Very frequent regeneration

Jb22

Well-known member
Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
I know this topic has been well documented here...the phase one fix seems to cause more frequent regens. My '15 se seems to regen two or three times each tank, and many times more than once per day, often within the same hour. Lately, I have been driving more locally as opposed to highway, so I expect a little more frequency. Is anyone else experiencing this same thing? One note which may be related - our local chain of c-stores was purchased by Circle-K, so Sunoco brand diesel has been replaced by whatever is cheapest for them to buy when they are running low.
 

tdiatlast

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Jan 21, 2009
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Fort Worth, Texas
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2009 Sportwagen (boughtback); 2014 Passat TDI SEL (boughtback)
Can you document how many MILES between regens? "...many times more than once per day..." isn't specific enough to evaluate.
You probably already know that city driving will fill the DPF quicker than highway, causing more frequent regens...
 

VeeDubTDI

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Do you interrupt them or do you let them finish? If you interrupt them around town, the computer will keep trying to do them, causing reduced fuel economy and more frequent extreme heating cycles on the equipment. For longevity purposes, I recommend waiting for DPF regenerations to finish before turning off the engine.
 

Jetta_Pilot

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Apr 14, 2005
Location
West Hill, Ont.
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2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
How would the average person even know when regen is happening?

I only know because I have two custom gauges on my ScanGauge II. When I see the temperatures well over 1,000 degrees I know regen is happening, when driving I just carry on and watch the temps drop. Only once I had to wait it out at home until the temps had come down to around 300 degrees.
 

VeeDubTDI

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How would the average person even know when regen is happening?
I only know because I have two custom gauges on my ScanGauge II. When I see the temperatures well over 1,000 degrees I know regen is happening, when driving I just carry on and watch the temps drop. Only once I had to wait it out at home until the temps had come down to around 300 degrees.
Most of the time, the average person won't know. That's why I recommend ScanGaugeII with PIDs programmed to show exhaust gas temperatures in at least two locations plus coolant temperature and boost pressure. Knowledge is power.
 

D-Cup

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Jul 22, 2017
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San Antonio TX
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2010 Jetta TDI Cup Edition, 2003 Jetta GLS, 2000 Jetta GLS, 2012 JSW
How would the average person even know when regen is happening?
I only know because I have two custom gauges on my ScanGauge II. When I see the temperatures well over 1,000 degrees I know regen is happening, when driving I just carry on and watch the temps drop. Only once I had to wait it out at home until the temps had come down to around 300 degrees.
Normal idle my tach sits right at 800rpm.
When I get to a stop light, or my destination, sometimes that idle will be at or slightly above 1000rpm, with the fan blowing louder than normal (with no ac/heat on). That's a regen. (To my understanding - please correct me if I'm wrong.)
I have engine code CJAA (2010), so yours may be different?
 

Jb22

Well-known member
Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
Can you document how many MILES between regens? "...many times more than once per day..." isn't specific enough to evaluate.
You probably already know that city driving will fill the DPF quicker than highway, causing more frequent regens...
Fair enough. It just so happens that I did write down where the regens occurred in relationship to the last two tanks of fuel. At 36 miles, at 47 miles, at 142 miles, then at 318. On this tank of fuel, I had a regen at 47, 52 (though that was interrupted) and 118 (which finished). I refueled the first tank at 560ish miles, so there's a chance that there was one or more that I didn't realize.

"Do you interrupt them or do you let them finish? If you interrupt them around town, the computer will keep trying to do them, causing reduced fuel economy and more frequent extreme heating cycles on the equipment. For longevity purposes, I recommend waiting for DPF regenerations to finish before turning off the engine."

VeeDub - I really try to wait until it finishes. I will say, though, that I learned something in your reply...I didn't realize that stopping the car stopped the regeneration. I always thought that it was still regenerating - I am guessing that it's just trying to cool down if it's interrupted? I'm going to pay attention closer to that, my guess is that this case is closed.

Thanks guys
 

Funguy

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Jan 18, 2005
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Front Range of Colorado
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2015 Golf Sportwagen dsg and 2015 Passat 6 M/T
My six speed will ask me to shift up at higher speeds when a regen is in progress. Like it will ask for 5th at 45 mph instead of 6th.

I just use my SG II and when the DPF is over 800 I know a regen is happening
 

Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont.
TDI
2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
My six speed will ask me to shift up at higher speeds when a regen is in progress. Like it will ask for 5th at 45 mph instead of 6th.

I just use my SG II and when the DPF is over 800 I know a regen is happening
Actually you are shifting down from 6 to 5!

Right now here in Mexico the Diesel is still LSD, so on the infrequent times I drive the car, I force regeneration by driving in a lower gear (DSG) at highway speeds for some 10-15 minutes. Cheaper to burn more fuel than replacing emission parts.
 

Jb22

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Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
So....
I haven't been doing a lot of driving still as it's a slow time of year for me. I'm on the same tank as my last post - where my most recent regeneration was at mile 118 on the trip meter. There has been no regeneration since, but after dropping the kids off at school today, mile 345, low and behold, a regeneration. I'm wondering if there is a time component as well? It's been a week and a day since my last one. It's also been fairly cold here the past week or so, compared to weeks prior. Also, fuel economy is still terrible - my last two fuelly readings were 33.9 and 32.1 (and the never trusty flow meter looks the same for this tank as those), down from a lifetime average of 38.4. That could be the new fuel at my station, winter blend, more local driving, lots of regens, or a combo. It's just weird this year - of course it's my first in a passat as opposed to my jsw (which was my favorite car ever).
 

Funguy

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Joined
Jan 18, 2005
Location
Front Range of Colorado
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2015 Golf Sportwagen dsg and 2015 Passat 6 M/T
If it is cold and you are just doing short trips around town then your mpg won't be very good and you will have more DPF cleaning cycles
 

VeeDubTDI

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Springfield, VA
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‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
So....
I haven't been doing a lot of driving still as it's a slow time of year for me. I'm on the same tank as my last post - where my most recent regeneration was at mile 118 on the trip meter. There has been no regeneration since, but after dropping the kids off at school today, mile 345, low and behold, a regeneration. I'm wondering if there is a time component as well? It's been a week and a day since my last one. It's also been fairly cold here the past week or so, compared to weeks prior. Also, fuel economy is still terrible - my last two fuelly readings were 33.9 and 32.1 (and the never trusty flow meter looks the same for this tank as those), down from a lifetime average of 38.4. That could be the new fuel at my station, winter blend, more local driving, lots of regens, or a combo. It's just weird this year - of course it's my first in a passat as opposed to my jsw (which was my favorite car ever).
Cold weather plus short trips and local driving will result in low 30s. It takes a lot of energy to get the engine and emissions components up to temperature. This causes the first 10 minutes of vehicle operation to use significantly more fuel than it would during normal steady state driving.

Multiple short trips separated by cold soak periods (think holiday shopping trips where you go to one store for an hour, hop in the car and go to another store for an hour, repeat) are some of the worst. Don't expect much above the high 20s in this type of driving.

DPF regenerations are initiated based on a couple of factors. One is a differential pressure sensor that measures restriction in the DPF. When it reaches a certain point, the car will initiate a regen. This trigger is usually experienced in short driving conditions. Diesels produce more soot when they're cold, so short winter trips will result in more frequent regenerations as the system traps more soot.

The other component is distance driven. Regenerations will happen after X number of miles regardless of the DPF's internal restriction. This trigger usually happens on highway trips where the car is driven at steady state for hours on end. The least amount of soot is produced during steady state driving.
 

Jb22

Well-known member
Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
Cold weather plus short trips and local driving will result in low 30s. It takes a lot of energy to get the engine and emissions components up to temperature. This causes the first 10 minutes of vehicle operation to use significantly more fuel than it would during normal steady state driving.
Multiple short trips separated by cold soak periods (think holiday shopping trips where you go to one store for an hour, hop in the car and go to another store for an hour, repeat) are some of the worst. Don't expect much above the high 20s in this type of driving.
DPF regenerations are initiated based on a couple of factors. One is a differential pressure sensor that measures restriction in the DPF. When it reaches a certain point, the car will initiate a regen. This trigger is usually experienced in short driving conditions. Diesels produce more soot when they're cold, so short winter trips will result in more frequent regenerations as the system traps more soot.
The other component is distance driven. Regenerations will happen after X number of miles regardless of the DPF's internal restriction. This trigger usually happens on highway trips where the car is driven at steady state for hours on end. The least amount of soot is produced during steady state driving.
Thanks, veedub. This explanation pulls it all together. It brings me to two more questions.
1- Earlier, it's mentioned that a normal idle is aroung 800 rpm, and during regen, it's closer to 1000. Are there times when an idle would be higher than 800 while the car is still warming up - like when it's cold?
2- You mentioned scan gauge II with PIDS. The google machine pointed me to the tool - and I see that exhaust temp is readily available. What is PIDS?
 

Funguy

Veteran Member
Joined
Jan 18, 2005
Location
Front Range of Colorado
TDI
2015 Golf Sportwagen dsg and 2015 Passat 6 M/T
Thanks, veedub. This explanation pulls it all together. It brings me to two more questions.
1- Earlier, it's mentioned that a normal idle is aroung 800 rpm, and during regen, it's closer to 1000. Are there times when an idle would be higher than 800 while the car is still warming up - like when it's cold?
2- You mentioned scan gauge II with PIDS. The google machine pointed me to the tool - and I see that exhaust temp is readily available. What is PIDS?
https://en.wikipedia.org/wiki/OBD-II_PIDs
 

KERMA

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here
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FWIW

http://forums.tdiclub.com/showpost.php?p=5354542&postcount=4

There are several criteria for DPF regen
1) soot loading: This is usually the limiting factor and what triggers regen most (all) of the time. It is determined 2 ways, Measured soot and calculated soot. Measured soot comes from the d/p sensor. Calculated soot comes from the ECU's internal model, based on time and how much load is on the engine. You can see both of these numbers in VCDS. One thing you will likely notice, "calculated" soot is usually higher than "measured" soot. if you pay close attention, you will also see that "measured" soot can increase, and also decrease due to passive regen starting at ~350-400C. But "calculated" soot only increases with time and proportional to load. You will also recognize that regens are only triggered on "calculated" soot load. This is not only because the number is usually higher, but the ecu developers deemed it "more accurate". In the EA288 cars the trigger is set at 24g.
2) engine operating time: in this application the time is set to an impossibly high number like 32767 minutes of engine run time, so it will never trigger a regen.
3) Distance between regens, set at 750 km.
4) Fuel burned, setpoint is ~120 liters. About 30 gallons, so at 40 mpg that works out to about 1200 miles.
Each or any of these criteria could trigger a regen. Usually, it ends up being the dpf soot loading because that ends up being way more conservative than the other trigger points. After regen these counters are reset to zero.
DPF pressure reading is in hPa or millibar. So when you see 300 it is NOT 300 PSi, but 300 mbBar... more like 4 psi or so. 1 Bar = 14.7 psi
 

VeeDubTDI

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Springfield, VA
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Thanks, veedub. This explanation pulls it all together. It brings me to two more questions.
1- Earlier, it's mentioned that a normal idle is aroung 800 rpm, and during regen, it's closer to 1000. Are there times when an idle would be higher than 800 while the car is still warming up - like when it's cold?
2- You mentioned scan gauge II with PIDS. The google machine pointed me to the tool - and I see that exhaust temp is readily available. What is PIDS?
1.) Yes. The car will run at high idle any time the 1,000 watt auxiliary cabin heater is running. This is frequently the case on a cold start in cold weather.

2.) PID is the data block, for lack of a better term, that ScanGauge is displaying.

There are at least four exhaust gas temperature sensors. You'll want to make sure that you're displaying the pre-turbo sensor (EGT1) as well as one of the others. I think I'm also using EGT3 on the Passat to monitor the temperature coming out of the DPF. Unfortunately I don't know what the PIDs are for the 2015s, but I think that information can be found in other threads.
 

VeeDubTDI

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Jb22

Well-known member
Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
1.) Yes. The car will run at high idle any time the 1,000 watt auxiliary cabin heater is running. This is frequently the case on a cold start in cold weather.
2.) PID is the data block, for lack of a better term, that ScanGauge is displaying.
There are at least four exhaust gas temperature sensors. You'll want to make sure that you're displaying the pre-turbo sensor (EGT1) as well as one of the others. I think I'm also using EGT3 on the Passat to monitor the temperature coming out of the DPF. Unfortunately I don't know what the PIDs are for the 2015s, but I think that information can be found in other threads.
This is great info. I really appreciate it. It looks like winter will foil my plans of simply looking for 1000rpms for the two months a year I travel less. Scan Gauge it is! Thank you again.
 

AreaMan

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Apr 12, 2013
Location
Cincinnati, OH
TDI
2013 Passat 6M
If you have a Scangauge II, in addition to the several EGTs there is a DPF "load" type of reading that you can set. It goes from 0-100 (I think), and I have found that when it gets over 70 or so that a regen is likely next time your driving pattern is suitable.

Also, when in regen, besides the EGTs going up to a steady 1000+, the DPF reading jumps to 100, and when done jumps down to usually the low teens and starts the cycle again. I found the PID somewhere on this site a while ago, I'll see if I can dig it up.
 

roni024

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Mar 31, 2007
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Syracuse, NY
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2015 Passat TDI SEL DSG
It looks like a cool device. Personally, it's not worth $275 to me. I'd probably be so distracted reading all the different data on it I wouldn't be able to concentrate on driving. It would just be more cause for worry. I have VAG-COM to use whenever I want to see that info tho.

BTW, I see you're in Syracuse. Greetings from Fairmount!
 

d2freeman

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Aug 8, 2013
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NC
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Best $275 I have spend so far.
Plugs into the can-bus and adds screens to your MFD.
If I remember correctly you can have up to 10 screens with 4 parameters per screen.
My main screen shows the following parameters:
Exhaust Gas Temp
Boost PSI
DPF Soot mg
DPF Miles (Since last regen)
 

Jb22

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Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
It looks like a cool device. Personally, it's not worth $275 to me. I'd probably be so distracted reading all the different data on it I wouldn't be able to concentrate on driving. It would just be more cause for worry. I have VAG-COM to use whenever I want to see that info tho.

BTW, I see you're in Syracuse. Greetings from Fairmount!
Nice to meet you! We're in Fayetteville. Where do you bring your cars? Believe it or not, we've had good luck at the dealer, but looking for a little more pep after the fix. I'm afraid of them always reflashing back to zero.
 

Jb22

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Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
Best $275 I have spend so far.
Plugs into the can-bus and adds screens to your MFD.
If I remember correctly you can have up to 10 screens with 4 parameters per screen.
My main screen shows the following parameters:
Exhaust Gas Temp
Boost PSI
DPF Soot mg
DPF Miles (Since last regen)
I'm thinking along those lines - probably helps you avoid shutting down while regenerating!
 

jrm

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Oregon
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2013 Passat SE with nav (totaled)
there is a thread for auto polar screens, but yes the idle jumps by 100 rpm and the fans run so fast It sounds like your driving a leaf blower when in regen
 

roni024

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Mar 31, 2007
Location
Syracuse, NY
TDI
2015 Passat TDI SEL DSG
Nice to meet you! We're in Fayetteville. Where do you bring your cars? Believe it or not, we've had good luck at the dealer, but looking for a little more pep after the fix. I'm afraid of them always reflashing back to zero.
I bring my vehicles to Burdick. I would imagine you're a Romano guy due to location.

If you ever need access to a VAG-COM, let me know.
 

Jb22

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Joined
Apr 27, 2014
Location
Syracuse, NY
TDI
2015 Passat DSG
I bring my vehicles to Burdick. I would imagine you're a Romano guy due to location.
If you ever need access to a VAG-COM, let me know.
I really appreciate the offer, that's generous. Thank you!

I go to Burdick, too. It's where I bought my first and most recent TDi, and they've been good to me.
 

New Guy

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Jan 5, 2021
Location
St. Louis
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‘15 Passat TDI SEL
Can you document how many MILES between regens? "...many times more than once per day..." isn't specific enough to evaluate.
You probably already know that city driving will fill the DPF quicker than highway, causing more frequent regens...
At what temp should my car be (and how long should it run at that temp) for a regen cycle to not be necessary?
 
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