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Old 2nd July 2011, 20:20   #1
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Default Diesel Particulate Filter

I found this Diesel particulate filter - Wikipedia, the free encyclopedia on the wikipedia but there doesn't seem to be much on team bhp (did search with different keywords - mods please merge with the relevant thread if I missed it).

HEre are my questions:
  1. Do all diesel cars have DPF?
  2. What are the maintenance requirements for DPF?
  3. How will it effect driving if some fault develops in DPF (blockage etc.) - basically as an average driver how can you figure out there is a problem, when to suspect a problem?
  4. Can it be replaced/cleaned/maintained in a DIY?
  5. anything else ...
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Old 2nd July 2011, 21:52   #2
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Default Re: Diesel Particulate Filter

No
DPF are not there in present cars. (As far as I know)
But with BS5 it will be mandatory.

-It blocks soot particles from the exhaust emissions.
-When it gets filled. Soot is burned automatically by injecting diesel.
-For burning effectively, the exhaust temperature has to be high enough. Not sure if city drive can achieve it.
-So the Future of Diesel in India is a big ?.
-Be sure to experience increased cost, lower torque & possibly lower FE with the advent of BS5.
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Old 2nd July 2011, 23:44   #3
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by oxyzen View Post
No
DPF are not there in present cars. (As far as I know)
But with BS5 it will be mandatory.

-It blocks soot particles from the exhaust emissions.
-When it gets filled. Soot is burned automatically by injecting diesel.
-For burning effectively, the exhaust temperature has to be high enough. Not sure if city drive can achieve it.
-So the Future of Diesel in India is a big ?.
-Be sure to experience increased cost, lower torque & possibly lower FE with the advent of BS5.
The passat that was recently launched in India is available with DPF internationally, but for India, they say the fuel quality is not good. Well I believe that this is again a strategy by govt. to provide bad fuel and let have DPF so that maintenance increases and they get revenue every time car is serviced.

That apart, Peugeot-Citroen were amongst the first to make DPF available. OD had one very good article back in 2003-4. The thing is that when the car is running high speeds, the burning of the particles would take place. At high speeds ( like highway driving ), one would not even know when the particles were burnt.

Another thought ( not sure if implemented or not ) is that when the car is idling for long in traffic, the burning procedure can take place. This is more applicable if the amount of particles is not very high. That even before a prerequisite amount of particles have build up in the filter, the burning can take place when car is idling in traffic and the driver will not even know that this procedure is done.

Regular maintenance can help avoid the loss of performance and reduction of FE.


PS : Do update me if I am wrong. I am posting what I had earlier read.
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Old 2nd July 2011, 23:57   #4
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by oxyzen View Post
No
DPF are not there in present cars. (As far as I know)
But with BS5 it will be mandatory.
apparently CVs and Figo have it. Ford Diesels have it basically to meet BS4. MJD doesn't have it yet AFAIK, but Tata (non-MJD) and Mahindra may have it too.

Quote:
Originally Posted by oxyzen View Post
...
-When it gets filled. Soot is burned automatically by injecting diesel.
-For burning effectively, the exhaust temperature has to be high enough. Not sure if city drive can achieve it.
...
-Be sure to experience increased cost, lower torque & possibly lower FE with the advent of BS5.
Thanks

Apparently ECU initiates late-diesel-injection to provide enough diesel to increase exhaust temperature and burn the soot down. However as can be guessed this kills FE (and so does the extra back pressure). Also this doesn't get rid of ash that is generated.

I was wondering why Ford diesel has lower torque/FE than MJD - now we know at least a part of the reason.
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Old 3rd July 2011, 00:07   #5
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by aaggoswami View Post

Another thought ( not sure if implemented or not ) is that when the car is idling for long in traffic, the burning procedure can take place. This is more applicable if the amount of particles is not very high. That even before a prerequisite amount of particles have build up in the filter, the burning can take place when car is idling in traffic and the driver will not even know that this procedure is done.
For this purpose, there is an additional heater near the DPF.

And even with proper maintenance FE will deteriorate
-Back pressure
-Post injection to Burn soot
-Heater at DPF


Quote:
Originally Posted by vina View Post
apparently CVs and Figo have it. Ford Diesels have it basically to meet BS4. MJD doesn't have it yet AFAIK, but Tata (non-MJD) and Mahindra may have it too.
I am not sure if Ford has it. Please contact Mustang101 for the info.
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Old 3rd July 2011, 03:05   #6
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by vina View Post
Do all diesel cars have DPF?
No, DPF is just like cat-con. Just to reduce emissions. So my guess and like oxygen mentioned older cars might not have them.
Quote:
What are the maintenance requirements for DPF?
I'm unsure about the maintenance required for DPF, but I do know that, DPF regeneration requires some serious temperatures in exhaust and hence, it is NOT advisable to do short trips regularly in a Diesel with DPF. There is only a certain percentage(80%?) of soot accumulated, that can be cleared by either active or passive regeneration. If more, you will have to visit the A.S.S and AFAIK, it might be a VERY expensive affair.
Quote:
How will it effect driving if some fault develops in DPF (blockage etc.) - basically as an average driver how can you figure out there is a problem, when to suspect a problem?
Well, cars should throw up a visual warning if soot levels are above average. As for behavior, I guess more soot = more back pressure and hence less performance and FE.
Quote:
Can it be replaced/cleaned/maintained in a DIY?
I don't think so. All I know is that it might be an expensive replacement.

=================================================

Quote:
Originally Posted by aaggoswami View Post
The thing is that when the car is running high speeds, the burning of the particles would take place
This is called Passive regeneration.

There are two types of regeneration of DPF's. (1) Passive and (2). Active

AFAIK, passive regeneration, is not ECU controlled, and as you mentioned, at high revvs, exhaust reaches the required temperature for the soot to burn up.

Where as Active Regeneration is ECU controlled. The main purpose of post injection is DFP Regeneration.
Quote:
Originally Posted by aaggoswami View Post
Regular maintenance can help avoid the loss of performance and reduction of FE.
Umm.. What kind of maintenance are you suggesting for a DPF?. I have heard that DPF's have a long life but, are extremely expensive.
Quote:
Originally Posted by oxyzen View Post
For this purpose, there is an additional heater near the DPF.
Umm.. well.. not all cars have heater near the DPF. The purpose is to effectively burn off the soot particles, and many methods are being implemented for that.

In some cars, the DPF is placed nearer to the exhaust so that higher temperatures are achieved. In some, the temperature at which the soot particles burnt is reduced by using certain additives.

Last edited by dhanushs : 3rd July 2011 at 03:07.
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Old 3rd July 2011, 10:57   #7
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by oxyzen View Post
For this purpose, there is an additional heater near the DPF. ...
What kind of a heater? Electrical? Outside (near) the DPF? Please consider the temperature needed to burn soot, which is inside the DPF. And DPF is mounted just after the manifold.
Quote:
Originally Posted by dhanushs View Post
... I do know that, DPF regeneration requires some serious temperatures in exhaust ...
Quote:
Originally Posted by dhanushs View Post
... Well, cars should throw up a visual warning if soot levels are above average. ...
Sounds impractical, doesn't it? How would you measure soot accumulation directly? Even indirectly (say increase in back pressure) the measurement would be clouded with more than one influence vying for attention.

Quote:
Originally Posted by dhanushs View Post
... In some, the temperature at which the soot particles burnt is reduced by using certain additives.
Correct, but perhaps you should consider paraphrasing it. 'Additive' gives a different impression of adding something from outside, which in vehicles with DPF we don't.

This is done by NOx, which is a combustion by-product. Not sure whether 'post' injection causes inefficient or over-efficient combustion, but that's what produces NOx I think.
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Old 3rd July 2011, 11:26   #8
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by dhanushs View Post
No, DPF is just like cat-con. Just to reduce emissions. So my guess and like oxygen mentioned older cars might not have them.
Thanks, I figured as much though. However apparently DPF is worse than catcon in increasing back-pressure.

Quote:
Originally Posted by dhanushs View Post
I'm unsure about the maintenance required for DPF, but I do know that, DPF regeneration requires some serious temperatures in exhaust and hence, it is NOT advisable to do short trips regularly in a Diesel with DPF. There is only a certain percentage(80%?) of soot accumulated, that can be cleared by either active or passive regeneration. If more, you will have to visit the A.S.S and AFAIK, it might be a VERY expensive affair.
That doesn't sound good at all.

Quote:
Originally Posted by dhanushs View Post

Well, cars should throw up a visual warning if soot levels are above average. As for behavior, I guess more soot = more back pressure and hence less performance and FE.
The thing is, I am seeing some behaviour (described here http://www.team-bhp.com/forum/offici...ml#post2412735) that I guess one would expect if the back pressure is too much, or there is a blockage in air inlet or something like that, on my new Figo. I have been told by other BHPians that this is a problem to be expected on all cars and especially diesel - and I'm going to TD a Figo diesel for dealership tomorrow to confirm, but just wanted to see if DPF can also be a factor (I'm thinking another reason may be turbo doesn't generate enough air flow in 1st/2ng gears at low rpm, given the low air flow and also very little power - meaning hardly any flue gas energy)

Whether there is really a problem with my Figo or not - knowing this is surely a good thing. Also knowing about DPF will be good in itself.
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Old 3rd July 2011, 17:55   #9
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Default Re: Diesel Particulate Filter - Skoda Yeti

Here is some information about DPF specific to Skoda Yeti:

"Code 7GG, 7MB or 7MG on the vehicle data sticker, indicates that the vehicle is equipped with a diesel particle filter. The vehicle data sticker is located on the floor of the luggage compartment and is also stated in the Service schedule" which is supplied with new cars.

"The diesel particle filter filters the soot particles completely from the exhaust. The soot is collected in the diesel particle filter and burnt regularly. To assist this procedure, it is recommended not to drive regularly over short distances." Short distances are defined as distances less than 4 km.

If the diesel particle filter is clogged or there is a fault, it is indicated by the "warning light for DPF".

If the DPF warning light comes on, this means that soot has accumulated in the diesel particle filter because of the frequent short distances.

The following sequence of actions is recommended in the manual

ACTION I:

In order to clean the diesel particle filter, the vehicle should be driven at an even speed of at least 60 km/h at engine speeds of 1,800 - 2,500 rpm for at least 15 minutes or until the warning light goes out with the 4th or 5th gear engaged (automatic gearbox: position S) when the traffic situation permits it.

This increases the exhaust temperature and the soot deposited in the diesel particle filter is burnt.

The warning light goes out after the successful cleaning of the diesel particle filter.

If ACTION I FAILS the indications are:

If the filter is not properly cleaned, the warning light does not go out and the glow plug system warning light begins to flash.

In the information display * appears "Diesel-particle filter: Owner's manual."

Afterwards the engine control unit shifts the engine into the emergency mode, which only has a reduced power output. After switching the ignition off and on again the warning light "control system for exhaust" comes on.

ACTION III

Have the vehicle inspected without delay by a Skoda Service Station.

What does the service manual say?

At 180 000 km, then every 30 000 km: – Check diesel particle filter - Common Rail diesel engines

Diesel particle filter:

– Inspect all wiring and sender of diesel particle filter for con‐ nection and tightness.
– Inspect diesel particle filter for tightness, damage and attach‐ ment.

The volumetric efficiency of the particle filter volume is interroga‐ ted during the diesel particle inspection.

– Connect diagnostic unit, select function “Self-diagnosis” and then “Engine” and “Read measured value block” ⇒ Vehicle di‐ agnosis, testing and information system VAS 5051.
Operate the diagnostic unit according to operating instructions and by following the indication on the display.

TDI CR engines (1st generation):

– Select “Measured value block 108” and read off the actual value in the display field 1 (volumetric efficiency of the particle filter volume; in ml which is 175 ml).

TDI CR engines (2nd generation):

– Select text field “particle filter, ash loading” and read off the actual value in this field (volumetric efficiency of the particle filter volume; in grams which should be 70 grams).

I believe that Yetis sold in India have second generation. Perhaps some BHPian (Pramod if you this) might confirm.


PREVENTIVE ACTIONS:

1. Avoid too many short runs.

2. Once every other week go on a long drive (at least 20 km).

3. Don't ignore the DPF warning. Take the vehicle on an open non-crowded road and carry out recommended ACTION I.

4. Regardless of what the service manual says, I have been advised by more knowledgeable BHPians, to insist on each service that DPF is cleaned. It is free of cost for the first three services. Make sure that it is entered on the Job Card. The service guys may suggest it is not needed but just insist.

Last edited by SushilBajpai : 3rd July 2011 at 18:00. Reason: Correct for spellings and style errors
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Old 3rd July 2011, 18:25   #10
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Default Re: Diesel Particulate Filter - Skoda Yeti

Quote:
Originally Posted by SushilBajpai View Post
...


PREVENTIVE ACTIONS:

1. Avoid too many short runs.

2. Once every other week go on a long drive (at least 20 km).

3. Don't ignore the DPF warning. Take the vehicle on an open non-crowded road and carry out recommended ACTION I.

4. Regardless of what the service manual says, I have been advised by more knowledgeable BHPians, to insist on each service that DPF is cleaned. It is free of cost for the first three services. Make sure that it is entered on the Job Card. The service guys may suggest it is not needed but just insist.

I think too short runs too many times is anyway bad for the car, your pocket and your health.

Regarding the DPF cleanup - can you let us know exactly what these guys do to clean the DPF next time you go for a service? Also can you kindly ask how much they would charge if it is done outside of free service?
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Old 3rd July 2011, 18:35   #11
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Default Re: Diesel Particulate Filter - Skoda Yeti

Quote:
Originally Posted by vina View Post
I think too short runs too many times is anyway bad for the car, your pocket and your health.

Regarding the DPF cleanup - can you let us know exactly what these guys do to clean the DPF next time you go for a service? Also can you kindly ask how much they would charge if it is done outside of free service?
Couldn't agree more about short runs.

I have no idea what it entails. I did try to ask what they would be doing, but the guy couldn't explain.

Next service is due after 15,000 km. That's a long way to go.

Perhaps Anshuman or Pramods could shed some light on this.
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Old 3rd July 2011, 20:34   #12
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Default Re: Diesel Particulate Filter

Sushil, you are right Yeti has second generation CR engine, the best way to avoid DPF problem is to use the vehicle for long drive and for some duration and higher RPM or higher speed that burns the shoot, this process is called regeneration and all DPF are designed to do that, provided they get the heat and opportunity. This is only possible when you do "long drives" or "high speed" drives, that means running your car at higher RPM.
To keep the car healthy you need to do this regularly or else go on long drives!
-Pramod
PS: DPF are mostly not serviced outside, at least I don't know off, but they are very high mileage component and with few precaution should serve you for more than 200K kms with out any failure!


Last edited by pramods : 3rd July 2011 at 20:39.
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Old 4th July 2011, 00:45   #13
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by DerAlte View Post
Sounds impractical, doesn't it? How would you measure soot accumulation directly? Even indirectly (say increase in back pressure) the measurement would be clouded with more than one influence vying for attention.
Aniruddha Sir, thanks for mentioning. I read quite a bit on the topic and most DPF systems just predict the conditions. but then, the back pressure is said to be being continuously monitored. Back pressure is directly related to the mass of soot accumulated in the filter. This value, when it reaches a threshold, ECU triggers the Active DPF regeneration.

If possible I will get more details on how it is done, in a few days. Right now, I have insufficient knowledge, so cannot comment.

EDIT: Also, this uncertainty of the ECU, is said to be the cause of main concern for tuners, as it alters the general conditions, and hence problems arise.

EDIT2: btw, does somebody know, or is there any bhp'n who have modded their cars (like intake) and still running with DPF? Hows the reliability of such mods in a car with DPF?

Last edited by dhanushs : 4th July 2011 at 00:52.
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Old 4th July 2011, 01:18   #14
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by dhanushs View Post
Aniruddha Sir, thanks for mentioning. I read quite a bit on the topic and most DPF systems just predict the conditions. but then, the back pressure is said to be being continuously monitored. Back pressure is directly related to the mass of soot accumulated in the filter. This value, when it reaches a threshold, ECU triggers the Active DPF regeneration.

If possible I will get more details on how it is done, in a few days. Right now, I have insufficient knowledge, so cannot comment.

EDIT: Also, this uncertainty of the ECU, is said to be the cause of main concern for tuners, as it alters the general conditions, and hence problems arise.

EDIT2: btw, does somebody know, or is there any bhp'n who have modded their cars (like intake) and still running with DPF? Hows the reliability of such mods in a car with DPF?

From what I have found in the internet: most systems with DPF monitor pressure both before and after the DPF - this way they get an idea of the pressure drop across the DPF (not merely back pressure at the DPF, which will also rise for example if the catcon/exhaust have a flow problem), which indicates how clogged it is.

Now this doesn't mean the clogging is due to soot (it may be accumulated ash) but this is the information ECU uses to initiate a regeneration - you get a warning light is the regeneration doesn't succeed.
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Old 4th July 2011, 01:35   #15
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Default Re: Diesel Particulate Filter

Quote:
Originally Posted by vina;2415853... this way they[I
get an idea[/i]of the pressure drop across the DPF ...
"PM emissions are a function of the specific engine operating conditions, combustion characteristics, vehicle drive cycle, fuel type, lubricant type, and lubricant consumption rate, among others.

Once deposited on the DPF, the soot is eventually oxidized either through a passive process, such is the case with catalytic systems, through active DPF regeneration, or some combination of active and passive processes. Exhaust gas temperatures, flow rates, and composition (specifically NOx/PM ratio), DPF soot loading levels, catalyst formulations, and the quality, i.e. completeness, of the regeneration are all factors influencing the amount of soot oxidized over a given time interval. Lastly, while the amount of soot escaping the DPF is generally small, <1%, this value can become much larger when the integrity of the particulate filter is compromised through any one of a number of failure modes.


Additional complexity arises from the fact that the loading state of the DPF is continually changing. Not only soot, but also inorganic ash accumulates in the DPF over time. This ash consists primarily of incombustible lubricant additives and engine wear and corrosion particles, which unlike soot, are not consumed during the regeneration process. Over time, ash build-up in the DPF leads to increased exhaust flow restriction, a reduction in soot storage capacity, and negatively impacts vehicle fuel economy. As a result, DPFs are periodically removed for ash cleaning, which is mandated to be no more frequent than every 150,000 miles. DPF ash levels after 150,000 miles of on-road use may comprise more than 80% of the total accumulated material (ash and soot) in the DPF. The significant amount of the DPF volume occupied by the ash affects both the soot distribution in the filter as well as local soot loading levels. Previous studies with ash loaded filters subjected to periodic regeneration have shown an increase in local soot loads toward the front of the filter by more than 30%, in some cases.


Given the large and complex number of factors influencing the amount of soot accumulated in the DPF, and the increasingly stringent regulatory framework within current systems must operate, it is quite surprising that pressure drop measurements form the backbone of most DPF soot load measurement systems. In addition to the factors outlined above, pressure drop across the DPF is itself also a function of exhaust conditions, namely flow and temperature, DPF type and configuration, as well as the distribution and amount of both soot and ash in the filter. Confounding the issue even further is that fact that many of the most common DPF materials currently in use exhibit a non-linear initial increase in pressure drop with soot load, due to the soot first accumulating in the filter pores (depth filtration) prior to forming a layer on the filter surface (cake filtration). Depending on the filter's operating history, the pressure drop response may exhibit a significant hysteresis as a result of the relative amounts of soot accumulated in the filter pores and cake layer. Several studies have attempted to quantify the variability and error in pressure-based DPF soot load measurements, reported in the range of + 50% of the measurement"

Source: http://info.ornl.gov/sites/publicati...s/Pub24198.pdf

Now you can imagine the accuracy of the pressure drop measurement.

Last edited by aah78 : 5th July 2011 at 07:46. Reason: Link corrected on request.
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