Neue LLM Regelung und Neuheiten VW/Audi | Posts 16+

My dealer contacted me (on behalf of VW) and asked me not to use biodiesel (BD) with my AXR engine, contrary to the owner's manual!



Hello Bertil,
We also have a G4 with an AXR engine. The car is still under warranty.
What was the reason that VW or your dealer sent you that document?
We didn't receive anything like that. And our dealer also knows that we occasionally drive BD vehicles.

How about the PD elements? Have there been any problems with them due to BD? I don't think they are necessarily comparable to ESPs (in terms of BD).

Greetings.

Eike.

Hi Eike.

eike wrote:

...For what reason did VW or your dealer send you the document?

I can only guess...
The letter was from my dealer, and I suspect the reason for it is a promotion from Volkswagen.
Sometimes, however, the dealers are so clever that they want to protect themselves and proactively inform the customer about the situation.

Quote:

...What about the PD elements? Have there been any problems with them due to BD? I don't think they are necessarily comparable to an ESP (in terms of BD).

I also believe that PD (positive displacement) elements are more robust than the good old VP (vane pump). They are certainly not comparable (more like a series pump). Nevertheless, I am skeptical about the use of BD (belt drive) in PD vehicles.
BD has a higher viscosity (is thicker), which leads to two problems:
- The biofuel may not penetrate as effectively into the (desired) cavity of the pump element, which can lead to poorer lubrication (the same effect as with gasoline), even though the biofuel is supposed to have better lubricating properties. We know that PD elements are lubricated, among other things, by the fuel.
- The BD (blowdown) generates higher forces in the PD (pressure differential) element (it is harder to push through the nozzles), and consequently, higher forces on the ZR (zero-resistance) drive. Since the PD drive (in this case, a ZR) is already the weak point of the PD system, I would like to reduce the load on this drive as much as possible.
The stress on the peripheral equipment (pumps, ESDs, etc.) in CR (common rail) and PD (pump-injector) engines is extremely high. Not so long ago, these stresses were simply unmanageable (at least from an economic point of view).
Unfortunately, I don't have much information about the corrosion resistance of PD components. However, this is also a problem with BD systems.