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The EcoBoost twin turbos are water cooled. Water cooling the bearings solved the problem. During normal operation, engine coolant is cycled through the center bearing. When the engine shuts off and the water pump stops, the coolant flow reverses and the EcoBoost uses thermal siphoning for water cooling. Coolant near the extremely hot bearing picks up heat, boils and flows away from the bearing water jacket. This pulls fresh, cooler coolant into the bearing water jacket, which picks up heat and cools the bearings. This cooling process continues silently until lower temperatures are reached, providing key-off protection for the turbo bearings.
To test this thermal siphoning process, Ford ran the EcoBoost engine at Wide Open Throttle and maximum boost for 10 minutes. Then the engine and all the cooling was abruptly shut down. The turbos were allowed to "bake" after this high-speed operation. This is exactly the conditions that would "coke" a center turbo bearing from the 1980s. They repeated the test 1,500 times without an oil change. A teardown of the turbo and inspection of the bearings validated the method of water cooling the turbo bearings.
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