Urea injection for diesel

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Originally Posted By: Garak
Well, it is unfortunate, and diesel is already behind the 8 ball in a lot of ways. It's not an easy situation for everyone involved. If we want to see more diesel engines, their emissions controls are going to have to get more modern and reliable. If we want their emissions systems to get more modern and reliable, we're going to see some teething problems.


Agreed. What is so frustrating is the perceived lack of testing by the OEM's. The concepts of EGR and SCR are fairly simple but the execution leaves something to be desired. Carbonized intakes should either not require maintenance until significant miles have been reached OR cleaning should be relatively easy to perform by the owner.

Same goes for the SCR. If I need to rinse it out with distilled water prior to refill make it so instead of choosing to do nothing and just replace parts when they fail*.

*My car is on its third trip to the dealer over a Urea leak. The system for some reason decides to let the pump run after it evacuate a line and pump DEF out of the vent tube onto the ground.
 
Originally Posted By: JHZR2
It is a reagent in the catalytic process to get rid of NOx. In the USA, we're held hostage by California's geography and thus we can call 8 MPG SUVs "partial zero" emissions vehicles, while diesels are "gross polluters" when they return 50 MPG - and are forced to have this claptrap.

Actually Id rather have urea than not, and go another route. I think the processes to prevent NOx in diesels are worse than the aftertreatment...


Correct, reduced NOx. The leaner an engine gets, the higher propensity to produce NOx. It is a bad pollution. Urea is far better alternative to the DPF which uses Raw Fuel in the exhaust stroke to burn off particulates and reduce NOx. That is wasteful and unused heat energy.

Basically the 80% N2 in Air becomes reactive with Excess O2 due to not using it for combustion (read very lean). It is an undesireable byproduct of being a lean efficient engine.
 
I read about people not liking EGR. It is the best alternative to reducing NOx because it introduces O2 starved exhaust gas at low power demand conditions (idle or cruise) and reduces the formation of these pollutants. The selection of where manufacturers select the exhaust gasses is important. Too close to the turbo is too Hot. Before the turbo, too much soot formation. far from those, cooler and reduced soot and then "cleaner" air and less residue build up in the intake manifold.

Gassers have EGR tubes less than 3/8 inch (10 mm). Diesels have huge diameters, mine is 3/4 inch (20 mm) on a 1.9 liter Tdi. That much exhaust air is bound to carry residual intake manifold build up that requires a maintenance program to periodically eliminate. Any ideas on how to perform such a task?
 
Originally Posted By: bobthefarmer
I read about people not liking EGR. It is the best alternative to reducing NOx because it introduces O2 starved exhaust gas at low power demand conditions (idle or cruise) and reduces the formation of these pollutants. The selection of where manufacturers select the exhaust gasses is important. Too close to the turbo is too Hot. Before the turbo, too much soot formation. far from those, cooler and reduced soot and then "cleaner" air and less residue build up in the intake manifold.

Gassers have EGR tubes less than 3/8 inch (10 mm). Diesels have huge diameters, mine is 3/4 inch (20 mm) on a 1.9 liter Tdi. That much exhaust air is bound to carry residual intake manifold build up that requires a maintenance program to periodically eliminate. Any ideas on how to perform such a task?
you're basically correct. EGR lowers combustion temps (less O2) which lowers NOX formation. You have either a high pressure EGR or a combination High & Low pressure EGR.

As for cleaning you just pull off the intake or use a product to dissolve the carbon and send it down stream to be burned off.

FWIW the HP EGR for the BMW M57 is attached to the exhaust manifold and it sends a lot of soot back into the intake when open.
 
Originally Posted By: Thermo1223
Originally Posted By: Miller88
Why not kick all of this EPA garbage to the curb and go back to reliable, simple diesels?

Oh, wait, then Al Gore wouldn't be a multi billionaire ...


Because then you'd have a diesel generating 100hp and 300tq out of 8 liters of combustion.

The reasons diesel's run so well and make so much power is the multiple computer controlled injection events. Mechanical simply cannot do that. It may be more reliable but that is the only benefit.

Why not ditch FI and go back to carbs? Simpler right?


Well, not quite sure how the response related to the question here. The EPA goodies have nothing to do with power and torque. And no, you do not need computer controlled engine to generate serious power. You would be real hard pressed to convince an owner of the Cat 3406B mechanical diesel engine that is putting 1000 hp to the ground along with 2250 lb of torque that he can't do that without an ECM.

Or the carb thing? Again, what does that have to do with urea, diesels, and the EPA? FI has been a part of standard diesel components for longer than the EPA has been in existence.
 
"you're basically correct. EGR lowers combustion temps (less O2) which lowers NOX formation."

- Here you have whats troblesome with egr.
It lowers combustion temperatures...
-This means that you have to use more fuel since it is the temperature of the expanding gasses thats drives your engine.
Lower the temperature and output will be lower.
Then there are other problems like soot, large egr coolers and the assorted plumbing and valves but these are merely solvable
problems unlike the lower temperature wich have to follow a natural law and to that theres nothing you can do.
 
I wouldn't agree that EGR is the best method for reducing NOx. This could have all been handled quite well outside the engine with SCR, either in Urea DEF form or with a cartridge substrate solidified form like has been developed by Amminex. All emissions cleanup could be handled downstream of the diesel engine. The EPA, who has never turned a wrench on an engine, is behind the EGR idea. EGR on gassers is one thing, it is quite another on a diesel. With a diesel you need to have a cooler unit that will cool the exhaust gasses before feeding them to the intake. This puts tremendous loads on the cooling system over an above the engine needs itself. And when one of those coolers blows a leak, just hope you catch it before you need an engine rebuild.

Between the soot loading back into the engine, the required cooling of the EGR gasses, and the reduced combustion efficiency, which in turn increases the level of soot (talk about a dog chasing his tail), there is not one good thing about EGR and diesel engines. It was primarily because of the increased soot generation brought on by EGR that diesel particulate filters were mandated.

I currently am using a '98 EPA certified 2000 model 12.7 Detroit 60 in my 2013 model year truck. This engine has had some nice ECM tuning work done and it generate 550 hp and 1850 torque, and barely even soots anything. The stack tips remain very clean. No EGR and no DPF. That was not the case with my previous Cummins ISX with EGR. The soot loading on that one was tremendous. And along with the lower soot loading of the engine I use now, it puts the other engine to shame in fuel efficiency. I easily get 20-25% better fuel economy.
 
Originally Posted By: TiredTrucker
I wouldn't agree that EGR is the best method for reducing NOx. This could have all been handled quite well outside the engine with SCR, either in Urea DEF form or with a cartridge substrate solidified form like has been developed by Amminex. All emissions cleanup could be handled downstream of the diesel engine. The EPA, who has never turned a wrench on an engine, is behind the EGR idea. EGR on gassers is one thing, it is quite another on a diesel. With a diesel you need to have a cooler unit that will cool the exhaust gasses before feeding them to the intake. This puts tremendous loads on the cooling system over an above the engine needs itself. And when one of those coolers blows a leak, just hope you catch it before you need an engine rebuild.

Between the soot loading back into the engine, the required cooling of the EGR gasses, and the reduced combustion efficiency, which in turn increases the level of soot (talk about a dog chasing his tail), there is not one good thing about EGR and diesel engines. It was primarily because of the increased soot generation brought on by EGR that diesel particulate filters were mandated.

I currently am using a '98 EPA certified 2000 model 12.7 Detroit 60 in my 2013 model year truck. This engine has had some nice ECM tuning work done and it generate 550 hp and 1850 torque, and barely even soots anything. The stack tips remain very clean. No EGR and no DPF. That was not the case with my previous Cummins ISX with EGR. The soot loading on that one was tremendous. And along with the lower soot loading of the engine I use now, it puts the other engine to shame in fuel efficiency. I easily get 20-25% better fuel economy.


It would be nice to not need EGR. I guess current SCR systems can only convert a certain amount of NOX because I'm sure OEMS would've done away with EGR. Maybe in the not so distant future it will happen.

Interestingly it seems that only passenger cars and light trucks Diesels are likely to have EGR issues whereas OTR trucks do not.
 
With EGR my camper wall above and behind the stack used to get soot deposits.
With the EGR cooler in the garage (replaced by a plate) there is no more soot buildup on the camper, or in the air. So I've traded somewhat more NOx for much less soot emission. And no more risk of potential engine-deadly EGR cooler leak (already happened once at 12000 mi, replaced with revised part under warranty).

Charlie
 
As to whether the OEM's would have dropped EGR since we have SCR, not so sure. There is a lot of regulatory stuff going on behind the scenes. The OEM's are pretty much at the mercy of what the EPA is going to allow or not allow them to do in meeting emissions requirements.

Could it be to cover for when the DEF might be frozen in the lines before the engine has warmed up and coolant circulated to thaw the DEF? Could be it. But the cartridge that Amminex has had developed for a while now would circumvent that issue.

What I find truly amazing is that Navistar bought into Amminex to the tune of 50% ownership, and has yet to even put one of these on their commercial trucks. Since they got into a mess with the EPA regarding their non use of SCR and trying to meet regs by heavy dosing EGR, they had to finally put on SCR. They could have done the cartridge thing and made many folk's life easier. But they didn't. Go figure.
 
Navistar adopted the EPA's emissions control technology that relied heavily on EGR, and then found their engines couldn't pass production audit testing. Now they're trying to catch up to the rest of the manufacturers that have been using SCR, and it's good to see. Maybe Navistar will survive as a diesel engine manufacturer.

I sat through a presentation a couple of years ago given by Wayne Eckerle, who was director of research at Cummins. He discussed their on-highway emissions strategy. Cummins did an extensive design and testing program comparing EGR and SCR NOx control systems. After extensive testing, their decision was to go with SCR because there was a 10% fuel economy advantage, and the trucks would be cheaper to operate, even considering the cost of DEF.
 
Well I read the newer off road Diesels can meet previous emissions requirements with SCR only. Seems getting to current on-road requirements is going to be tougher.
 
Originally Posted By: Wesbo
Could you pee in the tank to get enough solution to get home? I'm only partly kidding...


Human urine does not contain near enough urea. DEF is ~32% urea while human urine is roughly 2.5% urea.
 
Originally Posted By: JHZR2
The regen thing I get, the warm up??? Other than some higher thermal efficiency, I dont see a substantial difference to warm up a diesel than a ga$$er, because if the same alloys, lube types, etc. are used, and the same power is output, its a matter of mass and heat capacity.

The diesel is more efficient, but the few % dont make a big difference given the quantity of waste heat. The engines are heavier, but that heat capacity difference can be calculated, and if normalized, wouldnt be any longer. Practically speaking it may not be any different.


At 20C outside there's no real appreciable difference - My Subaru will show normal temp in a couple of blocks, my VW TDI will take a block or two longer. At -20C the TDI won't be showing anything on the temp gauge after 5km, my Subaru will be halfway to warm. With heat on full blast at -20C, even on the highway, the TDI will show a few needle widths under normal temp until I back off the blower fan.
 
I believe that one of the reasons for this is that way a diesel burns fuel. Instead of a homogeneous mixture like in an SI engine the mixture in a diesel isn't homogeneous, it burns closer to the centre of the combustion chamber where it's injected. This leaves an insulating layer of air between the combustion process and the cylinder walls that reduces the amount of heat going into the coolant. It's kind of like a turbine engine which protects it's burner cans with relatively cool air flow from the compressor that's not used to burn fuel.

Obviously there's more going on, take model diesel engines vs. glow engines. They use a homogeneous mixture yet run cooler than the alcohol-fuelled glow engines.
 
Not so long ago every one was uppset by the fact that
you need to fill your diesel with urea and they thaught that urea was expensive....
So the manufacturers invented cooled egr....
 
Originally Posted By: ac_tc
Not so long ago every one was uppset by the fact that
you need to fill your diesel with urea and they thaught that urea was expensive....
So the manufacturers invented cooled egr....

What I encountered was not that people were offended by having to buy DEF.
They were upset that the engine would have an extra thing that needed to be maintained.

And cooled EGR is used on engines with DEF.
 
Originally Posted By: artificialist
Originally Posted By: ac_tc
Not so long ago every one was uppset by the fact that
you need to fill your diesel with urea and they thaught that urea was expensive....
So the manufacturers invented cooled egr....

What I encountered was not that people were offended by having to buy DEF.
They were upset that the engine would have an extra thing that needed to be maintained.

And cooled EGR is used on engines with DEF.


True, but Caterpillar ACERT and Navistar EGR engines (for 2010 EPA NOx emissions) really crank up the EGR, which puts quite a bit more of a load on the cooling system.

I'm not as well-versed on modern passenger car diesels, but I'd assume the same deal with them too.
 
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Originally Posted By: A_Harman
Navistar adopted the EPA's emissions control technology that relied heavily on EGR, and then found their engines couldn't pass production audit testing. Now they're trying to catch up to the rest of the manufacturers that have been using SCR, and it's good to see. Maybe Navistar will survive as a diesel engine manufacturer.

I sat through a presentation a couple of years ago given by Wayne Eckerle, who was director of research at Cummins. He discussed their on-highway emissions strategy. Cummins did an extensive design and testing program comparing EGR and SCR NOx control systems. After extensive testing, their decision was to go with SCR because there was a 10% fuel economy advantage, and the trucks would be cheaper to operate, even considering the cost of DEF.


That's true, Navistar went with high EGR, and got bit in the backside for doing so. That just makes things even more confusing. Since they bought a 50% share of Amminex, who makes SCR solid cartridges to use in place of DEF tanks, why didn't Navistar then, or now, go with the system. It seems like a best of all worlds solution. You get SCR to keep the EPA happy, and it is in a solid cartridge form that is designed to go the length of a typical oil change interval. Easy to take a used cartridge out and slide in a new one. And a spare cartridge could be carried in a side box if needed. No risk of spilling or corrosion.

Instead, they adopted Cummins SCR technology with DEF. Go figure.
 
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