Newer VW Gen3 engines with blue smoke?

[scrllock]

So it couldn't be a manufacturing defect which allows oil to weep into the exhaust

Generally if a brand new turbo goes on a car and it's smoking, it's because the car has oil/crankcase pressure issues, not because the rings are bad.

Their purpose isn't really even to seal oil in, it's to keep pressure from the turbine/compressor housings out of the bearing cartridge (which would pressurize the crankcase). It's a gas control ring, not a oil control ring.


https://www.cartechbooks.com/blogs/techtips/anatomy-of-a-turbocharger-whats-inside-and-how-it-works

Except for the carbon face positive oil seals used in the turbos applied to carbureted engines before the widespread use of fuel injection, turbos don’t really have oil seals. Those early applications used the positive oil seals because the turbo’s compressor was subjected to vacuum frequently due to being applied to a throttled engine in what was known as a pull-through turbo system. The pull-through system referred to pulling the air through the carburetor as opposed to blowing it through. These two systems were debated frequently as to which was best because they each had their merits. But fortunately both are now passé, along with the carburetor.

There is what’s called a piston ring on both the compressor and turbine ends. The name comes from the fact that they look just like very small piston rings. Like piston rings, their primary purpose isn’t oil control, it is to seal the boost pressure and exhaust gas pressure from entering the oil drain cavity and consequently pressurizing the engine’s crankcase, an undesirable condition indeed.

Here's a video explanation:

 

[Jetronic]

Idle, just off of idle, or decel will be the occasions where there is a significant amount of vacuum in the intake manifold. I wouldn’t think the EA888 engine would pull very much vacuum even under light load. The turbos are small and are spooled at very low rpm. Even at low throttle openings, the intake charge is being pushed past the TB, not being pulled through it. But I guess you are correct, there may be slight vacuum under low load driving conditions, but there is never as much vacuum as an NA engine. This conversation makes me curious, I’m gonna log MAP pressure on my Tiguan and see how much vacuum occurs during the various loads/driving conditions the engine sees.

You are correct on a diesel though, with no throttle, there would be virtually no scenario where there is vacuum.

the bypass valve will be open unless more power is asked than can be delivered by athmospheric pressure.