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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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I spent some time going through this thread and have a couple of thoughts to share. I’m not a CSI investigator but I have extensive background in turbos and tend to get unhinged when every engine problem on a turbocharged engine eventually gets blamed on the turbocharger.
The thread starts with describing an extreme thermal excursion for the entire engine. Now in this situation the turbo is happily idling away and not exposed to conditions to form varnish much less hard coke. However being an air-cooled engine if the oil is at an excessive temperature so are the head temperatures.
Everyone who has experience with non turboed air-cooled Porsches, aircraft or the lowly VW knows you will find coke chunks in the oil strainers. Without turbos, how can this be?
Because they are air-cooled and the coke is being formed in the extreme temperature areas localized around the exhaust valves and moving outward as the mineral based oils are being cooked. There is also the very real problem of all turboed engines; blow by. This forms similar accumulations in the vent hoses, oil tank, etc.
I pose one more question for you. If these chunks shown in the initial posting were formed in the turbo bearings, how did they get through TWO close tolerance pumps, the oil scavenge then the oil pressure pump without being pulverized?
I think these were formed in the cooling rail oil delivery path during repeated running and hot shutdown extremes throughout the life of this motor. This last extreme was the killer.
If you can’t except coke, obvious you can’t, use synthetic oil, as do all the gas turbines in the world.

Last edited by copbait73; 12-08-2007 at 02:09 PM..
Old 12-08-2007, 01:52 PM
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