Turbo Bearings

[fabrisuzu]

I've always wondered what the difference between the ball bearing turbos and the non ball bearing turbos. We'll yesterday i found one that might make a difference to some people. According to a basic model for life of a bearing, the difference between normal roller bearings and ball bearings is quite a bit. The over all equation has several different factors but the difference is that if its a ball bearing you cube part of the equation (makes a big difference) while if its just a normal roller than you raise it to the 0.3 . Now i totally understand that this is just an equation, and that there are a lot of other variables, but given two exactly same situations, a ball bearing turbo will last a lot longer or will hold up a lot better under higher loads than a non ball bearing. The real reason for this post is to have people fill me in on this as well because i dont know if i can totoaly believe that. I mean if this does hold true there would be no reason to no run ball bearings because you can use much smaller or less of them to have the same effect/life. What do you all think about this? I am looking at eventually buying the peak boost top mount kit but i dont know if i would trust anything but a ball bearing turbo now. Any thoughts?

[the converted]

That's all fine and dandy but there are no roller bearing in "normal" turbos. They use a journal bearing which is pretty much the same as main and rod bearing inside your bottom end. So it's a spinning shaft, thin film of oil, and a soft metal (brass?) bearing surface.

I was looking through my machine design trying to find some sort of correlation back and forth between the two and of course it says that only real world testing will provide any measurable results. Judging by all of the late 80's early 90's turbocharged cars with journal bearings I don't think there is any issue with them.

[fabrisuzu]

Ya that is very true. I mean in a perfect world neither would fail, it was just an interesting tid bit i stumbled upon.

[Hijacker]

The journal bearings in a turbo are a floating bearing design, unlike the bearings you find in your motor. This means it will spin independently of the races holding it in place.

The major pro of using a journal bearing turbo is maintenance. Rebuilding a bushed (ie journal bearing) turbo is easy and cheap, where as with a ball bearing turbo, you have to usually replace the center cartridge, as the ball bearing is pressed into the center housing. I can buy a rebuild kit for a bushed turbo for around $100. The cost of a new CHRA for a T28 style turbo ranges from $600-$900.

I've seen turbo volvos clear 200,000 miles without requiring a turbo rebuild, and they're bushed turbos. Turbo life expectancy is much more dependent on use and power output. The formulaic lifespan of a turbo will never be actualized as you will kill a turbo due to abuse long before old age will take it.

[the converted]

The major pro you will kill a turbo due to abuse long before old age will take it.

Come on, none of us on here abuse anything.

[fabrisuzu]

Nice thats pretty cool too. I mean ive been looking at lot at the full race top mount kit with twin scroll bearing and it makes pretty good power and such. Its weird how much of a price difference the rebuilds are, but just like anything else the more to replace the more cost involved. Good to know.

[Hijacker]

Twin scrolling isn't a bearing solution, btw. Twin scroll refers to the seperation of the exhaust flow going over the turbine wheel. Mitsubishi is well known for doing it on the Evos.

Most modern turbos use a center housing utilizing dual ball bearings for stability. Which is probably why you have twin in your head.

[fabrisuzu]

haha wow well thats good to know. I thought that it used twin scroll bearings. Well i thank you for correcting me b4 i made a huge a$$ out of myself. Thanks!

[nzmoman]

and these posts are the reason why I am wanting to ditch the ball-bearing. I know that many of us will build a car and we don't put many miles on it before we sell but I drive the crap out of my s14 and when its time to have more power I want to be able to rebuild that sucker because it may become a track car someday and I hat seeing even the lowend prices on used turbos vs the cost of getting a new rebuild/refresh kit.