AGR Problems: Retrofit Filters & Solutions

Hello everyone,

Next week, I'm getting a retrofit filter installed in my Audi from the dealership because my exhaust pipe is rattling, which will cost me 330 euros.
My EGR valve is broken due to a metal sheet, and I'm actually okay with that.

Now the question: Will this cause problems for the filter? Or am I even preventing its regeneration?


Thank you very much!

Martin L. wrote:

Hello everyone, Next week, I'm getting a retrofit filter installed in my Audi from the dealership because my downpipe is rattling, which will cost me 330 euros. My EGR valve is broken due to a metal sheet, and I'm actually okay with that. Now the question: Will this cause problems for the filter? Or am I even preventing its regeneration? Thank you very much!

Hi,

Without wanting to overstate things, but higher levels of NO2 in the exhaust can actually be beneficial for a DPF, as the stored nitrogen oxides are broken down into nitrogen and oxygen by the catalytic converter. This oxygen and the resulting temperature are advantageous for the DPF's regeneration process.

ja, diesen Aspekt sehe ich auch. Thank you.

But:
When the EGR system is malfunctioning, the exhaust gas temperature decreases, at least under partial load conditions.
However, during a full-throttle run on the highway, I observed the same temperature.
I just have very low NOx emissions there.
Then the question arises: at what load level does the regeneration occur?
'Fortunately, nothing really bad should happen (e.g., a blockage), as it's a soot trap that can simply be blown through if necessary. But that shouldn't be necessary. I can also reactivate the EGR valve.'

Deactivated EGR --> higher combustion temperature, increased thermal NOx.
Functional EGR (Exhaust Gas Recirculation) --> Combustion inhibited by exhaust gas mixing in the intake air, resulting in lower temperatures and reduced thermal NOx emissions.

To be honest, the retrofitted DPF isn't working perfectly... so just let it be, and occasionally drive with full power, and it will be fine!

matthiasTDI96 wrote:

Deactivated EGR --> higher combustion temperature, more thermal NOx. Functional EGR (Exhaust Gas Recirculation) --> Combustion inhibited by exhaust gas mixing in the intake air, resulting in lower temperatures and reduced thermal NOx emissions. Okay, to be honest, the retrofitted DPF isn't great because it doesn't really work optimally... so just accept it and occasionally drive with full power, and it will be okay!

The temperature readings for these open systems, specifically regarding regeneration, are very low. If these aren't just wishful figures from the manufacturers (around 200°C), the filter should almost always remain clear during normal operation. However, with Exhaust Gas Recirculation (EGR), you experience significantly higher exhaust temperatures due to the inhibited combustion – a less lean combustion (as fuel doesn't mix well) – leading to slower combustion and higher exhaust temperatures.

But if these manufacturer's specifications for the retrofit filter are correct, then there shouldn't be any problems either way.

Thank you for the answers.
I will post my experiences then, if I find anything noteworthy.