Q - how does the water flow through the turbo?
A - it intentionally depends on thermosyphon thus assuring continued
cooling even after the engine stops.
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Q - how long should oil stay in the turbo. For example, if I prime it how
long should it take to drain out.
A - the oil needs to be relatively free to drain out to assure that it
isn't likely to get past seals etc. The priming of the feedline is still
effective since it runs uphill and will remained filled (I wonder if
aftermarket guys consider this!)