Regeneration Frequency Issue: MAF Poll

[AH64ID]

Correct. DEF is used in the exhaust to convert the nitrous oxide produced by the heat. EGR is a means of lowering cylinder temperature to reduce nitrous oxide emissions. If the cylinder/exhaust temperature is lowered in the engine, then there is no need for DEF except for when it is regening or under high boost/load conditions when turbo boost cuts down on the amount of EGR because of high intake pressure. The time frame I’m referring to is 2022 or late 2021.
My 2018 used twice as much DEF as the 2022 is using and never had a regen problem regardless of the fuel or air filter used.

You say correct, but are comparing DEF useage to regen. They have nothing to do with each other.

Once the exhaust is up to temp and fuel is being combusted DEF is being injected, to only use DEF during high boost/load would lead to a LOT more EGR use and that’s a bad idea.

Your 2022 should use considerably more DEF than your 2018 did.

Do you know what kind of DEF mileage they both got/get?

 

[OLEJOE]

You say correct, but are comparing DEF useage to regen. They have nothing to do with each other.

Once the exhaust is up to temp and fuel is being combusted DEF is being injected, to only use DEF during high boost/load would lead to a LOT more EGR use and that’s a bad idea.

Your 2022 should use considerably more DEF than your 2018 did.

Do you know what kind of DEF mileage they both got/get?

No. I said the only time mine uses DEF is when it is regening or when towing and keeping the boost up and exhaust temperature up. The only times it will passively regen is towing and running 75+ on the interstate. That’s the only way to get the exhaust temperature hot enough and then it will use DEF. I don’t keep a log on my DEF usage but I haven’t put any in the DEF tank since July and it’s still between half and three quarters of a tank. I don’t fill it completely up when I add to it.

 

[AH64ID]

No. I said the only time mine uses DEF is when it is regening or when towing and keeping the boost up and exhaust temperature up.

It uses DEF more often than that, or you would have set CEL.

The only times it will passively regen is towing and running 75+ on the interstate. That’s the only way to get the exhaust temperature hot enough and then it will use DEF.

Unrelatd, no connection between DEF usage and passive regen. The exhaust temp needed to get DEF to inject is around 350°F in the SCR.

The only minor correlation between DEF and regen is that the EGR closes during active regen (since we don’t want to intake unburned fuel) so DEF is the only way to reduce NOx during active regen. Passive regen uses both DEF and EGR for NOx reduction.

I don’t keep a log on my DEF usage but I haven’t put any in the DEF tank since July and it’s still between half and three quarters of a tank. I don’t fill it completely up when I add to it.

How many miles is that?

Hook up a monitor like a CTS3 and you’ll really be able to see when DEF is used, and it’s constant.

 

[OLEJOE]

Would it be possible for too much or too high of a percentage of EGR reduce exhaust temperatures down to the point that it couldn’t passively regen without towing or high load situation ? Will it still use DEF if EGT’s are below the threshold for injection?

 

[AH64ID]

Would it be possible for too much or too high of a percentage of EGR reduce exhaust temperatures down to the point that it couldn’t passively regen without towing or high load situation ? Will it still use DEF if EGT’s are below the threshold for injection?

You would then get an excessive EGR flow code, and even then it won’t reduce them that far.

My 2018 used a lot more EGR and still did plenty of passive regen.

The SCR only needs to see EGT’s around 350°F for DEF injection, that’s pretty cold for the SCR. I say around 350° because that’s personal observation and nothing I’ve read.

 

[OLEJOE]

You would then get an excessive EGR flow code, and even then it won’t reduce them that far.

My 2018 used a lot more EGR and still did plenty of passive regen.

The SCR only needs to see EGT’s around 350°F for DEF injection, that’s pretty cold for the SCR. I say around 350° because that’s personal observation and nothing I’ve read.

Ok. Thanks Would it throw a code if it was programmed to do that?

 

[mbarber84]

My 2022 HO uses considerably more DEF than my previous 2017 HO did. I haven’t tracked exact numbers but I’m usually about 2.5 gallons per 75-80 gallons of fuel. I fill my fuel tank (50gal) when it reaches 1/4 full. I add 2.5 gal. of DEF when my DEF gauge reaches 1/4 full. Usually takes me two fill-ups on the fuel tank to need one fill-up on the DEF tank. I’d much rather have the truck consume more DEF than utilize more EGR. Standalone In-cylinder NOx strategies (like 2007.5 to 2012 trucks) used EGR exclusively. It was a lousy way to tackle the NOx emissions. Too much soot build up in the intake side of the engine and it was hard on valve seats, sensors, and required more intensive cleaning as part of routine maintenance. When they started adding the SCR systems, that greatly reduced the amount of EGR needed to meet emissions targets. This greatly enhanced the cleanliness of the system and reduced the service needed. The only downfall to the DEF systems is that they can be temperamental in some situations.

 

[AH64ID]

Ok. Thanks Would it throw a code if it was programmed to do that?

No, but it’s not programmed to do that. These newer motors use less EGR, so they should passively regen more on that theory.

FWIW EGT1 temps are very similar to what I saw with a post-turbo pyro on my tuned 05 that didn’t have an EGR.

Injection timing will have a bigger effect on passive regen then EGR will. Generally more advanced timing means better fuel economy and reduced EGT’s, so retarded timing will yield hotter EGT’s for passive regen but worse fuel economy. When the truck is in active regen it retards the timing to help increase the EGT’s.

 

[DougB]

My 2022 HO uses considerably more DEF than my previous 2017 HO did. I haven’t tracked exact numbers but I’m usually about 2.5 gallons per 75-80 gallons of fuel. I fill my fuel tank (50gal) when it reaches 1/4 full. I add 2.5 gal. of DEF when my DEF gauge reaches 1/4 full. Usually takes me two fill-ups on the fuel tank to need one fill-up on the DEF tank. I’d much rather have the truck consume more DEF than utilize more EGR. Standalone In-cylinder NOx strategies (like 2007.5 to 2012 trucks) used EGR exclusively. It was a lousy way to tackle the NOx emissions. Too much soot build up in the intake side of the engine and it was hard on valve seats, sensors, and required more intensive cleaning as part of routine maintenance. When they started adding the SCR systems, that greatly reduced the amount of EGR needed to meet emissions targets. This greatly enhanced the cleanliness of the system and reduced the service needed. The only downfall to the DEF systems is that they can be temperamental in some situations.

My truck sips DEF. Unless I missed recording a fill up, I’m getting 2000mpg in DEF usage. Wonder if that’s because the I do mostly city driving where the EGT 4&5 temps don’t get that high to require DEF. I don’t pay attn to those temps.

Doing a lotta interstate miles this week and next so will see what the DEF mileage looks next week when I can add to it.

Also, with this interstate driving the passive regen is working well. I’m at about 800miles since last active regen and the dash DPF is still on zero. The iDash started at 24 when I started the trip. Got up to 45-48 and stayed there most of the trip. Crept to 55 once we arrived and did some mixed driving. EVIC still on zero. Hoping to go the entire trip without getting into active regen.

 

[OLEJOE]

My truck sips DEF. Unless I missed recording a fill up, I’m getting 2000mpg in DEF usage. Wonder if that’s because the I do mostly city driving where the EGT 4&5 temps don’t get that high to require DEF. I don’t pay attn to those temps.

Doing a lotta interstate miles this week and next so will see what the DEF mileage looks next week when I can add to it.

Also, with this interstate driving the passive regen is working well. I’m at about 800miles since last active regen and the dash DPF is still on zero. The iDash started at 24 when I started the trip. Got up to 45-48 and stayed there most of the trip. Crept to 55 once we arrived and did some mixed driving. EVIC still on zero. Hoping to go the entire trip without getting into active regen.

Mine sips DEF also.

 

[AH64ID]

My truck sips DEF. Unless I missed recording a fill up, I’m getting 2000mpg in DEF usage. Wonder if that’s because the I do mostly city driving where the EGT 4&5 temps don’t get that high to require DEF. I don’t pay attn to those temps.

Doing a lotta interstate miles this week and next so will see what the DEF mileage looks next week when I can add to it.

Also, with this interstate driving the passive regen is working well. I’m at about 800miles since last active regen and the dash DPF is still on zero. The iDash started at 24 when I started the trip. Got up to 45-48 and stayed there most of the trip. Crept to 55 once we arrived and did some mixed driving. EVIC still on zero. Hoping to go the entire trip without getting into active regen.

Your SCR is hot enough with city driving for DEF injection.

2000mpg is unrealistic on a functioning system, CEL Free, so I’m going to guess you missed a fillup.

 

[OLEJOE]

My truck sips DEF. Unless I missed recording a fill up, I’m getting 2000mpg in DEF usage. Wonder if that’s because the I do mostly city driving where the EGT 4&5 temps don’t get that high to require DEF. I don’t pay attn to those temps.

Doing a lotta interstate miles this week and next so will see what the DEF mileage looks next week when I can add to it.

Also, with this interstate driving the passive regen is working well. I’m at about 800miles since last active regen and the dash DPF is still on zero. The iDash started at 24 when I started the trip. Got up to 45-48 and stayed there most of the trip. Crept to 55 once we arrived and did some mixed driving. EVIC still on zero. Hoping to go the entire trip without getting into active regen.

If you missed a fill up, what does that bring you down to? 1500 mpg?

 

[DougB]

If you missed a fill up, what does that bring you down to? 1500 mpg?

Assuming I filled once in the middle of that stretch, that’s 5000mi on 5gal or 1000mpg. If I filled twice that would be 5000/7.5 or 667mpg.

I’m near half tank of DEF on almost 1300mi. About 500mpg.

I’ll be sure to better track my DEF fills in my app, Road Trip.

 

[OLEJOE]

Assuming I filled once in the middle of that stretch, that’s 5000mi on 5gal or 1000mpg. If I filled twice that would be 5000/7.5 or 667mpg.

I’m near half tank of DEF on almost 1300mi. About 500mpg.

I’ll be sure to better track my DEF fills in my app, Road Trip.

I just started tracking my fuel mileage. I’m going to try to keep up with the DEF from now on too.

 

[AH64ID]

I didn’t catch the exact temp that DEF injection started this morning but both EGT 4 and 5 were below 300°. The motor was still quite cold and not much of a load, so nearly all driving will be hot enough.

I’ll continue to watch and see if I can catch it a bit better.

 

[gorilla57]

Just track your fuel gallons used and your DEF fill amount. Then calculate our your DEF usage. According to sources online, it should be between 2 and 3% of your fuel usage. I calculated the DEF usage in my 2020 Ram 1500 diesel and now in my 2023 Ram 2500. Both have averaged about 2.6-2.9% DEF usage. You can't get exact numbers unless you refill DEF at the pump every time. I throw in a 2.5gal jug of DEF when the gauge reads 1/2 full. So, not exact, but pretty consistent.

 

[Walstib52]

I have an AARFN and have not experienced regen issues, but my duty cycle is a lot of that reasoning. I suspect I would if I DD’d it more, but that’s just a hunch. So I’m not voting, just yet.

The MAF theory is sound, IMO, because I have seen some odd readings on the regen % PID especially at low rpms and low airflow.

That being said, I have nothing to compare it to.

I have a 21 Ram 2500 HD 4WD with the Cummins bought new in May of 21 with about 35K on the meter. Had a 2006 GMC Duramax also bought new before the Ram -did all maintenance and repairs (outside of warranty work) myself over 15 years of ownership. I really like this Ram truck a lot. Happened across this forum about regeneration. Call me an ignoramus, but what the heck is regeneration? Never heard the term used in the context of vehicles/engines before. I work in a technical field where we use a lot of acronyms. I find it extremely frustrating when they are never defined throughout an article (or thread), and I make an effort to at least define it once, before first use of the acronym in things that I write. All of the respondents in this thread seems to know all about regeneration, but for someone like me it's unfamiliar. PID in my world is a photoionization detector. What is it here? What is DPF? DD'd it? Please enlighten me on this regeneration issue. I'm sure I'm not the only one who doesn't know about it. Thanks

 

[mbarber84]

I have a 21 Ram 2500 HD 4WD with the Cummins bought new in May of 21 with about 35K on the meter. Had a 2006 GMC Duramax also bought new before the Ram -did all maintenance and repairs (outside of warranty work) myself over 15 years of ownership. I really like this Ram truck a lot. Happened across this forum about regeneration. Call me an ignoramus, but what the heck is regeneration? Never heard the term used in the context of vehicles/engines before. I work in a technical field where we use a lot of acronyms. I find it extremely frustrating when they are never defined throughout an article (or thread), and I make an effort to at least define it once, before first use of the acronym in things that I write. All of the respondents in this thread seems to know all about regeneration, but for someone like me it's unfamiliar. PID in my world is a photoionization detector. What is it here? What is DPF? DD'd it? Please enlighten me on this regeneration issue. I'm sure I'm not the only one who doesn't know about it. Thanks

Regeneration is the process that the trucks emission system uses in order to clear out trapped soot in the diesel particulate filter (DPF).

As you drive the truck, the soot gets trapped in that filter. The soot is constantly trapped inside it, and then systematically removed through a process called regeneration. There are three types of DPF regeneration cycles that can occur in your truck. These are “Active Regeneration (aka automatic regeneration)”, “Passive Regeneration”, and “Forced Regeneration (aka stationary desoot or parked regeneration”

Active regeneration cycles occur in one of two ways. Either based on the current soot load in your DPF or every 24-25 hours of engine operation. In the soot-load based mode, the cycle will automatically initiate when the % of soot in the DPF reaches a pre-programmed threshold. In our trucks, that threshold is about 50% on the in-dash DPF gauge. Once it starts, it will continue until the % reaches zero, or the operator does something to inhibit the cycle (putting the truck in park or shutting it off) If the cycle is inhibited by the operator, it will pick back up when the truck begins to move again and conditions in the engine and emissions systems are favorable for regeneration to continue. In the timed mode, the same cycle will initiate every 24-25 hours of engine operation regardless of the % soot load in the DPF. Active regeneration initiated either at the 50% soot load threshold, OR at the 24 hour engine timer. Whichever scenario happens first. The timer always resets when a cycle is completed, regardless of which type of initiation started it. In both the scheduled and threshold based active regeneration cycles, diesel fuel is being injected into the exhaust stream to raise the temperature in the DPF high enough to burn away the accumulated soot. You should do your best to allow this cycle to continue once started, and preferably during highway driving. When the truck is in an active regeneration, if you scroll to the DPF gauge in the dash, you’ll see a message that says “automatic exhaust system regeneration in progress”.

Passive regeneration is another way the DPF is cleared of soot. In this type of regeneration, the truck is generating high enough exhaust temperature that the temperature inside the DPF is raised to a point where soot will naturally begin to burn away. Passive regeneration happens naturally while you drive, without any additional fuel added to the exhaust steam. The only requirement is that the truck is working hard enough to generate high enough EGT’s to maintain the reaction in the DPF. The DPF has to remain at around 600-660°F or higher in order for passive regeneration to continue. Passive regeneration usually takes longer to clean the DPF out especially when the trucks engine is operating under a reduced load (unloaded or not towing) This type of regeneration typically only happens at highway speed or while towing continuously. There is no message on the dash when this type of regeneration is occurring. The only way you’ll know it’s happening is a visible reduction in the % soot load gauge on the dash screen.

Forced regeneration is the third type of regen cycle. It is similar in function to an active regeneration cycle as mentioned before. The only difference is, a forced regeneration occurs while the truck is sitting in park. It must be initiated by either a service scan tool, or in the case of the chassis cabs, by means of an option on the display. These are often referred to as “stationary de-soot” cycles. They are extremely effective at cleaning the DPF out because the truck has full control of the engine RPM and fuel dosing, and can thus increase and hold the temperature in the DPF to a very high level for a continuous length of time. These types of regeneration cycles are only needed if the other two types of cycles are not regularly allowed to occur.

 

[Walstib52]

Regeneration is the process that the trucks emission system uses in order to clear out trapped soot in the diesel particulate filter (DPF).

As you drive the truck, the soot gets trapped in that filter. The soot is constantly trapped inside it, and then systematically removed through a process called regeneration. There are three types of DPF regeneration cycles that can occur in your truck. These are “Active Regeneration (aka automatic regeneration)”, “Passive Regeneration”, and “Forced Regeneration (aka stationary desoot or parked regeneration”

Active regeneration cycles occur in one of two ways. Either based on the current soot load in your DPF or every 24-25 hours of engine operation. In the soot-load based mode, the cycle will automatically initiate when the % of soot in the DPF reaches a pre-programmed threshold. In our trucks, that threshold is about 50% on the in-dash DPF gauge. Once it starts, it will continue until the % reaches zero, or the operator does something to inhibit the cycle (putting the truck in park or shutting it off) If the cycle is inhibited by the operator, it will pick back up when the truck begins to move again and conditions in the engine and emissions systems are favorable for regeneration to continue. In the timed mode, the same cycle will initiate every 24-25 hours of engine operation regardless of the % soot load in the DPF. Active regeneration initiated either at the 50% soot load threshold, OR at the 24 hour engine timer. Whichever scenario happens first. The timer always resets when a cycle is completed, regardless of which type of initiation started it. In both the scheduled and threshold based active regeneration cycles, diesel fuel is being injected into the exhaust stream to raise the temperature in the DPF high enough to burn away the accumulated soot. You should do your best to allow this cycle to continue once started, and preferably during highway driving. When the truck is in an active regeneration, if you scroll to the DPF gauge in the dash, you’ll see a message that says “automatic exhaust system regeneration in progress”.

Passive regeneration is another way the DPF is cleared of soot. In this type of regeneration, the truck is generating high enough exhaust temperature that the temperature inside the DPF is raised to a point where soot will naturally begin to burn away. Passive regeneration happens naturally while you drive, without any additional fuel added to the exhaust steam. The only requirement is that the truck is working hard enough to generate high enough EGT’s to maintain the reaction in the DPF. The DPF has to remain at around 600-660°F or higher in order for passive regeneration to continue. Passive regeneration usually takes longer to clean the DPF out especially when the trucks engine is operating under a reduced load (unloaded or not towing) This type of regeneration typically only happens at highway speed or while towing continuously. There is no message on the dash when this type of regeneration is occurring. The only way you’ll know it’s happening is a visible reduction in the % soot load gauge on the dash screen.

Forced regeneration is the third type of regen cycle. It is similar in function to an active regeneration cycle as mentioned before. The only difference is, a forced regeneration occurs while the truck is sitting in park. It must be initiated by either a service scan tool, or in the case of the chassis cabs, by means of an option on the display. These are often referred to as “stationary de-soot” cycles. They are extremely effective at cleaning the DPF out because the truck has full control of the engine RPM and fuel dosing, and can thus increase and hold the temperature in the DPF to a very high level for a continuous length of time. These types of regeneration cycles are only needed if the other two types of cycles are not regularly allowed to occur.

Thank you very much for that informative response. I never look at the gauge function you refer to. I'll have to check it out. Is an increase in idle speed from around 700 up to 1000 to 1100 while warming up in the driveway on a cold morning part of a regen cycle? What does PID refer to? DD'd? Thanks again!

 

[oledirteh]

i just hit the milage tracker on mine when i filled my def. i put about 2800 miles a month on my truck if its a light month. average 3000-3200. i dont think i have filled up def since end of october. just filled up from just over the line before the light comes on to tell me im low.

my truck would regen maybe every 500 or so i think, i dont know really. last for about 45 miles to clear out. made some changes to the truck and it regened for 15 miles rather then 45-50.

ill note the milage and report back when i have to refill. I have 88k and will check what sensor i have.