the_glass_man

iTrader: (2)

I wanted some feedback from you single guys on Ball Bearing Turbos.
I'm not talking about the single bearing Turbonetics crap either.
While I know that the turbo's are supposed to be somewhat more reliable and spool a few hundred RPM's sooner.

I wanted to get get some user feedback and expert advice.

Any of you BB guys had any problems?
Is it worth the extra cost?
What are you going to do when it come to rebuilding time???

artguy

you know what Id say...its totally worth it.

for me...tis all about the response because of where i drive the car...Im in the LA area...traffic traffic traffic

j

suprfast

geez, i never really thought turbonetics was crap. well thats what i get for reading and not actually testing them. id like some info on the BB's too.
kris

1FooknTiteFD

To my understanding, BB turbos spool faster, are stronger, can boost a lot more and more durable towards compression surge compared to non-BB turbos. However I hear that they are very prone to heat and also are very costly to rebuild. Furthermore, a lot of single turbos noadays that are non-BB spool just as quickly as some BB turbos do. I have the apex'i rx6 kit. So far, I am very happy with the response and power delivery. I also hear that IHI BB turbos are very nice compared to other BB turbos(the RX6 BB is the same turbo used on honda indy cars and they boost upwards of up to 40psi!)

Brad

Yeah, for one race...then they throw it in the trash can and put a brand new one on for the next race

ThirdGenRX7

bah... minor details

87GTR

iTrader: (61)

I vote yeah!! im going for twin GT28's

glemmers

A few points that everyone needs to know about turbos and bearings.

1. Everytime a turbo spools, it passes through critical speed (natural frequency). Now, I have never seen a ball bearing turbo disassembled, but unless the have squeeze film bearings (high pressure oil behind the outer bearing race), which I doubt, there is no dampening to minimize the destructive forces created by the turbines passing through critical speed. The forces on the bearings at critical speed are generally 10 - 100 times higher than typical loads. These loads can very quickly destroy a bearing and turbine wheel. A journal bearing on the other hand has a natural dampening effect, and greatly reduces bearing and turbine stress at critical sped. In fact, most aerospace corporations (where extremely high MTBF's are typical), if operating super critical, or above the critical speed, journal bearings or spueeze film bearings are an absolute must.

2. Rolling element bearing have a finite life. This means that they will fail. For a propoerly desinged bearing, this could be tens of thousands of hours of operation, but they do have a finite life. Journal bearings on the other hand, have an infinite life. This is because there is no metal to metal contact once the bearing is spinning. If the oil is kept clean, journal bearings will last virtually forever.

3. Most often on high speed application, such as turbos, journal bearings are more efficeint than rolling element bearings. This means they will spool faster. Just because a journal bearing turbo doesn't spin when you blow air with your mouth at it doesn't mean it will spool slower than a ball bearing. Once a journal bearing is pressurized with oil and is spinning in the hydrodynamic region, there is very little drag. Oil sprayed at rolling element bearings, required to cool and lubricate, in fact can cause excessive power consumption and drag if not properly controlled.

4. Journal bearings can carry significantly higher loads than rolling element bearings for any given equivalent volume. Plus, the faster the shaft is spinning, the more load they can carry. Rolling elemnet bearings do not have this advantage, and in fact, the faster they spin, the higher the forces on the outer race created by the rolling elements. This forces increases proportional to speed squared The only way to reduce this is to run lighter weight elements, ala ceramic. Ceramic ***** have pros and cons which I won;t go into. The biggest con though is excessive cost. Thus the expense to rebuild these turbos.

With all the talk of ball bearing turbos these days, I thought people should be aware of the above issues. Use it as you may.

Glenn
'93 CYM

wptrx7

now i'm more confused than ever. choosing a single turbo is so much harder than i thought.

luigi

93redFD

how much sooner does a bb spool up????? I heared that it was ony about 500-600 rpm sooner.. If thats true then I would rather not have one for the cost.. i think the only way somebody knows how much sooner it spools up is have the same turbo but swich to bb option, not swich from a t51r to gt35/40!!

Greg

need a manifold?

Greg

Match a good build DBB Turbo with a Fully divided and well designed manifold and you will be ing