another regen question - Nissan Titan XD Forum
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post #1 of 33 Old 01-07-2019, 08:24 PM Thread Starter
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another regen question

I have read where the truck is set to regen every 24 hours of run time. I recently went on a 923 mile pulling about 7500 lbs trip one way. I topped off the DEF before I left and I had to add DEF before I got there. I drove it straight through and the same thing happened on the way back. I just turned 10k miles and truck is stock. Help me understand the regen setup. This is my first diesel with DEF, I am a long time diesel owner from the 1980's but first DEF truck

2018 Titan XD SV, 4 door, 4x4, 5.0 Cummins
2017 Nissan Titan Model S, single cab 2wd
2017 Nissan Titan Model S, single cab, 4x4
2004-Dodge 3500 Crew Cab, 5.9 Cummins H.O.
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post #2 of 33 Old 01-07-2019, 08:38 PM
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If you are working the motor it will go into Regen more.
Lots of short trips will also kick it into Regen.
The best thing you can do is just drive it & fill up the Cat Piss tank when you get a warning.
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2016 Black XD Pro4x.....
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post #3 of 33 Old 01-07-2019, 10:51 PM
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Def and regen reaponds to soot buildup. Sensor measures amount of restriction of exhaust flow by soot buildup. Towing builds soot alot as does stop and go driving. I average bout 1300 miles but the cat piss is driving me nuts and imagonna fix that da** cat...
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post #4 of 33 Old 01-08-2019, 12:10 PM
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In actuality, DEF usage is not dependent or driven by DPF regen. DEF usage is dependent the amount of NOx emissions produced by the engine. The harder you work the truck, ie: towing heavy, the more NOx the engine produces due to elevated cylinder temps. This is normal, but requires more DEF to react with the NOx emissions in the SCR. So you should expect to use more DEF when towing or working the truck.

An active regen is in the ECU code to trigger every 24hrs run time whether the DPF needs it or not. There are no indicators for this type of regen, and in the 2016's & 2017's the only way to tell is thru the instant fuel economy, but that indicator was removed in 2018. The best way to tell if/when you are going into a regen is with an OBD2 scan tool/reader. I use an OBD2 scan tool and monitor the DPF load on my phone. And for the past year and a half I have reset the trip computer upon regen completion and it goes into regen every 24hrs run time like clockwork. During a regen you will use more DEF as the engine shuts off the EGR and runs hotter producing more NOx. Also the elevated DFP temps and soot burning produce NOx.

Working the truck will not make it regen more. Unless you do a lot of stop and go or short trips, you will likely regen every 24hrs. What does change is the length of the regen. Working the truck actually keeps the DPF cleaner due to elevated temps - passive regen begins to occur above 600deg F (though more efficient near 1000deg F). So working the truck is good - shorter regens when they do occur.

If you get the indicator on the dash that the truck is in regen, be concerned - this indicator is for urgent attention and requires a minimum of 1 hour at highway speeds. If not done immediately, the truck will go into limp mode and require a trip to the dealer for a DPF removal for a bench regen
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post #5 of 33 Old 01-08-2019, 12:35 PM
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Originally Posted by JBouy View Post
In actuality, DEF usage is not dependent or driven by DPF regen. DEF usage is dependent the amount of NOx emissions produced by the engine. The harder you work the truck, ie: towing heavy, the more NOx the engine produces due to elevated cylinder temps. This is normal, but requires more DEF to react with the NOx emissions in the SCR. So you should expect to use more DEF when towing or working the truck.

An active regen is in the ECU code to trigger every 24hrs run time whether the DPF needs it or not. There are no indicators for this type of regen, and in the 2016's & 2017's the only way to tell is thru the instant fuel economy, but that indicator was removed in 2018. The best way to tell if/when you are going into a regen is with an OBD2 scan tool/reader. I use an OBD2 scan tool and monitor the DPF load on my phone. And for the past year and a half I have reset the trip computer upon regen completion and it goes into regen every 24hrs run time like clockwork. During a regen you will use more DEF as the engine shuts off the EGR and runs hotter producing more NOx. Also the elevated DFP temps and soot burning produce NOx.

Working the truck will not make it regen more. Unless you do a lot of stop and go or short trips, you will likely regen every 24hrs. What does change is the length of the regen. Working the truck actually keeps the DPF cleaner due to elevated temps - passive regen begins to occur above 600deg F (though more efficient near 1000deg F). So working the truck is good - shorter regens when they do occur.

If you get the indicator on the dash that the truck is in regen, be concerned - this indicator is for urgent attention and requires a minimum of 1 hour at highway speeds. If not done immediately, the truck will go into limp mode and require a trip to the dealer for a DPF removal for a bench regen
Kudos for the best info on Regen I've seen.
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post #6 of 33 Old 01-08-2019, 02:02 PM
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Quote:
Originally Posted by JBouy View Post
In actuality, DEF usage is not dependent or driven by DPF regen. DEF usage is dependent the amount of NOx emissions produced by the engine. The harder you work the truck, ie: towing heavy, the more NOx the engine produces due to elevated cylinder temps. This is normal, but requires more DEF to react with the NOx emissions in the SCR. So you should expect to use more DEF when towing or working the truck.

An active regen is in the ECU code to trigger every 24hrs run time whether the DPF needs it or not. There are no indicators for this type of regen, and in the 2016's & 2017's the only way to tell is thru the instant fuel economy, but that indicator was removed in 2018. The best way to tell if/when you are going into a regen is with an OBD2 scan tool/reader. I use an OBD2 scan tool and monitor the DPF load on my phone. And for the past year and a half I have reset the trip computer upon regen completion and it goes into regen every 24hrs run time like clockwork. During a regen you will use more DEF as the engine shuts off the EGR and runs hotter producing more NOx. Also the elevated DFP temps and soot burning produce NOx.

Working the truck will not make it regen more. Unless you do a lot of stop and go or short trips, you will likely regen every 24hrs. What does change is the length of the regen. Working the truck actually keeps the DPF cleaner due to elevated temps - passive regen begins to occur above 600deg F (though more efficient near 1000deg F). So working the truck is good - shorter regens when they do occur.

If you get the indicator on the dash that the truck is in regen, be concerned - this indicator is for urgent attention and requires a minimum of 1 hour at highway speeds. If not done immediately, the truck will go into limp mode and require a trip to the dealer for a DPF removal for a bench regen
Well written! Would just like to clarify one thing for the audience.
The DEF dosage (injection) rate is not determined by any reading of NOX sensors or measuring of exhaust.
The dosage rate is determined by your fuel economy and fuel consumed.
Obviously if you are burning more fuel then you are burning more exhaust which is really what you stated.
Just wanted to make sure folks know that fuel economy calculations determines the DEF dosage and injection rate and not any exhaust system component.
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post #7 of 33 Old 01-14-2019, 10:29 AM
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Would REALLY like to see there reasoning for regen every 24hrs whether it needs it or not !! (It's obvious usage of fuel is NOT their concern and they'd rather have a "clean" DPF then partially restricted.) However, GM & Ford have a much "better" algorithm for regen that is not based on time. Using MAF, RPM, DPS to create a Calculated Soot (Soot Load PID).
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post #8 of 33 Old 01-14-2019, 11:11 AM
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Engineers are like People, they have their own opinions on best way to deal with the need.. Just saying, why Ford GM, etc engineers look at the glass of half empty or half full..

Drive Safe Enjoy the Ride

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post #9 of 33 Old 01-14-2019, 12:07 PM
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Quote:
Originally Posted by Arice View Post
Well written! Would just like to clarify one thing for the audience.
The DEF dosage (injection) rate is not determined by any reading of NOX sensors or measuring of exhaust.
The dosage rate is determined by your fuel economy and fuel consumed.
Obviously if you are burning more fuel then you are burning more exhaust which is really what you stated.
Just wanted to make sure folks know that fuel economy calculations determines the DEF dosage and injection rate and not any exhaust system component.
Thanks, Arice. As this truck is my first diesel I'm kind of a diesel newb, so took the time to research the emissions system to understand how it works.

There was a thread on this site some time ago that discussed NOx dosage, and if I remember correctly it was verified that there are sensors on the SCR that monitor NOx concentration incoming and outgoing. I know there are PID's for the sensors as I have watched them. I do not recall if the sensors were verified as the controlling factor for dosage, but why would they be there if not for that purpose?
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post #10 of 33 Old 01-14-2019, 01:35 PM
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There is a video on YouTube from a Nissan tech explaining the XD after treatment and how it works.
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