Turbo hotside swap - Balance required?

[VPrime]

Do I need to balance the turbo if I am switching the hotside? (16G)
Thanks.

[nctalon]

if your swapping the turbine then yes

[fwdmaster]

You dont have to balance your turbo if your swapping your hotside, the only time you do that is when you take your turbo apart or rebuild it

[VPrime]

Ok thanks guys

[jusmx141]

Originally Posted by fwdmaster

You dont have to balance your turbo if your swapping your hotside, the only time you do that is when you take your turbo apart or rebuild it

A common misconception.

Even when the turbo is disassembled it does not require a rebalance unless the wheels have contacted the housings, or the wheels require some type of machine work.

[delta448]

Just for clarification, are we talking about the turbine housing or the turbine blades and shaft?

I imagine that anytime a wheel is swapped you'll need rebalancing, ...at least I know I would want it.

[jusmx141]

Originally Posted by delta448

I imagine that anytime a wheel is swapped you'll need rebalancing, ...at least I know I would want it.

It is my understanding that all Mitsubishi turbos come from the factory component-balanced, meaning the wheels are balanced seperately and can be reassembled in any position and retain reasonable balance.

Think about it- would you rebalance a tire / wheel when you remove it to change brakes? Probably not....unless the tire is wearing unusually. Same is true for a turbo- if there is no damage to the wheels, there is no reason to rebalance.

[delta448]

Thanks Justin, that's really good info.
I was not aware that the wheels are component balanced from Mitsu, is this a standard practice for all turbo manufacturers?
And is the compressor wheel retaining nut balanced with the compressor or with the turbine?

[jusmx141]

Almost every compressor wheel and / or turbine shaft I've ever purchased has had balance markings in it from the factory....both on the backplate of the wheel, and on the front somewhere near the center axis. This leads me to believe that the wheels are balanced before they are ever sold.

I've been assembling turbos using this theory for years and I haven't run into one balance issue yet as a result of a new wheel being unbalanced when it was received. It makes sense that if both wheels are perfectly balanced individually that you would not need to balance them together....it would be a wasted step.

Regarding the locknuts- I believe they're balanced with the turbine assembly....however, I've only seen the 6-point hex nuts with balance marks. All of the newer replacement compressor locknuts are 12-point, and have a much better centrifugal balance because of this.

[Defiant]

Originally Posted by jusmx141

It is my understanding that all Mitsubishi turbos come from the factory component-balanced, meaning the wheels are balanced separately and can be reassembled in any position and retain reasonable balance.

I'd like to hear some backup on this before the thread keeps going. Seems that with all the turbine bolts that are mis-shapen by grinding, balancing is at least touched-up on the complete assembly.

Think about it- would you rebalance a tire / wheel when you remove it to change brakes? Probably not....unless the tire is wearing unusually. Same is true for a turbo- if there is no damage to the wheels, there is no reason to rebalance.

Yes, but if the tire's removed from the wheel, do you just mark the stem and re-mount with the old weights on the rim? Sounds like the same kind of shortcut.
And we still need VPrime to explain if he's talking about just changing the snail, or if he's changing the exhaust paddle-wheel as well.

[1992awdlaser]

I'm with Defiant.

You have to think about the whole assembly. What if the shaft wasn't perfectly balanced? How would they make up for this? By turning the wheels a certain way or by doing the grinding on the nuts/bolts that hold the wheels on. If you don't put them back on exactly the same way then it will be out of balance.

The tire thing doesn't make sense. You don't balance a wheel/tire combo with the brakes, axles, and all the other variables in mind that it will be hooked up to. You balance it so it is balanced and hope the rest of the system is fine. There is an exception of course. There is a wheel balancer out that balances it while it is on the car. I have never seen one of these in a shop though, only in ads. Not many places will have them.

[delta448]

This is exactly what I was thinking with my second post in the thread, and why I asked about the retaining nut specifically. I think there's a very good probability that the balance would not be perfect regardless if components were balanced individually.

How imprecise do any miniscule imbalances have to be if they are lined up less than 135-180 degrees from each other when assembled to cause premature failure? When you're spinning at 150,000 rpms, even a fraction of a fraction of weight difference will cause a tangential moment of inertia.

[jusmx141]

Originally Posted by Defiant

I'd like to hear some backup on this before the thread keeps going. Seems that with all the turbine bolts that are mis-shapen by grinding, balancing is at least touched-up on the complete assembly.

It's hard to find a turbo builder who will give you an honest answer because they make money off of balancing. Of course they're going to tell you that new parts need balanced....they're profiting from it!

I got an honest answer from my parts supplier about 4 years ago. I asked if the new parts I was buying needed to be balanced prior to assemble, and I was told exactly what I posted above....Mitsubishi turbo parts are balanced before they leave the factory. In theory (and according to what you've said in this post: Balancing a Turbo...) the parts can then be assembled in any fashion and be within balance spec.

This does not hold true for all turbos....Holsets, for instance, come from the factory with alignment scribes on the compressor wheel and shaft. On Holsets, the turbine wheel and compressor wheel are balanced as a unit and require alignment for a proper balance tolerance.

I have some new TD05H turbines and assorted new Mitsu 16G compressor wheels at the shop- I'll post some pics of the balance grinds for you.

[VPrime]

Sorry for the confusion, I am just changing the housing, nothing else

[Defiant]

Originally Posted by jusmx141

It's hard to find a turbo builder who will give you an honest answer because they make money off of balancing. Of course they're going to tell you that new parts need balanced....they're profiting from it!

A valid point. Whether it's a valid suspicion is another thing. I just don't know.

As for dynamic wheel balancing, it used to be a fairly common procedure- the little Texaco station I used to pump gas at and did some repairs (back when we pumped the gas, checked the oil and even checked tire pressures), we had on. Not really much to it, just a motor with a friction wheel and a strobe light, not much bigger than an upright vacuum cleaner.

[jusmx141]

Here we have two brand new TD05H turbines....I personally cut the sealing tape on both boxes so I know they weren't tampered with.

You can see in this photo the difference in the balance grinds near the center of the turbine wheel. One is a little more shallow than the other:


This pic shows the backplate where the majority of the balance grinding is done. This clearly shows the two wheels having completely different grinds:



The next group of photos compares 16G compressor wheels. The balance cuts are more subtle, but still present.

In this photo I'm simply showing the wheels next to the box they came in, and you can actually see permanent marker on the wheels in different places:


Here you can see the small cuts near the outside of the wheel....the cuts on the wheel in the left of the photo are slightly deeper than those of the wheel on the right:


It's very hard to see the balance grinds at the center of the wheel (near the shaft) in this photo, but you can see a little of the permanent marker on the opposite side of the wheel's nose:

[DSMunknown]

Thought this vid was pretty cool and decided to share.


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