Discovery 2017

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  • Room101
    Member Since: 09 May 2018
    Location: Sacramento
    Posts: 8
    United States 
    2017 Discovery Td6 HSE Aruba

    QUOTE "You are correct about a regen that's interrupted midstream, if each cylinder does not complete an extra exhaust cycle before it stops. Thing is, it's not a mechanical system, it's electro-mechanical. As soon as you hit the STOP button, the fuel is cut off at the injectors, and each of the cylinders, no matter where they are in the cycle, continue with momentum through a complete cycle. So any fuel injected just at the moment of shut-off will get pushed out through the exhaust port, and no other cylinders will get their post-injection dose."
    =========================================================================================

    This is widely cited as the mechanism causing diesel to enter the oil but it is not the main source of the problem. Jaguar Land Rover likes to hear it repeated because it points toward "driving style" as a contributory factor. Beware of propaganda. The dilution percentage actually correlates, not with the number of interrupted regenerations, but with the total time that post injection is operating. The interruptions serve to increase the overall time that post injection has to operate because an incompleted regeneration usually has to re-start with a cooled engine and exhaust necessitating an additional 10 minute warm up period using "post injection associated with retarded ignition" just to get the DPF back up to regeneration temperature (1100 F).

    The main dilution process occurs when a tiny proportion of the atomised, post injected fuel is adsorbed into the oil film rather than being ejected through the exhaust valve. On each subsequent induction stroke the scraper ring collects a proportion of this concentrated diesel-oil admix and deposits it into the sump. With each stroke the diesel concentration increases by a minute amount as the oil film is progressively washed off and replaced by fuel. Compression rings become less effective and the rate of dilution gradually increases throughout the post injection sequence. This is when metal to metal contact can occur resulting in loss of material from the cylinder walls and piston ring pack. Further damage occurs immediately after the restart because the oil film needs time to re-establish.

    When the engine stops rotating before it has had a chance to replenish the oil film, there is little oil seal left to prevent the final injection from running straight into the sump but this is a small amount of diesel in comparison to what has been lost already. In a 20 minute regeneration cycle the engine has processed no fewer than 180,000 post injections when rotating at 3,000 rpm: the impact of the final post injections into 2 clinders is negligible by comparison.

    This is one of many scientific papers describing the phenomenon.
    http://j-mst.org/On_line/admin/files/25-04152_2526-2533_.pdf
    8th Nov 2018 11:17 am
  • DieselRanger
    Member Since: 12 Oct 2017
    Location: God's Country, Colorado
    Posts: 770
    United States 
    2017 Discovery Td6 HSE Silicon Silver

    You're 100% correct, but what I'm saying is that shutting the engine off does not allow fuel to pool in the cylinder, so just shutting the engine off in itself does not directly result in increased dilution. Until the engine gets to the point where the rings and walls are so worn that there's blow-by in both directions, post-injected diesel will go right out the exhaust port.

    And I don't believe in this case that it's a "driving style" issue because my oil analysis indicates the vehicle is drastically over-estimating fuel in oil. This is way better than under-estimating it, as it causes more frequent oil changes than necessary thus preserving engine life, but it is resulting in unnecessary expense and inconvenience for owners.
    8th Nov 2018 2:01 pm
  • Yorkietiger
    Member Since: 09 Sep 2018
    Location: Leicester
    Posts: 41
    United Kingdom 
    2017 Discovery Td6 HSE Santorini Black

    Based on what Bogblaster has said on feedback from someone who works at JLR, it looks like my decision to stick with my D4 will not just be short term, any replacement of this with a D5 looks ever more distant as more information creeps out. I cannot see how fiddling with the software is ever going address this problem.

    If they reduce the sensitivity so that FIO prediction are assumed to be lower then you have less oil changes, but on the downside if there is excess FIO then there will be increased engine wear Big Cry Or, they keep it as is, and you end up changing oil every few thousand miles with all the cost and inconvenience that that entails Crying or Very sad Either way you are screwed.

    Seems to me the only possible way to address this is to put a sensor into the sump to actually measure oil dilution (if that is even technically possible), and admit that oil changes may be required more frequently than has been the case in the past. Then you would at least know when a change was actually needed, and you would be buying the car in full knowledge of what you would be taking on.
    8th Nov 2018 2:19 pm
  • JonM
    Member Since: 30 Jun 2016
    Location: North Yorkshire
    Posts: 599
    United Kingdom 
    2022 Discovery SDV6 HSE Carpathian Grey

    The D4 uses exactly the same process and must be susceptible to FIO dilution to a similar extent as the D5 TD6 but it's never been recognised as a problem. I suspect that the reason for that is that the car didn't try to calculate dilution so no one ever bothered about it. I doubt that it is any better in reality than the D5.

    The oil dilution measurements obtained by people actually measuring it suggest that it's not a real problem on the TD6 - just a calculation error.

    My SD6 doesn't seem to be affected (so far).

    If a software update can stop the TD6 D5 irritating its owner by demanding unnecessary oil changes and allow oil changes at the same interval as the D4, I see no logical reason to think that the D5 engine is at any risk of reduced longevity compared to the same engine in the D4.
    MY2022 D5 HSE D300 - with extra nice bits added
    MY2019 D5 HSE 3.0 SDV6 - sold to a dealer for a crazy price!
    8th Nov 2018 5:29 pm
  • IndusD4
    Member Since: 28 Jan 2018
    Location: Sydney
    Posts: 698
    Australia 

    I would guess it is any diesel with DPF that has oil dilution to some degree. I've had a Nissan Pathfinder diesel in the past that had the issue, I only noticed because the oil level on the dipstick went up without engine oil being added.

    Ron
    2016 D4 TDV6
    IIDTool BT
    8th Nov 2018 6:23 pm
  • DieselRanger
    Member Since: 12 Oct 2017
    Location: God's Country, Colorado
    Posts: 770
    United States 
    2017 Discovery Td6 HSE Silicon Silver

    I would say any vehicle that must rely on post-combustion fuel injection to clean the DPF has oil dilution as an eventual issue if you leave the oil in there long enough, but the rate of accumulation should never be this fast so early in a vehicle's life unless the tolerances were incredibly loose to start. In that case, these things would be blowing smoke and have horrendous fuel economy, and that's not the case.

    If I do a little math in public, 6.1% of fuel in 6 liters of oil by volume is about 366ml. That's a lot of diesel fuel to accumulate in the oil in as little as a couple thousand miles given the tolerances of a new engin, and given the extremely fine vapor that comes out of the fuel injectors at tens of thousands of psi. It just doesn't add up for me.

    There are methods of directly measuring oil vicosity through resistivity measurements, either electrical or vibroacoustic. They don't appear to be used on the D5.
    8th Nov 2018 11:20 pm
  • Yorkietiger
    Member Since: 09 Sep 2018
    Location: Leicester
    Posts: 41
    United Kingdom 
    2017 Discovery Td6 HSE Santorini Black

    Jon M. suggests the D5 should not be any different to a Euro 6 D4 as regards the likelihood of FIO. He may be correct, but there are some differences between the set ups. The most obvious one being the SDV6 in the D4 is twin turbo whereas the TD6 is a single one. I do not have information on how the actual layout of the respective exhaust systems differ, but as we have learned already the distance between the turbo outlet and the DPF is critical in ensuring that the necessary temperature is attained to enable passive regeneration to take place.

    One thing that suggests to me that there are key differences is the amount of adblue use some TD6 users seem to be experiencing. I have driven my D4 26,000 miles since buying it second hand, and so far it has only needed one top up at its last service at 24,000 miles. I checked yesterday and it now has done 30,700 miles, and the DEF fluid level read out says it has 10,000 miles left in it.
    9th Nov 2018 12:09 pm
  • chicken george
    Member Since: 31 Mar 2018
    Location: N. Yorks
    Posts: 51
    United Kingdom 

    D5 adblue use will be more than D4 , because basicaly its working harder to achieve a cleaner emissions.

    passive regens are not common on any car, diesel engines do not get hot enough in all but the heaviest of use, So a passive regen should be seen as a bonus event rather than normal. Often a high speed motorway run will not be hot enough to cause a passive regen, maybe dropping a gear and using more revs would help.
    Chicken George, Land Rover owner for decades , and proud buyer of British products.
    9th Nov 2018 1:26 pm
  • DieselRanger
    Member Since: 12 Oct 2017
    Location: God's Country, Colorado
    Posts: 770
    United States 
    2017 Discovery Td6 HSE Silicon Silver

    D5 AdBlue usage may also be higher than D4 usage because of a tighter compliance regime in the wake of VW's shenanigans. The Td6 has been around a long time, and to my knowledge, earlier L494 RRS's (2014 was the earliest in the US with the Td6) didn't suck down the AdBlue like they do today.

    But AdBlue usage isn't directly tied to the DPF as the SCR is downstream of the DPF and is necessary to address oxides of nitrogen rather than soot. However, NOx generation and soot generation are opposed - if you design the engine to limit one, the other is negatively affected. Design in a cooler intake charge to inherently reduce NOx generation, then you use less AdBlue in the exhaust, but you generate more soot, which requires a DPF and potentially post-injection to keep it functioning.
    9th Nov 2018 2:03 pm
  • Room101
    Member Since: 09 May 2018
    Location: Sacramento
    Posts: 8
    United States 
    2017 Discovery Td6 HSE Aruba

    QUOTE passive regens are not common on any car, diesel engines do not get hot enough in all but the heaviest of use, So a passive regen should be seen as a bonus event rather than normal. Often a high speed motorway run will not be hot enough to cause a passive regen, maybe dropping a gear and using more revs would help.
    =========================================================================================

    Passive regeneration occurs during normal diesel engine operation and involves a slow conversion of the particulate matter deposited in the DPF into carbon dioxide. Passive regeneration is a continuous process (rather than a countable "event" with a defined beginning and end condition, as implied above) which operates anytime that the DPF temperature exceeds 480°F . On any vehicle where the DPF is mounted relatively close to the turbo-charger outlet (such as the JLR Jaguar XE/XF saloons and coupes) passive regeneration is virtually constant under most driving conditions which significantly reduces the requirement for active DPF regeneration. This means less post injection events, slower fuel dilution of the oil and the ability to offer extended service intervals.

    The quoted statements are not correct for diesels in general, but they are true in respect of several JLR SUVs lacking a close-coupled exhaust architecture of the type used on the Jaguar XE/XF. In JLR's own words:

    "Duration / distance to complete a full regeneration on [some JLR SUVs] is longer than on 2.0L diesel XE / XF, increasing the likelihood of an interrupted regeneration. Due to hardware and architecture differences between model lines, the amount of post injection required to achieve a similar burn rate is much higher on [some JLR SUVs] in comparison to 2.0L diesel XE / XF. This combines to significantly increase the fuel in oil contribution for each successful regeneration event."

    https://disco5.co.uk/gallery/10682/XEXF.jpg
    10th Nov 2018 6:39 pm
  • stingray
    Member Since: 09 Apr 2017
    Location: North Wales
    Posts: 29
    Wales 
    2018 Discovery Td6 HSE Silicon Silver

    My MY18 TD6 has covered just over 3,000 miles, and today showed service required in 1050 miles. I did a twelve mile journey and checked it again and it showed 1,000 miles till service. As I was sitting looking at it, it dropped to 950!
    11th Nov 2018 9:51 pm
  • Ed Snow
    Member Since: 28 Nov 2017
    Location: Norwich
    Posts: 79
    United Kingdom 
    2017 Discovery Td6 HSE Scotia Grey

    Sounds to be in line with other 2017 and 2018 vehicles. What we all need to understand is if the 2019 SDV6 has fixed the issue? JonM feedback suggests it may have done but would be good to hear from others with a few months under their belt......
    11th Nov 2018 9:55 pm
  • chicken george
    Member Since: 31 Mar 2018
    Location: N. Yorks
    Posts: 51
    United Kingdom 

    Room101 wrote:
    QUOTE passive regens are not common on any car, diesel engines do not get hot enough in all but the heaviest of use, So a passive regen should be seen as a bonus event rather than normal. Often a high speed motorway run will not be hot enough to cause a passive regen, maybe dropping a gear and using more revs would help.
    =========================================================================================

    Passive regeneration occurs during normal diesel engine operation and involves a slow conversion of the particulate matter deposited in the DPF into carbon dioxide. Passive regeneration is a continuous process (rather than a countable "event" with a defined beginning and end condition, as implied above) which operates anytime that the DPF temperature exceeds 480°F . On any vehicle where the DPF is mounted relatively close to the turbo-charger outlet (such as the JLR Jaguar XE/XF saloons and coupes) passive regeneration is virtually constant under most driving conditions which significantly reduces the requirement for active DPF regeneration. This means less post injection events, slower fuel dilution of the oil and the ability to offer extended service intervals.

    The quoted statements are not correct for diesels in general, but they are true in respect of several JLR SUVs lacking a close-coupled exhaust architecture of the type used on the Jaguar XE/XF. In JLR's own words:

    "Duration / distance to complete a full regeneration on [some JLR SUVs] is longer than on 2.0L diesel XE / XF, increasing the likelihood of an interrupted regeneration. Due to hardware and architecture differences between model lines, the amount of post injection required to achieve a similar burn rate is much higher on [some JLR SUVs] in comparison to 2.0L diesel XE / XF. This combines to significantly increase the fuel in oil contribution for each successful regeneration event."

    https://disco5.co.uk/gallery/10682/XEXF.jpg



    Sorry its not as simple as that, your quote refers to active regens not the rare on any diesel passive regen.
    Stated hardware and achitecture does not implicitly imply the problem is solely due to the DPF not being close coupled,

    "The majority of regenerating (as opposed to disposable, Figure 1) diesel filter systems utilize thermal regeneration, during which the particulates are oxidized to produce gaseous products. The temperature of the diesel exhaust gas is, however, too low to sustain auto-regeneration of the filter. That problem may be solved by either (1) decreasing the required soot oxidation temperature to a level which is reached during regular engine operation or (2) increasing the temperature in the filter to the point where the trapped soot starts oxidizing. The first approach is used in passive filter systems, the second in active filter systems."

    https://www.dieselnet.com/tech/dpf_sys.php
    Chicken George, Land Rover owner for decades , and proud buyer of British products.
    12th Nov 2018 9:05 am
  • Room101
    Member Since: 09 May 2018
    Location: Sacramento
    Posts: 8
    United States 
    2017 Discovery Td6 HSE Aruba

    All I am concerned about is getting JLR to resolve a situation that they readily admit to knowing about:

    "Duration / distance to complete a full regeneration on the Discovery 3.0L TDV6 is longer, increasing the likelihood of an interrupted regeneration. Due to hardware and architecture differences the amount of post injection required to achieve a similar burn rate is much higher on the Discovery 3.0L TDV6 in comparison to 2.0L diesel XE / XF. This combines to significantly increase the fuel in oil contribution for each successful regeneration event."

    Generalized explanations about passive-active regeneration are irrelevant unless I can drive my Discovery further than 4,000 miles without it demanding another oil change. I don't care how they do it, I just want them to do it.
    14th Nov 2018 12:31 am
  • chicken george
    Member Since: 31 Mar 2018
    Location: N. Yorks
    Posts: 51
    United Kingdom 

    fair enough, the point being that there is hope of a software solution, its more than a matter of saying " the dpf is too cold, its never going to work"
    Chicken George, Land Rover owner for decades , and proud buyer of British products.
    14th Nov 2018 12:40 am
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