I have one coming in a few days. I will be getting tuned on MS109 at the end of the month and I will report back with what it can do.

 

Anyway a BB is the way to go, you want it for sure.

 

I have spent countless hours swapping parts to see what works and what doesnt. if you dont want to gain knowledge from that experience its no skin off my back. I did the swapping for my own knowledge gain.

in the end the reason they say there is a 15% gain is because outside this forum the term spool is used to describe both spool and transient response. when you group the two terms together the statement works.

I could give you a more technical reason why there is no spool gain but dont have the 10 minutes to give you. if you want to go on believing there is a spool gain because garrett said so feel free to do so.

 

Exactly right. They just used a word play and bloated stats to convince you. Their 15% was probably the best of 100 trials where the other 99 was a meager 7-10%.
Then you toss in the common reference of spool and you' e just been fooled.
I dont exactly agree that they are exact. Anytime you remove friction it will increase accell. However it wont be remotely noticable so for arguements sake i will stick with they spool the same.

 

So while initial "spool" isn't any better with a bb turbo, the transient response is?

 

Exactly right. They just used a word play and bloated stats to convince you. Their 15% was probably the best of 100 trials where the other 99 was a meager 7-10%.
Then you toss in the common reference of spool and you' e just been fooled.
I dont exactly agree that they are exact. Anytime you remove friction it will increase accell. However it wont be remotely noticable so for arguements sake i will stick with they spool the same.

 

That Garrett quote to my knowledge was published when their Ballistic line of Ball Bearing CHRA's were first released which means they would have been comparing it to 40 year old journal bearing turbo technology and probably a p-trim or q-trim wheel which would have been larger than the GT30R and 35R's they would have been comparing them too. So that number is skewed by a lot and you'll find if you take a like sized turbo in jb and bb and test them you will never see 15% better initial spool response in real world testing. You might be able to replicate it on a test stand with some "wizardry" but put it on a car and you wouldn't notice.

The reason BB offers better transient response is that it doesn't slow down as much when you let off the throttle it retains more inertia (shaft speed) so that when exhaust is reintroduced at a high rate it doesn't have far to go to reach it's target shaft speed.

-Michael

 

100% correct. You are using a known force to accelerate a known mass (The Engine blowing into the Turbine) You can't magically accelerate something faster with the same force unless you change the mass of the turbine wheel itself which Mitsu had done on the TME turbo. It was good for the VIII's but I have read that the IX's TME turbos start to break when pushed beyond stock turbo limits.


Anyways, get a BB, different ball game in around town driving, not even a discussion. Drag racing when the turbo is spooled it stays so for a reasonable amount of time between shifts so you are in boost longer.

Initial spool-up? Not an ounce of change.

 

What about the friction a JB provides Vs. a BB? Is there anything in there to hurt spool-up in a 100% completely healthy turbo?

 

Probably this is OT, but the question about frictional losses and the lower friction of ball bearings vs. Journal bearings, reminded me about my daughter's roller hockey skates.

The wheels on those skates didnt originally come fitted with ballbearings. So, we used to swap out the OEM wheel bearings for aftermarket, replacement, ceramic ballbearings.

I just remember the night and day difference in how the ballbearings allowed her to sustain her coasting speeds when skating. With the ballbearings she could effortlessly sustain her coasting speed whereas, by comparison, with the non BB wheels she could not sustain speed while coasting. This kinda jives with what FP's Michael stated above.

 

This seems like the same question just asked a different way, but the answer is still no. Frame for frame there is no difference in initial response going from JB to BB.

-Michael

 

I think it's well enough on topic as it applies to the mechanics behind it.

If you were to push your daughter up to 5mph the initial force required would be the same from bearing system to bearing system though. Unless you changed the weight of the person, incline, head wind, etc.... then the intial force would remain constant.

-Michael

 

Boost threshold is not changed regardless of bearing type is that what we all agree upon?

 

Correct.

As long as by boost threshold you mean the point where there's enough exhaust gas to spin the wheel quick enough for enough air to be generated by the compressor wheel to fill the intake tract of the vehicle and see positive manifold pressure.

-Michael

 

Would the rate of spool be identical on two identically configured turbos differing only in the bearing type? One of the two turbos spinning on journal bearings whereas the other spins on ball bearings.
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