-7 thrust bearings worn

[MrStabby]

After the manifold to turbo gaskets failed (heat?) turbos were removed and apparently the thrust bearings are worn but otherwise the turbos are good. They've been on the car for maybe 50,000kms with quite a few track days, and i'm diligent with oil changes.

So, would that be considered early failure? Do thrust bearings usually go first? If not, why would they fail early?

334kws on -7 is high, could the tune be too aggressive? (I can post it when i get the car back).

[GTSBoy]

If the thrust bearings show signs of wear considerably earlier than any other part of the turbo, it suggests that there is a significant axial load (in one direction or the other) when in use.  I suppose you can loo at which direction the thrust wear is and determine if there is excessive suction in the intake (because restrictive) or excessive EMP.  Solving the thrust issue then comes from solving whatever was causing the thrust load.

[MrStabby]

Could running -7s hard be a reason for excessive EMP? And maybe -9s with their more open turbines would be a more reliable option?

EDIT: i guess hooking up a vac gauge on the inlet wont be too hard. I have stock air box and piping.

[GTSBoy]

Yuh, vac gauge on recirc piping into turbo inlets is good.  Drilled & tapped fitting on ex manis can be instructive for only a little effort too.

[MrStabby]

3 minutes ago, GTSBoy said:

Yuh, vac gauge on recirc piping into turbo inlets is good.  Drilled & tapped fitting on ex manis can be instructive for only a little effort too.

Ok - since its all apart now's the ideal time for that.

[GTSBoy]

OOhh!  Mental note if you are going to go forward with it.  Make the tapping ports in the ex manifolds suitable for taking a stainless thermocouple gland.  So.....1/8" BSP or something like that, that will swallow a 3mm thermocouple.  Use the holes for measuring pressure, and plug them afterwards.  But if you ever want to put pyrometers in....presto.

[hypergear]

Its usually result in an unbalanced pressure load on the turbine shaft. I believe most of bolt on GTR's full exhaust system is too small for the twins, I would put an bleeder valve on the front cat. With bush bearing -7s, you can install over sized thrust collar assembly and increases the capacity of load, or go bb cores. 

Edited January 28, 2019 by hypergear

[MrStabby]

Is the bleeder valve suggestion so that a pressure gauge can be connected?

I thought all the R34-N1s/-7s were ball bearing, or are you referring to the earlier R32 nismos?

[hypergear]

You can use an actuatored bleeder valve on the front pipe to resolve back pressure issue to certain extend. 

I was more or less referring to topic.  For BB models they don't have a thrust bearing wear problem, it wears on the bearings and race way of the cage. There is no alternative way of repairing them apart from installing new bearing kit. 

Edited January 30, 2019 by hypergear

[MrStabby]

Oh so the balls take the thrust loading too? There is no side to side play, just in & out, so i guess that means the groove the balls run in has worn wider but not deeper.

[hypergear]

Yes, there are two angular contact bearings in side a bearing cartridge. In most of cases it's the raceway of the bearing wears resulting that play.

[MrStabby]

Tao - how much to rebuild -7s?

When i try to message you it says "hypergear cannot receive messages."

[hypergear]

Mail box is active now. I've emailed u the quote. Thanks.