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SCRF versus CSF - Are we on the bleeding edge?

77K views 153 replies 24 participants last post by  Rediscovery 
#1 ·
Up until 24th October 2017 the soot particulate filter had always been referred to on the forum as the "DPF". Then I received "the letter" from the Executive Board with this statement: "The SCRF (Selective catalytic reductant filter) component was inspected and soot was found on the rear face. This component contains the diesel particulate filter." Initially this statement made no sense to me, and subsequently I mis-identified the SCRF component as the DOC: https://www.discosportforums.co.uk/viewtopic.php?f=8&t=5379&p=76180&hilit=SCRF#p76180

Since then every time I have searched the web for "SCRF" at least one of the results has it written SCRF® implying that these devices contain protected intellectual copyright material. Trying to get to the bottom of this, today I found a scientific paper called "A Study of the Soot Combustion Efficiency of an SCRF® Catalyst vs a CSF During Active Regeneration" by Lasitha Cumaranatunge et al. The abstract immediately caught my attention:

The soot combustion efficiency of a Pt-based catalyzed soot filter (CSF) was compared to a Cu-SCR catalyst-coated soot filter (SCRF® catalyst) under active regeneration conditions. The CSF was found to have a significantly higher soot combustion efficiency compared to the SCRF® catalyst under typical active regeneration conditions (550-600 °C). Despite the thermodynamic equilibrium limitation of the NO oxidation reaction at high temperatures and the relatively small quantity of NOx in diesel exhaust compared to O2, there is sufficient NO2 production capacity in a CSF where the impact of NO2 to the overall soot combustion efficiency under active regeneration conditions is significant. The differences between a standard porosity filter typically used for a CSF vs a high-porosity filter used for an SCRF® catalyst can only account for a minor portion of the difference in the soot combustion efficiency observed between the CSF and SCRF® catalyst. The fast consumption of the NO2 produced in situ in the CSF by soot may be driving the thermodynamic equilibrium of the NO oxidation reaction to continuously produce more NO2 for further soot combustion during active regeneration, resulting in a significant increase in the soot combustion efficiency in a CSF compared to an SCRF® catalyst or an uncoated filter.

If the JLR component referred to in the letter actually does employ SCRF® technology, this opens up a new avenue of possibilities regarding the root cause for the unfathomably poor performance of the DPF and (with the glass decidedly half-full, to coin a phrase) maybe it points to the possibility of an early hardware fix. Any ideas?
 
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#2 ·
I think SCRF® belongs to Johnson Matthey: http://ect.jmcatalysts.com/catalyst-technologies-johnson-matthey/scrf-system

The SCRF® system integrates Selective Catalytic Reduction (SCR) with a soot filter - the next step for diesel NOx control.

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.

The SCRF® system allows improved thermal management of the catalyst on the vehicle, is technically a very demanding system and may require additional SCR/ammonia slip catalyst (ASC) to maximise NOxconversion.
Looking promising....next question - Are JLR a customer of JM?

EDIT - Yes, very probably...
 
#3 ·
So to summarize (and clear at least my head on this), I read that SCRF is poor compared to CSF in terms of soot burning performance. So any hardware fix is replacing the SCRF (as now fitted and mentioned in the letter) with separate CSF and a possible secondary system for NOx reduction by injection of AdBlue?
 
#4 ·
Dashnine said:
So to summarize (and clear at least my head on this), I read that SCRF is poor compared to CSF in terms of soot burning performance. So any hardware fix is replacing the SCRF (as now fitted and mentioned in the letter) with separate CSF and a possible secondary system for NOx reduction by injection of AdBlue?
Yep and a better DOC and we're done .
 
#5 ·
Barnsh said:
Dashnine said:
So to summarize (and clear at least my head on this), I read that SCRF is poor compared to CSF in terms of soot burning performance. So any hardware fix is replacing the SCRF (as now fitted and mentioned in the letter) with separate CSF and a possible secondary system for NOx reduction by injection of AdBlue?
Yep and a better DOC and we're done .
It all sounds rather straightforward in theory but getting there is a completely different matter. Hardware fixes are the most difficult to accommodate in any situation and the space restrictions in place here make it even more difficult (and costly).
 
#6 ·
Dashnine said:
So to summarize (and clear at least my head on this), I read that SCRF is poor compared to CSF in terms of soot burning performance. So any hardware fix is replacing the SCRF (as now fitted and mentioned in the letter) with separate CSF and a possible secondary system for NOx reduction by injection of AdBlue?
Not unlike the way it is explained here:

Gesture Font Gas Parallel Engineering
 

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#7 ·
Oh brother! I just spotted a section of common DNA spliced into the advertising blurb from Johnson Matthey :

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.
Maybe the "British driving style" isn't compatible with the "European drive cycle", it's 240 volts all over again.
 
#8 ·
VeryDiscoSport said:
Oh brother! I just spotted a section of common DNA spliced into the advertising blurb from Johnson Matthey :

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.
Maybe the "British driving style" isn't compatible with the "European drive cycle", it's 240 volts all over again.
And that from a British company ;)
 
#10 ·
A bit more bedtime reading VDS. But interesting.

Just glancing through the first few pages I notice:

Page 3 - Key features of an SCRF® catalyst

Enables smaller overall system volume (First bullet point).

So have they chosen the SCRF because everything else available is bigger or for other reasons.

If they have then a "bigger" solution is a no go.

Or have I misunderstood something?
 
#11 ·
Chippy said:
A bit more bedtime reading VDS. But interesting.

Just glancing through the first few pages I notice:

Page 3 - Key features of an SCRF® catalyst

Enables smaller overall system volume (First bullet point).

So have they chosen the SCRF because everything else available is bigger or for other reasons.

If they have then a "bigger" solution is a no go.

Or have I misunderstood something?
I see the hand of chemists in this design, as opposed to car engineers. I don't see the SCRF as particularly small, do you?
 
#12 ·
VeryDiscoSport said:
Oh brother! I just spotted a section of common DNA spliced into the advertising blurb from Johnson Matthey :

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.
Maybe the "British driving style" isn't compatible with the "European drive cycle", it's 240 volts all over again.
It's back to everything being about getting the car through the emissions test, not how it's actually used.
 
#13 ·
Dashnine said:
VeryDiscoSport said:
Oh brother! I just spotted a section of common DNA spliced into the advertising blurb from Johnson Matthey :

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.
Maybe the "British driving style" isn't compatible with the "European drive cycle", it's 240 volts all over again.
It's back to everything being about getting the car through the emissions test, not how it's actually used.
100% agree.
 
#15 ·
Dashnine said:
VeryDiscoSport said:
Oh brother! I just spotted a section of common DNA spliced into the advertising blurb from Johnson Matthey :

The schematic below demonstrates how the SCRF® system for light duty diesel improves system compactness and is an example of how, over the European drive cycle, it warms up more quickly than an SCR downstream of a CSF (due to its closer proximity to the engine) enabling earlier NOx conversion.
Maybe the "British driving style" isn't compatible with the "European drive cycle", it's 240 volts all over again.
It's back to everything being about getting the car through the emissions test, not how it's actually used.
I think without doubt that is the issue , compliance comes first .....and let the owners pick up the tab for it with some issues due to time and cost constraints.
 
#17 ·
Barnsh said:
I think without doubt that is the issue , compliance comes first .....and let the owners pick up the tab for it with some issues due to time and cost constraints.
It was never any different nor will it be. So long as money and greed rule the world that is and that too was also always so and ever will be.
 
#18 ·
There are currently two competing technologies for diesel NOx control: SCR and NOx adsorber catalysts (NACs) (9), each with advantages and disadvantages.

An elegant solution is to integrate the SCR coating onto the particulate filter (10), thus enabling the SCR coating to heat up and become active more quickly, whilst also improving the compactness of the system (Figure 2). Such SCR coated on filter (SCRF®) technologies are now in series production - another world fi rst for Johnson Matthey, Royston. Design challenges include the incorporation of significantly higher coating loadings onto a filter than were required for CSF, leading to a requirement for high porosity filter substrates and optimisation of the filtration efficiency and pressure drop characteristics.
Clearly there is a tech-war going on between SCR and NAC; more answers in here:

View attachment ICCT_NOx-control-tech_revised 09152015.pdf
 

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#19 ·

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#21 ·
chicken george said:
When do I get my apology???
Not until hell freezes over is one phrase that immediately sprang to mind. I was told by an extremely reliable source who got it from an actual design engineer from Jaguar Land Rover that the pipework architecture is too long on the DS for the chosen exhaust hardware to work properly. Everything I have discovered bears out the statements that were repeated to me: having selected this particular chemistry set, it was found that it won't all fit as designed into the available space and has to be spread out.

This is a quote from Johnson Matthey's Chris Morgan writing in 2014 when SCRF was just emerging commercially:

Due to the thermal mass of the CSF (required to withstand uncontrolled soot regeneration) and heat losses from the exhaust pipe in the urea mixing zone in front of the SCR, it can take many minutes of city driving before the SCR warms up sufficiently to provide high levels of conversion efficiency. An elegant solution is to integrate the SCR coating onto the particulate filter (10), thus enabling the SCR coating to heat up and become active more quickly, whilst also improving the compactness of the system (Figure 2). Such SCR coated on filter (SCRF®) technologies are now in series production - another world first for Johnson Matthey, Royston.


It could all work so beautifully - were it not for those two hulking great pieces of pipework which turn a great Compact Design Goal into a Spread-out installation that then requires higher than expected amounts of post-injection because a) the DOC doesn't get hot enough to do anything in normal driving and b) the SCRF is too far back to heat up quickly and efficiently as the patent holder intended.

THE VISION

Rectangle Slope Font Parallel Plot


THE REALITY

Light Bicycle part Font Line Tool
 

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#22 ·
That's exactly the issue VDS, in pretty much the same explanation from DEKRA.

Tinkering with software adjustments may bring some small benefits, but as per the JLR PDF the above picture is exactly the "hardware and architecture differences " mentioned .

The only complete remedy is a redesign to get the componants to operate correctly. The hard part is that this has to be achieved without compromise to the internal layout of the DS which is class leading and we all love.

Some definate head scratching will be happening in the emissions department of JLR without doubt, maybe that's why they advertised to fill many positions with emissions engineers a few weeks back.

Especially when the new emissions tests as mentioned in the VED tax rise make the Discovery D5 look so poor with Compliance.

I don't think there would have been so many vociferous conversations on this forum if JLR had achieved an average of 15-16k for servicing on the DS, but to achieve an average of 9/10k out of a planned 21k is just plain wrong and madness. I would hazard a guess some even more vociferous conversations took place at JLR when these early oil changes started appearing across the affected vehicles.

It would have been better if JLR had just said sorry instead of trying to blame everyone's driving style which only antagonises and disappoints owners. The free oil is just a stop gap to stem some complaints and placate owners, it is also a vast expense for a company to accept if no "full" fix is found.
 
#23 ·
Seems Audi screwed up the Q& as well then :roll:
Product Font Automotive tire Aircraft Engineering


As well as many other manufacturers

generic pics and home made alterations dont prove anything

particulate filter too cold is a generic explanation for poor dpf performance, well known by all manufacturers,

I will say again the DS does not have a close coupled design, the pipe work length is not the issue, Infact the length between the doc and scrf is needed to allow def infection and proper swirling/mixing of the def before it reaches the scrf.
 

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#24 ·
Barnsh said:
I don't think there would have been so many vociferous conversations on this forum if JLR had achieved an average of 15-16k for servicing on the DS, but to achieve an average of 9/10k out of a planned 21k is just plain wrong and madness.

I would hazard a guess some even more vociferous conversations took place at JLR when these early oil changes started appearing across the affected vehicles.

It would have been better if JLR had just said sorry instead of trying to blame everyone's driving style which only antagonises and disappoints owners. The free oil is just a stop gap to stem some complaints and placate owners, it is also a vast expense for a company to accept if no "full" fix is found.
The engineer said they pleaded the case for 12K or 16K before launch but were told it was a done deal. So they went to market with a brochure that contained misleading statements in order to make the cars appear more attractive in respect of servicing intervals and we know from the conversations reported to me by my source that at least one person in JLR management knew that the brochure was misleading at the time. The thing is that once you've told the first lie you have to keep on lying in order to cover up the first one. But just how orchestrated was the deception between June 2016 and July 2017 when another engineer gave me a hard copy of JLRP00100 and it all started to unravel? It would be interesting to hear a few dealers declare for the record where the stories of "service interval set for the old engine", "problem with the phone app", "bad batch of oil", "incorrect service interval", "software upgrade coming soon", "software glitch, keep driving up to 21K miles" first came from.

I mean - they are all lies, right? So, did the dealers just instinctively improvise these erroneous explanations? Or were they told what to say to concerned customers by CRC? The first round of untruths had quite a good run based on the posts on the forum and was still going well in July 2017, even a couple of weeks ago there are fresh reports here and on other forums with dealers nonchalantly dismissing the relevance of the Service Message. But when did "driving style" first appear? A cursory trawl through the posts shows it was first being linked with early service messages around March/April 2017 and that one also had a good run until very recently. With some co-ordinated and dedicated "amateur" sleuthing I think that we might have finally forced the management to swallow the truth potion.

Honest John emailed me today after I reported the successful rejection. He said that JLR now admits that the DPF will remain too cold to passively regenerate when the car is driven short distances and that they will also change the oil service schedule to a more sensible one. Having seen the entire text of the four page letter I received on 24th October he finished by noting that "because it has gone to such great lengths in its replies to you, I'd suggest that your detailed complaint influenced the company." Coming from the straight guy himself, that's not bad for somebody who has been openly accused of peddling "fake news".
VDS
 
#25 ·
chicken george said:
Seems Audi screwed up the Q& as well then :roll:
audi-q7-adblue-tank.jpg

As well as many other manufacturers

generic pics and home made alterations dont prove anything

particulate filter too cold is a generic explanation for poor dpf performance, well known by all manufacturers,

I will say again the DS does not have a close coupled design, the pipe work length is not the issue, Infact the length between the doc and scrf is needed to allow def infection and proper swirling/mixing of the def before it reaches the scrf.
No-one is trying to prove anything, this is just a forum for exchange of information and ideas. But, whilst we are being mutually critical, the diagram you have reproduced is from an altogether different system architecture. There no shortage of data available about SCRF, please go and please read what Chris Morgan and others say about the strengths and weakness of their system versus the competing ones. There's an excellent powerpoint on here somewhere that shows how slowly it removes soot compared to other systems, but conversely how good it is at NOx reduction - in the right conditions.
 
#26 ·
I hear what your saying CG, all manufacturers do have an issue with temperature. It's one of the critical items in the process to be efficient.

This is why most new systems including the XE/XF ( I use this example as that is what JLR used on their PDF, I also use this example as it has the same 2.0L ingenium engine).now have close(r) coupled systems.

Comparing an audi system is throwing another different componants and design in the mix. And as you can see in the diagram you showed DEF is added after a DPF. Different engine different amount of soot.

Do you not think if space had been available that they would have used the same system on the DS as the working XE/XF ? ( maybe jag and Land Rover don't communicate).
But:
Do you not think they would have used the same system on the 30L D5 as the working in line mounted 2.0L D5? Only difference is space available.

For an identical 2.0L ingenium engine the only difference in emmissions system is layout , componants and space available. Therefore it's a backward step to add distance so that the well known temperature issue is exacerbated. The lack of space to me has forced the componants and architecture into that position of the old issue of lack of temperature.

The XE/XF/D5 2.0L ingenium doesn't need an early service to the extent the DS and other affected vehicles do.

The longer pipe just acts as a heat sink.

Your right many manufacturers have screwed up over this in the past, but most have overcome it too, or at least in the past couple of years improved it. JLR dropped the ball somewhere in the design stages of these vehicles, they for sure didn't do it deliberately.
 
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