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billjam billjam is offline
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Join Date: Aug 2007
Location: Perth, Western Australia
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Quote:
Originally Posted by boostfix View Post
Could the oil flow through the turbo be less volume than ideal? Obviously you have enough flow for lubrication or your turbo would be seized but is there enough flow for adequate cooling? With a reduced flow would the oil not take on a higher temperature rise than normal and thus create a coking problem?

BTW - I like your idea of a pressure guage ahead of the filter on the oil return line.
As soon as I get a chance I will be looking at this issue. I plan to disconnect the hose at the tank and cap or plug the tank fitting so I can run the engine to see what sort of flow rate I have at the end of the line. If I think it looks too slow, I'll have to get at the oil feed line to the turbo and see what comes out of there.
I am not looking forward to doing this with my nice clean engine.

Quote:
Originally Posted by ClickClickBoom View Post
Well, If you think beyond the obvious, the cooldown theory is confirmed. By default the turbo is hotter than the oil, in fact if it is in the 400F range you will experience coking no matter what the oil choice. The fact that the temp guage rose is twofold, 1#-your cooling fan is rotating slowly, 2#-the oil is in fact doing its job, cooling the motor, turbo and removing the built up heat to outside the motor and turbo. Oil cooling is more than 40% of your total cooling. Don"t be confused, its not logical until you think about it.
Hola
eric

I agree, Eric.
I have since thought this through and came to same conclusion.
However, I am sure there is a point in time where the decrease in turbo temp starts to be offset by the increasing engine temp. The turbo still has hot exhaust gas pushing through it so there must be some point beyond which it won't cool any further, and may start to get hotter again due to higher oil temp.
I guess that would be the optimum time for a turbo-timer to run.
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Bill
1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
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Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911
Old 02-23-2009, 01:37 PM
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