BB turbos vs. Journal bearing turbos

[beachbum_jon]

Besides the obvious price of a bb turbo, is there any other disadvantage with them compared to a traditional journal bearing? The turbo I am thinking is a 3788 BB Garrett, which i beleive is in the neighborhood of a 64/73/14. Also looking at the 4288 to run wit twins.

Thanks.

[DaveH]

Generally the ball bearing chra's are not rebuildable, so if something happens to the bearing system you replace the whole center section. Also, they are usually water cooled where the journal bearing aren't, so you need to run coolant lines.

[revolutionz_s13]

from what i've read though, and I might be wrong, is you dont need water lines, they just help prevent heat soakback and coking of the oil after shut down, which can also be prevented with a turbo timer. while the car is running, the oil does all the lubrication and cooling of the turbo. did i understand that right?

[zbrown]

I belive that to be the case for a standard journal bearing setup, but I think the coolant for the ball bearing units is more critical

[revolutionz_s13]

I didnt think most journal bearings even have the option for water lines? Either way, I guess im gonna be the test dummy cause I'm not gonna run water lines with my GT3076R. Just a turbo timer.

Taken from Garrett turbotech http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
Following a hot shutdown of a turbocharger, heat soak begins. This means that the heat in the head, exhaust manifold, and turbine housing finds it way to the turbo’s center housing, raising its temperature. These extreme temperatures in the center housing can result in oil coking.

To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking. The water lines utilize a thermal siphon effect to reduce the peak heat soak-back temperature after engine shut down . The layout of the pipes should minimize peaks and troughs with the (cool) water inlet on the low side. To help this along, it is advantageous to tilt the turbocharger about 25° about the axis of shaft rotation.

It seems to me that the water does absolutely nothing while the car is running, just after shutdown.

[DelSlow]

Journal bearing does have the option to run coolant lines. All depends on the manufacturer. In some cases the coolant lines have some additional benefits; look at Matts four door...thing heats up in like a block because of the turbo's coolant lines.

[kylush]

As I also understand it's important to run some type of restrictor in the oil inlet line to a bb turbo because the center section can't handle the higher pressures that a journal bearing center section can.

[SPANISH-RICE]

Alot of bb turbos have the restrictor built in. External restrictors are usually needed for journal bearing turbos.

[revolutionz_s13]

I think that depends on who you get your turbo from. mine did not come with a built in restrictor, I had to get one.

[DelSlow]

revolutionz_s13;318553 wrote:
I think that depends on who you get your turbo from. mine did not come with a built in restrictor, I had to get one.

Duh..