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Thread: DPF From horses mouth

  1. #1
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    DPF From horses mouth

    There seems to a lot of misconceptions going around regarding DPF regeneration, what it does and when it does it. I realised I didn't understand it myself so did a bit of digging and found what to me is the most comprehensive explanation yet. Warning !!! its a bit nerdy and heavy going in places. I removed the persons name from it just in case. Happy bedtime reading.


    Courtesy of ***** ******* Volkswagen Technical Support Specialist

    Diesel Particulate Filter (DPF)

    Detailed below is important information outlining the function and features of the Diesel Particulate filter which all members of your team need to be aware of.

    Diesel particulate filters are becoming more commonplace on diesel engines, particularly sizes 2.0L upwards. This is in order to reduce the exhaust emissions as required by European legislation.

    The prime reason for a DPF is to reduce particulate matter entering the atmosphere. Particulate matter is found in the form of soot, which is produced during diesel combustion. The DPF traps most of the soot which would normally travel down the exhaust and into the atmosphere. The DPF can hold a certain amount of soot, but not a huge quantity and therefore it needs to go through a process called ‘regeneration’ in order to clear the soot loading. When the soot goes through a ‘regeneration’ process it will be converted to a much smaller amount of ash. The ash is non-removable. There are two types of ‘regeneration’, passive and active.

    During long motorway journeys, passive regeneration will occur. This needs no intervention from the engine control unit. Due to the raised exhaust temperatures on a long journey (temperatures between 350 and 500C), the procedure occurs slowly and continuously across the catalytic-coated (with platinum) DPF. The catalytic-coated DPF is situated close to the Engine, therefore the exhaust gas temperature is high enough (500C) to ignite the soot particles. Due to this soot is burned-off and is converted into a smaller amount of ash.

    Active ‘regeneration’ is when the ECU intervenes when the soot loading in the DPF is calculated to be 45%. The procedure lasts for about 5 – 10 minutes. Specific measures are taken by the ECU to raise the engine exhaust temperature to above 600C, these include switching off the exhaust gas recirculation and increasing the fuel injection period to include a small injection after the main injection. The soot particles are oxidised at this temperature.

    The ECU will trigger a regeneration process, if for some reason this is aborted, ie. customer slows down, stops etc, the process will be resumed when regeneration conditions are once again met, above 60km/h (38mph). This will continue for 15 minutes.

    If after 2 attempts of 15 minutes, a successful regeneration has not been possible, the loading will increase. At 50% soot loading, the ECU will continue to maintain maximum exhaust temperatures of 600C to 650C to cause a regeneration process. The system will try to run a regeneration process for 15 minutes. If unsuccessful, the system will repeat this process for a further 15 minutes, if still unsuccessful, the DPF light on the driver display panel will then be lit.

    The owners handbook states, the DPF symbol lights up to indicate that the diesel particulate filter has become obstructed with soot due to frequent short trips. When the warning lamp comes on, the driver should drive at a constant speed of at least 60 km/h for about 10 minutes. As a result of the increase in temperature the soot in the filter will be burned off. If the DPF symbol does not go out, the driver should contact an authorised Volkswagen repairer and have the fault rectified.

    At 55% soot loading the DPF light is lit on driver display panel. At this point the customer should follow the advice in the handbook. If they ignore this information and continue driving the vehicle until the soot loading reaches 75% without successful regeneration, additional warning lamps will light up. At this point the customer will also be complaining of lack of power, etc.

    At 75%, regeneration is still possible with the use of the VAS tester. Only when the loading is above 95%, is it necessary to replace the DPF unit.

    Operating Status System Response

    45% DPF Load Level 1
    Normal Regeneration

    50% DPF Load Level 2
    Regeneration at maximum exhaust temperatures

    55% DPF Load DPF lamp
    Regeneration from 60 km/h onwards
    ("See operating manual")

    75% DPF Load DPF, SYS and MI lamp
    Torque limitation, EGR deactivation,

    Regeneration via VAG tester only
    95% DPF Load Replace the DPF Unit

    The Warranty department has confirmed that if there is no fault on the vehicle and DPF regeneration has been unsuccessful due to the customers driving style and the customers failure to comply with the instructions in the handbook, DPF replacement will not be paid for by warranty.

    Common causes for complaint

    • Frequent short journeys – Regeneration conditions are not met.
    Not recommended for sale in the Channel Islands and inner city driving.

    • Customers who continue to drive the vehicle with DPF light on – Continued
    driving with the DPF light on and without successful regeneration results in
    excessive soot loading of the DPF, to a point where it is above 95% loaded.
    At this point regeneration is not an option and replacement of the DPF is

    • Fault 18434 particle filter bank 1 malfunction – Common fault code. This does
    not only relate to the DPF itself, but the entire exhaust gas handling system. This
    can be caused by defective temperature sensors, pressure sensors, additive
    system components (if applicable), poor connections, wiring issues, etc.

    Important Information

    • Before diagnosing a problem vehicle or attempting to perform an emergency
    regeneration, it is important to obtain a full diagnostic log and read out relevant
    measured value blocks. These MVB’s contain important information on the
    condition of the DPF system and are essential in diagnosing the fault. When the
    DPF light is illuminated, it does not necessarily mean that the DPF requires
    regeneration. For further advice, please contact Technical Support with the
    information from the diagnostic log and MVB data.

    • If a problem vehicle arrives with the DPF light, the engine management light and
    the emissions light on. If during your diagnosis and reading of relevant MVB’s,
    you find that the soot loading exceeds 75% (but is still below 95%), an
    emergency regeneration procedure must be performed with the VAS tester.
    Further to this, the customer needs to be educated. They need to understand
    why the lights have appeared on the dash panel. Their attention needs to be
    brought to the owners handbook instructions, so that they are aware of what the
    DPF light means and what to do when it appears. This should prevent
    unnecessary repeat visits for regeneration purposes.

    I have also found that as the car gets older 30K+ miles, you will notice that the regeneration takes place more often.

    ALWAYS, check your oil before any long journey, as DPF regeneration can use a fair bit of oil.

    Some questions and answers that may help;

    Question: The glow plug symbol is flashing. Why? What should be done?

    Answer: The DPF regeneration has not been completed during normal
    driving and now DPF has reached its maximum saturation at which it can
    still be regenerated. The limit value depends on variant and Model Year,
    but is in the range of 105% - 125%.Possible causes for this are:

    a.) Frequent short distance journeys, i.e. high soot loading while at
    the same time regeneration of the DPF does not take place because the
    conditions necessary were not fulfilled.

    b.) Frequent
    interrupted regenerations, i.e. the engine was switched off during
    regeneration. Applies to short journey drivers who have at least
    fulfilled the conditions for triggering regeneration. If the glow plug
    light flashes, the vehicle

    a.) Engine running since start for
    longer than 2 minutes.
    b.) Calculated saturation higher than 80%.

    c.) Coolant temperature over 70C for at least 2 minutes.
    d.) No
    DPF-relevant faults stored in system.
    e.) A defined vehicle speed
    threshold must have been exceeded (e.g. for >80% loading, 100 km/h)

    Question: Under what conditions is regeneration
    interrupted/ended once it has started?

    Answer: Normally when
    regeneration has been successfully completed, or:

    a.) After a
    maximum regeneration time (20 - 25 min.).
    b.) If the engine is
    switched off or has stalled.
    c.) If the engine is left idling for a
    long time (5 - 10 min.).
    d.) If 1000C is detected by the exhaust
    temperature sensor.
    e.) If during regeneration, a fault is detected
    on the components relevant for combustion (injection/intake system).

    a regeneration is interrupted once started but before it has been 50%
    completed, the glow plug lamp flashes on the next engine start (cold or
    hot) and regeneration begins again once the operating conditions (see 3)
    have been fulfilled.

    Question: How long does complete
    regeneration take? a.) In the most favourable case? b.) In the least
    favourable case?

    Answer: a.) Under constant conditions, i.e.
    the exhaust temperature necessary for regeneration always lies above the
    required value, for example during motorway/cross-country driving, the
    average regeneration time is 10 minutes.

    b.) Vehicle
    conditions such as long down-hill descents, frequent driving in the
    low-load range (city driving, idling) allow the exhaust temperature to
    fall. If the conditions for triggering regeneration were fulfilled, the
    active regeneration time can be extended up to 25 minutes (depending on
    engine type). If complete regeneration is not possible within this
    period, the regeneration will be interrupted.

    How does regeneration affect the oil life?

    Answer: On each
    regeneration or attempted regeneration, a certain diesel fuel amount is
    injected into the engine oil which reduces the oil life. If the "INSP"
    light in the instrument cluster comes on, the engine oil is exhausted
    and must be changed. Failure to do so could damage the engine.

    Last edited by charlesh; 06-02-17 at 07:36.
    2014 Sharan SEL BMT 2.0 TDI-CR

  2. Thanks Crasher, dannyP, MickyF thanked for this post
  3. #2
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    Very informative, especially the point about the flashing glow plug light on start up indicating an interrupted regen. I'm currently collecting stats each week regarding distance between regens and type of journeys undertaken with Shell Nitro diesel. At the end of Feb I'm going to switch to Shell standard diesel for 3 months and collect the stats. I want to see if the 'quality' of the fuel has any effect on the distance between regens.
    2013 Touran SE 2.0 TDI-CR (CFHC - D91) DSG (PBF -G1A) Acapulco Blue Metallic, Retro Fit Front Fog lights, Westfalia Detachable Towbar
    2015 Skoda Fabia SE (Mk3) 1.2 TSI(110) DSG Silver. ( I was previously posting as thamestrader)

  4. #3
    Senior Member Gazwould's Avatar
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    Quality ?

    What is the Cetane number of both dervs ?

  5. #4
    Administrator Keithuk's Avatar
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    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.

  6. #5
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    Quote Originally Posted by Gazwould View Post
    Quality ?

    What is the Cetane number of both dervs ?
    I don't know the cetane numbers of the either Shell Nitro or Shell std diesel, the Nitro is perceived as the 'quality' fuel, as a result of its (unknown) additional additives. It is reputed to burn cleaner - whether that actually translates to a cleaner burn in day-to-day usage with a reduction in soot and thus ash in the DPF is what I am attempting to determine.

    I've been using Shell Nitro for the last 2 years, in the hope that it would extend the life of the DPF. If Shell Nitro has little or no effect on the regen frequency then I'm wasting my money by using Shell Nitro. Now that I have VCDS I'm in a position to check it.
    2013 Touran SE 2.0 TDI-CR (CFHC - D91) DSG (PBF -G1A) Acapulco Blue Metallic, Retro Fit Front Fog lights, Westfalia Detachable Towbar
    2015 Skoda Fabia SE (Mk3) 1.2 TSI(110) DSG Silver. ( I was previously posting as thamestrader)

  7. #6
    Administrator Crasher's Avatar
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    Some of the points he made are a little dealer centric in their approach, there are some alternative methods and procedures which do work.
    2003 Skoda Octavia VRS Estate. APR 98RON remap, APR R1 diverter valve, Jetex exhaust, K&N panel filter, 7.5x18 Alutec Monstr wheels with 225/40 18 Uniroyal Rainsport 3 tyres.
    2006 Polo GTI 1.8T, APR 95RON remap
    1988 Golf 2 GTI 16 valve, 2.2 with Weber Alpha injection
    1983 Golf 1 GTI 8 valve, 2 litre with Eurospec racing 42/36 head
    1972 1302LS auto 1641cc conversion

    Vile Invention

    Dark was that day when Diesel conceived his grim engine that begot you, vile invention, more vicious, more criminal than the camera even, metallic monstrosity, bale and bane of our culture, chief woe of our Commonweal. How dare the Law prohibit hashish and heroin yet license your use, who inflate all weak inferior egos? Their addicts only do harm to their own lives: you poison the lungs of the innocent, your din dithers the peaceful, and on choked roads hundreds must daily die by chance-medley. Nimble technicians, surely you should hang your heads in shame. Your wit works mighty wonders, has landed men on the Moon, replaced brains by computers, and can smithy a "smart" bomb. It is a crying scandal that you cannot take the time or be bothered to build us, what sanity knows we need, an odorless and noiseless staid little electric brougham.

    W.H. Auden (1907-1973), A Curse:

  8. #7
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    new to the forum...
    I have a problem with warning lights and son-in-law did checks and appears that the PDF sensor is faulty. Got one today from VW dealer but he can’t see where it’s located to change it?


  9. #8
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    Robertaf - Surprising how google is supposed to be your friend but it all goes quiet when they just don't want you to know when economic interests or politics are involved. If it's anything like a Hyundai (it is) the DPF will be hidden away half way down between the engine and the bulkhead. You'll have to get underneath.
    2013 Passat B7 2.0 TDI-CR

  10. #9
    Senior Member Gazwould's Avatar
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    But at least with a Hyundai the manufacturers smoke coefficient value isn't on the VIN plate , it's a sticker all by it's self that could easily fall off so back to the default...

    Now for some real dpf cleaning..

  11. #10
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    If I ever notice that sticker, it fell off years ago.
    2013 Passat B7 2.0 TDI-CR

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