I’ve heard that some compressors have ball bearings in the intake side only and some have ball bearings on both sides. What is used if it doesnt use ball bearings? Is this worth the added expense? Just curious.
I’m no expert, but basically if ball bearings aren’t used, turbos use a floating bearing, relying on oil pressure for the bearing surface and for sealing, which is why having adequate lubrication is critical with turbos. This is why it’s a good idea to let the engine idle for a bit after running hard, to let the oil cool the bearings down and keep circulating until everything is adequately cool and slowed down. If you just stop the car, the oil stops flowing, and if it’s still too hot or the turbine is spinning too fast, then you’re going to cause oil coking on the bearings, which will cause the turbo to eventually fail.
The main advantage to ball bearings is that there is less drag on the turbo shaft so it tends to spool up a bit faster than non-ball bearing turbos. I believe BB turbos tend to last a bit longer as well, but I’m not 100% sure on that. BB turbos are still oil lubricated and cooled, so lubrication is still critical, but they will supposedly spool faster than conventional ones.
My understanding is that if you’re looking for maximum possible performance, then you’ll go with a BB turbo, otherwise a conventional one will work fine. BB turbos do tend to be quite a bit more expensive as well. One set of turbos that might be worth looking into is the IHI line (the ones they use in wrx’s), I believe they have at least one side as ball bearing, but are still I believe in the same price range as many conventional turbos, but I haven’t had the chance to look into them further, so that may just be some rumor or something.
I’m pretty sure all of this is correct, but someone please correct me if I’m wrong.
You were almost right 
The stock WRX turbo is actually a Mitsu 13g turbo. The same one that comes on the automatic first gen DSMs. But has an IHI style turbine housing to mate to the manifold.
The main advantage of BB turbos is a higher efficiency because of less friction. And fast spool (also because of less friction.) Cool down time doesn’t change. And actually, people nowadays cool their turbos way too much. When you cool a turbo for say 3 minutes, your oil pressure gets REALLY low, starving the turbo for oil. Even at idle it spins fairly fast relative to your motor, so it needs all the oil it can get. In a regular off/low boost commute, there is no cool down time needed. A few quick full boost runs let it cool for about 30 seconds. And if you’re really beating on the thing let it sit for a minute and 30. The BEST way to save a turbo is go easy (off boost) the last 2 miles or so from your stopping point.
EDIT: Personally, if you’re going with a low boost daily driver, stay away from BB turbos. Their slight increase in efficiency and spool time isn’t going to be needed.
Cool, thanx Formz!
::in best arnold voice:: no problemo.
formz, you say with a low boost application to stay away from BB turbos, they’re not needed. is this to save money or is there really no proven noticable gain at low boost with a BB?
It’s a little of both. running a max of 10psi isnt going to be anywhere near the max efficiency of either non-BB or BB turbo. So spending the extra money for a more efficient turbo is going to do nothing but waste money IMO. I personally would rather spend the money you save on the non-BB turbo and buy a little bigger intercooler. But that’s just me, and everyone hates my opinions
what is the typical cost difference. I’m not really interested in purchasing a turbo, but am just thirsty for knowledge - thought it might be worth mentioning
depends on the vendor. usually I think it’s around 3-$400.