Sharan CFFB regeneriert alle 30km | Posts 16+

Blackfrosch wrote:

Quote: However, even the variant with 2 actual physical connections at the DPF does not help with the error, because the engine control unit only receives the differential pressure as a signal, not the absolute value from the two pressure sensors. Of course, that helps: It's about the pressure drop across the DPF, and that is always correctly measured with 2 measurement points. ...

"No, I don't think that's correct. As far as I know, the differential pressure sensor doesn't transmit pressure 1 and pressure 2 to the engine control unit, but rather only the difference between the two pressures."
You can certainly try to convince me otherwise, but in the measurement blocks, those two pressures should appear somewhere.

This means that a differential pressure sensor connected before and after the DPF doesn't actually measure any differential pressure across the DPF if you put a potato in the exhaust pipe.
That's also correct.

The "economy version" with a connection between the turbocharger and the DPF, and the "air pressure" reference (the 2nd connection from the differential pressure sensor goes to the open air), on the other hand, detects the "potato" in the exhaust, as it doesn't measure the differential pressure across the DPF, but rather the entire remaining exhaust system. And the pressure drop across the "remaining" exhaust system is modeled in the engine control unit, which allows for a relatively accurate estimation of the pressure difference across the DPF.

chli1976 wrote:

The SCR catalyst was clogged, which is why the DPF filled up so quickly.

Hello, what did you do about the clogged catalyst? Did it have to be replaced? I'm having the same problem; the measured soot mass is increasing very quickly, regardless of whether I'm accelerating or the engine is running in idle mode. The pressure at the differential pressure sensor is increasing to 600 hPa during acceleration.
Best regards, Jens.

I removed it and took the function out of the software, but you will lose the operating permit.

chli1976 wrote:

I cleared it out and removed the function from the software, but you will lose the operating permit

.

If you want to continue operating legally, you can also purchase refurbished SCR catalytic converters as replacements online. They are typically about half the price of new ones.
I had one of these installed 30,000 km ago, and it's still running without any problems.

Regards,
Ralf.

Thank you for the responses. I've already looked into it, and it seems the SCR catalytic converter is quite rare for the Audi Q3. I'll see if the ones from other models with a 2-liter diesel engine might be compatible.
Once I've looked into this matter, I'll get back to you. I wish everyone a happy start to the new year.

Best regards, Jens.

Hello.
Here's another update on my problem with frequent regenerations.
It wasn't the SCR catalytic converter that was the problem, but the DPF itself. To check, the exhaust pipe behind the DPF was disconnected. However, the high pressure difference remained. Then, a nearly new replacement DPF (with approximately 4,000 km of mileage) was purchased and installed. It was an incredibly complex job and took about 10 hours with two people. This is an Audi Q3 Quattro with a 2.0 CR TDI engine and 110 kW.
The ash content was then adjusted to 1 gram, and now it runs for approximately 400 km before requiring regeneration. During this period, the measured ash content decreases to as low as -4 grams during regeneration.
Now, the only question that remains is why the old DPF was so severely clogged after only 130,000 km.

I hope I can help with that.

Jens Grundmann.

Thank you for the feedback! Inappropriate engine oils that could produce more ash during combustion might be a cause.

Therefore, always use an oil that meets the specified standard.

Hello.
"No problem, someone who's having trouble always looks forward to a final solution. I don't find the car's diagnostic system sufficient for this particular problem."
Regarding oil, I have always used the recommended Liqui Moly 5W30 longlife oil and have never experienced significant oil consumption. I have always changed the oil every 15,000 km. However, I have always added an additive to the fuel tank that is supposed to lower the combustion temperature of soot to 400 degrees Celsius. I believe the product is called Eolys and is used by PSA in some models.
Perhaps one shouldn't do something like that .

Best regards, Jens.

No, you shouldn't do that. The system is designed in such a way that it can burn off the resulting gas. Since this gas ignites at a certain temperature and oxygen concentration, everything should be fine. However, if your substance accelerates this process, it could lead to excessively high temperatures in certain areas, causing the material to sinter together.

If you still have the DPF: Use an endoscope on the inlet side, or use the flexible scope. I bet you have completely blocked channels.

Generally: To all those who are reading this: Only the fuel specified for a particular vehicle should be put in its fuel tank. When it comes to engine oil, it's also important to adhere to the standards, and you can choose between low viscosity (LL) and "normal" viscosity according to your preference.

If you don't exclusively drive short or very short distances...

Specifically: Because your issue is unusual, this additional cost is certainly a reason. However, there might be another reason (excessive oil consumption due to a faulty component, a defective fuel injector, etc.). Investigate this, otherwise you'll soon be back to the same problem.
The Russmass (exhaust gas mass) being below 0 is likely due to the loading factor you specified being too low (1). Is this a DPF from "eBay"? They always seem to have only 4,000 km on them, which is a bit suspicious.
"Especially with all-wheel-drive vehicles that have a transversely mounted engine, any work between the turbocharger and the exhaust system is simply awkward. Therefore, find all the underlying causes, otherwise you'll be doing this again soon."

Thank you for your assessment; there might be something to that. He hasn't been using excessive amounts of oil, and the injectors are still within the normal range according to the test results.
I will continue to monitor the situation and report if there is any new information. Unfortunately, I can't find the function in VCDS to calibrate the differential pressure sensors, so I'm apparently too clueless.

Best regards, Jens.