Turbo balancing

[Nathan79]

Hello all,
Once a turbo (td04L-14T) Is taken a part, Is it necessary to have the turbines reassembled EXACTLY like they were before disassembly?

As you can probably tell. I didn't mark the turbine orientation before teardown & rebuild.. Reason for rebuild was during a cylinder head install , I noticed plenty of caked oil all over turbo & figured "while I am here, might as well reseal it"...

Thanks in advance for any input
Nathan

[SuperHerman]

Yes. For proper balance the unit should be reassembled in the same position as it was when balanced from the factory. The turbo spins at incredibly high speeds so balance is important. Even more so than your car tires.

With that said, I have read of people that made the same mistake you made just put it back together and had no problem (at least that is what they claimed).

A turbo has three basic parts, the turbine wheel and shaft, the compressor wheel, and the cartridge assembly. The cartridge assembly is irrelevant for balance (although it does contain the bearings that would absorb any imbalance). Assuming the compressor wheel is a highly machined part and pretty much in balance, just like the turbine wheel and shaft, balancing requirements should be minimal.

If you look at your turbine wheel and shaft you will notice that the end (fixed nut end) is ground a little bit. This is done to balance the unit. In a perfect world, the compressor wheel will be true and its position would be irrelevant. Same holds for the turbine wheel and shaft. Well, as the factory balances the unit by grinding away some material, it is clear it is not perfect. You can look at your unit and see how much is ground off and make a decision based on this.

You have four options, 1) buy a new complete cartridge 2) send the assembly to be balanced, 3) buy a complete used unit and pay attention, or 4) bolt it back together and drive the car.

I personally have never put the unit back together exactly how it was from the factory, even when I had the turbo balanced. Close, but not exact. These turbos have been fine and when they left me some had over 15k of miles after the rebuild. My educated guess is if the unit is not perfect it will not last as long, the internal bearings and sealing ring will wear faster. I don't think the unit will explode before it starts to fail and smoke. You should have some warnings - pay attention to them. Now if you are going monster boost that is another story. Stock I think you will be fine.

Were it me, I would put it back together and drive the car. If the turbo starts to cry I would take it apart again, rebuild and have it balanced or buy a new cartridge. It is your time and money. The downside is not that big a deal. I don't see how shaving off a tiny amount on one end really does that much, but if you want to get to 250k it makes sense.

[jonesg]

I bought the complete balanced cartridge from ebay, balanced to 140K rpm and ready to fly. $185. Shipped from the UK.
Noticed the grinding on the end nuts matched end to end, figured it was for balance and reference mark.