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Old 30th October 2021, 19:03   #1
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Default All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

I am a Diesel Calibration Engineer by profession specializing in DPF calibration for Indian vehicles . I see a lot of queries and some misunderstanding about BS6 in general and DPF specifically on this forum. So as an expert I would like to clarify some of your doubts and questions regarding these things. So post your questions and queries below and I will try my best to answer them for you.

Here are some basics about BS6 and DPF in general.
BS6 emission regulation came into effect on April 1st 2020 all over India. The aim it is to improve air quality in our country and reduce tail pipe emissions. In diesel cars there is 70% reduction in NOx (Nitrogen Oxides) emissions and 90% reduction in PM (Particulate Matter) emissions compared to BS4. PM reduction was done by using a DPF which traps these PMs and NOx reduction is done with the help of either EGR+LNT(NSC) or EGR+SCR technology.

A DPF needs to periodically regenerated when its completely filled with soot particles coming from the Engine and this is generally done at high temperature inside the DPF. Diesel fuel is deliberately released in the exhaust of the vehicle which is burnt in the Oxidation catalyst (DOC) and the heat released from this combustion is used to burn the soot collected in the DPF.
This is the basic principle by which a DPF system works without getting too technical about it.

So post your questions below and lets learn

Last edited by Samurai : 2nd November 2021 at 11:20. Reason: typo
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Old 31st October 2021, 19:04   #2
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Welcome to TBHP and what a timing to start this thread

Thanks for sharing your insights and without wasting time, my questions :
  1. What are the variables involved in the DPF being full ?
    I am guessing engine speed, running duration which would increase the EGT, capacity of the DPF.
  2. What about passive regen(if I have named it correctly) ?
    The automatic clearing of the DPF when the vehicle is being driven in a highway setting.
  3. Don't diesels generate more soot when the throttle input increases ?
    Deriving from a lot of cars spewing black soot while accelerating, so wouldn't that be counter productive especially if someone is trying an Italian tuneup ?
  4. Do driving on mountain roads with higher rpms cause the DPF to clear up ?
    And how much does it impact when the altitude increases to say 12000 feet above sea level ?
  5. What is the driving style which fills up the DPF the fastest ?
  6. Is there any driving condition under which the DPF never fills up requiring a manual regen over 1 lakh kms ?
  7. Does the DPF need changing due to age or usage ?
  8. Would you recommend a BS6 diesel car for the following use cases expecting a 2000km running per month :
    a. 90% city with a monthly 300km highway trip in the plains
    b. 70% city and 30% highway on plains
    c. 60% city and 40% mountain roads
    d. 60% city 20% highway in the plains and 20% high altitude areas
  9. What is are the differences in calibrating DPF for Indian conditions as compared to other countries ?
  10. Keeping in mind the current issues with the DPF and expecting stricter emissions in the next emission standard BS7/8, what is your view on diesels continuing in smaller vehicles 2-3 years down the line ?

Feel free to club multiple questions in an answer if they're related and ignore the noob ones.
Sorry for too many questions and I have more but will keep them aside for now

Last edited by shancz : 31st October 2021 at 19:20. Reason: formatting
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Old 31st October 2021, 19:23   #3
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

i've one question too.

With BS4 fuels, we hardly heard about a DPF issue in BS4 engines. It had more sulphur content at 50 ppm(five times)than BS6 diesel, yet the cars were running fine with no DPF clogging. Now why do we have more cases of DPF in the BS6 era(ppm 10)when the fuel is much more cleaner?
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Old 31st October 2021, 19:44   #4
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by Bibendum90949 View Post
Now why do we have more cases of DPF in the BS6 era(ppm 10)when the fuel is much more cleaner?
Did we have DPFs in BS4 ?
I doubt it, this link also confirms that but I am not sure.
But if it was then quite an interesting question.

Last edited by shancz : 31st October 2021 at 19:50. Reason: ccl
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Old 31st October 2021, 20:18   #5
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

@Ninjanayak, many thanks for offering your expertise here on a burning issue (pun intended)
As an aspirant new car buyer, have read up about this issue ad nauseum and keep posting questions here and elsewhere, though all that I receive are anecdotal reassuring responses, primarily by owners who drive mostly on highways.I surprisingly find even people professionally connected with automobile world unaware of the issue(or its gravity), let alone owners. I strongly feel that the manufacturers need to make their customers explicitly aware of these issues, to avoid further grievances.
My primary impression now is: BS6 diesels are primarily meant for highway drivers who can rev their engines beyond 2500RPMs for most of their journey- and who have an about 500km monthly trip on their itineraries anyway.
Am I right? No more BS6 diesels for city dwellers? Do we have any realistic hope with any fuel additives?
And to what extent do you see diesel engines continuing in various vehicle segments e.g. small cars, SUVs and commercial vehicles, especially with the onslaught of EVs?
Also, can you offer your insights on what went wrong with Ford diesels?
https://www.team-bhp.com/forum/india...nsparency.html (Ford India struggles with DPF problems in 1.5L TDCI | Poorly handled & utter lack of transparency)

Last edited by Nikhil Beke : 31st October 2021 at 20:31.
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Old 31st October 2021, 20:45   #6
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Welcome to the forum. At what DPF temperature does it start burning off soot? I use an obd scanner to monitor parameters and at idle rpm with engine warmed up, my DPF temperature is 38-39 degrees.
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Old 1st November 2021, 13:20   #7
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Note from Support: Please DO NOT post replies within quotes. Thank you!


Quote:
Originally Posted by shancz View Post
What are the variables involved in the DPF being full?
I am guessing engine speed, running duration which would increase the EGT, capacity of the DPF.
The driving behavior and the payload are the main variables I would say. Soot fills up faster in low speed (less than 20kmph) and fully loaded or overloaded vehicle. So avoiding these two patterns in your driving as much as possible will help.
EGT design also has an important role into this especially in Indian conditions, which many OEMs are finding out now.
Quote:
What about passive regen (if I have named it correctly)?
The automatic clearing of the DPF when the vehicle is being driven in a highway setting.
Passive Regen occurs when the DPF is operating at 250-400degC temperature, when the Nitrogen Oxides in the exhaust react with the Soot particles to generate CO2. This temperature is present when driving at more than 20kmph and at sightly higher average engine rpms as I said in previous question. So if you're driving at decent speeds the DPF will observe good passive regen.
Quote:
Don't diesels generate more soot when the throttle input increases?
Deriving from a lot of cars spewing black soot while accelerating, so wouldn't that be counter productive especially if someone is trying an Italian tuneup?
The major problem with driving at full throttle is poor combustion in case of small engine sizes and bad turbochargers. Full throttle = poor combustion = more soot.
Same can be observed in uphill driving conditions, when engines are at full throttle combined with less air you get a lot of black smoke.
So I would suggest operating at part throttle at 2000-2500rpms for 40-60mins once every 10 days or so, should help with these issues. Also avoid overloading your vehicle as much as possible as this is a major problem from my experience.
Quote:
Do driving on mountain roads with higher rpms cause the DPF to clear up?
And how much does it impact when the altitude increases to say 12000 feet above sea level?
Normal uphill driving i.e. without overloading the vehicle or operating at full throttle all the time should help clear the DPF, just like it will help in sea level or flat driving conditions.
Most Indian OEMs have thoroughly tested their BS6 offerings till 13000ft, but due to COVID and its related restrictions, good validation in these conditions are not well documented. So there are decent chances that an out of spec vehicle will cause issues at these conditions. During the upcoming winter season most OEMs may complete these tests and solve issues if any.
Quote:
What is the driving style which fills up the DPF the fastest?
As I replied earlier, very low speeds (less than 20kmph), overloading the vehicle and frequent start-stops are the major causes for fast DPF filling.
Quote:
Is there any driving condition under which the DPF never fills up requiring a manual regen over 1 lakh kms?
In case of trucks (more than 2.5L engine capacity) the regen interval can be as high as 3000-5000kms. But for most passenger car applications the regen interval is the range as shown below:
  • City: 200-500km
  • Rural or semi-urban: 500-800km
  • Highway: 1000-2000km.
No going around it I suppose.
Quote:
Does the DPF need changing due to age or usage?
Depending on the OEM, the EGT is designed for the full useful life of the vehicle. Most Indian vehicles are rated for 1,00,000-2,00,000km. So unless something really goes wrong with the EGT or the Engine there should not be a reason to replace it until it's full useful life.
Quote:
Would you recommend a BS6 diesel car for the following use cases expecting a 2000km running per month:
If your daily commute in city drive is less than 25 minutes with a lot of very low speed driving , I would suggest a bigger diesel engine car or a Petrol one. Small engine sizes (less than 1.5L) can cause issues in condition(a). Apart from that, all other conditions should be fine for Diesel cars with suggestions mentioned above.
a. 90% city with a monthly 300km highway trip in the plains:
b. 70% city and 30% highway on plains
c. 60% city and 40% mountain roads
d. 60% city 20% highway in the plains and 20% high altitude areas
Quote:
What is are the differences in calibrating DPF for Indian conditions as compared to other countries?
Indian consumers especially commercial vehicle operators routinely overload their vehicles, so this was a major problem for us during the calibration. Another problem was specific to e-commerce/delivery vehicles or garbage collection vehicles where the drive pattern was very challenging for soot filling and regeneration.
Quote:
Keeping in mind the current issues with the DPF and expecting stricter emissions in the next emission standard BS7/8, what is your view on diesels continuing in smaller vehicles 2-3 years down the line
This is a tough one as I am sure OEMs also don't have an answer as of now.
The technology is available, be it SCR or PM sensor or OBD. It will come down to economics of the car I suppose.
In case of sufficient volumes and customer demands, OEMs will try hybrid options.
But for commercial vehicles there is no suitable alternative.

The problems with DPF are mostly solved as far as I know. There are remote cases where there are still few problems and OEMs have been trying hard to solve them since 1.5 years, in-spite of COVID and all its problems. Remember BS6 was a huge technology jump for all OEMs and issues were expected. OEMs especially M&M and TATA have done a very good job regarding this.


Hope I have answered questions to your satisfaction .

Last edited by aah78 : 1st November 2021 at 20:20. Reason: Quotes separated. All BOLD font removed. See note.
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Old 1st November 2021, 16:32   #8
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by ninjanayak View Post
Hope I have answered questions to your satisfaction
Yes, clears out a lot of misconceptions and validates some assumptions including the future of small diesels in the city going forward.

Thanks for taking the time and the detailed reply

I had completely forgotten about smaller commercial vehicles like the garbage collection vehicles and autos like the Ape they should be migrated to CNG/Electric as I don't see a practical solution in their use cases.

Just a clarification, by EGT i meant Exhaust Gas Temperature, apologies for not mentioning it earlier.
Since you said EGT design are you talking about something else?

PS : Took the liberty of linking your post to some other threads I was a part of and discussing DPFs.
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Old 1st November 2021, 16:33   #9
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by Nikhil Beke View Post
@Ninjanayak, many thanks for offering your expertise here on a burning issue (pun intended)
As an aspirant new car buyer, have read up about this issue ad nauseum and keep posting questions here and elsewhere, though all that I receive are anecdotal reassuring responses, primarily by owners who drive mostly on highways.I surprisingly find even people professionally connected with automobile world unaware of the issue(or its gravity), let alone owners. I strongly feel that the manufacturers need to make their customers explicitly aware of these issues, to avoid further grievances.
I understand that people are disappointed or frustrated regarding BS6, but remember BS6 was a huge technology jump for all OEMs and issues were expected. OEMs especially M&M and TATA have done a very good job regarding this.

Last edited by moralfibre : 1st November 2021 at 20:16. Reason: Trimming quoted post.
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Old 1st November 2021, 17:55   #10
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by ninjanayak View Post
Passive regeneration: where the engine isn't actively trying to burn the soot occurs mostly between 250-400degC. This temperature is present in regular city driving conditions after the EGT is warmed up.
I have few basic questions about regen:
  • What happens to the remains of the burnt soot after the regen?
  • Is it completely gaseous or fine powder?
  • How are they ejected completely?
  • Are they not harmful any more? What about any smell or black colour
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Old 1st November 2021, 18:29   #11
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by ninjanayak View Post
Yes, EGT is Exhaust Gas Treatment.
By EGT design, I mean the location of DOC+DPF or the SCR relative to the engine position.
Thank You, makes sense, it would help passive regen.

My concern still is that the diesels have spoiled a lot of drivers to carry low rpms to maximize FE, now that's going to be counter productive in this situation.

How much diesel is needed for each auto regen if its possible to estimate it ?

Please correct me if I am wrong but if a regen happens every 1000km which I am assuming is equivalent to a 60min drive at 2500rpm which would be about 70-80kms at highway speeds at an FE of 20kmpl that is 4 litres of diesel.
Is this heading in the right direction or I doesn't make sense at all ?
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Old 1st November 2021, 18:36   #12
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
I have few basic questions about regen: [list][*]What happens to the remains of the burnt soot after the regen?
It's just a gas, Carbon dioxide

Quote:
[*]Is it completely gaseous or fine powder?
Gaseous

Quote:
[*]How are they ejected completely?
The gas just passes through the filter and comes out of the tailpipe as CO2

Quote:
[*]Are they not harmful any more? What about any smell or black colour
CO2 is a clear gas and doesn't have any health effects as far as I know, but it is a contributor to climate change

This is the reaction that happens during regen,
Soot(Carbon) + O2 + Heat ----> CO2 + Heat

Quote:
Originally Posted by shancz View Post
Thank You, makes sense, it would help passive regen.

My concern still is that the diesels have spoiled a lot of drivers to carry low rpms to maximize FE, now that's going to be counter productive in this situation.

How much diesel is needed for each auto regen if its possible to estimate it ?
From the projects I have worked on, it took roughly 200-250ml of extra diesel to do an active regeneration. Bigger engines will consume a slightly higher amount. More clarity below.

Quote:
Please correct me if I am wrong but if a regen happens every 1000km which I am assuming is equivalent to a 60min drive at 2500rpm which would be about 70-80kms at highway speeds at an FE of 20kmpl that is 4 litres of diesel.
Is this heading in the right direction or I doesn't make sense at all ?
Some things to clarify:
  1. Passive regen doesn't consume any extra fuel, it happens spontaneously without any special input from the ECU (Engine Control Unit). So the FE you get regularly will apply here as well.
  2. Passive Regen is a very slow process and takes a long time to clear the DPF. That's why you have mentioned the 60 minutes in your post.
  3. Active Regen specifically triggered by the ECU, typically lasts for 20-25 mins. Most cars have a lamp on the cluster indicating Active regen, you can time this for your reference.
  4. Active Regen process consumes extra fuel. The fuel penalty you incur happens only during active regen i.e if you regularly get 20kmpl FE, during an auto regen every 1000km it drops to 17-18kmpl for 20-25 minutes.
Hope that helps

Quote:
Originally Posted by Nikhil Beke View Post
@Ninjanayak, many thanks for offering your expertise here on a burning issue (pun intended)
As an aspirant new car buyer, have read up about this issue ad nauseum and keep posting questions here and elsewhere, though all that I receive are anecdotal reassuring responses, primarily by owners who drive mostly on highways.I surprisingly find even people professionally connected with automobile world unaware of the issue(or its gravity), let alone owners. I strongly feel that the manufacturers need to make their customers explicitly aware of these issues, to avoid further grievances.
While I agree to an extent that OEMs can do a better job to address these issues and communicate them to customers, I would also like to point out that apart from enthusiasts or aficionados, most people don't care about the technical aspects of their cars, they just want it to work.
Most problems with DPFs or BS6 are solved or are being actively worked on by companies.
These are time consuming tests, in the projects I have worked on, it took us 18-20 months of tests and validation to arrive at a finished BS6 product. These are teething issues which will mostly be solved by Feb-March of next year.

Quote:
My primary impression now is: BS6 diesels are primarily meant for highway drivers who can rev their engines beyond 2500RPMs for most of their journey- and who have an about 500km monthly trip on their itineraries anyway.
Am I right? No more BS6 diesels for city dwellers? Do we have any realistic hope with any fuel additives?
Not necessarily, most cars operate fine unless in very extreme driving cases like very low speed driving (less than 20kmph), frequent start-stops and overloading conditions. OEMs have made sure that there are no problems in most driving conditions. So as I mentioned in a previous reply, with decent care, 95-98% of vehicles sold would not face any issues in city conditions.

And to what extent do you see diesel engines continuing in various vehicle segments e.g. small cars, SUVs and commercial vehicles, especially with the onslaught of EVs?

Small cars already don't have diesel options. SUVs and commercial vehicles will continue to offer diesel engine options up until 2030 as per estimates, as EVs are just not a viable solution or have their own deficiencies.

While I dont know the problem in detail, the projects I worked on and Ford vehicles probably share the same software architecture. We also came across similar problems during our validation and were able to solve them. There is not much that can be done by end users, Ford has to solve them from their side and flash the new software onto problematic vehicles.

I understand that people are disappointed or frustrated regarding BS6, but remember BS6 was a huge technology jump for all OEMs and issues were expected. OEMs especially M&M and TATA have done a very good job regarding this.


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Old 1st November 2021, 21:15   #13
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Many thanks @Ninjanayak for sparing times to clear lot of these doubts
Quote:
very low speeds (less than 20kmph), overloading the vehicle and frequent start-stops are the major causes for fast DPF filling.
What's your take on the ISS(idle start stop) systems on few of the small diesels, in context of DPF?
Anyway, mods, do we have a system for promoting a newbie to a BHPian status for awesome contributions at debut itself? Seen quite a few off late- comprehensive study on Ford India was another.
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Old 1st November 2021, 21:24   #14
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by ninjanayak View Post
1. From the projects I have worked on, it took roughly 200-250ml of extra diesel to do an active regeneration. Bigger engines will consume a slightly higher amount.

2. Active Regen process consumes extra fuel. The fuel penalty you incur happens only during active regen i.e if you regularly get 20kmpl FE, during an auto regen every 1000km it drops to 17-18kmpl for 20-25 minutes.
1. Thanks, so not a significant number and rests the concerns over FE hits.

2. I was talking about active regen only so the 60 mins was way off the mark.

I have a far better understanding now than when the day started
Will let others use your time now and will be back with some questions later on.

Thank You for your time and effort

Last edited by shancz : 1st November 2021 at 21:25. Reason: ccl
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Old 1st November 2021, 22:16   #15
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Default re: All your questions about DPF & BS6 Diesel answered by a Diesel Calibration Engineer

Quote:
Originally Posted by ninjanayak View Post
I am a Diesel Calibration Engineer by profession specializing in DPF calibration for Indian vehicles . I see a lot of queries and some misunderstanding about BS6 in general and DPF specifically on this forum. So as an expert I would like to clarify some of your doubts and questions regarding these things. So post your questions and queries below and I will try my best to answer them for you.
Hey, thanks for bringing your expertise to the Team-BHP open forum. Not many folks dare do this due to their commitments to their company, but I'm glad you decided to bring this to us at first hand.

A few quick questions from my side:

1. When calibrating the DPF and its behaviour, do you use specific quality of diesel, or do you randomly fill from any pump to allow for adulteration and poorer quality?

2. When calibrating DPF at high altitudes, do you take into account the presence of kerosene in the winter diesel that is supplied in those regions?

3. Do you routinely check fuel quality for compliance with BS6 / Euro-VI norms of refinement, sulphur quantity etc.?

4. Are there any engines, whether of small or high displacement, where DPFs are actually tested / calibrated for use under heavy load + low rpm conditions?
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