Will running oil pressure < boost pressure cause metal on metal contact in the turbo's bearings?
If I have 30 psi oil pressure, but 40 psi boost pressure, will the oil be forced out of the bearings because of the pressure difference?
Is there a 40 psi load on the turbo shaft at said boost level?

 

I wouldnt think so b/c there's no "boost" in the cartridge of the turbo.

 

From what I've read, when running a turbo with no charge pipes (not building boost) the oil seals can leak letting oil out. If this is true, It may be possible that running boost higher than the oil pressure can allow boost pressure to go past the oil seals. However, I have no clue how much pressure those seals are able to hold back. This is all speculation on my part, I'm just forming an idea based on what I've read. I don't think that 30 psi is your pumps pressure at 40psi of boost, so I'm assuming you're running a restrictor. Worst case, use an adjustable restrictor and turn it up a bit to even it out a bit.

 

thanks, isn't that what seals are for but i was refering to the tangential (or side to side) load on the shaft when boost# > oil#.

this q is related to a gas turbine project, where the boost is 40 psi, and the oil pressure is 30 psi
the turbo in question is a Garrett T4 .50/.70 internally gated.
i'm using an efi fuel pump for oil pump, max pressure = 30psi.
would 40psi - 30 psi = 10 lbs tangential load on shaft, physically squeezing the oil from the bearings?

 

I'd call garrett o that one I'm sure they have a spec on how much oil pressure you are supposed to run

 

i will be using charge pipes, with the same amount of load/backpressure on the charge air as in a car, eg... restriction caused by turbine backpressure and combustion instability
i just do not want the oil to be forced out of the bearings by the dynamic load on the turbo shaft caused by the boost pressure it is supporting, will this be a problem?
thanks

 

what kind of dynamic / tangential load is on a turbo shaft at its highest mass flow speed?
what are some factors that contribute to turb shaft load?
THANKS NIGLETS

 

anyone
JD AbaZ hotcheeks?