to the vehicles themselves.

I also ran across some information on actual NOx emissions from diesels in Europe vs. spec. They're all running about 3 times the spec values, on road.

Guess that means the spec are unrealistic for diesels. Could also mean that diesels may be legislated out IF THEIR SPECS ARE REALISTIC. Cities in Europe are getting choked by acid air. So guess they are.
 

RalphVa

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Another thing I noticed was that the typical NOx emissions for gasoline cars is far more than the spec for diesels.
 

GoFaster

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Another thing I noticed was that the typical NOx emissions for gasoline cars is far more than the spec for diesels.
How's that?

The last few generations of Euro standards have had tighter NOx standards for gasoline engines than for diesel engines. Only with Euro 6 have they done what the USA did years ago, and made the standards the same regardless of fuel source.

Gasoline engines don't have a lot of difficulty controlling NOx via 3-way catalysts. While it's entirely possible that "real driving" will result in NOx exceeding the prescribed limits, it's not to the extent that diesels have been having trouble with.

I've been hearing that gasoline engines are having a problem with CO when it comes to "real driving" emissions.
 

wxman

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Yes, CO emissions seem to be a problem for petrol cars in Europe.


http://tinyurl.com/jf4osrw


Upstream ("well-to-pump") emissions can be calculated from Argonne National Laboratory's GREET model, which is available at https://greet.es.anl.gov/ .

Just completed an analysis of WTW emissions of BMW's 2016 3-Series gasoline (PZEV-certified version) and diesel models (328i and 328d), using both EPA and GREET emission factors for upstream emissions. This is what I get for each scenario.








Methodology is available at http://webpages.charter.net/lmarz/emissions2016.html .
 

GoFaster

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Interesting; the small cars have the biggest CO problem.

And there's a fair chance that it's because gasoline engines have to run rich near full load to protect themselves and their catalysts from self-destructing, and small engines will have to run near full load a greater amount of the time.

A downsized turbocharged engine will start reaching those thermal limits at around the same engine load that a non-turbo engine would. The entire region when it is under boost is likely the rich-protection regime.
 

dmarsingill

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Interesting; the small cars have the biggest CO problem.

And there's a fair chance that it's because gasoline engines have to run rich near full load to protect themselves and their catalysts from self-destructing, and small engines will have to run near full load a greater amount of the time.

A downsized turbocharged engine will start reaching those thermal limits at around the same engine load that a non-turbo engine would. The entire region when it is under boost is likely the rich-protection regime.
Exactly.....that is why the BMW did a better job on the WV tests.

Donald
 

n1das

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Exactly.....that is why the BMW did a better job on the WV tests.
Donald
IIRC, BMW uses both types of systems (LNT + SCR) in their design to control NOx. With a BMW X5 35d for example, BMW can afford to build the extra cost of doing it right into the cost of the car. The X5 35d was the BMW model that "performed as expected" in the ICCT and WVU studies that discovered the high NOx levels from TDIs.

I added wxman's latest emissions page to my sig below. :cool:
http://webpages.charter.net/lmarz/emissions2016.html
 

dmarsingill

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IIRC, BMW uses both types of systems (LNT + SCR) in their design to control NOx. With a BMW X5 35d for example, BMW can afford to build the extra cost of doing it right into the cost of the car. The X5 35d was the BMW model that "performed as expected" in the ICCT and WVU studies that discovered the high NOx levels from TDIs.

I added wxman's latest emissions page to my sig below. :cool:
http://webpages.charter.net/lmarz/emissions2016.html

But in general, a bigger displacement needs less heat to do the same work, thus producing less NOx.

Donald
 

GoFaster

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I'm not buying that argument in the case of the BMW X5 diesel. It may indeed have a larger engine but it's also a much heavier and larger vehicle! "Per unit of displacement" that engine works ~ just as hard as the VW's smaller engine. The fuel consumption is almost in proportion as well (~ 50% higher). The cylinders are ~ the same size. It has 50% more of them in order to push 50% more weight and 50% more aero drag and it's burning 50% more fuel to do that. Each cylinder is working just as hard.

The BMW diesel engine passed the WVU tests because it has an emission control system that, evidently, was properly designed for the application, and the VWs was not.

The CO problem (rich operation) under load is a petrol engine issue, not a diesel engine issue.

A 1.0 litre engine (doesn't matter turbo or not) in a 800 - 1000 kg car is working harder per unit of displacement than a 2.5 litre engine in a 1200 - 1500 kg car. Or even a 2.0 litre engine.
 

dmarsingill

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I'm not buying that argument in the case of the BMW X5 diesel. It may indeed have a larger engine but it's also a much heavier and larger vehicle! "Per unit of displacement" that engine works ~ just as hard as the VW's smaller engine. The fuel consumption is almost in proportion as well (~ 50% higher). The cylinders are ~ the same size. It has 50% more of them in order to push 50% more weight and 50% more aero drag and it's burning 50% more fuel to do that. Each cylinder is working just as hard.

The BMW diesel engine passed the WVU tests because it has an emission control system that, evidently, was properly designed for the application, and the VWs was not.

The CO problem (rich operation) under load is a petrol engine issue, not a diesel engine issue.

A 1.0 litre engine (doesn't matter turbo or not) in a 800 - 1000 kg car is working harder per unit of displacement than a 2.5 litre engine in a 1200 - 1500 kg car. Or even a 2.0 litre engine.
The 335d only weighs 400 lbs more than the Sportwagen. That's nothing in diesel world.

Donald
 

dmarsingill

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But the 335d was NOT the vehicle in the WVU test. It was an X5 - which weighs a lot more.
You are right. But I'm sticking to my theory.....I know the burn temps in the BMW are lower. It has to be related.

Donald
 

GoFaster

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The BMW had a properly designed and calibrated emission control system. The VWs did not!

How do you know the burn temps in the BMW are lower? Did you measure them? How do you know this?

Each of those 500cc cylinders is working about as hard in the BMW as in the VW, making about as much (part load) power per cylinder while the vehicle is rolling down the road.

If the BMW has lower burn temps ... it's because of its properly-designed and properly-calibrated emission control system, not because it's making less power per cylinder!
 

TDIMeister

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High emissions of any of the regulated emissions in gasoline engines almost always points to something deficient in the aftertreatment system, whether by design or calibration, rather than upstream of it. If small cars seem to be more affected, it's probably because cost sensitivity leads the OEM to cut corners... the cost of the precious metals in the TWC does not respect whether installed into a Kia or Bentley. Smaller engine displacements also mean a higher proportion of crevice volume and greater heat losses. Plus with stop-start systems becoming commonplace (letting the catalyst cool down from light-off temperature and not letting the engine maintain full operating temperature), real-world emissions are going to be worse relative to lab and rolling-road certification results...
 

GoFaster

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Thanks for your input Dave ... (long time no hear ... I'm in Detroit on business all this week)

My econobox (old school non-turbo port-injected tiny engine) has a secondary air injection system that squirts extra air into the exhaust ports, when an ECU-controlled solenoid valve commands it to operate. The scangauge says it remains operating in closed-loop mode through all this. Probably it is maintaining lambda=1 after the air injection in order to allow the 3-way catalyst to do its thing while still allowing the engine to run a bit rich when the engine is at full load (which happens a lot). The new model, which has a turbocharged (but not direct-injected) engine, doesn't appear to have that system, but the new engine has intake ports with a lot of attention paid to generating in-cylinder tumble in the interest of getting combustion done faster (and limiting knock). The new engine is not heavily tuned. Boost pressure is pretty high, so is the compression ratio, it's intercooled, but power output isn't extraordinary ... which smells like very mild intake cam timing. The new one uses a little less fuel despite being in a bigger car with more power. (Not 25% less fuel as they claim, though)

https://www.youtube.com/watch?v=XNvRhWL1stQ
 

TDIMeister

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Yup, fuel enrichment will certainly throw a wrench into closed-loop emissions control. And it's usually the econobox motors that are the worse offenders; they'll go into enrichment on the slightest provocation into high load excursions. GDI raises the threshold but doesn't eliminate it - at least it doesn't in OEM calibration implementations of which I'm aware - and poor calibration/implementation of GDI presents the other huge problem of particulate emissions.

It is my educated opinion that ANY combustion engine - Diesel, GDI, PFI, etc. - should have particulate filters mandated.

Brian, we should talk soon. Are you coming up my way anytime soon?
 
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