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2010 X5 E70 35D M57
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Discussion Starter · #1 ·
I've been monitoring my Soot Mass, DPF backpressure and Regens for a while now.

DPF Backpressure is high and hence Soot Mass ramp up quickly, and within approx 20 mile the ECU kicks off another Regen. The cycle repeats...

So the obvious conclusion would be a blocked end-of-life DPF which needs replacing.... But, the strange thing is that sometimes the back-pressure is low and the Soot Mass remains constant or even reduces with passive regen. This is about 10% of the time. Looking at the Backpressure reading with the engine not running, it appears to have a random offset of anything up to 25mbar.

This made me suspect the pressure sensor #6 below and I changed it

DPF Capture3.png


However the erratic backpressure readings continue.

Being fed up with the continuous regens, I disconnected this sensor expecting there to be an error reading of 8192 mbar, but the back-pressure readings continue as normal, but this time the values are lower and the Soot Mass undulates and increases very slowly overall - as I would expect it to behave...

So the questions are:
1) Where is the back-pressure measurement coming from when the sensor is disconnected?
2) What is causing the erratic readings when the backpressure sensor is connected?
 

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Hi mate,

Did you get any luck with the sensor and the often regens? My dpf was making often regens, so I took it out for a deep burn and ash removal. I was expecting it to behave as almost as brand new after the cleaning procedure, but surprisingly it builds up the backpressure and soot lever as it did before. So I was thinking that the sensor might not measure correctly, although it does not bring sky high or crazy values, but rather normal. With the engine not running it shows 8192mbar.

Did you disconnect the connector from the sensor or you have pulled the hose out when doing your sensor test? After the disconnection, do you drive with the connector/hose out and does the car still brings normal values?

Thanks in advance.
 

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2010 X5 E70 35D M57
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Discussion Starter · #3 ·
I've come to the conclusion that the DPF is end of life.

I disconnected the DPF pressure sensor electrically by pulling off the connector. I had previously replaced the sensor with a new one.

I assume now that the backpressure value is from a sensor upstream near the turbo, and that the DPF pressure reading is after the DPF and added to this upstream sensor to create a before and after delta-pressure.

The one good thing is that now the readings stay more consistent, though are increasing slowly. This is good in that there arent continuous regens being requested every 20-30miles, which arent having any effect. I need to install the new DPF I bought and plug in the DPF pressure sensor again. In the meantime I have to contend with DPF dash warnings which come on after 10mins driving.

The one thing that does puzzle me is when the DPF sensor was plugged in, how the backpressure reading looked normal occasionally... but I suspect there are elements with filtering and inferring of final values that may be confusing the issue...
 

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2012 X5d
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What mileage were you guys at when the DPF started acting like described? Did you guys us the mid saps oil or something else? Just today I was looking at ISTA+ and checked my DPF data. At 115k mile the car says my remaining life is 62,000km and at idle it jumps around from 2 to 8mbar while in park. At 2k rpm in park it's ~40mbar.

I'm pretty surprised the cleaning didn't have an effect- doesn't make sense. Do you know exactly what cleaning method was used?
 

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Discussion Starter · #5 ·
Car has 130kmiles though only the last 4k by me. Previous owner (a friend) started acting a bit funny by giving me £1k off the price but only mentioned a few small issues as problems. So chances are it had started playing up earlier. DPF Ash is low and miles left are quite high so I think somebody reset the DPF in a hope that it would fix the problem. DPF looks old...

Car mileage is about where a DPF needs changing so it's the next step for me. I'm doing the work myself and I bought a cheap non-BMW DPF off eBay. If it doesn't work, I'll get the original cleaned and put it back on.
 

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@dang, thanks for the feedback. Unfortunately your conclusion (and many others in forums) makes me believe that the DPF has come to an end as well.... I'll try your method of disconnecting the connector and will take a look at the numbers, but even if the constant regens gets more rare, it will not fix the problem of why the filter gets clogged so fast.

@robinasu - I bought the car six months ago (E71 2008) at 220K km and been monitoring the dpf since then. Acting as clogged (fast fill and frequent regens) I decided to give a good clean by baking it at high temp of 1000C degrees for a few hours, then blowing away the ash residuals. I believe it is a good method overall, but if the dpf is not working as expected (inner part not good anymore) obviously any cleaning method will not make it act as new again.

Re the dpf burn cleaning method I used you may see in in that link (thats my dpf being filmed):

The guy who cleaned it measured it afterwards for backpressure:


Before the cleaning procedure the pressure was 30 units, after the cleaning it dropped to 20 (visible from the video). He told he took out 70 grams of ash out of it. My opinion is that the filter was not that clogged (these 30 units of backpressure are not a big value) and 70 grams are basically nothing. I was having the same effect by going into regen (I'm using Btool android app to follow live data) and the soot drops to zero when regen finishes. Problem is afterwards when it gains soot to 30-40g for an eye blink.

As I was expecting a great behavior from the filter after cleaning, I was shocked with backpressure raising up from 2mbar to 15mbar for just 40km of urban cruising. So I took it out for a highway test and I got 130km between two regens, which is bad (that's after the cleaning). This made me suspect the backpressure sensor, but after reading many posts in the net, most probably the filter reached its potential (225K km on odometer) and I'm planning to remove it soon.
 

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Interesting. Any other codes reported by the car? I'm curious how the off-brand dpf works out!

I would think most of the DPF health score would derive from the differential pressure. My understanding is over time it fills up with contaminants that can't be burned off, which is why the emission equipment friendly oil is essential. If you have it cleaned I would have somebody ultrasonically clean it in a hot bath as one of the steps.

I think I read the dpf can hold like 100g, but I don't know what that means. For example, not sure if that's 100g of contaminates or max 100g of soot to be incinerated. Clearly it's not a 100g lifetime capacity of ash. Most cars emit grams/km of CO2 so a lifetime capacity of 100g off ash will not get us far. This obviously is all speculation on my part. :D
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 105K miles NOKIAN WR G3 20K miles
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DPF’s burn soot to ash, reduced at about 600ºC to a chemically inert form. The ash capacity estimated at 100 grams is by a model and calculated from differential pressures. The associated DTC are just nags as @n1das has explained many times.
 

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Discussion Starter · #9 ·
Doug, isn't it more correct to say that Soot mass is inferred by Differential Pressure and Ash mass by number of Regens? Otherwise why would my Ash mass be so low - it's 14.1g at the moment which makes me believe one of the previous owners did a DPF reset.

The erratic readings are still bothering me. For example, usually at idle I would have approx 17g soot, but occasionally I'd have 6g soot. No Regens happened in between those readings...

We are in the middle of house moving at the moment, so I cant do the DPF swap for a while....
 

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Probably unrelated but I had a few issues with my DFP also (2007 E70 30D). It got clogged, and I made it cleaned by a dfp regen specialist, however after 6month or so, back from vacations in Ardeche (small mountains in south of France with moslty very small roads, so no way for the regen to take place for a while) the DFP money light light up again.

After looking with Rheingold, I noticed an error code related to the intake valve. I checked, and sure, it was dead. Not sure for how it was dead, but I'm a bit surprised this error does not imply a service message at least; I mean this valve on a diesel is used only for 2 things, smoother shut down of the engine... and increase the temperature of the engine to perform DFP regen... So a non working intake throttle is the garanty the DFP light is on some time after that....

Anyhow, I replaced the throttle and could get my regens run again, but I noticed also the differential pressure across the DFP stayed pretty high all the time.
Last week, I've decided to check a bit more, and since the differential pressure across the DFP in this car is not a direct measure, there are 3 possible causes:
  • the DFP itself too clogged
  • the pressure senor down the DFP, or
  • the ambient pressure sensor.

So I checked the live pressure values, and bingo, the ambient pressure stays always at the same 980-ish mbar value! (the ambient pressure was around 1010mbar this day).

So, long story short: make sure both your pressure sensors are ok before accusing your DFP.

Note that this ambient pressure sensor lives on the DDE itself: I've open it this afternoon to try to change the sensor (Bosch DS-U3), and boy! it's a pain in the neck to open that box and get the PCB out of there! I finally managed to extract the PCB... hopefully I did not broke it... I'll replug it in the car tomorrow to check (while waiting for the replacement sensor)...
[edit] yup, still works! I'll replace the DS-U3 as soon as I receive it [/edit]

David
 
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