- Joined
- May 27, 2008
- Location
- Rockland County, NY
Too much thrust play could certainly cause a compressor side leak.
I know I've said this before here but it's worth repeating: the piston rings are *gas* seals, as in air and exhaust gas. They prevent blow-by and leakage of boost and exhaust gas into the center housing. They are not, and cannot act as liquid oil seals. The difference in gas pressure across the piston ring is what keeps liquid oil from leaking out while running. When the engine is under load and in boost, there should always be positive pressure inward into the turbo's center housing, on both sides.
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Interesting. I always assumed they acted like oil rings on a piston. How does that explain oil not leaking when idling or heavy decel? There is no positive pressure on the compressor side then, or am I missing something?
Garrett (sample link) does talk about the pressure differential, however it also says this:
"At the turbine end, the sealing system is simple. After the oil has finished its work in the bearings, it travels along the shaft until it reaches the hub, where the spinning oil thrower literally throws the oil outwards by centrifugal force and it meets the inside face of the center housing where it drops down under gravity to be collected by the oil drain and returned to the engine sump. In addition to that, one or two piston rings are used which fit into a very accurately machined “stepped bore”. Unlike the piston rings inside the engine cylinders, these piston rings do not move. During the assembly process, the piston rings are compressed and once they are correctly located, the piston ring never changes position."
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