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2025 Cummins Regen Observations

scdo said:
UPDATE

I was out of town a bit and then only drove on a series of short trips (not ideal) after returning from the long trip from SLC to Phoenix.

Recap, over the first 17 hours (700 miles) I was at 30% on the DPF gauge.

From that point, I was able to make it to 23 hours, 48 minutes total before the first regen was triggered. DPF gauge was still only at 30% so I expect this was actually the 24 hour mark contrary to what Trip A showed.

The vehicle took 63 minutes driving to complete the regen (35 miles). This was a combo of high speed highway (not much), significant traffic, then city streets.

Interestingly, the EGT2 and 3 temps hovered around 650 the entire time in regen. My 2023 was more aggressive with temps running closer to 1,000. I find this surprising but maybe it’s better / easier on the system.

Let me know of any questions. Thus far I’m pleased to make it a full 24 hours eventhough I showed 30% on the dash. There was no sudden run/spike like I was seeing on the prior truck.
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Thanks for the ongoing information - very helpful. Does it take the DPF guage down below 10% or so after the regen ?
 
HarryN said:
Thanks for the ongoing information - very helpful. Does it take the DPF guage down below 10% or so after the regen ?
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Yes, it ran it down to 0% and then kept going for another 15 mins or so.
 
How do you tell when it goes into regen? Light in the dash? Just picked up a new Laramie Dually 8 days ago and have close to 3000 miles on it. Have not noticed it doing anything different. Coming from an ‘03, this is new territory for me.
Love the smoothness and quiet over the the ‘03.
 

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aogmitch said:
How do you tell when it goes into regen? Light in the dash? Just picked up a new Laramie Dually 8 days ago and have close to 3000 miles on it. Have not noticed it doing anything different. Coming from an ‘03, this is new territory for me.
Love the smoothness and quiet over the the ‘03.
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Annoyingly, the all digital dash doesn’t tell you when it goes into regen. This has been the case since 2023. Old trucks used to show it if you were watching the DPF gauge.

I’m using a Bluetooth OBD reader and an app on my iPhone to monitor it. Honestly it’s totally unnecessary, I got into the habit because I had frequent regen issues on my old truck.
 
63 minutes to complete a routine regeneration with a starting soot load of 30% sounds a bit excessive to me, but i suppose it could have been due to your up and down drive cycle on that trip. On my 2022, 20 minutes was about average with a few going into the 30 minute mark whenever drive cycles were less conducive to efficient regeneration (heavy rain, slower traffic, etc). Anytime it takes an hour or more to complete a regen, I would be somewhat concerned.

I’ll see what I can dig up in terms of the actual regeneration strategy. I would suspect the general process is the same in terms of triggering it, with the only changes being the physical reorganization of the components (DOC right off the engine, SCR ahead of DPF, and new dedicated HCI (7th injector pre-DPF) instead of relying on the engine injectors to fuel active regeneration.
 
mbarber84 said:
63 minutes to complete a routine regeneration with a starting soot load of 30% sounds a bit excessive to me, but i suppose it could have been due to your up and down drive cycle on that trip. On my 2022, 20 minutes was about average with a few going into the 30 minute mark whenever drive cycles were less conducive to efficient regeneration (heavy rain, slower traffic, etc). Anytime it takes an hour or more to complete a regen, I would be somewhat concerned.

I’ll see what I can dig up in terms of the actual regeneration strategy. I would suspect the general process is the same in terms of triggering it, with the only changes being the physical reorganization of the components (DOC right off the engine, SCR ahead of DPF, and new dedicated HCI (7th injector pre-DPF) instead of relying on the engine injectors to fuel active regeneration.
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I agree it was certainly longer than my prior truck.
 
aogmitch said:
How do you tell when it goes into regen? Light in the dash? Just picked up a new Laramie Dually 8 days ago and have close to 3000 miles on it. Have not noticed it doing anything different. Coming from an ‘03, this is new territory for me.
Love the smoothness and quiet over the the ‘03.
Click to expand...

The best way without an aftermarket gauge is to watch instantaneous fuel mileage. Mileage while in a regen is significantly less. For instance, while coasting it'll indicate 99mpg when not in a regen, and something like 67mpg while in regen.
 
mbarber84 said:
I“with the only changes being the physical reorganization of the components (DOC right off the engine, SCR ahead of DPF, and new dedicated HCI (7th injector pre-DPF) instead of relying on the engine injectors to fuel active regeneration.’
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That is a huge improvement. Now the truck is not dumping excess fuel into a cylinder for the regen and there is no risk of “making oil”. There still is the issue of lower fuel economy but that is a minor issue compared to potentially ruining your engine. I would be a lot less concerned about excessive regen with this change.
 
mbarber84 said:
I’ll see what I can dig up in terms of the actual regeneration strategy. I would suspect the general process is the same in terms of triggering it, with the only changes being the physical reorganization of the components (DOC right off the engine, SCR ahead of DPF, and new dedicated HCI (7th injector pre-DPF) instead of relying on the engine injectors to fuel active regeneration.
Click to expand...

I wouldn't be surprised if they still use some in-cylinder fuel dosing during a regen to get the pre-dpf temp high enough to be able to dose fuel with the hydrocarbon doser during light load use. Also I would think there would have to be a small DOC built in to the DPF assembly to be able to oxidize the fuel being sprayed into it, I wouldn't think just spraying fuel into the DPF would work without something to oxidize it? What do you think?
 
superjoe83 said:
I wouldn't be surprised if they still use some in-cylinder fuel dosing during a regen to get the pre-dpf temp high enough to be able to dose fuel with the hydrocarbon doser during light load use. Also I would think there would have to be a small DOC built in to the DPF assembly to be able to oxidize the fuel being sprayed into it, I wouldn't think just spraying fuel into the DPF would work without something to oxidize it? What do you think?
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I thought the same thing. I would’ve thought the fuel would need to be added upstream of the DOc. Not sure what they’re doing. I haven’t had a chance to see one in person.
 
superjoe83 said:
I wouldn't be surprised if they still use some in-cylinder fuel dosing during a regen to get the pre-dpf temp high enough to be able to dose fuel with the hydrocarbon doser during light load use.
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It’s likely similar to the older trucks where fuel just isn’t injected if the DPF temp is too low. I’ve had regens take hours to complete on back roads when the exhaust was too cold to inject fuel during an active regen.
 
mbarber84 said:
I thought the same thing. I would’ve thought the fuel would need to be added upstream of the DOc. Not sure what they’re doing. I haven’t had a chance to see one in person.
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I took a screenshot of the DPF from a YouTube video, the first pressure differential tube is about 5 inches down from the edge of the DPF canister, I bet there is a secondary DOC there, right before where that tube taps in

25DPF.jpg
 
mbarber84 said:
I thought the same thing. I would’ve thought the fuel would need to be added upstream of the DOc. Not sure what they’re doing. I haven’t had a chance to see one in person.
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Do we know where the 7th injector is? If it is post-engine but pre-DOC, the DOC reaction would ramp up the exhaust temps downstream of the DOC sufficiently to regenerate the DPF.
 
Dodgeman said:
Do we know where the 7th injector is? If it is post-engine but pre-DOC, the DOC reaction would ramp up the exhaust temps downstream of the DOC sufficiently to regenerate the DPF.
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The information posted puts it just ahead of the DPF, post DOC.
 
Dodgeman said:
Do we know where the 7th injector is? If it is post-engine but pre-DOC, the DOC reaction would ramp up the exhaust temps downstream of the DOC sufficiently to regenerate the DPF.
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I haven’t had a chance to crawl under one, but from the videos I’ve seen online it would appear the HCI is post-DOC, pre-DPF
 
i had the larger screen in my 21 and it showed it as well. my idash shows it in regen as well. as much as my truck has in it tech wise, why id didnt have the bigger screen dash is odd but what ever lol
 
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