Hi Folks,
I suddenly started wondering about something for which I have no answer. It looks to me that in a 914-6, or a 911 for that matter, the scavenge oil pump is plumbed to a line that dives into the tank and emerges in the filter console and the filtered oil is then released into the tank so everything stays clean. Air bubbles are constantly entrained by the scavenge pump and there are separator baffles to move the air away from the oil in the tank.
In my experience it is hard to get air to go through a wetted filter element. Am I wrong on this. Air is smaller than oil so I can believe it, but wondering if I am looking at it wrong. To me it is still a mystery.
Full Version: Scavenge air go through filter in 6?
Usually the oil mist that is present in the air in the oil tank is so light and thin that it does not cause a problem with oil vapor saturating an air filter. In the 911, the vent from the oil tank goes into the air cleaner housing such that it is introduced into the intake air downstream of the filter. Any oil that separates out of the air stream drains out of the housing through a small tube at the bottom of the housing. The only time that the oil mist is a problem is when the engine has excessive blow-by.
Scavenge oil is (or can be) highly aerated but is pushed at high pressure.....I've read up to 160ish PSI in some cases. It WILL go thru a filter. There is a hi-pressure relief valve in a proper oil filter to bypass it if necessary......which is why a Porsche approved oil filter is a real good idea.
QUOTE(J P Stein @ Mar 1 2012, 08:04 AM) 
Scavenge oil is (or can be) highly aerated but is pushed at high pressure.....I've read up to 160ish PSI in some cases. It WILL go thru a filter. There is a hi-pressure relief valve in a proper oil filter to bypass it if necessary......which is why a Porsche approved oil filter is a real good idea.
So the oil mist is permeable to the filter element. I figured the oil would be coming out of the pump at high pressure. OK. Now I understand it. Hopefully we won't be bypassing our filter elements under normal circumstances. Thanks.
It is a closed system all or which is under constant pressure as long as the engine is running. Air or vapor has no place to go other than through the element. If the much larger oil molecule passes through, air is no problem.
QUOTE(J P Stein @ Mar 1 2012, 05:31 PM)
It is a closed system all or which is under constant pressure as long as the engine is running. Air or vapor has no place to go other than through the element. If the much larger oil molecule passes through, air is no problem.
Yeah I know about the chemistry, but I also know that in my lab once you wet a filter it tends to not want to let air through. That was really the basis of the question. Yesterday I sawed a 911 oil tank apart lengthwise to see how it goes together and there is no question about how things are routed.
Going to use the fittings on a home welded aluminum tank. Maybe. If my welds don't suck.
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