the downfall of the garret gt turbo

[igottasicjb]

i was watching the turbo tech section of the serious performance 8 dvd and to my suprise garrett in thier wisdom made the bearing cages in their gt series turbo from plastic. apparently they work fine so long as the coolant line's a connected, good oil and good filtration are used and proper engine run downs are done. even though i'm still no happy with plastic supporting a shaft running around the 100000 plus rpm mark :glare:

[Junkers]

Other than plastic being cheaper than metal, maybe they did it for less inertia/resistance.. maybe?

[igottasicjb]

bearing cages don't rotate anywere near as fast as the inner race does so inertia wouldn't come into consideration,they did it because its cheap, the bearings that we use in jet engines at work have silicone nitride balls and cages. much more durable and they can be purchased for the gt turbo's if you have bank balance resembling richard branson's :x

[merlin]

hmmm, well I had a chuckle when I read this.
Silicon nitride is indeed good stuff, it features on most of the line guides on my lighter weight fishing rods.
funny though, the rods for marlin and suchlike feature steel rollers with brass bushes! go figure.

[igottasicjb]

i never new it was used on fishing rod runners, the reason we a starting to use them at work is
if for some reason you get oil contamination or on shutdown jet engines suffer just like turbo's do if you don't run your engine down "turbo timing" oil bakes on bearing surfaces. if silcon nitride bearings get surface minor damage they will re-burnish the ball surfaces and still remain in a servicable state, don't know how though :?