Thanks Michael. I am just trying to get a clearer understanding in my own mind, of the rotational advantages of the ball bearing center sections as opposed to the older journal bearings . I appreciate your weighing in on the topic as you are helping to clear up some of the myth and assumptions surrounding this subject. So, thank you very much and thanks FP.

In the first place, I am not totally clear on the terminology. To what extent are the terms that are being used such as, rate of spool, turbo spool, spoolup, initial spool, threshold, transient response, synonymous? I was not real sure so I mentioned the term, "rate of spool". More exactly, does rate of spool, mean the same thing as the less precise term, " turbo spool"?

I appreciate the discussions on frictional loss, inertia, shaft speed, and etc. Moreover, I appreciate everyone's, and especially, but not limited to, High PSI, 94AWDCoupe, FP's Michael, Ratty, Joseph 143, ctfpevoVIII, GTijoejoe, blackenedwings, evo unknown, BDecker9, and jerdeitzel's, et al, knowledgeable and enlightening commentaries and questions. Thanks Guys! Enjoy a Happy Easter everyone!

 

Well I've been thinking about boost threshold and while we're here:

Frictional losses require energy to overcome so to keep the shaft speed at say 130,000 the ball bearing would be more efficient correct?

So does it go implied that the turbo the ball bearing would be able achieve the target shaft speed with slightly less energy than its jb counter part? By roughly the same energy that jb robs?

Theoretical lower boost threshold : amount of energy required for target boost level

Does that seem logical ? The difference would have to be there, but it could be just a matter of splitting hairs? 25 rpm?

 

Boost Threshold - The time it takes for the turbo to go from idle (not createing boost at say hwy cruise speeds) to creating positive manifold pressure so from zero to 1psi.

Transient response - How long it takes the turbo to recover from a shift and create positive manifold pressure.

Lag - The time it takes from boost threshold to reach target boost pressure. Some people say when it "kicks" in but it's better to think of it in a more quantifiable way.

Spool/Turbo spool/Spoolup/initial spool - All are terms that I figure people would use to describe boost threshold but they may also mean lag. Either way this is a non technical term and we'll omit it for this discussion.

In terms of comparing "spool" characteristics we should stick to talking about Boost Threshold. Want a good physical demonstration of journal vs. ball bearing go to your local hardware store and go to the tool boxes. Find one that uses conventional bearings and another one that uses ball bearings. Pull open a drawer and see if you can tell the difference in force required to open the conventional one vs. the ball bearing one. You'll notice they both require the same amount of force to open. However if you remove the power source the ball bearing will continue to move while the conventional one does not. Of course this is all heavily dependent on weight of the drawer is the conventional one properly lubricated, yada yada yada but you get the idea.

Turbochargers are the same way as the weights of the wheels are identical the force to move them is the same. Only once the force is removed (exhaust gasses stop flowing) one will continue to operate at a higher shaft speed. Which is why ball bearing offers better transient boost response.

Now lag is a bit different but still applies in a perfect world where conditions are EXACTLY the same you won't know a difference between JB and Ball Bearing. Basically to put it in a nutshell the parasitic drag effect the JB's have is only an issue when the car goes into a transient state. Otherwise it creates no adverse effects during boost threshold or lag.



When speaking in terms of the sort of forces we're dealing with there would be no more measurable force required to keep the journal bearing turbocharger at a sustained 130,000RPM. Is there more force, on a extremely small scale I'm sure there is but in terms of operation and longevity, engine out put, heat etc..... it would be impossible to measure and definitely wouldn't negatively impact the performance of the turbocharger.

Well if you want to get down to the MS level I'm sure there's a difference but put it on a car and operate it and there will be no difference. The BB might reach it's target shaft speed 5MS before the journal bearing does if you were to put them on a test bench. Again though real world application there isn't an ECU or Dyno on the planet that could tell the difference, especially not a butt dyno.

-Michael

 

Awesome!

 

The TME turbo was only offered on the TME. The faster spooling variant offered on the 8's had the normal Al comp wheel, but had the TiAl turbine (lower mass) which decreased spool (lag) time. The TiAl turbine is denoted by the addition of the letter 'A' after TH05-HR in the code stamped on the comp housing. What they changed on the 9RS turbo (there was 2 made the '570' and then later '571') was to add a magnesium compressor wheel paired to the TiAl turbine. The hotside is also made from A3N material (vs the standard F5) for better stability at high temps. The rotating assembly is extremely light and as a result this turbo is the fastest spooling MHI/oem turbo. Transient response is also excellent, not due to reduced friction/higher shaft speeds as with the BB centers but due to the lower rotating mass. The 570 variant experienced comp wheel failures when boost was increased from stock. The 571 variant is fine up to ~1.7 bar and many have run this for 5+ years safely.

 

Thanks!!! Great post.

Now for someone to make one BB and add an 80MM intake!

 

Thank you... I believe i said this a few days ago. Glad someone if finally approaching this logically...

If you remove friction from a rotating mass, the energy required to reach a given speed is less, to maintain the given speed is less, and therefore the amount of time to reach that speed is less.

Whether its noteable in this scenerio is a different story. But physics says they spool at different rates.

 

I get lost a bit when the discussion goes conceptual. I have a limited capacity for the theoretical. Sure I'd like to understand but it ain't gonna happen for me.

The FP Red, even in JB format was a great turbo for its time. In fact, you could say that it was a landmark in terms of the evolutionary development of higher flowing stock appearing 16G based turbos. In BB format The Red's legend lives on and is still cutting edge. But, time marches on and eventhough the JB Red was a cutting edge turbo just yesterday, today it is no longer even manufactured by FP. In fact, FP no longer will even repair or rebuild the poor thing, will they?

 

There's rally teams in the UK that do BB centre evo 9 turbos you could try and track one down. Not sure if the 80mm intake is needed given the CFM they move and if it's antisurge it will slow spool.

I love in rally onboard cam hearing the turbos hit full rpm in such an incredibly short time span, that kind of response would be wild to drive. The 9RS is a blast, the power/tq is just so immediate, it doesn't make any more than a normal 9 turbo up top, but when you're on/off the throttle or find yourself down around 3K when you've braked for a car/road hazard the response and early torque is really fun. Due to their response and better low end, they're hard to beat on short course stuff.

The FP guy said a slight difference may be measurable on a bench, as you say a slight difference *should* exist, but in a car, would you be able to tell the difference? No ones going to feel 25rpm.

 

to the OP....


why not get a BB Green or something along those lines if you wanted more torque?

 

Whether or not the IX RS turbo is the "fastest spooling" of the 16G variants due to the lower rotational mass of its lighhtweight Magnesium compressor wheel is at least open to debate. Sure, if you base the conclusion strictly on relative rotating mass then you could probably assume that the IXRS would be the fastest spooler. But, there are other factors aside from relative wheel mass that should also be included in the comparison.

 

For those who want to do a little more reading about the effects of bearings on turbo performance check out these links:

http://www.turbobygarrett.com/turbob..._ball_bearings
http://www.motoiq.com/magazine_artic...-bearings.aspx

I worked at Garrett for a little while circa 1999-2000 and was involved in the ball bearing development. The differences between the testing done internally at Garrett and what FP might see is the size of turbo relative to engine. No Garrett customer specifies a turbo anything like FP; the engine displacement vs. turbo will always be much closer in terms of flow capability. To these ends power loss to the bearing is a much larger percentage of overall power required to spool the turbo, and thus the effect of bearing frictional drag is much greater.

I'm in no way knocking FP's matches, they are appropriate for their customers. What I'm saying is that you'll never see an OEM selling a single turbo 500whp 2.0L as it'll never meet a zillion of their performance specifications. Really, off the shelf Evos have pretty big turbo's for an OEM. Bugatti Veyrons are 1200hp, 8.0L, quad turbo jobs -> 4x 300hp, 2.0L, single turbos.

 

can we go back to the original question of which turbo will spool faster?

the 3b or the red