I was curious if the orientation of the turbo, specifically considering the orientation of the axis of the rotating assembly relative to the ground, mattered in terms of maintaining balance.

I should think that it doesn't for a number of reasons. . .the strongest being that when one climbs a hill, the turbo is no longer in the same orientation relative to the pull of gravity as it was on flat land. Being that hills exist, it would be a poor design to have one that its orientation relative to level determines it funcitonality. Another reason that I think it doesn't matter, is that I've never heard of anyone advising against any specific orientation and I've seen plenty of different orientations.

Now, the reason that I ask, is that in handling my BRAND NEW GT42R, when placed such that the axis is pretty close to being level and the rotating assembly is spun by hand, it does so unimpeded. however, if the angle between the axis and level is changed, and the rotating assembly is spun, at some angles, an ever so slight mechanical whisp is heard, indicating that VERY minor rubbing is occuring.

The only thing I can think, is that it is caused by the fact that I'm spinning it at ~100 RPMs by hand, and it's balanced for ~100-1000 times that speed, at which point the centrifugal forces keep it centered in the housings regardless of orientation relative to anything else.

Just wanted to ask to see what people had to say on the matter in case I'm being retarded and overlooking something

Thanks
ryan

 

Orientation has nothing to do with balance of the rotating assembly. Your turbo should always be mounted as close to LEVEL as possible, and it has nothing to do with the rotating assemblies balance or lack of. Its the oiling system, its gravity drained, therefore it needs to be mounted close to level for proper feeding/draining. When you spin the turbo up by hand level it'll spin slightly faster and longer, when you hold it 90* out or plumb / square relative to the ground, the weight of the rotating assembly is now causing a thrust load instead of the only axial load when level (and only being spun at low rpm by hand). This is normal, as your inducing thrust load via gravity, when the turbo is on the car and actually making boost it'll be seeing this thrust load any way (a lot more load then what gravity is making). And things aren't balanced for certain RPM's. Once things are balanced, their balanced PERIOD. Theres more accurate or precise balancing which would lead to less vibration which means higher RPM's can be run up before wobble. In other words, something that is balanced for 2X RPM's will be just as balanced at 1X RPM's ignoring harmonics. Now this does not mean that the balancing is accurate enough to be run at 3X RPM's though, but if its good for 3X RPM's, it'll be good to 0X. You’re over thinking things lol, slap that GT42 on and let'er rip!

~Mike..........

 

So what of the orientation dependant rubbing that I hear? I guess that is really the heart of my longwinded post, what causes that?

I have no intention of mounting the turbo in some crazy fashion, I know that the oil is gravity drained, but good looking out.

just wondering. Thanks for the reply
ryan

 

Other than trying to keep your drain within 15 degress or less of vertical, you should try and keep the turbo as level as possible.

-S-

 

paranoia is born of simplicity. and maybe i'm oversimplifying, but if it's brand new, like you said, then isn't that probably just friction since the bearings haven't been primed yet?

 

Well, like I said, I'm probably just being dumb, but I can't understand why the rubbing noise is orientation dependant.

Thank you Zero R for your quantifiable advice. Sincerely.
ryan

 

Didn't you read my post??? You hear it only when its tipped over 90* from level because the rotating assembly has mass to it, and when its orientated like that it gives it a THRUST LOAD that normally isn't there when its sitting level and not spinning FAST producing boost. ITS NORMAL for some drag and a slight noise to be heard, however its not normal for wheels to contact housing. Its most likely just the thrust loads on your bearings your hearing / feeling in your fingers as you spin it when its tipped over.

~Mike.............

 

wow . . . i need a cup of coffee. . .

I misunderstood your post when I read it the first time. I just went back and reread it and it is clear that what you just said is what you said a couple of hours ago.

Sorry about that, brainfart. . .

Thanks, however from memory, the angles at which the noise is produced aren't entirely consistent with that.

I'll approach it much more methodically next time I play with it and post again. Previously, I just observed it and never bothered forming a real hypothesis and then testing it. Being a bum/stretched for time lately.

Thanks again
ryan

 

Is the turbo new?

If not, I would first make sure that what you are experiencing isn't wheel rub. Thrust bearings shouldn't be too loud. Try grabbing the wheel and pulling it axially while spinning it to feel if there is indeed rubbing.

If it is a ball bearing turbo, there isn't a thrust bearing, so you really shouldn't hear any whisping sounds when it spins.

Kevin

 

The turbo is a brand new GT42R, so yes, ball bearing.

I will be stopping by the workshop today after work, so I'll provide a much clearer description of the exact phenomenon after that. I'm sure that everything is fine, and that I'm just being paranoid. . .the turbo is brand new, and from a reputable vendor. If there is a problem, I'm sure it can be cleared up in short order.

Thanks for chiming in CarbonR1.
ryan

 

Make sure both the compressor and turbine housings are fully seated and tight when spinning the wheel. If one or the other is not fully tightened down, you could get a slight wheel contact.

~Mike..........

 

Very good point!

Anthony