Quote:
Originally Posted by SAM@GTM
Not exactly, Oil drainage on a ball bearing turbo is a lot more critical then a journal bearing one, Every factory turbo car out there have the oil lines much higher then the oil level line. Also you are forgetting the positive crank case pressure in the oil pan that could vary form one engine to the other .
Another thing you have to remember, is that the oil coming out of the turbo is not a nice liquid. It just went through a blender and comes out very frothy and aerated. So, it does not flow very well nor does it reintegrate with the liquid oil in the pan as easily. That is another reason why it is so critical that the oil return is higher than the oil level in the pan.
We had customer that did not drill the oil pan and just added a spacer without any issues . the best way is to have the oil return as high as possible . Adding the oil pan is not a bad idea to increase oil capacity witch will help improve oil temp .
Sam
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Sam, don't forget that PVC pressure will be found throughout the entire crankcase, all the way to the valve covers, so the PVC pressure is irrelevant to how high you return oil.
Larger turbo oil returns lines are used on turbo cars to make sure that the turbo oil systems pressure differential occurs at the turbo. Turbo oil seals will mostly block air from being introduced to the oil, so frothing should be minimal.
As you mentioned your customer with the spacer.. The spacer plate is well below the oil surface level, so it is the same thing isn't it? Plenty of 350z have been doing it below the oil level for almost 10 years now, even with ball bearing turbos... I have personally done it as directed in other turbo systems, although hesitant at first myself, but after more thought and experience I have not had it cause any issues for me... So I have no hesitation to doing it again when it makes sense.
Have you had a project that was burning oil until you raised the oil returns?