Why does the oil drain line from the turbo have to have a straight graivity fed shot to the oil pan? I know it does but I don't know the logic behind it. I mean if you have the oil pump pumping oil into the top of the turbo, shouldn't the oil just be forced out of the hole no matter where it is positioned? It has no where else to go, or does it? Theoretically shouldn't you be able drain the oil wherever you wanted, including a position above the turbo? This has been picking at my head today so thought I would share it with ya'll.
~Tyler

 

When the oil comes out of the turbo it is not oil you are used to seeing. Its more like a wipped cream and does not flow smoothly, if it does not get back into the pan to settle down to normal oil it can backup easily because its so thick and end up getting into your exahust and burning there. I know someone will explain this better.

 

I think I understand, but the Maximum Boost book and everyone I've talked to say that the only thing drawing oil away from the turbo is gravity. But if there's pressure feeding it, then it should be forcing it out.

Rales, what is the stock boost on your Merkur XR? That's the turbo I'm using. I belive it is 10psi. Please correct me if I'm wrong.

Thanks.

 

there is pressure in the feedline but no nearly as much once u get into the center cartiridge of the turbo. think of it as a faucet and sink kind of. theres pressure in the faucet but once it sprays out into the much larger sink it looses most of its pressure and velocity. then it goes down the drain "aka return line" and then into a sewer i guess"aka oil pan".

the inside of the turbo isnt not meant for such high pressures and if the oil sits there to long it will fry from the extreme heat the turbine creates. so if u rely on pressure to push the oil out its gonna eventually blow past the seals in the turbo or just cook inside the cartridge and smoke like a cheeba. thats also the reason why the return line is also a lot larger than the feed...so the oil can get in and out quickly..

tried to put it into simple words so its easier to understand

 

Good deal! Did a good job of explaining that.

 

Good Question, and some good answers. Applications that require the turbo to be mounted to low for a gravity drain to work can use a small resovoir and an additional oil pump to move the oil back into the pan. Some applications where crankcase pressure is abnormally high can also benefit from the use of a return pump.

 

The stock boost pressure of a XR4Ti is 15psi on manual cars and 10 psi on auto cars. The t3 is good up till about 20 psi but its a little out of its efficency range.