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- chicken george
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- VeryDisco5
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- chicken george
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- VeryDisco5
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- DG
- Member Since: 27 Apr 2016
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VeryDisco5 wrote:
, it looks very much as though like there is a consistent, rational explanation exists for the issue.
Isn't that a tiny part of the explanation of how DPF regeneration operates?
....tbh you write as though this is a conspiracy when the full write up of exactly how it works is available for all to see in TOPIx -
- chicken george
- Member Since: 31 Mar 2018
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- VeryDisco5
- Member Since: 02 Sep 2017
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CG said "Yes and you are taking their worst case scenario as a minimum requirement"
I believe, and engineers have confirmed, that the DOC lights up on demand and then takes 10 to 15 minutes to get the remotely-located DPF up to temp (580 degrees). What happens next has little to do with how the vehicle is driven (unless you are pulling one of your combine harvesters up a 1:10 hill) because it takes 25-30 minutes to burn a full soot load (36%) to the point where the pressure sensors say it's completed the regen (10% full). I make that between 35 and 45 minutes. In the 24th October 2017 letter, JLR said that journeys of an hour must be in the driving mix because (I assume) they want to build in a safety margin to ensure that the minimum number of interrupted regens occur - and because they don't provide a light to help drivers know when it's finished.
But then the handbook implies that this all takes place in as little as 10 to 20 minutes: quite a big difference with what we know happens in the real world. If you take a look at the May 2015 document (front section shown below) you'll find there's a totally different description of how the regens were supposed to work, where passive regeneration was originally intended to contribute something. But in the real world of 2018, empirically and as confirmed in writing, it turns out that passive regen doesn't work at all and in turn this impacts active regeneration, making it run for longer and more frequently. This is the expanded version of the explanation given by JLRP00100.
DG wrote "you write as though this is a conspiracy".
Your words not mine. I just know from speaking to JLR staff that it was fairly well understood by the powertrain exhaust system designers in Spring 2015 (before a single Ingenium DS had even left the factory) that there would be problems meeting the 2 year / 21K service intervals on these cars. The problems that duly emerged were caused, as expected, by early diesel dilution due to too much post injection being necessary to actively regenerate the DPF. The brochures containing the misleading claims about service mileage, convenience and cost of ownership, were finally withdrawn last June at about the same time the SCN appeared.
Document Link: https://www.discosportforums.co.uk/download/file.php?id=7630 -
- DieselRanger
- Member Since: 12 Oct 2017
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- VeryDisco5
- Member Since: 02 Sep 2017
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Apples and Oranges? Well, Yes and No, so humour me for a moment and follow a train of thought to see where it leads...
Focussing on the similarities between the cars' exhaust problems we'd get a list like this:
1) The vehicles are from the same manufacturer.
2) They were designed to comply with the same emissions regulations (EU6 NAS Level 3).
3) The coatings and exhaust components would have been signed off at some point in the management hierarchy by the same person.
4) Both vehicles have a significant in-service problem with premature diesel dilution.
5) The diesel dilution is being caused by too much post-injection of diesel caused by "architecture and hardware differences" between these two cars (and two others with the V6 engine) on the one hand and a Jaguar XE/XF on the other.
6) The manufacturer has lumped the problems together with 5 cars under one compliance notification.
7) What's happening on both cars is that the active regenerations are being inadvertently interrupted before they have completed, meaning the process has to start all over again the next time the car is started from cold.
8 ) Free oil services are being provided by the manufacturer for all these vehicles.
We could go on, but you get the general picture. Now, apply Occam's razor, i.e. go for the simplest conclusion: "The issues manifest themselves in exactly the same way, therefore there is probably a common cause."
Next, let's say that the cause of the problem with one of these cars (the DS) is known. The problem is caused by heat-sink effects in the pipework connecting the components together resulting in the DPF not getting hot enough for passive regeneration to occur in normal driving. Question: can we identify anything in the second vehicle that would fit perfectly with this definition of the problem?
Sure we can. Because there is a cross-over pipe connecting the RHS exhaust manifold to the LHS and the common pipework leading to the DPF. This means that half of the gas arriving at the DPF has travelled a significantly longer distance where it would have lost much of its heat energy. Before or after they are united, both gas flows from all 6 cylinders also have to pass across the turbine section of the turbo-charger which cools the gas further. What heat is left then gets served up to the DPF to do its regeneration work. Might it be accurate to say of this architecture:
The problem is caused by heat-sink effects in the pipework connecting the components together resulting in the DPF not getting hot enough for passive regeneration to occur in normal driving???
It's only a hypothesis and all I am trying to do is help - please feel free to shoot it down. After all it's your car and after this, if I DO ever get one, I've already decided that it will have the 2.0L Ingenium based on what I know about the V6. -
- DG
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- chicken george
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- DieselRanger
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- Craigp
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- VeryDisco5
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DieselRanger wrote:
#4 is a presumption not yet supported by evidence - i.e., results from oil testing from D5 TD6 engines. In other words, the system believes oil dilution is occurring based on an estimation the reality is unknown.
Very true, only laboratory analysis can reveal the true state of the oil. But the estimation software (which counts post-injection cycles) has been found to be reasonably accurate on the DS, although it is slightly conservative. e.g. my first sample was estimated at 4%, found to be 3.4% at the lab.
DieselRanger wrote:
#5 - remove the words "too much" and stop after the word "diesel". Now it's factually correct.
#6 - The same compliance notification that my dealer says does not exist and is not shown as canceled or rescinded - it's simply not there.
#8 - Yes, they want owners to be happy regardless of whether there's an issue. It's a "customer satisfaction program" as stated in the notice that doesn't exist any more.
There's no doubt about the existence of the SCN, the original copy came directly from a JLR employee. But I've just noticed something in it that supports your dealer's stance which no-one on any forum has raised before. The existence of the problem is acknowledged in 2 engine/vehicle clusters by the following text on page 2:
The amount of post-injection required to achieve a similar burn rate is much higher on the 3.0L diesel Range Rover / Range Rover Sport / All-New Discovery and 2.0L diesel Evoque / Discovery Sport. Fuel in oil increases at a much faster rate on the Land Rover models.
Therefore the L462, according to one of JLR's own TSEMs, is known to share the premature FIO problem with the other 3.0L vehicles. However, the provision of free oil services arises only where brochure claims of a certain service mileage weren't qualified with the text contained in the User Handbook to the effect that "driving style" might increase the dilution rate and drag down the nominal mileage. This explains why, in a bullet point further down on page 2, it doesn't include the All-New Discovery :
The 6.1% dilution will trigger the "Service Required" message. Based on a customer's driving style this value may be reached in advance of the service interval quoted in the online marketing and brochure for the vehicle (3.0L diesel Range Rover / Range Rover Sport - 16k miles/12 months or 2.0L diesel Evoque / Discovery Sport - 21k miles/24 months).
This document clearly lists the D5 among the affected models, but doesn't go on to grant its owners the same corrective measures as those afforded to RR and RRS owners, simply because of differences in the brochure.
DieselRanger wrote:
Now, back to #2.
The TD6 engine and exhaust system, if I understand correctly, have been employed to meet EU6 regulations since 2014, correct? And they've been deployed on Range Rover Sport, full-fat Range Rovers, the LR4, and now the D5 since then. Since the platform is identical between the RRS and the D5, right down to the wheelbase and track, engine and transmission, these vehicles are functionally identical from an emissions standpoint. And how many RRS, FFRR, and LR4 vehicles have had the problem prior to MY17?
Plenty, especially RRS, PM me for details of the forum URLs.
DieselRanger wrote:
Since EU6 regs have been in place for several years, but only now are we seeing problems, what has changed?
Here are the options - please feel free to add if I missed any:
1. They changed something about the diesel exhaust system
2. They changed something about the engine
3. They changed something in the software that controls the engine and/or exhaust system.
Show me evidence of #1 and/or #2.
Absent that, #3 is the only other viable cause I can think of.
What changed specifically in the 16MY vehicles (the first ones affected by the problem and produced from September 2015) was the introduction of EU6 (Sept 2014 to 2015 implementation window) with a requirement to reduce from EU5:
CO – 0.50 g/km
HC+ NOx – 0.23 g/km
NOx – 0.18 g/km
PM – 0.005 g/km
PM – 6.0x10 ^11/km
To EU6:
CO – 0.50 g/km
HC+ NOx – 0.17 g/km
NOx – 0.08 g/km
PM – 0.005 g/km
PM – 6.0x10 ^11/km
This is when AdBlue and SRC/SCRF technology became necessary. In order for non-stochiometric turbo diesels to meet the new regulations (in respect of NOx) one of the first defensive measures is to run the engine much cooler. But this in turn increases the production of unburned HC and particulate matter in the exhaust and causes a double hit on the older-style DPF unless it can be bolted straight to the turbo outlet. This is the main reason why the XE/XF and the 2.0L Ingenium F-pace and L462 D5 cars continue to perform properly in respect of HC/PM disposal: because passive regeneration still makes a positive contribution as per design.
The reason this couldn't be achieved on the L538 and L550 is obvious just by looking under the bonnet and comparing the space to the size of the XE/XF DPF canister - there's just not enough room. On the L462 V6 there's another issue to be overcome in that a close-coupled DPF would need to have been fitted to twin turbos on both the LHS and RHS manifolds. They must have quickly concluded that this was neither practical nor cost-justifiable and for five cars (3 TDV6 SUVs and 2 2.0L transverse diesels), they needed to looked for a different approach.
The latest emissions architecture proposed at the time by JM comes in two flavours, both of which have an oxidation catalyst as the first device with a DPF and SCR slotted in somewhere behind. In both architectures the DOC is designed to facilitate three oxidation streams, one turns some of the NO into NO2 (easier for the SCR to deal with downstream) while the other two (CO + ½ O2 → CO2 / [HC] + O2 → CO2 + H2O) make a start on the HC/PM to lighten the workload of the DPF.
SCRT schematic for TDV6
SCRF schematic as used on Ingenium 2.0L transverse
Unfortunately, there is a difference between JM's "idealised" architecture as depicted for use with their specialist, patented coatings and the JLR implementation of it on the five cars. JM diagrams always show the TURBO-DOC-DPF triplet being very close-coupled so that while the DOC is performing the initial oxidation, the DPF receives enough heat to work in passive regeneration mode, thus minimising the amount of soot it has to store for the active regeneration to come. On the DS it's about 36 inches back (inside the SCRF) and heavily lagged against heat loss but only up to the DOC - while on the V6 it is closer to the LHS-mounted turbo outlet behind the DOC (labelled CSF) but for half of the exhaust flow volume there is, as I have said, the heat loss in the cross-over pipe to consider.
Whatever the cause, something doesn't appear to work properly in the passive mode and - because it IS a "passive" process - it is unlikely imho to have much to do with software "control".
I think the explanation for the problem is that, up to the point when the DOC is lit up during a regen "burn", the gasses arriving in the DPF on all the affected cars are laden with large amounts of (relatively) cool HC/PM and there's just not enough heat there to perform any meaningful passive regeneration. The consequence on all cars is more frequent periods of active regeneration (these are also longer on the 2.0L because of other reasons not relevant here) but once active regeneration starts on the L462, L494 and L405 it should be short and sharp because the DPF front face is literally touching the back of the DOC. How hard can it be to get the software right for a burn when the components are that close?
When an active regeneration is called for, the software responsible for operation of DPF regeneration cycles also has to co-ordinate EGR ON-OFF, adjust injection timing and a host of other variables (powertrain stop-start logic for instance) that are too complex to describe here. The D5 was launched with this set-up but for the other TDV6 cars which share the engine/exhaust architecture from 16MY onwards (L405 RR, L494 RRS), because of tighter emissions requirements, the manufacturer had no choice but to:
a) change something about the diesel exhaust system (introduce DEF injection/SCR devices);
b) change something about the engine (make it burn cooler, introduce EGR, EGR cooling etc); and
c) change something in the software that controls the engine and/or exhaust system (agree).
DieselRanger wrote:
I would encourage D5 owners to have oil samples independently tested before they take them in for service. We'll see what that reveals.
I couldn't agree more. Take some oil when you get the Service Light and find out what is really going on. You might be surprised by some of the dilution levels being planned in order to cause less Service Required messages.
Last edited by VeryDisco5 on 14th May 2018 7:25 pm. Edited 16 times in total -
- VeryDisco5
- Member Since: 02 Sep 2017
- Location: Southern England
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