Hi Matthew,
Don't forget the Ash % is not real, your filter is not blocked 54%, and your ash code P242F will not come on till it gets between 90 to 100%.
Hopefully by then will will have convinced Porsche to fix this fault.
Hi Guys
Without prejudice
I have just spent a few hours this afternoon looking to see how you calculate how much volume is inside a GPF filter.
The estimated volume of a GPF is calculated by multiplying the engine displacement by a factor of 1.0 to 1.4, ensuring the filter has sufficient capacity to manage exhaust flow and soot loading without excessive backpressure. For example, a 2.0L engine would typically require a GPF volume to be between 2.0L and 2.8 L
Our 2.0 718 vehicles have an engine displacement of 1,988 cm3.
It got me thinking of how is the volume calculated when the GPF is connected to the Catalytic Convertor.
This is a very complex thing to do, Calculating the combined volume in litres of a catalytic converter and a Gasoline Particulate Filter (GPF) involves determining the internal volume of the ceramic substrate (honeycomb) in each component and adding them together.
Plus lots of figures and data, that I have on file.
I then thought let's have a look at our algorithm to see if there is any pointers regarding the volume calculation.
The algorithm designed to cover the ash volume in a Gasoline Particulate Filter (GPF) must calculate a long-term, non-reversible, accumulative value based on engine operating parameters (primarily oil consumption) and, in advanced systems, a correction factor derived from pressure drop changes after regeneration events. Unlike soot, ash is not removed by thermal regeneration. Therefore, the algorithm estimates ash accumulation over the life of the vehicle.
I looked for reference points in our algorithm that mirror the information found on the information above and couldn't find anything that was on our information.
Ash is written into the google algorithm information I have on file, but again it may not be correct
That doesn't mean to say my information is correct, but I was hoping for something to compare.
So I moved on to Google searches regarding any issues with GPF and Catalytic Convertors regarding Ash problems.
I used this search text
Are combined catalytic converter and gpf filters fitted in 2019 more prone to false ash load readings than a single gpf
This is what came back
Yes, combined catalytic converter and Gasoline Particulate Filter (GPF) systems—often referred to as close-coupled or coated GPFs (cGPF)—introduced around 2019 are generally more prone to complex, and potentially false, ash load readings compared to a standalone (uncoated) GPF.
This susceptibility is driven by the physical, thermal, and chemical complexities of integrating a TWC (Three-Way Catalyst) directly into the porous structure of the GPF, which complicates differential pressure-based modeling.
Why Combined Systems (2019) Are More Prone to Misreading
- Non-Linear Backpressure (Ash vs. Soot): In combined systems, ash accumulates in thin layers and plugs, suppressing deep-bed filtration of soot. This causes non-linear backpressure, making it difficult for the Engine Control Unit (ECU) to differentiate between a high, harmless ash load and a high, dangerous soot load.
- Reduced Filtering Capacity Monitoring: Because ash reduces the active filter volume and alters the soot distribution towards the front of the filter, the pressure drop sensors can be misled.
- Thermal and Chemical Interference: The combined unit often works in closer proximity to the engine. Ash, particularly from oil additives, can deposit inside the three-way catalyst coating, reducing the Oxygen Storage Capacity (OSC) and confusing the emission monitoring systems.
- Sensor Limitations: The differential pressure sensors used for these systems can be affected by high engine bay temperatures and electrical interference, which can cause them to report incorrect values, especially as ash builds up.
Key Differences vs. Single GPF
- Single GPF (Uncoated/Separate): Typically acts purely as a filter (similar to a diesel DPF but lower capacity), where pressure drop is more directly correlated with soot accumulation, making ash calculation more straightforward.
- Combined/Coated GPF (2019+): The substrate serves a dual purpose—active emission conversion (chemical) and soot trapping (physical). As ash accumulates, it interferes with both, creating a more "opaque" reading for the ECU.
While these systems are durable, the 2019-era implementation of combined filters often requires more precise, and thus more easily fooled, calibration to distinguish between ash (permanent blockage) and soot (burnable blockage).
Interesting, if we compare our 4.0 GPF engine cars, they don't seem to have have any of our ash reading issues, and the ash loading you see seems to be acceptable for the mileage and age covered.
I then searched for.
What would happen if the calculated volume of a catalytic and gpf was too small, how would it affect ash load readings.
This is what came back.
The calculated volume of a catalytic converter or Gasoline Particulate Filter (GPF) is set too small in the engine control unit (ECU), it creates a mismatch between predicted and actual exhaust flow dynamics. This error primarily manifests as
artificially high ash and soot load readings due to incorrect backpressure modeling.
Impact on Ash and Soot Load Readings
- Falsely Elevated Ash Estimates: The ECU estimates ash and soot mass by correlating measured differential pressure (backpressure) against a stored volume model. If the software "thinks" the filter is smaller than it actually is, it will interpret normal pressure drops as being caused by a more "crowded" filter, leading to an overestimation of ash load.
- Increased Pressure Sensitivity: A smaller calculated volume implies a higher velocity of exhaust gas through the filter walls for a given flow rate. This causes the system to be overly sensitive to minor pressure changes, resulting in unstable or "noisy" load readings.
- Premature Regeneration Triggers: Because the ash load is a calculated value used to offset the soot load baseline, an undersized volume model causes the "clean" pressure drop to be interpreted as already partially filled with ash. This forces the vehicle into more frequent and unnecessary regenerations, as the soot mass limit is reached faster in the software's logic.
Performance and Reliability Consequences
- Reduced Filtration Efficiency Modeling: Ash typically forms a "membrane" that improves filtration. If the volume is under-calculated, the ECU may incorrectly model the filtration efficiency, potentially leading to false-positive emissions faults.
- Thermal Management Risks: During regeneration, the ECU manages heat based on the expected soot mass. Overestimating the soot/ash load due to a volume error can lead to excessive exhaust temperatures, risking damage to the filter substrate or catalytic washcoat.
- Fuel Economy Penalty: Constant overestimation of load leads to a permanent backpressure penalty in the software's logic, causing the engine to operate in less efficient modes to compensate for "restricted" exhaust flow that isn't actually restricted.
To resolve these issues, ensure the
ECU Adaptations are correctly reset and the specific component volume parameters are verified against the manufacturer's technical specifications.
Are you experiencing specific
fault codes (like P242F or P2463) or seeing
abnormally high backpressure readings on a diagnostic tool?
The last comments above, abnormally high backpressure readings, and ECU Adaptations are very revelant to our investigations.
On our cars we cannot adapt either the differential pressure sensor, or the GPF, and we have no backpressure.
We certainly need to push on with these backpressure checks, they are the key to unlock this ridiculous situation we are in.
No back pressure means no blocked filter.
Sorry to go on, but all this information backs up the problem we are having with these cars.
Its unacceptable that our 2.0 and 2.5 cars are not the same as our 4.0 cars, regarding Ash management.
Dave
