AVF Turbo Problems: Causes & Solutions

Hello,
'I'm having the following problem. The car is emitting a lot of white smoke from the exhaust, not blue or black, but white. The smell isn't clearly identifiable. Now here's the thing: there's oil leaking from the flexible pipe between the turbocharger and the catalytic converter, about 1 drop per second when the engine is warm, as well as from the exhaust clamp underneath the vehicle. I disconnected the downpipe from the turbocharger, and lo and behold, there was no smoke or oil leakage. When I reconnected the downpipe, the smoke and oil leakage reappeared. Why does the oil only leak out of the turbo when the exhaust system is connected? Is the turbocharger faulty, or is the exhaust system too restrictive, or is it the catalytic converter? Please help. The turbocharger's return line is not blocked.'

Does the loader shaft have any play? Horizontally or vertically?

Axial play: no. Approximately 2 mm of radial play, which appears to be within the normal range – neither the compressor wheel nor the turbine wheel are touching the housing.

Perhaps the oil simply drips down without turning into mist if there is no exhaust system.

Hello,
I ran the engine for an hour without the downpipe and constantly checked for oil leaks. I found nothing. I also removed the catalytic converter to check if it was clogged, and sure enough, it was empty. Since the flange connecting the catalytic converter to the exhaust pipe was connected with hardware store screws, I suspect that the catalytic converter was intentionally emptied, and the individual parts were not directed towards the rear silencer to clog it. When disconnecting the tube, a significant amount of oil leaked out.

Quote:

Why does oil only leak out of the turbo when the exhaust system is connected?

Perhaps because the turbocharger seals tightly when stationary, or only leaks oil under load .

I started the engine without a flame pipe.
The loader seals both the oil side and the turbine/compressor sides behind the impeller blades by creating a defined overpressure. The question is whether there is excessive back pressure on the exhaust side, which I suspect could cause the overpressure behind the turbine wheel to collapse, potentially leading to oil leakage. On the compressor side, this situation occurs with heavily clogged air filters.

A 2 mm play in the hinge is definitely not normal. Is that just a gut feeling?
Where is the oil coming from on the loader? There should be visible oil traces on the turbine wheel or housing.
Forget about the sealing theory for now.
hg
Herbert.

The turbine wheel is dry, but the housing IS completely oiled on the inside.
You need to explain to me how the charger is sealed against oil leakage.

Is it oily on the suction side or the exhaust side?
hg
Herbert.

P.S.: For example, oil pressure is typically between 5 and 7 bar; boost pressure is typically 2.5 bar measured externally on the radial compressor (i.e., it will be lower in the area near the axis).

The compressor side is dry, while the turbine side is wet and oily.

schlauchdruide wrote:

On the compressor side, it is dry, while on the turbine side, it is soaking wet.

I speculate that the back pressure from the installed AgA (axial gas generator) slightly pushes the impeller shaft towards the compressor (because it has some axial play that you didn't notice during the feeler problem), and this creates a small oil leak at the turbine-side seal.
Without the AgA, the wave will likely be pushed out of the turbine.
Perhaps the oil is also leaking into the compressor housing, but you haven't noticed anything yet because the engine hasn't been running without the AgA for long enough.

Quote:

The compressor side is dry, while the turbine side is soaking wet.

Is the exhaust manifold dry on the inside?
hg
Herbert.

The exhaust manifold is dry on the inside.
'I'm ashamed to admit that I forgot the most important thing, or only realized it today. If the vacuum hose on the VTG (Variable Turbine Geometry) is not connected, there is no smoke or oil leakage. When I connect the vacuum hose, the VTG fully engages, which is normal since it receives the greatest vacuum at idle. However, this immediately causes a lot of smoke, and after about 10 minutes with a warm engine, oil starts leaking again from the flexible pipe.'
The cause is therefore the charger.

The question is only 'why???'

It's hard to be any clearer than that.
The oil is coming out from the exhaust side; the more exhaust flow and turbocharger speed, the more oil.
The leak could be directly at the shaft; the play suggests this, or perhaps it's a crack.
That just leaves us with the option of swapping.
hg
Herbert.

Thank you for your help.