Comparing different approaches to emissions

[4tillingdirt]

I believe the two main approaches are using a DPF, with some using a catalyst and a DPF, or using a catalyst with a cooled EGR and no DPF. I know Massey and Mahindra tout their approach with no DPF and no regen cycle, which on the surface appear to be superior. Does anyone have any good information on why the no DPF route would be more trouble than manufacturers claim they are?

 

[3Lfarms]

I can foresee a problem with those systems. With an active regeneration system, when the system sees the catalyst plugging up, it will initiate a regen burn.
On the passive systems that are always supposed to be burning off the soot, if for some reason, say a dirty injector, causes the engine to produce soot, once the catalyst plugs up, there is no way for the user to clean it out.

 

[jeff9366]

I can foresee a problem with those systems. With an active regeneration system, when the system sees the catalyst plugging up, it will initiate a regen burn.

Beginning about thirty-three horsepower most tractors have Diesel Particulate Filters (DPF).
If not DPF, the less used alternative emission technology is Diesel Oxidation Catalyst (DOC).
Both the DPF and the DOC are honeycomb ceramic filters.
The DOC forces engine exhaust over a honeycomb ceramic structure coated with platinum, palladium, and rhodium catalysts. These catalysts oxidize carbon monoxide and hydrocarbons into carbon dioxide and water at hot exhaust temperature.


There is no catalyst associated with a Diesel Particulate Filter. A DPF is a ceramic matrix which accumulates particulates/soot at temperatures below soot ignition temperature. During regeneration, when DPF achieves and maintains at least 500 degrees Fahrenheit, the temperature of a hot kitchen oven, accumulated soot incinerates during a few minutes.


Operator Manuals for DPF equipped compact tractors do a poor job of explaining DPFs and a poor job of explaining regeneration cycles. For instance, two manuals i have viewed do not inform that soot accumulates faster during low weather temperatures, none inform time required for DPF to attain 500 degrees fahrenheit, the ignition temperature for diesel soot and none address faster soot accumulation at higher altitudes. It seems to me a DPF temperature readout on electronic instrument panels would address many DPF complaints, as would more descriptive technical writing.


As off-road diesel engines increase in displacement and horsepower emission treatment becomes increasingly complex. DPFs as a final particulate treatment are primarily associated with diesel engines <75-horespower.


Keep in mind emission standards for over-the-road diesel engined vehicles are much tighter than emission standards for off-road engines AT THIS TIME.

 

[ericm979]

Emission Standards: USA: Nonroad Diesel Engines

There's three power categories for CUTS: under 25.47hp, under 75hp, over 75hp. The requirements get stricter with each category. Under 25hp can be met without EFI or DEF or DOC.

For 25-75hp there are three solutions currently in the market: EFI + DPF, EFI + DOC and EGR, and DOC + DPF. Branson does the last one. Mahindra and some Masseys do EFI + DOC. Everyone else does EFI + DPF. That solution requires active regen, the other two do not. Regen systems usually inject additional fuel to get the DPF up to temp. Branson's DOC + DPF doesn't do that. EFI + DOC probably doesn't either but I'm not sure.

Regens can be nearly un noticeable if the tractor's hot and working hard. When it's cold out, especially with smaller engines, it can be difficult to get the DPF up to temp. Kubota B3350s are notorious for that (the turbo does not help). Bransons have mechanical injection and do a low temp continual regen. If you don't run the tractor hard enough often enough the DPF can clog. For example if you're somewhere with cold winters, only do loader work all winter and don't run the engine in the recommended rpm range. There's a warning light that comes on before the DPF gets too clogged. Working the tractor hard will unclog the DPF. One way is to put it in high range and run it up and down the road for a while.

With a regen system you can run the tractor at low rpm all the time and it'll just do more regens. But you'll be having to put up with regens. If you're clogging the DPF quickly by not running it hard then you'll be doing parked regens where the ECU runs the rpms up for 20 minutes or so.

I'd say that if you're going to be doing loader work inside all cold winter, get a tractor that does regens. If you want to remove the DPF, that's easy on a Branson. However I suggest keeping it until it actually causes a problem. If you're going to run the tractor hard periodically and follow the manufacturer's recommendations, all the systems will work well.

With any of the systems, a clogged injector that's spewing fuel (don't they usually spray less when clogged?) would cause the DPF or DOC to clog quicker. In which case you'd be notified by the system monitoring it (by more frequent regens on a regen system) and could take action. On a non regen system you can get the filter hot by running the tractor hard and cook off the soot.

 

[TractorNH]

There is no catalyst associated with a Diesel Particulate Filter. A DPF is a ceramic matrix which accumulates particulates/soot at temperatures below soot ignition temperature. During regeneration, when DPF achieves and maintains at least 500 degrees Fahrenheit, the temperature of a hot kitchen oven, accumulated soot incinerates during a few minutes.

Great write-up. The only correction is the regen temp for DPF is 600 deg C or about 1100 deg F which is why some systems use a diesel injector in the DPF to help get the temperature up to burn off the carbon buildup.

 

[TractorNH]

I believe the two main approaches are using a DPF, with some using a catalyst and a DPF, or using a catalyst with a cooled EGR and no DPF. I know Massey and Mahindra tout their approach with no DPF and no regen cycle, which on the surface appear to be superior. Does anyone have any good information on why the no DPF route would be more trouble than manufacturers claim they are?

DOC functions in the same way as a catalytic converter for a gas engine, it's basically the same thing.

 

[MaineGuy1]

I had the Massey mechanic at my place the other day to pressure test my coolant system, found a loose hose. Anyway, I was talking to him about the different engines and emissions controls. He said the biggest pain and problem is the operator because they don't get the engine up to temperature or load the engine up enough. After a couple failed regens the only way to fix it is by hooking the computer up to it. In cold weather he has to tell his customers some of the tractors need cardboard placed in front of the radiator or else the temps won't get high enough. I purchased the 1735M with the Shibaura engine that uses the DOC and EGR. He likes them better ONLY because the operator really can't screw anything up

 

[finn1]

The op asked the same question over on the Kioti section, and I will give the short answer as I see it here.

Banking and Trading and Fleet Average emission implementation strategies impact what a manufacturer ultimately implements on a specific model.

If I sell a broad range of tractors and can bank emission credits on some models, or buy credits from someone like Tesla, I can sell some tractors that are above the standards.

It is a common strategy in the engine business.

 

[finn1]

Doc controls HC emissions, with only a minor effect on PM.

 

[jeff9366]

With a regen system you can run the tractor at low rpm all the time and it'll just do more regens. But you'll be having to put up with regens. If you're clogging the DPF quickly by not running it hard then you'll be doing parked regens where the ECU runs the rpms up for 20 minutes or so.

Quickly?? Bear in mind the average residential user clocks eighty (80) engine hours per year.

Regeneration is an infrequent event for my Kubota three cylinder engine.
Generally once every sixty engine hours. (Consistent in Florida due to warm weather.)

60 hours X 60 minutes = 3,600 minutes.

16 regeneration minutes /3,600 = .00444 = 4/10s of 1% of engine time is parked regeneration.

Fuel cost for sixteen minute parked regeneration @ 2,200 rpm ~~$1.00.



I clock 250 to 300 engine hours per year.