pauld

So...I thought about this today as I was glass bead blasting the turbine wheel on my garrett T3 I'm rebuilding for my b18a....Many people say that you dont need to re-balance the turbo if you carefully mark the compressor wheel before dissasembly, then line it back up....etc. Others argue that you should balance it always....blah blah
My thought is that on a turbo with any mileage on it, there is such a buildup of combustion by-products on the turbine wheel, it couldnt possibly be anywhere close to "well balanced", yet it still works.....Also, as I noticed today, most of that buildup is towards the outside of the wheel, where it should have the LARGEST impact on balance... And the deposits CERTAINLY arent even around the wheel. So is it possible that around 90% of factory (or otherwise) turbo'd cars are running around with turbos that are nowhere close to being in balance???? makes me wonder about the whole "rebuild balancing debate"
Any opinions on my little geek thought?

shortyz21

deposits ive seen were quite even...

u spin anything at 100 000 rpm and if its not balanced its gona expletive the bearings in an instant.

pauld

True,100,000 rpm is alot of speed, but it seems that it wouldnt be very likely that all the weight of the combustion deposits could possibly be so evenly dispersed that it wouldnt change the balance of the wheel....Wonder if any of the Pro turbo rebuilders have ever put a well "deposited" assembly onto their balance machine and spun it up just to see how far out most wheels really are....after all, most wheels have quite a bit of crap on them, right out where the centrifugal force should be making the TINIEST imbalance a really big deal according to many people...

pauld

Actually, I just remembered another little tidbit to add fuel to the balance/no balance debate. Back in the day, I seem to remember old-school guys actually changing out the comperssor wheel on their turbo setup (marathon boat racing), and DID NOT change anything else...just took off the compressor wheel, bolted another on, and off they went, boosting away on a 900+ HP CHEV big block racing motor ....No way to balance that, yet it worked...I also seem to remember reading somewhere (VERY old turbocharging book) that because most turbos use a full floating bushing,(oil inside and outside the spinning bearing surface) balance and harmonics aren't quite as critical as many may think, but I'm not some mega turbo expert.....

da_dude

I am going to using a t04E compressor on my garrett t3. No balancing at all. My cousin also did the same thing too with a t04b compressor on his t3 turbo. He been running that turbo for about a good 3-4 years now with no problem. He just recently took it off about a month ago, but his younger brother is throwing it on his car.