mCRD

[TomIre]

How is the Diesel Oxidation Catalyst different / better than a DPF system? I was told by Mahindra dealer that a DPF system cost $6k to replace and that it had a finite life. Does DOC last forever? Not having a high heat generating DPF sounds good to me but why does everyone else use it? Maybe I'm missing something?

 

[Peter 315]

It most likely is cost difference The mahindra runs hotter all the time to burn off the soot, Where the others run a regen cycle

 

[s219]

Mahindra marketing has done a good job making everybody think they have escaped Tier 4 magically, and some of their dealers are a bit too "verbose" about it (my polite way to describe it) but they just use a different type of system. It's debatable what is better. Neither is as good as pre-Tier-4 obviously, and both have a lot of computer controls and sensors that are probably more of a worry than the actual type of filter or catalyst that is in the plumbing.

From what I have heard, the life of a DPF is not something most of us will ever have to worry about.

I am skeptical of a $6K replacement cost, as it would have significantly impacted the prices of new tractors if that were the case. I never saw very much price increase when Tier 4 tractors came along, not any more than we normally see with yearly price increases and new models.

I have a Tier 4 Interim tractor, which was the standard before these Tier 4 Final tractors came along. I like my tractor because it's so simple (no computer, no electronics) and have been skeptical about the Tier 4 Final tractors. However, aside from a couple models, it seems like the Tier 4 Final tractors have been fine for the most part. So I probably wouldn't let it deter me from buying a new tractor.

 

[RNeumann]

Interesting replies- both Kubota owners..... #2 is false and three is a stretch with a lot of conjecture.

DPF is just what it says- a filter. The “regen” tries to burn off the buildup in the filter but over time it will need serviced and or replaced. It is a known wear item- just google DPF servicing- it’s an industry! Because of the materials in the filter the replacement cost is high.
Mahindra uses a little catalytic converter to achieve the Tier 4. While not a cheap replacement it is not known as a replacement item. I don’t know if a car sold in the USA in the last 30 years that doesn’t have a catalytic converter. They are known to work well for many years.

Most over the road trucks use the DPF. The regen typically occurs while they are driving. With tractors and and other shorter trip type vehicles (fire engines come to mind) they will need the regen done manually every so often- this is a 5-20’ process. You will also need to keep DEF in the machine.
Both can be eliminated however the DPF is more involved. It senses the need to regen based on inlet and outlet pressure. So any work around will need to maintain those sensors in order to trick the computer and not throw codes. I’m not sure what would need to be done for the DEF side of things. The Mahindra would involve adding about 8” or exhaust pipe where the converter was. The converter doesn’t have a sensor in it.....that I saw anyway.
Bottom line- tens of thousands of vehicles use both technologies. Both seem to work. The DPF takes more user input (maint, regen, DEF) but it’s not the end of the world.
I wouldn’t base your decision solely on the emissions. But if you are weighing both I’m sure one will meet your needs more than the other.

 

[deserteagle71]

Don't know about other tractors but my Kubota M7060 has a Diesel Particulate Filter but DOES NOT use DEF. I know all the newer diesel pickups have to use it, so I don't know how the Kubota engineers got away without having to include it.
But the regen process is no big deal...I notice the "regeneration" light come on in the dash and then a few minutes later it goes off. Can't tell the difference when the tractor is working, regenerating or not.

 

[jeff9366]

Mahindra marketing has done a good job making everybody think they have escaped Tier 4 magically, but Mahindra just uses a different type of emission system.

It's debatable what is better. Neither is as simple as pre-Tier-4 obviously, and both have a lot of computer controls and sensors that are probably more of a worry than the actual type of filter or catalyst that is in the plumbing.

From what I have heard, the life of a DPF is not something most of us will ever have to worry about.

I concur.

There are good reasons to choose one tractor brand over another, but not on emission control basis.

Contributors here grumbled as Tier IV reached the market in 2012. A few still do. Real life, there have been few owner complaints regarding Tier IV, other than the price increase the equipment instigated. A two to four horsepower increase is a bonus with Tier IV not generally acknowledged.

The average residential tractor user clocks just eighty hours per year on tractor engine, according to industry sources. I have to re-gen my Tier IV Kubota @ 2,200 rpm for SIXTEEN MINUTES ($1.00 in diesel) every sixty engine hours.

 

[Peter 315]

Interesting replies- both Kubota owners..... #2 is false and three is a stretch with a lot of conjecture.

DPF is just what it says- a filter. The 途egen tries to burn off the buildup in the filter but over time it will need serviced and or replaced. It is a known wear item- just google DPF servicing- it痴 an industry! Because of the materials in the filter the replacement cost is high.
Mahindra uses a little catalytic converter to achieve the Tier 4. While not a cheap replacement it is not known as a replacement item. I don稚 know if a car sold in the USA in the last 30 years that doesn稚 have a catalytic converter. They are known to work well for many years.

Most over the road trucks use the DPF. The regen typically occurs while they are driving. With tractors and and other shorter trip type vehicles (fire engines come to mind) they will need the regen done manually every so often- this is a 5-20 process. You will also need to keep DEF in the machine.
Both can be eliminated however the DPF is more involved. It senses the need to regen based on inlet and outlet pressure. So any work around will need to maintain those sensors in order to trick the computer and not throw codes. I知 not sure what would need to be done for the DEF side of things. The Mahindra would involve adding about 8 or exhaust pipe where the converter was. The converter doesn稚 have a sensor in it.....that I saw anyway.
Bottom line- tens of thousands of vehicles use both technologies. Both seem to work. The DPF takes more user input (maint, regen, DEF) but it痴 not the end of the world.
I wouldn稚 base your decision solely on the emissions. But if you are weighing both I知 sure one will meet your needs more than the other.

No def in the Kubota

 

[Turbys_1700]

New Holland utilizes a catalyst in the Workmaster 50/60/70 series. I've owned a 50 two years now. Not one iota of trouble with the emissions or tractor. If you research Fiat Powertrain Technologies they invented direct injection technology for diesels and sold the rights to Bosch. They build great engines.

 

[MatHaas]

How is the Diesel Oxidation Catalyst different / better than a DPF system? I was told by Mahindra dealer that a DPF system cost $6k to replace and that it had a finite life. Does DOC last forever? Not having a high heat generating DPF sounds good to me but why does everyone else use it? Maybe I'm missing something?

Google search is great tool... lol.

DOC is a catalytic converter. The exhaust gas passes through a material which oxidizes/breaks down the environmentally "harmful" stuff. "The diesel oxidation catalyst is designed to oxidize carbon monoxide, gas phase hydrocarbons, and the SOF fraction of diesel particulate matter to CO2 and H2O"

A DPF is a more extensive breakdown system. It usually has a DOC, then a DPF. Some systems also use Diesel Exhaust Fluid (DEF), in addition, which is yet another addition, spraying that fluid the exhaust to further break down the "harmful" particles.
" Exhaust gas passes through the DOC and then into the DPF where Pariculate Matter is collected on the walls of the DPF. The PM collected is then oxidized to remove it from the DPF. This is known as regeneration. When operating conditions maintain sufficient exhaust temperatures, the DPF is continually self-regenerating. This is known as passive regeneration and results in clean exhaust out of the tailpipe. On very infrequent occasions, an active self-regeneration is required to remove a build-up of PM in the DPF, due to insufficient exhaust temperatures. Exhaust temperatures are raised by injecting a small amount of fuel upstream; The resulting chemical reaction over the DOC raises exhaust gas temperatures high enough to oxidize the PM from the filter."

To the best of my knowledge, the Mahindra Common Rail Diesel engine was designed with the modern electronic components to properly manage and optimize fuel used in the engine, this results in minimal excess waste, which the DOC can take care of. Specific components are things like the Bosch CB18 fuel pump which has a mechanic side to bring fuel form the tank to the pump, then an electronically controlled metering system (which receives input from multiple sensors) that limits the amount of fuel in the high pressure side and up to the fuel rail and injectors. Things like the engine speed sensor, rail pressure sensor, etc all help the ECU to fine tune the perfect amount of fuel to get to engine, but not excess. Then things like the EGR system help eliminate excess pollutants out of the exhaust before the DOC. So little to no unburned fuel and pollutants out the exhaust.

Realistically, this is all just making the engine and fueling efficient and there is no excess. That's why these tractors arent puffing black smoke like all of the old stuff. Old models did everything mechanically, where it would only grossly calibrate how much fuel was being put in to the engine, wasting more and polluting more.

It's essentially like the transition from carburetors to fuel injection. A computer monitoring and managing everything to make it as efficient as possible. Sure it's a little more "complicated" but I prefer to say complex. and yea, it can be a pain when sensors arent working or there isn't good ECU software support (which Mahindra does struggle with here in the US). But all things aside, it's actually a decent design. and it can have it's benefits.

I guess it's kind of like pick your poison, an engine with less electronics to make fuel use efficient will need the more extensive exhaust oxidation system to meet emission requirements. The other side is the use more electronics to make the engine more efficient which requires less exhaust oxidation treatment.


-Haas

 

[MatHaas]

It most likely is cost difference The mahindra runs hotter all the time to burn off the soot, Where the others run a regen cycle

False, that's not how it works. Actually the opposite compared to DPF.

 

[Peter 315]

False, that's not how it works. Actually the opposite compared to DPF.

Well , That' what I read somewhere , So I was wrong Do you think that the filter on the Mahindra is not going to plug up after time ?

 

[RNeumann]

The Mahindra uses a catalytic converter. It’s not a known wear item- no catalytic converter is. In fleet service “known wear items” are given a replacement or inspection interval.

With regards to heat. The hotter (in general) the engineers can make a motor the cleaner it burns. As technically has improved and emission requirements have increased engine temps have risen. It’s been across the board- cars, trucks and tractors etc.

The regen adds enough heat to the DPF (as it burns off particulates) and exhaust that we’ve had it melt a spot on the asphalt in our back lot. Different manufacturers have dealt with this differently- heat shields, redirect exhaust etc. Kubota added vents to the hood to help get rid of the heat buildup.
This isn’t a knock on one vs the other. It’s just the reality of modern emissions. We are fortunate to have a choice between several different approaches with regards to tractors.

 

[Peter 315]

I know car catalytic converters are different but I know that they will plug up. I wonder if that system on the tractor will too ?

 

[s219]

Interesting replies- both Kubota owners.....

What has that got to do with anything? What is the purpose of your comment other than to turn this into a brand bashing thread?

The whole point of my post is that both systems are heavily reliant on computer control and sensors, and those are the weak spots. And I'll be fair to note that both Kubota and Mahindra have had issues with emissions software and control on their tractors. Anybody, including a salesman, who thinks it's super important whether a tractor uses a DPF or a DOC or whatever, is missing the point that the computer, the software, and the sensors are the complicated parts. What's inside a chamber on the exhaust plumbing is a minor factor. It's not that simple. If you want simple, get a Tier 4 Interim tractor without the computer or sensors.

 

[MatHaas]

I know car catalytic converters are different but I know that they will plug up. I wonder if that system on the tractor will too ?

I can't say I agree with you. With a proper running engine, the DOC should last a long time. I've never replaced a catalytic converter on any of my vehicles. I've owned about 15 different vehicles, ranging from production years 1980 to 2007, including vehicles i've put 200k+ miles on them personally. When a cat clogs up, it's likely from other engine issues allow excess contaminants in the exhaust; IE inefficient combustion, excessive blow by, burning oil, etc.

That's the point of the modern electronic engine management. Optimize the engine to fully burn the fuel put in the combustion chamber. Then additional circuits that recirculate exhaust gas to burn any other unburned fuel particles. resulting in a much "cleaner" final exhaust gas. which then runs over a simple catalyst material to further oxidize the gas.

 

[Peter 315]

I can't say I agree with you. With a proper running engine, the DOC should last a long time. I've never replaced a catalytic converter on any of my vehicles. I've owned about 15 different vehicles, ranging from production years 1980 to 2007. When a cat clogs up, it's likely from other engine issues allow excess contaminants in the exhaust; IE inefficient combustion.

That's the point of the modern electronic engine management. Optimize the engine to fully burn the fuel put in the combustion chamber. Then additional circuits that recirculate exhaust gas to burn any other unburned fuel particles. resulting in a much "cleaner" final exhaust gas. which then runs over a simple catalyst material to further oxidize the gas.

If it works the way it should ,But no matter what we are all screwed anyways

 

[MatHaas]

With regards to heat. The hotter (in general) the engineers can make a motor the cleaner it burns. As technically has improved and emission requirements have increased engine temps have risen. Itç—´ been across the board- cars, trucks and tractors etc.

I don't think it's generally the hotter the cleaner. It's that we've found the most efficient equation to (optimal temperature and amount of fuel) to get the most efficient combustion. there are plenty of materials that would hold up to an operating temperature of 300 degrees, but that's wouldn't make the combustion better, nor would it be "cleaner". yes, excessive heat will incinerate waste products in the exhaust, but that's where the DPF/regen/DEF come in; but we're talking about operating temperatures, and you can have operating temperatures through the roof and have poor combustion and excessive waste in exhaust. that's the number one reason you need to be careful on diesels; because more fuel adds more power, but it also adds more heat. you start dumping tons of fuel, pouring black smoke out the exhaust, making more power, and your EGTs go through the roof, some to the point of melting the exhaust valves, but your exhaust is FAR from cleaner.

not that you were exactly saying that, but it should be clarified. the only reason engines run "hotter", is because we found out that we weren't in optimum operating temperatures to have the most efficient fuel combustion. gas engines have had operating temps of 190-210 (+/- 10 or so degrees) for over 60 years, back when basic carbs were the cream of the crop. pretty sure diesels haven't varied substantially either over a similar time frame, just the gradual increase. limitations in efficient cooling systems were also likely a factor.

the physical properties of engine materials used, oil properties, etc all have a play an additional role on ideal temperature as well; but i think the main focus has been around the most efficient combustion.

 

[Bud Soda]

Well , That' what I read somewhere , So I was wrong Do you think that the filter on the Mahindra is not going to plug up after time ?

If you don't like the DPF take it off. I took mine off at 12 hours, about 200 hours now and never needed a regen.

 

[MatHaas]

What has that got to do with anything? What is the purpose of your comment other than to turn this into a brand bashing thread?

The whole point of my post is that both systems are heavily reliant on computer control and sensors, and those are the weak spots. And I'll be fair to note that both Kubota and Mahindra have had issues with emissions software and control on their tractors. Anybody, including a salesman, who thinks it's super important whether a tractor uses a DPF or a DOC or whatever, is missing the point that the computer, the software, and the sensors are the complicated parts. What's inside a chamber on the exhaust plumbing is a minor factor. It's not that simple. If you want simple, get a Tier 4 Interim tractor without the computer or sensors.

good point.

I think it's a bit early to tell, but the ultimate decision would be if you could calculate which lasts longer in the long run.
The computer software, electronic components, etc are all still a newer application. As well as the exhaust treatment systems.

In my opinion, i'd rather treat the root of the problem. And that's the engine, it's fuel management, and combustion efficiency.
I don't own a DPF/DEF vehicle, nor do i know the ACTUAL service life of them or cost.
I am familiar with electronic engine managment, and with the right components, they can be very reliable. We're still working on reliability & optimization though for these tractors though.

In my eyes, it's just like the transition from carbs to fuel injection. and i think fuel injection was a huge success. sure there's more parts, but once it's all figured out and the quality is there too, it's well worth it. but that is just my opinion.

 

[sd455dan]

I don't think it's generally the hotter the cleaner. It's that we've found the most efficient equation to (optimal temperature and amount of fuel) to get the most efficient combustion. there are plenty of materials that would hold up to an operating temperature of 300 degrees, but that's wouldn't make the combustion better, nor would it be "cleaner". yes, excessive heat will incinerate waste products in the exhaust, but that's where the DPF/regen/DEF come in; but we're talking about operating temperatures, and you can have operating temperatures through the roof and have poor combustion and excessive waste in exhaust. that's the number one reason you need to be careful on diesels; because more fuel adds more power, but it also adds more heat. you start dumping tons of fuel, pouring black smoke out the exhaust, making more power, and your EGTs go through the roof, some to the point of melting the exhaust valves, but your exhaust is FAR from cleaner.

not that you were exactly saying that, but it should be clarified. the only reason engines run "hotter", is because we found out that we weren't in optimum operating temperatures to have the most efficient fuel combustion. gas engines have had operating temps of 190-210 (+/- 10 or so degrees) for over 60 years, back when basic carbs were the cream of the crop. pretty sure diesels haven't varied substantially either over a similar time frame, just the gradual increase. limitations in efficient cooling systems were also likely a factor.

the physical properties of engine materials used, oil properties, etc all have a play an additional role on ideal temperature as well; but i think the main focus has been around the most efficient combustion.

Agree,
I think it is more about the actual injection pressure and timing control.
mechanical injection is generally between 2500-5000 psi .
When you get into common rail injection with CPU controlled electric injectors pressures jump up dramatically to well over 20,000 psi and with the Bosch CP4 systems now on some engines are over 36,000 psi These higher pressures allow for a much finer spray from the injector which is easier to ignite add in the ability to add multiple injection events and complete control of the timing it makes sense that fuel use and emissions can be reduced.