DPF Regeneration Question

[KPear]

I know that I'm bringing up a topic that has discussed and debated to death, but I can't find a solid answer to a question I have.

I understand that there are 3 basic types of DPF regeneration: Passive, which occurs when the exhaust temperatures are high enough to burn off accumulated soot (highway, towing); Active, which occurs when the engine injects extra diesel into the exhaust stream to burn off accumulated soot; Command-operated, which manually initiates an active regeneration with a diagnostic tool.

So here is my question: If a 6.7l Cummins owner is engaged in low-speed, near idle driving (think stop-and-go city traffic or 4wd low driving on a rough forest road) and a DPF alert on the dashboard indicates “Exhaust Filter XX% Full Safely Drive at Highway Speeds to Remedy,” will the DPF actively regenerate even if the driver continues at slow speeds? In other words, can the DPF actively regenerate even at very low speeds or near idle conditions?

I’ve got to believe that Ram built in some robustness to the emissions design which would accommodate different driving styles or real-world conditions. Or does Ram actually require you to end your current driving style and immediately get on the highway when that message appears?

The reason I ask, is that the Diesel Supplement for the Ram 1500 and 2500/3500’s is very vague on the subject. It basically says that when that message appears, you need to drive at highway speeds to allow the DPF to actively regenerate. But I also thought the whole reason Ram switched to SCR was to alleviate some of the DPF clogging issues that were present on the earlier Ram 6.7l’s?

Anyone have some factory literature on this subject?

 

[Badunit]

It will regenerate in stop and go traffic under normal conditions. Mine went thorugh one on my trip home from work this evening. But if it says to get on the highway, it is more clogged than usual and may not be able to clear itself sufficiently at low speed. I have not yet seen that message but I would follow its advice if I did.

 

[Newsa]

Never seen it tell me to drive hwy speeds.

But i think hwy speeds are better.

 

[Deleted member 995608]

In 60K + miles, I've gotten two messages reading "FILTER FULL", "SEE DEALER" and that's it. It goes away after a while. The only way I know my exhaust is doing its thing is there is a ticking noise and a light odor of something or ruther.

 

[KPear]

Okay so the message "Exhaust Filter XX% Full Safely Drive at Highway Speeds to Remedy" is more of a remedial regeneration rather than a normal active regen?

Active regen's can and do occur at slow speeds, correct? Do they stop when the vehicle is put into park? I'm interested to know just how burdensome these active regen's are; I know quite a few people who work their diesels in all kinds of settings besides pure highway. For example, a logger slowly traveling down an old forestry road can't afford to stop what he is doing and go find a highway to drive on for 30 minutes should the DPF suddenly need to regenerate.

 

[sag2]

Because a regeneration creates so much heat they don't like to do them when the vehicle is stationary or close to stationary. Most of the time if it's going to be completely full and can't regen there's something else going on with the truck causing excessive soot. Also, SCR has nothing to do with the DPF. It's there to reduce nitrous oxides.

 

[JR]

As Sag eluded to, the SCR was implemented to curb NOX which was previously done with copious amounts of EGR. SCR handles the NOX down stream of the engine by spraying DEF into the exhaust gas prior to the SCR catalyst which flashes off under normal operating exhaust temps to form carbon dioxide and ammonia. The ammonia reacts with the NOX as it passes through the SCR catalyst and breaks down into nitrogen and water.
Your referring to the DPF which traps soot (PM) until the filter is full in which case the vehicle needs to regen to bake the soot out. According to the 6.7 engine owners manual the exhaust SURFACE temperatures can reach upwards of 1300 degrees during an active regen. The only warning I've seen is directly related to the extreme temperatures of the exhaust and the risk of fire, property damage, or personal injury (burns). In other words, it won't hurt the truck to perform an active regen at low/stationary speeds but you should be aware of your surroundings while it's taking place.

 

[KPear]

Because a regeneration creates so much heat they don't like to do them when the vehicle is stationary or close to stationary. Most of the time if it's going to be completely full and can't regen there's something else going on with the truck causing excessive soot. Also, SCR has nothing to do with the DPF. It's there to reduce nitrous oxides.

I understand the SCR's task is different from the DPF's (reducing NOx versus Particulate Matter).

However, I do recall reading Cummins literature discussing how the introduction of the SCR alleviated some of the earlier DPF issues. The explanation, as I understood it, was that any engine tuning which decreased the NOx emissions had an inversely proportional affect on Particulate Matter output. Hence why the earlier trucks with only EGR and DPF's had more issues. The SCR has taken some of the burden off the EGR, so to speak, and also allows for a bit more NOx engine ouput (since it will be treated downstream) which in turn decreases the soot particulate matter output (and the load on the DPF).

Returning to my original question: so no one here as had a problem with the 6.7l Cummins conducting an active regeneration during very slow speed driving?

 

[Newsa]

I understand the SCR's task is different from the DPF's (reducing NOx versus Particulate Matter).

However, I do recall reading Cummins literature discussing how the introduction of the SCR alleviated some of the earlier DPF issues. The explanation, as I understood it, was that any engine tuning which decreased the NOx emissions had an inversely proportional affect on Particulate Matter output. Hence why the earlier trucks with only EGR and DPF's had more issues. The SCR has taken some of the burden off the EGR, so to speak, and also allows for a bit more NOx engine ouput (since it will be treated downstream) which in turn decreases the soot particulate matter output (and the load on the DPF).

Returning to my original question: so no one here as had a problem with the 6.7l Cummins conducting an active regeneration during very slow speed driving?

I didn't have a problem with it doing a low speed regen. It actually used to do a low speed regen with the 2013 programming that it came with from the factory.

But by 2015, they loaded a flash that stopped any low speed or near idle active regens.

 

[JR]

Returning to my original question: so no one here as had a problem with the 6.7l Cummins conducting an active regeneration during very slow speed driving?

Exactly what problems are you concerned with?

Keep in mind these exact engines/emissions components are used in construction and Ag, where speeds rarely exceed 10-15 mph. Take a crane for example that can be set up on outriggers for days or weeks or months at a time and goes absolutely nowhere. Like I said above the only warning in the 6.7 engine owners manual relates to the risk of fire, property damage, or personal injury (burns). This is true regardless of application and is merely a reminder to be aware of your surroundings while the engine is performing a regen.

 

[KPear]

I didn't have a problem with it doing a low speed regen. It actually used to do a low speed regen with the 2013 programming that it came with from the factory.

But by 2015, they loaded a flash that stopped any low speed or near idle active regens.

Did you hear that from a dealership technician?

Exactly what problems are you concerned with?

Keep in mind these exact engines/emissions components are used in construction and Ag, where speeds rarely exceed 10-15 mph. Take a crane for example that can be set up on outriggers for days or weeks or months at a time and goes absolutely nowhere. Like I said above the only warning in the 6.7 engine owners manual relates to the risk of fire, property damage, or personal injury (burns). This is true regardless of application and is merely a reminder to be aware of your surroundings while the engine is performing a regen.

Not worried about any specific problems per se. I just was reading through the diesel supplement and it had very explicit language about needing to drive at "highway speeds" should a certain DPF message appear on the dash....from the feedback so far, it seems that message isn't too common, but if it does come up and someone is slowly crawling along (in traffic or on a rough 4wd road) I just don't understand what options the drive has at that point.

 

[Newsa]

Did you hear that from a dealership technician?

No, with the old programming, i used to be able to tell when it was regenning actively. I can no longer tell since they reprogrammed with the flash update

 

[Wiredawg]

Right off the top, the C&Cs are clean idle certified, so they regen at idle: My old 2009 4500 would regen in town and the only way I could tell was slight increase in RPMs and EGT gauge would be around 11-1200 degrees. My new 5500, I never know when it regens. I have an EGT gauge, just haven't taken time to install it. Not sure this helped, but represents the C&C crowd.

Cheers, Ron

 

[Newsa]

No, with the old programming, i used to be able to tell when it was regenning actively. I can no longer tell since they reprogrammed with the flash update

My girlfriend used to ask why my truck was making a deeper/throatier engine noise and why it started hissing like the exhaust brake was being activated and about 150-200 RPM slight increase at idle.

I just assumed it was regenning. When truck was stopped it would only do it if i took my foot off the brake. Take my foot off the brake, and it starts growling again.

Doesn't do that with the newer flashes

 

[JR]

Right off the top, the C&Cs are clean idle certified, so they regen at idle: My old 2009 4500 would regen in town and the only way I could tell was slight increase in RPMs and EGT gauge would be around 11-1200 degrees. My new 5500, I never know when it regens. I have an EGT gauge, just haven't taken time to install it. Not sure this helped, but represents the C&C crowd.

Cheers, Ron

Technically the engines are all the same across the board. The difference being any truck over 14k GVW must carry the Clean Idle Certification or by law must be programmed to automatically shut down after 5 minutes of idling. Since pickup trucks are under 14k GVW they are exempt from the requirement and therefore not required to carry the certification which is vin specific at an added cost per engine.

 

[Newsa]

Exactly what problems are you concerned with?

Keep in mind these exact engines/emissions components are used in construction and Ag, where speeds rarely exceed 10-15 mph.

Aren't emissions standards for cranes and ag equipment different than over the road applications?

That's why Caterpillar stopped making engines for semi's.

 

[KPear]

I'm somewhat amazed that despite all the experience on this forum, no one can give me a straight answer on this.

 

[JR]

Aren't emissions standards for cranes and ag equipment different than over the road applications?

That's why Caterpillar stopped making engines for semi's.

They're all tier IV final. A QSB 6.7 has the exact same emissions components and meets the same regs as an ISB 6.7. Cat temporarily dropped out of the highway program because they went an entirely different direction than all the other manufacturers and it backfired on them big time. But they too are now back on scene with tier IV final compliant engines.

 

[Newsa]

Maybe the reason that construction equipment and ag equipment are less likely to start a fire when the emissions/exhaust equipment gets above 1000 F is that their exhaust systems don't usually run along the ground under the vehicle. The exhaust systems on these pickup and C&C trucks might ignite dry leaves, brush or spilled fuel???

I'm sort of making a case for mounting stacks on your truck..... As a safety precaution??

 

[JR]

I'm somewhat amazed that despite all the experience on this forum, no one can give me a straight answer on this.

If you would like I can take a picture tonight of the one and only warning in the engine owners manual I have regarding active regens. It is almost word for word what I posted above.
As to your specific question, did you read your entire owners manual regarding regens? I dont have mine handy but I do remember reading something about maintaining your current driving conditions during active regen. I monitor a couple of EGT points as well as dpf state and soot load percentage with a Scan Gauge and can tell you the active regen does not stop just because the truck is not traveling at highway speeds. I've been in stop and go traffic and stopped on the freeway due to an accident while my trucks been in regen. It just does its thing. If your looking for more than that or something in black and white Quickserve has all the information you could ever possibly seek.