Nissan Patrol 4x4 (Africa)

Stefan, the two sides of the turbo are seperate, in terms of operation, joined only by the shaft which is common.

Power is provided by the exhaust turbine, which drives the inlet turbine to generate pressure.

But the oil from the PCV valve is fed into the inlet air, before that air enters the turbo (it has to be fed in befor the turbo, because after the turbo the pressure is too high). Thus the oil in that air enters the turbo, the intercooler and then back into the engine.

Whether you need oil in the turbo's chamber is a different question entirely and depends on whether the turbo's bearings are connected to the engine's lubrication system. If it is, then adding oil to the air going through the turbo should not be advantageous in any way whatsoever. The reason I say this is because there should be no contact between the turbo impellors and casing, and there are oil seals between the chambers and the bearings, so this oil cannot reach the bearings anyway. The oil in the bearings is pressurized far higher than the air in the chamber anyway, so if the seal fails, the oil in the air still won't reach the bearings, instead the oil from the bearings would enter the air and the engine would lose oil pressure.

I personally remain to be convinced that recirculating the oil can be advantageous to the engine in any way, and the only advantage I am aware of is cleaner emissions.

Thanks Peter for the additional info. That is the way it was explained to me, I'm learning! :)

I've built a catch can for mine and will fit it as soon as time permits. I removed the fan on the top of my intercooler and fitted a larger one on the bottom two weekends ago. While I had the intercooler off, I soaked & flushed it with engine cleaner. There was a scary amount oil that had accumulated inside!

I can't imagine that the layer of oil inside will aid the cooling of air in the intercooler - quite the opposite I'd expect...

Christo, you are right. Tat oil does nothing for cooling and in fact aids in heat retention in the IC. Leon on the Nissan forum had these type of problems on the Terrano and it made a big change in performance when the IC was cleaned.

You have two sources of oil to your air intake. A very slight amount may be pushed passed that turbine bearing oil seal in the turbo at start up. It takes a few seconds for the oil pressure to come up and make the shaft "float" and push the seal up from behind. Not all trubo's do this, and like I said, it should be minimal and hardly noticeable in the intake.

The second one is the Tappet Cover breather. This is the problem child and on my 2.7TD, both motors pushed the same amount of oil, so I consider the amount I was getting to be normal. The whole "technology" around the breather into the intake I consider to be flawed. I mean a diesel engine runs on glorified oil (in fact mine actually does run on cooking and old engine oil along with some diesel, paraffin and 2stroke).

So what often happens when things go slightly south in the engine or turbo and you have to much oil in the intake, the motor can actually start running off it. This "fuel" supply is uncontrolled and even switching off the ignition does not stop the process. You now have a runaway engine on your hands...
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My buddy here in Parys has a 2.5 normally aspirated Nissan Custom bakkie that did this to him. It started accelerating coming up to a sharp corner at only 40Km/h. He climbed on the brakes and managed to get it stopped a block further in 5th gear with smoke coming out the brakes. The motor seems to develop a massive amount of torque running on just oil.

I actually find my torque is up, but mine does not rev as easy when I run on clean oil instead of diesel.

Damn, sorry, let me get to the point .... I have taken my breather off the intake and pass it through two catch bottles before expelling direct to atmosphere under the car into a chassis member under the rear seats. The amount of oil that does condense off the end of the pipe hardly collects dust, so I think it is clean enough. But give that same pipe a vacuum on it's end (like it will have in your air intake), and it creates a lot more oil vapour and soils the intake pipe fast.

I have been playing with the idea to build a venturi system on the exhaust pipe somewhere to dispose of any possible oil through the exhaust system, but I never get to it.