DPF OBD charts

May 27, 2015
DPF OBD charts
  • This is a discussion of data collected on a 70 minute drive in my 09 Jetta TDI wagon in October 2014.

    Data was collected with a Ross-tech VCDS, hooked up the OBD port. Sourced from the engine controller using advanced measuring values, and then logging the data, saving at the end of the run. Microsoft Excel was then used to look at the .csv format file, and to make the charts. The charts were then copied to a word document, and from there saved as photos.

    Horizontal axis is seconds for the charts that end at 4500. other charts (0 to 5321) horizontal is count of readings in the data set. all are from the same run.

    First is a graph of the coolant temperature. The car was still warming up when I started this data run. you can see the slope at the start is increasing at a slower rate, then ramps up after I hit the highway. then the thermostat is doing its thing, regulating coolant flow and temperature.

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    Active regeneration of the Diesel Particulate Filter (DPF) starts around 4700 seconds. After the car comes up to operating temp, and before the regeneration, the car is performing passive regens. (350-500c)

    You also can see spikes in the temperature five times before the longer elevated temperature. these shorter spikes of temperature are when
    the system is regenerating the NOX cat.

    see: http://www.natef.org/NATEF/media/NATEFMedia/VW Files/2-0-TDI-SSP.pdf page 71 for a chart which lays out the various emissions control cycles.

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    The ECU keeps track of distance, and fuel use since last regeneration. You can see it resets to 0 after the high temperature (600c)
    regeneration is complete.

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    Requested regenerations is not what you might think, but increments as the ECU software decides it needs a regeneration.

    Without the software source code, it is hard to know for sure, but seems the program uses this info for some regeneration parameter,

    Note it increases before the active regeneration period, and then decrements as the regeneration cycle proceeds.
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    The ECU has three ways described in the 2.0 Self Study Guide to decide when to run an active regeneration cycle.
    http://www.natef.org/natef/media/natefmedia/vw files/2-0-tdi-ssp.pdf

    First is calculated soot load, based on driving parameters and fuel use. Second is measured, and third is mileage based, in case the other two wait too long. The distance mileage limit was reduced from the range in the original self study manual [460 to 621 miles (750-1000 km)] to a lower level somewhere along the way to limit the soot load. This reduction is mentioned in service bulletins related to the DPF cracking and EGR soot load as "updated software"(see VW TSB 01 14 11 dated April 14, 2014 Emissions - MIL ON, DTC P0401 Set, May Accompany P2463) . The study guide for the new EA288 engine states the limit is 465 miles, when an active regeneration is called for, regardless of what the other two soot models say.

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    Hope you find this interesting.

    Seems to me the measured soot is most interesting, seems like it builds up a bit earlier in the drive, then decreases from passive regeneration, but then continues to increase.
    since I took this data, I picked up a PF03 device which lets me watch these values full time in real time.

    my calculated soot continues to trigger an active regen of the DPF at 16.5 mg of soot, while the measured soot level goes up and down, stays near 0 just after a regen, and then starts up higher (and back down as the engine warms up).
Plano Diesel and Sudhir Saxena like this.