Hi Guys & Girls
Without Prejudice
Well had another busy week, with more phone calls from drivers with our GPF failures.
We still have quite a few cars stuck in Porsche dealers at the moment, waiting for authority to replace these filters they say are needed to fix these cars.
We have reported on earlier posts, that even after these new filters have been replaced, they are still having issues with the oil ash load percentage figures increasing over very small mileages covered.
This is very worrying, and would suggest that the diagnostic checks to replace the GPF, may not be correct.
I would like to share with you this current Dealer diagnostic log on the GPF system taken from one of our cars,
page 42, of the Val report , and explain what's wrong with it.
From the top.
K211 soat load calculated 0.00%, and K221 soot load measured 0.00%. We never seem to get any readings on these that make any sense at all.
K231 oil ash load measured 100%, this puts on your engine light with the permitted to drive warning light showing.
T255 exhaust temperature in the filter 222.04 degrees C
T251 exhaust temperature upstream of filter 18.16 degrees C.
On all the cars where we have seen the oil ash at 100%, these temperatures have more or less been the same.
The upstream temperature which is nearer to the Catalytic Converter always shows a very low reading.
Both these temperatures should be the same give or take 10%.
But remember they are calculated.
This next reading K251 particulate filter differential pressure sensor is the best one of them all.
It's showing a very low figure of 2.32 hPa.
The differential pressure sensors function is to monitor the soot loading of the GPF, and when the pressure is at a pre determined level the warning light should come on.
This warning light alerts the driver to start the active regeneration process, as described in the drivers handbook.
So you can clearly see that when this GPF filter measured value got to 100%, the engine light came on, showing a trouble code of P242F, (ash load exceeded), which is not shown on this page.
You would however expect to see alot higher differential pressure reading to confirm this.
Because when the exhaust is blocked, you would certainly have high exhaust back pressure, seen from the pressure sensor.
Not on any of the cars we have seen so far.
It's quite easy to check for exhaust back pressure on these cars, it can be checked at the pressure sensor.
If you disconnect the thicker rubber pipe to the sensor you can read actual pressure of the GPF with a pressure gauge.
Also you can also connect a vacuum gauge on to a vacuum take off on the inlet manifold and this will confirm if the exhaust is blocked.
You start with an idle reading, then increase the revs to 2K, and watch for the reading decreasing, this also confirms an exhaust restriction.
This week hopefully we will be testing the above on a car thats just been diagnosed with our P242F fault.
And I will update you on the results
Good news, we have had confirmation of vacuum readings on these cars after a new Porsche AOS was fitted.
From cold 40 to 45 inches of water (inH20)
Hot engine, 30 inches of water (inH20)
The hot reading is lower than we have seen previously, and bearing in mind that these separators have been superseded since our 2019 cars where built, this could be another area of concern.
Dave.
Without Prejudice
Well had another busy week, with more phone calls from drivers with our GPF failures.
We still have quite a few cars stuck in Porsche dealers at the moment, waiting for authority to replace these filters they say are needed to fix these cars.
We have reported on earlier posts, that even after these new filters have been replaced, they are still having issues with the oil ash load percentage figures increasing over very small mileages covered.
This is very worrying, and would suggest that the diagnostic checks to replace the GPF, may not be correct.
I would like to share with you this current Dealer diagnostic log on the GPF system taken from one of our cars,
page 42, of the Val report , and explain what's wrong with it.
From the top.
K211 soat load calculated 0.00%, and K221 soot load measured 0.00%. We never seem to get any readings on these that make any sense at all.
K231 oil ash load measured 100%, this puts on your engine light with the permitted to drive warning light showing.
T255 exhaust temperature in the filter 222.04 degrees C
T251 exhaust temperature upstream of filter 18.16 degrees C.
On all the cars where we have seen the oil ash at 100%, these temperatures have more or less been the same.
The upstream temperature which is nearer to the Catalytic Converter always shows a very low reading.
Both these temperatures should be the same give or take 10%.
But remember they are calculated.
This next reading K251 particulate filter differential pressure sensor is the best one of them all.
It's showing a very low figure of 2.32 hPa.
The differential pressure sensors function is to monitor the soot loading of the GPF, and when the pressure is at a pre determined level the warning light should come on.
This warning light alerts the driver to start the active regeneration process, as described in the drivers handbook.
So you can clearly see that when this GPF filter measured value got to 100%, the engine light came on, showing a trouble code of P242F, (ash load exceeded), which is not shown on this page.
You would however expect to see alot higher differential pressure reading to confirm this.
Because when the exhaust is blocked, you would certainly have high exhaust back pressure, seen from the pressure sensor.
Not on any of the cars we have seen so far.
It's quite easy to check for exhaust back pressure on these cars, it can be checked at the pressure sensor.
If you disconnect the thicker rubber pipe to the sensor you can read actual pressure of the GPF with a pressure gauge.
Also you can also connect a vacuum gauge on to a vacuum take off on the inlet manifold and this will confirm if the exhaust is blocked.
You start with an idle reading, then increase the revs to 2K, and watch for the reading decreasing, this also confirms an exhaust restriction.
This week hopefully we will be testing the above on a car thats just been diagnosed with our P242F fault.
And I will update you on the results
Good news, we have had confirmation of vacuum readings on these cars after a new Porsche AOS was fitted.
From cold 40 to 45 inches of water (inH20)
Hot engine, 30 inches of water (inH20)
The hot reading is lower than we have seen previously, and bearing in mind that these separators have been superseded since our 2019 cars where built, this could be another area of concern.
Dave.
