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2025 Cummins Regen Observations

AH64ID said:
SCR has not ever needed or used in-cylinder dosing, why would they start now? Exhaust temps from driving are sufficient to let the SCR reduce NOx with DEF.

Adding in-cylinder dosing for the SCR, when it’s closer to the engine, would be the opposite of what they are trying to accomplish with the 7th injector. That’s the point.
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Look at the graph I've pasted few pages ago. Temps are normally around 600F - may be too low.
7-th injector is for DPF's DOC. First DOC afaik does not have own injector so there is no other way to heat it up.
You can see such event on the graph mentioned.
EGT2 and EGT3 went up having EGT1 not much elevated. This all with DPF temperatures being lower.
 
AndyRoos said:
Look at the graph I've pasted few pages ago. Temps are normally around 600F - may be too low.
7-th injector is for DPF's DOC. First DOC afaik does not have own injector so there is no other way to heat it up.
You can see such event on the graph mentioned.
EGT2 and EGT3 went up having EGT1 not much elevated. This all with DPF temperatures being lower.
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The DOC in the downpipe doesn't need fuel to work, it works like every other DOC that has been used outside of passive regen. It simply takes the heat from combustion and reduced carbon dioxide and helps burn any unburnt fuel. No post injection or separate injector needed. They start to work around 400°F.

The SCR will start to convert DEF into ammonia and reduce NOx at less that 400°F.
 
Just an FYI, the active regen not only works in Neutral when shifting from Drive when it's already in regen, but when shifting from Park where regen is off, to Neutral, it automatically kicks right back into regen. Now I'd just like to know if it's safe/effective to let it regen while parked in Neutral.



20250828_143214.jpg
 
PyroJoe said:
Just an FYI, the active regen not only works in Neutral when shifting from Drive when it's already in regen, but when shifting from Park where regen is off, to Neutral, it automatically kicks right back into regen. Now I'd just like to know if it's safe/effective to let it regen while parked in Neutral.



View attachment 89121
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Not sure what will happen in situation when DPF will be really loaded (I mean not only calculated that it is loaded but it will indeed contain a lot of soot).
However during idling it looks that radiator fan provides enough airflow below the chassis to keep exhaust quite safe from overheating.
 
AndyRoos said:
Not sure what will happen in situation when DPF will be really loaded (I mean not only calculated that it is loaded but it will indeed contain a lot of soot).
However during idling it looks that radiator fan provides enough airflow below the chassis to keep exhaust quite safe from overheating.
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It would be no different than an activated stationary de-soot.
 
Took a trip to DC with my son this weekend, a little over 300 mile round trip. Truck did it's third regen right at 75 hours. I caught it and watched the DPF page, I could see the bar going down from 25% to zero but even watching that page it gave me no indication it was regenning. I have the baby screen on my tradesman.
 
Same here yesterday on a 7 hour road trip. I kept watching the DPF meter go up to a little over 25%. Probably 45-60 minutes later I checked it and it was at 0%. Had no idea it was doing a regen while driving down the interstate.
 
Possum said:
Same here yesterday on a 7 hour road trip. I kept watching the DPF meter go up to a little over 25%. Probably 45-60 minutes later I checked it and it was at 0%. Had no idea it was doing a regen while driving down the interstate.
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That's probably because you were working the truck hard enough for it to passively regen instead of actively.
 
During normal unloaded driving. I have noticed the DPF gauge ratchet up to 30% and then drop down, presumably due to a regen cycle. However, when we towed our TH (20k) about 3k miles, the gauge never came off the 0% peg. It seems that if you use the truck as it was intended (hard work) it keeps the DPF clean. Does that seem reasonable?
 
Morpar said:
During normal unloaded driving. I have noticed the DPF gauge ratchet up to 30% and then drop down, presumably due to a regen cycle. However, when we towed our TH (20k) about 3k miles, the gauge never came off the 0% peg. It seems that if you use the truck as it was intended (hard work) it keeps the DPF clean. Does that seem reasonable?
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The truck will passive regen if worked.

It will still do an active regen every 24 hours regardless of DPF soot load.

Driving unloaded you will normally see the DPF gauge go to 45% before it does a forced (early) regen due to soot load.
 
With the 25 I've actually seen less correlation between passive regen (DPF guage going down) and longer drives / driving under load. It's almost like it doens't care howe we drive... I generally see the guage go up/down alsmost randomly through the 24 hour period. I've seen it climb on long highway drives and even drop when putting around town. I'm over 8k miles now and still have never had a forced regen. Very happy!
 
scdo said:
M. I'm over 8k miles now and still have never had a forced regen. Very happy!
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When say “forced”, are you referring to having the dealer hook the scan tool up and “force” a parked regeneration?

Or

Are you confusing “forced” with “automatic” (aka active regeneration)?

If you mean active / automatic regeneration then your truck has completed multiple of those. They occur every 24 engine hours unless one is called for sooner when the system reaches 50% capacity.

If you have a 2023 or newer truck, that is equipped with the fully digital instrument cluster (the one with no analog gauges) then you will never get a notification that the truck is conducting a routine active / automatic regeneration because the digital instrument cluster isn’t programmed to provide that message.
 
mbarber84 said:
When say “forced”, are you referring to having the dealer hook the scan tool up and “force” a parked regeneration?

Or

Are you confusing “forced” with “automatic” (aka active regeneration)?

If you mean active / automatic regeneration then your truck has completed multiple of those. They occur every 24 engine hours unless one is called for sooner when the system reaches 50% capacity.

If you have a 2023 or newer truck, that is equipped with the fully digital instrument cluster (the one with no analog gauges) then you will never get a notification that the truck is conducting a routine active / automatic regeneration because the digital instrument cluster isn’t programmed to provide that message.
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Sorry - my language wasn’t accurate.

To clarify, I monitor regen status with OBDLink so know when Regen is active. What I meant is that it only regens around the 24 hour mark. It’s never gone into a soot-load based regen outside of that schedule.
 
Noticed a major difference in regen activity after the latest ecm update. With my 22 I only had 24 hour regens never any soot loaded. However with my 25 I routinely was getting soot loaded regens and could watch the filter increase to 30%+ well before the 24 hours. Now after getting the update I’m not seeing it go above 10%. Not sure what changed but seems like a major improvement
 
I have a 2026, it seems like when it’s in a regen cycle and I’m at a stop light or driving slow it is cycling on / off, on /off, etc.

It’s the same sound my 20 and 22 made, but instead of a continuous sound it seems to cycle, anyone else notice this?
 
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