Hey guys,
I'm chasing some info on turbo's, my main question is how realiable are bush bearings in a turbo??? I know ball bearings are far superior i their reliability. But I was wondering how do bush bearings take to hi boost?? As in up to and including 18psi???

I know ceramic turbines don't like anything above 15psi in any turbo as they tend to fly apart.

But say a T25 that has been rebuilt but with a steel turbine with new bearings, still bush though. How well could this turbo hold 12psi in everyday use?? How about 18psi???

I know there are many factors to this quesiotn I'm just curious is to how realiable bush bearings are.


Thanks for anyones help

Damo

Well i ran 18psi thru a T03 for a year all day everyday and it never missed a beat.

as a member of the datsun community - anyone on here should realise that just because there is something newer, doesn't make the product replaced any less reliable or obsolete.

in fact, many a time the product replaced is superior to the newer product.

BB turbos are a great thing. faster spool time, cooler oil temps and a more stable shaft all equal better reliability.

that said, bush bearings are cheap(er) to rebuild and still provide equally reliable operation if you warm them down correctly - regardless if spool up time isn't as fast or whatever else the marketers will have you believe.

18psi on steel wheels isn't an isue as long as you run a butterfly bypass valve - or "blow off valve" as some like to call it - in a blow through situation. or you'll be spinning the compressor wheel off the shaft thru flow reversion in no time.

As pro-240-c said, you have to watch your oil temp more closely with bush type bearings. With these bearings it's all about oil pressure, you can certainly run high boost, but this creates excess oil particle friction, so to do this & maintain any sort of longevity out of your turbo you really need to be running a high pressure oil pump & an oil cooler & you should be very careful when switching off the motor after running at high rpm, coz if the turbo contiues to spin after the oil supply is lost.......bang. Hence the advent of turbo timers.
So to answer your question - a T25 with a metal spool should be o.k for 12 psi as long as you idle your engine down after going hard, but any higher boost & I would be looking at high pressure oil pumps etc.

just for the record my bush beringed ceramic wheeled turbo in my stock standard r32 skyline runs close to 12 psi on standard boost

Thanks for your input guys,
I think the main question I have is whether or not a steel turbined T25 could withstand 18psi, not every day but in the case of it being pushed that hard would it handle it or fail after a few mins???

Thanks again

Damo

I have seen a T25 running 15 psi constantly as a daily driver.

I have also seen a T25 running 20 psi but it had a 360 degree thrust bearing and left hand thread shaft for the compressor wheel.

An interesting item he runs is an American Accusump oiler system to supply oil to the turbo after shutdown. Works well.

The early CA18et engines ran t25s plain bearing none ceramic etc etc etc

that is a single cam CA

The critical factor that I belive that most people miss is 18psi on what engine if its a 2ltr, the turbo might have to spin at 200,000 rpm to maintain this boost
On a 1.5 that might only require 150,000

same as the 15psi cap on ceramic turbos

If a CA18det ceramic flys to bits at 15psi the same turbo on a VL turbo might fly to bits at 10psi

Surgestion look at the factory power figures that the turbo you choose produces and use this as a guid to how much power the turbo can reliably handel

Quote: Thats an interesting idea. From memory, the Accusump system was originally intended to pre-oil the engine prior to startup. Providing oil to a turbine that is spooling down sounds like a better idea.