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How long does active regeneration take?

33K views 61 replies 19 participants last post by  SailorDoc 
#1 ·
Given the well known issues with oil dilution, it makes sense not to interrupt active regeneration cycles when they start, if possible. However, I am unsure of the criteria for the active regeneration cycles, e.g. do they require certain speeds/rpm like forced regeneration cycles or could it complete on your driveway at the end of a journey if needed? How long do active regeneration cycles take in the DS, and does it vary depending on speed/rpm? Does stop/start resume after active regeneration is complete or later? This would all be so much simpler if there was a light that told you when active regeneration was occurring rather than having to guess!
 
#3 ·
Hmm. Sorry, didn't spot that. I should be clear that I've never seen any amber or red warnings. Presumably, therefore, if your average speed is less than 30mph such as in stop start rush hour city traffic the engine management shouldn't request DPF regeneration as it could not complete, and should request it once you are travelling constantly above 30mph. However, my car seems to do so, sometimes only a day after long motorway journeys at 70mph. I've done 5300 miles in this car from new in only a little under 3 months, yet it says service will be due in 10200 miles. If this trend continues, therefore, it will only do around 10,000 miles between services, in a car traveling up to 20,000 miles a year. That's a pretty appalling software design!
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#4 ·
Your final sentence says all. But it's not just the software that is, shall we say useless, but all the hardware. There's a lot on here about it.

Your assumption about the software not calling for a regeneration in city traffic is unfortunately incorrect and this is what is contributing to the oil dilution problem. The system starts a regeneration but if it can't finish it the excess fuel gets dumped in the sump and hey presto the problem is potentially there.
 
#5 ·
SailorDoc said:
This would all be so much simpler if there was a light that told you when active regeneration was occurring rather than having to guess!
This has been suggested by a few other folks as well in other threads on here. I agree with you, SailorDoc. I can only assume that they don't wish to expose under what conditions and how frequently this takes place.

The light on the dash is there. It wouldn't take much to add a new message to the information centre saying "Active Regeneration in Progress - drive to Birmingham and back" or something.

Would prevent a lot of DPF issues/misunderstandings, I think. Transparency would be the best strategy here:

"We understand we bought a Euro 6 diesel car that needs to be treated slightly differently (you can call it driving style if you want, JLR). Just let us know when the DPF is doing its thing and we'll keep it happy by driving an additional 20 miles up the motorway until it completes."

How ironic that these devices actually require us to drive at higher speeds, for longer periods, in order to keep the anti-pollution device happy. :roll:

Steve
 
#6 ·
My dealer told me ages ago that the German dealers association had, on numerous occasions, requested the addition of such a light but that this was always flatly refused by LR.
 
#8 ·
Chippy said:
Your final sentence says all. But it's not just the software that is, shall we say useless, but all the hardware. There's a lot on here about it.

Your assumption about the software not calling for a regeneration in city traffic is unfortunately incorrect and this is what is contributing to the oil dilution problem. The system starts a regeneration but if it can't finish it the excess fuel gets dumped in the sump and hey presto the problem is potentially there.
It's not so much that excess fuel is dumped in the oil if the regen fails, it's dumped throughout the regen, failed or good. So restarting regens after failed ones just means more fuel is dumped during (and until the end of a good) regen is completed. Fuel is injected on the exhaust cycle during regen to be sent down the exhaust, but some makes it past the piston rings into the oil.
 
#9 ·
If LR put a light (even a green one) on the dash to tell us the car is regenerating, then dealers, LR assist and this forum would be swamped with people asking what the light meant.
 
#10 ·
If the regeneration timings actually matched those in the Owners Hand Book there wouldn't be an issue. Two things frustrate the design and led to the description of the problem contained in JLRP00100.

1) Hardware and architecture issues can require a 10-15 minute warm-up period after DOC light-up. Source - JLR Engineer comments to JLR Dealer Service Agent October 2017.

2) A 4g/L soot load would require the DPF (SCRF) to be kept at 823K to 873K for 30 minutes. Source: Lasitha Cumaranatunge, Technical Program Manager JM, Presention to *CLEERS early in 2016.

Summary From Page 29 of JM Presentation

• The soot burn efficiency in a Pt catalyzed CSF is significantly higher than an SCRF® catalyst (or an uncoated filter) under active regen conditions (550-600oC)
• No significant differences were observed in soot combustion efficiency with and without NH3 injection for an SCRF® catalyst under active regen conditions (≥550oC).
• Location of soot in the filter seems to only have a minor impact on the soot combustion efficiency under active regeneration conditions.
• There are clear benefits to using an SCRF® catalyst and we need to adapt a suitable active regeneration strategy.
• A 4g/L soot load on an SCRF® catalyst can be fully regenerated at 600oC for ~30 mins
Increasing filter inlet temps to >600oC will be beneficial to reduce length of regen event
*Crosscut Lean Exhaust Emissions Reduction Simulations is an initiative funded by the U.S. Department of Energy (DOE) Vehicle Technologies Office to support the development of accurate computer simulation tools for use in the design, calibration, and control of next generation engine/emissions control systems that maximize efficiency while complying with emissions regulations.

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#11 ·
We should re title this topic "How long is a piece of string" 💣 🔥
 
#16 ·
One thing worth noting , if it is over generating the DPF will fail prematurely and there is an EU stipulation which states the "reasonable" life of a DPF they are expected to last at least 150,000 miles the last time I read the legislation/guidelines.

I haven't check the figure for more recent updates.
 
#18 ·
FFS! Today I spotted that average MPG and instant MPG were dropping during a drive (stop start hasn't really been working over last few weeks), made sure I continued to drive above 40mph until average MPG rose above 40 MPG again, and yet still 300 miles have been lopped off my distance to next oil service :x It would appear that driving style is mostly irrelevant - the car can never have been designed to achieve the stated service interval. :roll:
 
#19 ·
Although with impeccable timing I have received an email today from Land Rover saying:

"As part of Land Rover's drive for continuous improvement, we would like to invite you to take part in a survey about your ownership experience with your Discovery Sport.

Our designers, engineers and retail teams rely on customer feedback to plan improvements for current and future owners, so your participation is greatly appreciated. Please click below to start the survey"

Oh indeed I shall......
 
#20 ·
SailorDoc said:
It would appear that driving style is mostly irrelevant - the car can never have been designed to achieve the stated service interval.
According to one engineering source it was actually the other way round, the service interval wasn't designed to meet the capabilities of the car.

The exhaust design was fully optimised but it had to work alongside a number of immutable constraints: car body space, a need to meet EU6b and the choice of SCR on filter technology. The stated service interval could have been changed to reflect the known capability of the system. The problem they were up against was that an 8,000 mile service interval didn't look very attractive on a £40K car in 2015.
 
#21 ·
Has anyone been pulled over for speeding and used the excuse that I was complying with JLR's instruction to drive at 40mph to clear the DPF? 😁
 
#22 ·
Just had my first regeneration yesterday at 12,600 app, at lunchtime, driving through central Halifax!
Luckily we were able to get where we were going (Andy Thornton Antiques) and then a meal with friends, we were able to go back on the Chorley road then over towards Haworth, so we're (just) able to maintain 40 - 43 mph but the warning was there for over an hour, boy was I glad to see the icon go!

The best part - only passed ONE police car the whole time. Thank god for quiet country roads.

Bob
 
#23 ·
Techauthorbob said:
Just had my first regeneration yesterday at 12,600 app, at lunchtime, driving through central Halifax!
Luckily we were able to get where we were going (Andy Thornton Antiques) and then a meal with friends, we were able to go back on the Chorley road then over towards Haworth, so we're (just) able to maintain 40 - 43 mph but the warning was there for over an hour, boy was I glad to see the icon go!

The best part - only passed ONE police car the whole time. Thank god for quiet country roads.

Bob
It won't have been your first regeneration, they happen every couple of hundered miles (or even more frequently), but I guess it's your first 'Regeneration Required' warning.

I assume you've been trundling around for a couple of weeks with no opportunity for it to regenerate 'naturally'?
 
#24 ·
Fair point there -9, this was the ONLY message ever seen to date.

Never noticed sudden drop in economy because most of my driving is up or down some of the steeper twiddlier bits of Yorkshire and the figure seen usually varies enormously anyway.

My journeys tend to be some of very short distances but also some of 40+ miles most weeks to balance things out. Occasionally we do Windsor and/or Kenilworth but tend to go one way cross country and the other way motorway or M1.

My O/H commented that "why can't we just trundle on at relatively high revs in a lower gear instead of the 40 mph for 20 mins instead" - the short answer is "dunno!", is that possible?

Bob
 
#25 ·
Don't think so, as the requirements are speed and time based, see excerpt from handbook on P1 of this thread. It's easier to tell people to keep over a certain speed than revs over (for example) 1500rpm.

Whether the DS measures the road speed or engine speed to know when to start the regen is another guess!
 
#26 ·
I've read yesterday in TOPIX (Werkstatthandbuch/workshop manual?) that for the DPF regeneration a speed between 100 and 120km/h for 20min is ideal. In the owners manual I just can find between 60 km/h und 112 km/h for 10-20 min.

Hmmmm....
 
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