Lowering NOx in TDI's a simple fix?

[gregoron]

From this quote in a Jalopnik article, it seems like there is a simple fix to this Dieselgate issue:

“It could be something very small,” said Carder, who’s the interim director of West Virginia University’s Center for Alternative Fuels, Engines and Emissions in Morgantown, about 75 miles south of Pittsburgh in the Appalachian foothills.

“It can simply be a change in the fuel injection strategy. What might be realized is a penalty in fuel economy in order to get these systems more active, to lower the emissions levels.”

Source:
http://jalopnik.com/researcher-who-uncovered-vws-diesel-cheating-says-fix-s-1732537775

My question for those familiar with diesel combustion, would adding an EGR lower NOx as they do with GDI engines? Gasoline direct injection engines also deal with direct injection and NOx emissions. High levels of NOx come up when GDI's run ultra lean (i.e. stratified charge mode) and the compression ratio is high. This happens during light-load or acceleration running conditions, or constant low speeds. Fuel is actually injected just before ignition and not during the intake stroke.

For diesel engines, couldn't the EGR recirculate more of the NOx back to the combustion chamber?

 

[Sunnyinhollister]

More EGR, less injection timing, less cam timing, and less MPG. There's the rub. Are there any TDI's using DEF that are included in the scandal?

 

[bdcardinal]

More EGR would work, but absolutely kill power. Increasing the DEF injection amount would have the smallest effect on power and MPG.

 

[lubricatosaurus]

Yes, EGR reduces NOx. Not without tradeoffs. See http://www.cambustion.com/products/egr
where it says: "Since EGR reduces the available oxygen in the cylinder, the production of particulates (fuel which has only partially combusted) is increased when EGR is applied. This has traditionally been a problem with diesel engines, where the trade-off between NOx and particulates is a familiar one to calibrators. The deliberate reduction of the oxygen available in the cylinder will reduce the peak power available from the engine. For this reason the EGR is usually shut off when full power is demanded, so the EGR approach to controlling NOx fails in this situation."

Notice 2015 VWs have the newer modular EA288 engine version. This might be key to at least saving that model year as those engines already have a modular AdBlue pee-pee (yeah, wonderful, right?) injection system. "As part of this major redesign, the engine also features an entirely new exhaust aftertreatment system—a compact unit close-mounted to the engine, helping to lower heat and pressure losses. The system is modular. It can use an SCR system, or NOx storage, or oxy cat—essentially whatever the engine needs, without affecting the rest of the engine. At the time, Volkswagen said that the flexibility of the MDB would allow the engines to meet the coming EPA Tier 3, California LEV III emissions standards." see http://www.greencarcongress.com/2015/09/20150921-vw2l.html

 

[lubricatosaurus]

Originally Posted By: Sunnyinhollister
More EGR, less injection timing, less cam timing, and less MPG. There's the rub. Are there any TDI's using DEF that are included in the scandal?


See my earlier post. Yes DEF adblue on some, urea injection. 2015 models, and I think they use DEF on some earlier model year Passats with the previous generation engine.

 

[gregoron]

Originally Posted By: lubricatosaurus
Yes, EGR reduces NOx. Not without tradeoffs. See http://www.cambustion.com/products/egr
where it says: "Since EGR reduces the available oxygen in the cylinder, the production of particulates (fuel which has only partially combusted) is increased when EGR is applied. This has traditionally been a problem with diesel engines, where the trade-off between NOx and particulates is a familiar one to calibrators. The deliberate reduction of the oxygen available in the cylinder will reduce the peak power available from the engine. For this reason the EGR is usually shut off when full power is demanded, so the EGR approach to controlling NOx fails in this situation."

Notice 2015 VWs have the newer modular EA288 engine version. This might be key to at least saving that model year as those engines already have a modular AdBlue pee-pee (yeah, wonderful, right?) injection system. "As part of this major redesign, the engine also features an entirely new exhaust aftertreatment system—a compact unit close-mounted to the engine, helping to lower heat and pressure losses. The system is modular. It can use an SCR system, or NOx storage, or oxy cat—essentially whatever the engine needs, without affecting the rest of the engine. At the time, Volkswagen said that the flexibility of the MDB would allow the engines to meet the coming EPA Tier 3, California LEV III emissions standards." see http://www.greencarcongress.com/2015/09/20150921-vw2l.html


See that's the thing. EGR is only really used when the engine is at light-loads (no accelerating or requiring lots of power) such as coasting or idling. EGR is deactivated during full load or acceleration because it's not needed due to less NOx present during this mode. VW just has to come up with something during light-load running conditions. One way is just to increase fuel to air mixture or adjust the injection timing so it doesn't run ultra lean. The downside of course is fuel economy would suffer, but perhaps urea injection could be avoided.

 

[A_Harman]

EGR is not a simple fix. Cummins and other heavy duty diesel manufacturers used EGR for their NOx control strategy in the early 2000's. They used high pressure loop EGR, which forced them to run higher exhaust manifold pressure than intake manifold pressure, thereby making the engines do extra work to pump the exhaust out of the cylinder. The result was 10% higher fuel consumption than previous engines, which was a disaster for the truckers that bought them. In the past few years, Cummins had done side-by-side performance studies of EGR vs SCR emissions systems and got a clear-cut winner in SCR for fuel economy.

Diesel's are able to run on EGR rates up to 30% with no big combustion problems because they normally run with a minimum of 40% excess air, and much more under part-power conditions.

 

[gregoron]

Originally Posted By: A_Harman
EGR is not a simple fix. Cummins and other heavy duty diesel manufacturers used EGR for their NOx control strategy in the early 2000's. They used high pressure loop EGR, which forced them to run higher exhaust manifold pressure than intake manifold pressure, thereby making the engines do extra work to pump the exhaust out of the cylinder. The result was 10% higher fuel consumption than previous engines, which was a disaster for the truckers that bought them. In the past few years, Cummins had done side-by-side performance studies of EGR vs SCR emissions systems and got a clear-cut winner in SCR for fuel economy.

Diesel's are able to run on EGR rates up to 30% with no big combustion problems because they normally run with a minimum of 40% excess air, and much more under part-power conditions.


If this is the case, I'm thinking electrical supercharging to compensate for the extra exhaust pressure vs intake pressure. In that case, then maybe a hybrid electric and diesel technology would work.

PS. The electric motor runs when output needed is light, then the diesel engine takes over when you need full-load.

 

[lubricatosaurus]

About a potential fix, I'm wondering if the engineers in the organization are so psychologically frazzled that they can't go forward working on a fix. Knowing that your department, and maybe you in particular, has caused the company billions in charges and lost goodwill, well, they aren't robots. I think a new team will have to be recruited, trained, familiarized, and that means we lose some of the intellectual traction for a while.

 

[bullwinkle]

If they do get hit with $15B in fines, and potentially may have to re-engineer every affected TDI-I'm still not sure VW is going to survive, at least in its' current form.

 

[gregoron]

Originally Posted By: lubricatosaurus
About a potential fix, I'm wondering if the engineers in the organization are so psychologically frazzled that they can't go forward working on a fix. Knowing that your department, and maybe you in particular, has caused the company billions in charges and lost goodwill, well, they aren't robots. I think a new team will have to be recruited, trained, familiarized, and that means we lose some of the intellectual traction for a while.


That would make for an interesting documentary. Although it is sad, I can't help picturing their working environment as something out of Dilbert or The Office.

 

[GiveMeAVowel]

Originally Posted By: bullwinkle
If they do get hit with $15B in fines, and potentially may have to re-engineer every affected TDI-I'm still not sure VW is going to survive, at least in its' current form.


The hysteria here is almost comical. Just like Toyota and Honda, Both companies knew about their respective problems, VW will fix things and move on. At least from a consumer stand point VW issues did not directly contribute to killing anyone of their customers, and thus they will forgive and forget.

 

[gregoron]

Originally Posted By: GiveMeAVowel
Originally Posted By: bullwinkle
If they do get hit with $15B in fines, and potentially may have to re-engineer every affected TDI-I'm still not sure VW is going to survive, at least in its' current form.


The hysteria here is almost comical. Just like Toyota and Honda, Both companies knew about their respective problems, VW will fix things and move on. At least from a consumer stand point VW issues did not directly contribute to killing anyone of their customers, and thus they will forgive and forget.


Yup. There's no fixing death unless you're a life insurance agent.

 

[Andrew1972]

Originally Posted By: GiveMeAVowel
Originally Posted By: bullwinkle
If they do get hit with $15B in fines, and potentially may have to re-engineer every affected TDI-I'm still not sure VW is going to survive, at least in its' current form.


The hysteria here is almost comical. Just like Toyota and Honda, Both companies knew about their respective problems, VW will fix things and move on. At least from a consumer stand point VW issues did not directly contribute to killing anyone of their customers, and thus they will forgive and forget.


My wife/I are considering the Golf SportWagen and annoyingly they never had any TSI versions(cheaper) with manual on lot. Just 20 tdi's and one TSI with automatic. We thought the tdi was decent but not worth the price premium. Now I would not trust VW with a 10' pole the TDI "fix" does not ruin the longevity and reliability of engine. They cheated for some reason and are not being very forthcoming.

 

[Burt]

Originally Posted By: gregoron
Originally Posted By: lubricatosaurus
Yes, EGR reduces NOx. Not without tradeoffs. See http://www.cambustion.com/products/egr
where it says: "Since EGR reduces the available oxygen in the cylinder, the production of particulates (fuel which has only partially combusted) is increased when EGR is applied. This has traditionally been a problem with diesel engines, where the trade-off between NOx and particulates is a familiar one to calibrators. The deliberate reduction of the oxygen available in the cylinder will reduce the peak power available from the engine. For this reason the EGR is usually shut off when full power is demanded, so the EGR approach to controlling NOx fails in this situation."

Notice 2015 VWs have the newer modular EA288 engine version. This might be key to at least saving that model year as those engines already have a modular AdBlue pee-pee (yeah, wonderful, right?) injection system. "As part of this major redesign, the engine also features an entirely new exhaust aftertreatment system—a compact unit close-mounted to the engine, helping to lower heat and pressure losses. The system is modular. It can use an SCR system, or NOx storage, or oxy cat—essentially whatever the engine needs, without affecting the rest of the engine. At the time, Volkswagen said that the flexibility of the MDB would allow the engines to meet the coming EPA Tier 3, California LEV III emissions standards." see http://www.greencarcongress.com/2015/09/20150921-vw2l.html


See that's the thing. EGR is only really used when the engine is at light-loads (no accelerating or requiring lots of power) such as coasting or idling. EGR is deactivated during full load or acceleration because it's not needed due to less NOx present during this mode. VW just has to come up with something during light-load running conditions. One way is just to increase fuel to air mixture or adjust the injection timing so it doesn't run ultra lean. The downside of course is fuel economy would suffer, but perhaps urea injection could be avoided.


/\ This is it. All the silly speculation by liberal arts journalists is wrong. More EGR means lower NOx, but more carbon build up. I know from experience. VW can simply fix the problem with reprogramming. It won't hurt short term performance or MPG, but in 10-20,000 miles those engines will gunk up inside.

 

[andyd]

Wabbout water injection?

 

[GiveMeAVowel]

Originally Posted By: Burt

/\ This is it. All the silly speculation by liberal arts journalists is wrong. More EGR means lower NOx, but more carbon build up. I know from experience. VW can simply fix the problem with reprogramming. It won't hurt short term performance or MPG, but in 10-20,000 miles those engines will gunk up inside.


VW in Europe use an extra injector to periodically wash the valves to keep the carbon from building up on those engines, my guess is that these can be added on fairly easily to the US engines and then the reprogrammed ECU will complete the job. I'm pretty sure that it is used on the same basic 2L TDI we get in the states so it would seem to be a plug and play solution.

 

[JHZR2]

I think a def addition would be the best. I always felt it was silly to not have that and have to operate with less efficient means.

My biggest problem is that we're literally trading a few ppm of NOx for tons of CO2. It's just so silly.... IMO the CA cars should get ad blue, and the cars from states without those rules get optimal programming to maximize mpgs as a means of reducing total tonnage of emissions...

 

[ls1mike]

I am sorry. I just can't help it. In the grand scheme of things the whole thing is not a big deal. But I find the Meme...funny.

 

[gregoron]

Originally Posted By: GiveMeAVowel
Originally Posted By: Burt

/\ This is it. All the silly speculation by liberal arts journalists is wrong. More EGR means lower NOx, but more carbon build up. I know from experience. VW can simply fix the problem with reprogramming. It won't hurt short term performance or MPG, but in 10-20,000 miles those engines will gunk up inside.


VW in Europe use an extra injector to periodically wash the valves to keep the carbon from building up on those engines, my guess is that these can be added on fairly easily to the US engines and then the reprogrammed ECU will complete the job. I'm pretty sure that it is used on the same basic 2L TDI we get in the states so it would seem to be a plug and play solution.


I'm thinking that almost all VW gasoline engine variations in the future (esp in the US) will come with multi-point injection. VW got in trouble with Dieselgate because of the short-cut they took to release an TDI engine without DEF.

They are currently avoiding the whole carbon coking issues on some TSI/FSI gasoline direct injection engines - another short-cut. This latter problem could be remedied by an additional port injection to - as mentioned above - wash the back of intake valves from carbon deposits. They released this MPI technology in Europe because of more stringent emissions requirement, but NOT in the US. Now it's not as big of an issue as the TDI engines, but to those who own DI engines it might be later on.

Now, as in both issues of diesel emissions and gasoline direct injected engine carbon buildup, the problem really occurs when both engines are in lean burn combustion mode, which occurs during idling and low-load operations. That's when the highest levels of NOx is produced for the sake of fuel efficiency. It's a Catch 22.