Regen Cycle

Sublimize23

New member
Joined
Nov 9, 2017
Location
PA
TDI
2015 Golf TDI
Sorry for the noob question, only had the car a few days but put about 300 miles on it.

On my old Duramax truck it was very obvious when it was in a regen cycle, the idle was elevated and it sounded and drove different. Is there a way to tell when a regen cycle is happening? I did my usual commute today and noticed a steep drop off in mpg according to the computer (41 instead of 52ish) so I figured that's what was happening.
 

Ronner

Active member
Joined
Jul 4, 2017
Location
ontario
TDI
New 2015 Golf TDI dsg
My revs at idle go up from ~ 750 to 1000 rpm. If the car is turned off before finishing the fan stays on. ymmv.
 

The Tortoise

Veteran Member
Joined
Apr 24, 2017
Location
Ottawa
TDI
2015 GSW Trendline - White
I don't notice any changes to how the car drives.

I've I'm cruising on the highway I'll see slightly higher oil temperatures, around 106 C.

You can smell it if you turn the car off and get out mid-regen.
 

clacker

Veteran Member
Joined
Mar 29, 2000
Location
Oxford Mills, Ontario, Canada
TDI
2015 Golf Wagon TDI DSG Trendline, 2000 Jetta TDI auto, 2008 Mercedes R320, 2006 smart fortwo cdi
It is not that obvious, you will feel a slight change in acceleration, maybe a hesitation around 2000rpm, mostly when it engaging into regen mode you loose a bit of power like a/c coming on.
It is very obvious when you stop, the heat, the smell, the fans. Never shut it off, leave it run or keep driving. The turbo can only handle so much heat cycling and oil coking.
 

Cuzoe

Veteran Member
Joined
May 24, 2017
Location
Los Angeles
TDI
MK7 Golf S
Never shut it off, leave it run or keep driving. The turbo can only handle so much heat cycling and oil coking.
I understand the thinking behind this. But is there any documentation, VW guidance for it? Maybe even forum reports of problems caused by not doing it.
I'm asking because my wife drives the car as often if not more than I do and there's no way she's doing this. She will notice and tell me about weird noises, warning lights, or the car feeling different. But asking her to pay attention to the idle when she gets home after work and sit in the parking garage letting the car run if it's high is not going to happen.
Since the car is using more fuel during a re-gen would it not make more sense to let it finish the re-gen when on the way to work the next day instead of getting 0 mpg in the lot? FWIW we live about 2 minutes from the interstate which is then the next 45-ish minutes of our commute.
 

clacker

Veteran Member
Joined
Mar 29, 2000
Location
Oxford Mills, Ontario, Canada
TDI
2015 Golf Wagon TDI DSG Trendline, 2000 Jetta TDI auto, 2008 Mercedes R320, 2006 smart fortwo cdi
Vw will not admit it, but typically 1200-1300 was the limit on diesels for EGT, these run 1400-1500 on regen...shutting off at these temp without a collant over run pump/water cooled turbo is a bad idea for long term life, I am talking beyond 200k miles not warranty period. Oil cokes at those temps. My wife will just leave it running when it is regen or I take the car out for a spin when she gets home, idling is never a great idea but letting it cool down is needed. We have a scangauge showing EGT data.

The problems are already out there, many have documented short turbo lives on the forum. Will the dealer or indie tell them why it failed, they don't know or care. Prudent care is needed to own one of these cars for LONG time, not talking a few years but 15-20, the length the body will last when cared for. I have my 2000 Jetta tdi that we bought new nearly 18 years ago, plan on longer for it and this new tdi especially when it is the last diesel from VW.
 

Sublimize23

New member
Joined
Nov 9, 2017
Location
PA
TDI
2015 Golf TDI
FWIW the Duramax manual says only to keep driving if the message display tells you to keep driving, which only occurs when the DPF has failed to regenerate completely a couple of times. It's perfectly okay albeit more wasteful of fuel to go about your daily business in the middle of a regen cycle, turning it off. I can't say for sure on the TDI but most diesels have another fuel injector after the turbo to burn it in the exhaust directly, to heat up the DPF. Seems like it should be fine, the manual I don't believe makes any mention of this.
 

The Tortoise

Veteran Member
Joined
Apr 24, 2017
Location
Ottawa
TDI
2015 GSW Trendline - White
Vw will not admit it, but typically 1200-1300 was the limit on diesels for EGT, these run 1400-1500 on regen.
Is an extra 200F really going to have an impact on the longevity of those parts? And is oil coking as much of an issue with synthetic?
 

giuseppe_b

Veteran Member
Joined
Apr 29, 2007
Location
Albuquerque, NewMexico
TDI
2015 Golf SportWagen SE 6MT
My input on this topic is this:
I see on my 2015 regens every 230 - 300 miles, depending I guess on how much highway driving I do. The last regen was closer to 225 miles because my wife drove it for a few weeks with rarely any highway trips, only short trips to school and back with the kids, etc. My commute adds some highway time, maybe 15 minutes or so but doing that consistently yields the regens at closer to 300 mile intervals.
I use a Bluetooth dongle that connects to the car's OBDII port, and the $5 torque pro app on my phone to monitor the EGTs. I can tell when a regen is happening and usually I will keep driving until the temps start coming down from the >1000 F range. I wait until it is below 450 to turn it off, or below 400 if I can really wait a few minutes longer idling in the parking space, or the driveway before entering the garage. Some people use the ScanGauge, or other items out there that are a bit more expensive but maybe easier to use, less use of the phone while driving, etc, or for the wife to be more in touch with the car as was mentioned before. My wife is of the mind where she does not think of these things nor pay attention to it.

Volkswagen's stance on regens seems to be: if you turn off the car and the fans are running, it was likely in the middle of the cycle, and the regen will just resume when the car next drives and reaches 38 mph. I agree with
When driving on the highway it is not easy to tell that the regen is happening. If you accelerate hard, the car may pull a bit harder due to the increased amount of fuel being injected, and of course the MPG numbers will drop a bit. And of course if you are at a stop light, and the car's idle is around 1000, it is likely doing the regen, although there have been times that she is idling that high and the torque app readout indicates that the EGTs are normal level. I sometimes will get a slight diesel smell through the air vents but not always.

As far as the coking goes, I am interested in this topic too. Does that occur if you shut the motor off during the cycle when these components are at these high temps, not being allowed to cool down with oil circulation or exhaust flow? That makes sense, I used to own a 2.0T Jetta some years back and I learned that it is good to idle the car for 30 sec to a minute before shutting off the motor, to allow the turbo to properly cool down first so coking does not occur, especially after driving with lots of turbo use. I think some GTI people have talked about that on GTI forums.
Some of those gasser turbos had turbo failures and a few VW techs (one of them has over 20 y. experience) have attributed that to this coking thing by around 80k miles. But of course, that always varies.
I think a the TDI turbos are more often consistently engaged than the gasser ones because they spin up at lower RPMs so I believe it is a good thing to let it cool down before turning of the motor.

Sorry if that was too long and straying from the topic but I wanted to give the newbie some info.
Cheers.
 

Darth_Furious

Veteran Member
Joined
Aug 7, 2005
TDI
2015 GSW, DSG
From what I understand, the fans kick on until the engine drops to a certain temp. I know a regen is happening by the high idle, sound...etc when I leave the freeway and am at a light. I drive in the city for 10 minutes and I can see the car go back to normal as it wraps up the regen cycle. I park and see if the car is running ok and then turn off the engine. I hear the fans kick on because it is still too hot post regen.

Fans on don't always mean the regen is happening. Sometimes you finished the cycle and the turbo is not super hot anymore, the fans are on to cool everything down to prevent fires.

I put 100K on my mk6 driving it without worry and it served me well until i returned it for the buyback. I say drive more, worry less.
 

Freeze Plug

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Joined
Oct 27, 2012
Location
CT
TDI
Turd Sandwich
I was under the impression oil coking is not a problem with fully synthetic oil, is this not true?
 

Funguy

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Joined
Jan 18, 2005
Location
Front Range of Colorado
TDI
2015 Golf Sportwagen dsg and 2015 Passat 6 M/T
My Passat will ask me to down-shift during a regen if I am at a borderline speed. For example if I am in 6th at 45mph it will ask me to shift to 5th. My scanguage II will indicate a regen by the DPF temp rising above 800 degrees to over 1,400 degrees. I hate turning off the engine at this temp but sometimes I don't have the time to wait ten minutes for it to finish so I "worry less" and shut it off.
 

clacker

Veteran Member
Joined
Mar 29, 2000
Location
Oxford Mills, Ontario, Canada
TDI
2015 Golf Wagon TDI DSG Trendline, 2000 Jetta TDI auto, 2008 Mercedes R320, 2006 smart fortwo cdi
Oil coking is still a problem synthetic oil has not fixed that.

My concerns are for LONG TERM, not within the warranty period and not likely to happen within 150k miles. I am talking about 8-10 years that these problems start to accumulate. Turbos are already being replaced often, I am on a Facebook group for the emissions scandal with a couple thousand members and a surprising number have replaced the turbo already. None of them knew why. Was it the vanes warping and sticking, was it oil coking, did they blow up/complete failure. Cannot say. But shutting down when the exhaust temps are 1400-1500 is never a great idea. Just one of those things when owning these cars. Cost cutting shows it's ugly head here very much, why the emissions system was not stand alone (separate injector in the exhaust so engine stays cool and no oil dilution), why the turbo is not water cooled with an after run pump like most gas engines, it is clear VW did not design these with long term in mind but a band aid solution (and it was ripped off quickly to hurt!)
Everyone has an opinion, that is it-if expect things to last treat it well and avoid hot shut downs. I keep things a LONG time, not just 8-10 years but 20 years and more as I service it to last matters well enjoy the fruits of my labour.
 

2015vwgolfdiesel

Top Post Dawg
Joined
Jan 1, 2016
Location
Oklahoma
TDI
2015 VW Golf S DSG Silver
Will be doing the "fix"

And maybe that will be my only regret in the long term future.

I have not even noticed one for quite some time. (6,000 on the clock)

Last week I drove over to see Mom 2 times. Fairly sure it happened at that time.

Likely the first trip was it, because the MPG were less than I expected.
 
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