Small nicks.. effect on balance?

[mini_me1209]

I delicately took off my exhaust housing but still managed to get some tiny nicks in the wheel. The turbo had been freshly balanced when i received it. My question is how little is too much. Going by the pictures, should I just play it safe and have er' rebalanced?


http://i69.photobucket.com/albums/i61/mini_me1209/oilpressuresensor003.jpg
http://i69.photobucket.com/albums/i61/mini_me1209/oilpressuresensor006.jpg
http://i69.photobucket.com/albums/i61/mini_me1209/oilpressuresensor004.jpg
http://i69.photobucket.com/albums/i61/mini_me1209/oilpressuresensor007.jpg
http://i69.photobucket.com/albums/i61/mini_me1209/oilpressuresensor008.jpg

[IJ.]

They're not fresh and look like FoD.

[jetjock]

FOD is bad ;)

I'd get a new wheel. It's not so much a balance issue as a stress riser issue.

[mini_me1209]

anyone care to explain what FOD is?

[Spoolin turbo]

no way you nicked that with your housing.

[mini_me1209]

Reply from the distributor:
It looks some kind of trash went throught the turbine at one point of another , couldn't been suck in throught the intake or else the compressor would of been damaged, and ofcourse it has nothing to do with you taking out the back housing. Now ,it would be perfectly fine regarding performace and you shouldn't worry about it , here is a recent thread from a similar turbo condition on the mazda forum.


http://www.rx7club.com/showthread.php?t=713563&page=2

Scroll down to about halfway.



Any objections? Im not so much worried about the integrity of the wheel as i am about the balance. I know it doesn't seem like a lot but at those rpms every little bit adds up. I hope im not splitting hairs here!

[A-model_]

In aviation they smooth out small nicks like that on the compressor , turbine blades, to reduce the possibility of cracking. Can the compressor and turbine blades be dressed in the same manner?

[jdub]

Foreign Object Damage

The alloys used in a jet turbine is far different than on our puny compressor/turbine blades. The risk of stress (like JJ said) in the blade risers is much more likely. I'd replace the wheel.

[Doward]

Agreed - replace the wheel, and have the assembly re-balanced. No way did you do that, and I'd venture to say that the company you had rebuild it knew about it, and decided to ignore it.

[MDCmotorsports]

Damage like that can also be from turbine over heating, to where the tips of the turbine (inducer) actually become unstable and melt.

Replace the wheel. Little nics like that will destroy the balanace.

You can also have the wheel reground, but performance will suffer and the blades must be x-rayed before use if you want it to live.

[D-Dayve]

At 160k RPM, that's out of balance quite a bit and will cause it to wear out the bearings and seals until the turbine hits the housing, then you're really done. I've seen turbine wheels with less damage than that be out of balance enough to blow the turbo within a couple of weeks.