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I think the BW ceramic ball bearings will probably beat journal bearings long term, if you water cool the bearing housing like you are supposed to. It is interesting that Garrett reported that 70% of the load on turbo ball bearings is from the centrifugal force of spinning at 200K. Probably why BW went with ceramic.
The reason I think Titanium Aluminide is at the sharp end of the spear is not the lower inertia. The inertia advantage is pretty much erased by the turbine wheel design. Being lighter to begin with allows designers to implement the mixed flow wheel with full back disk on the turbine end. Google it. Others can explain it more simply than an engineer can.
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