Ständiger Ärger mit VNT15 am AFN | Posts 16+

mullemaus wrote:

but the compressor wheel looks good (or does it?). I believe that the discoloration isn't severe, as long as it hasn't caused the wave to become distorted. There are no signs of feeding or anything similar to be seen.

Take a look at the impeller at the 3 o'clock position. One of the blades is severely bent.
The wave hasn't been activated yet, which is correct, and it wasn't the cause of the malfunction. However, keep in mind that the turbocharger has only seen 15,000 km! The discoloration shouldn't be there; it will likely get worse over time as the mileage increases.

In the previous two turbochargers (which failed after 60,000 km and 45,000 km, respectively), the cause was a worn turbine shaft with excessive play. This manifests as deviations from the expected performance, where the pressure does not follow the specified characteristic curve. This was definitely not due to stiff guide vanes, which were fine in both cases. In the second-to-last turbocharger, the compressor was already very close to rubbing against the housing due to the excessive bearing clearance.
The turbos weren't making any unusual noises, and the failure occurred gradually over many hundreds of kilometers, until it became so severe that the engine control unit constantly went into limp mode due to control differences.
In the current turbocharger failure, the turbocharger is only able to generate a maximum boost pressure of 0.5 bar.

Regards,
Jens.

Jens 16syncro wrote:

In the previous two turbochargers (which failed after 60,000 km and 45,000 km, respectively), the cause was a worn rotor shaft with excessive play.

Hmm, if you believe the "lader theory," the waves shouldn't actually be able to enter, because they're supposed to be running in a cushion of oil pressure without making contact.
However, if the oil pressure drops too low (for whatever reason - perhaps due to excessively high oil temperatures?), the oil cushion may collapse. Could this be a possible explanation for your engine consuming oil?

And if oil and carbon deposits manage to get in there, which is likely given the high temperatures of the VNT 15, it will act like valve grinding compound between the rotor and the bearing.

"Some time ago, we also installed a 1.7 diesel engine with a turbocharger from a 1.6 TD into a friend's bus. It doesn't seem to be causing any problems with the engine; it's still running perfectly fine today. However, just adding the turbocharger alone won't do much, or very little - you also need to install a diesel pump with LDA (also from the 1.6 TD)."

I also have an AFN engine in my T3. It doesn't cause any problems, except that the hoses for the crankcase ventilation are positioned awkwardly due to the engine's angle. When the car sits for 2-3 hours, the oil that accumulates on the walls of the hoses doesn't flow back into the oil pan, but instead, a few drops end up in the turbo. When you first accelerate, it naturally gets blown into the engine - with a corresponding amount of smoke, which disappears after the first acceleration to a certain speed (about 150 meters). This doesn't bother the turbo, though; it's been like this since day one, and I've driven over 20,000 km like that.

I also suspect that you might be letting the engine cool down too often. While the TDI in the T3 runs cooler than the standard swirl chamber engines (in winter, below 80 km/h, all of the engine's waste heat is used to heat the vehicle), the heat can build up in the back when the engine is idling. I imagine that the turbocharger doesn't like that. This could also explain the worn shaft if the oil couldn't dissipate the heat. Also, the great coolant circulation pump doesn't make sense for the turbo if the oil circuit is stagnant. I removed mine.

"When I'm driving the bus and need to stop quickly, I let the engine cool down before turning it off (by reducing the load and using engine braking). If that's not possible, for example, at a highway rest stop, I let it idle for 1-2 minutes. Thanks to the sports air filter, this sometimes brings great joy to my neighbors... but needs must!"

Quote:

I have already driven more than 20,000 km with it. I would also guess that you often turn off the engine when it's still hot.

Hi,
No, it won't be due to the hot water being turned off; I'm aware of that issue.
"Please let me know again after another 80,000 km if your turbo is still okay. 20,000 km is far too short a distance to make a reliable assessment of its durability. My first turbo lasted 65,000 km before it completely failed."

Regards,
Jens.

Hello,

I also have an AFN engine in my T3. So far, I've driven 45,000 km without any problems. The engine now has approximately 115,000 km on it.
Could it be that the oil feed/return line to the turbo is clogged or leaking? That could also explain the overheating damage.

Rolf.

Hi everyone,
Hi Jens, and my condolences.

While I can't offer a solution either, perhaps it might help with speculation if I compare it to my bus.

I also have a 16" syncro camper van with an AFN engine. Mine weighs about 100kg less, and the engine's mileage before and after installation is roughly the same. I have a smaller radiator (original GIII) and no oil cooler. Otherwise, everything is the same as Jens', including the transmission.
The original turbo is still working in my car. It's probably not as tight as it used to be; after being parked for a long time (overnight), there's always a puff of blue smoke initially, but it still functions perfectly. The only issue is that the oil consumption has increased slightly (from none to about 0.2 liters per 1000 km).

The only difference I notice between our buses is the usage profile. I don't use mine for extreme off-road driving, towing, or high speeds. Therefore, my fuel consumption is almost never above 10 liters per 100 kilometers.

Greetings,
dieter

The blue smoke doesn't necessarily have to be coming from the turbo. In my case, the hoses from the crankcase ventilation system are positioned awkwardly (due to the engine's angle), so the oil mist doesn't drip back into the oil pan, but instead goes directly into the intake manifold. The lowest point of the intake manifold is the turbo. The oil accumulates there, and then, the first time you reach 60 km/h, it's forced into the engine and comes out as blue smoke from the exhaust. After about 1000 meters, everything is normal again. I initially thought it was the turbo, but if I park the bus so that it's tilted heavily to the right, then even after a day of standing, no blue smoke comes out.

Hi,

Would this control unit [link] be suitable?

suitable for serving the purpose described in this thread?

Regards,
Jens.

Hi.
I also had the same problem with my AFN engine in the T3. After the second turbocharger, Tubo Tapp (in Langenselbold) told me the same thing: the turbocharger's angle was too steep because the turbocharger's oil drain was too low. The engine's oil level should not be above the turbocharger's drain.
Ideally, it should be like this. But with a T3 AFN engine, it's practically impossible.

His proposed solution was:
Redirect the turbo's exhaust flow to a lower container and then use an electric oil pump to pump it into the engine. This was done in a certain Porsche sports car.
The idea is good, but difficult to implement. (Oil pump: where will it come from? The container must be located below.)
The oil pan offers insufficient ground clearance.

My proposed solution:
The charger's outlet, including the fittings, is approximately 12-14mm in size.
and adjust the engine slightly, raising it a bit (so that the oil pan is no longer perfectly horizontal).

I switched from 10W-40 to 5W-40 motor oil.

It was probably a combination of factors, but my car has been running well for about a year and 40,000 km.
Without complaint.
Best regards, Hagen.