Originally Posted by

**ashtonsser** **Spool time is based on exhaust energy, weight of the shaft its having to turn and restriction in the shaft. **

At any given rpm the exhaust energy is the same given a journal bearing vs BB turbo of the same size.

So take two identical sized turbos one journal one bb, The bb shaft is only going to take very very slightly less energy to turn the shaft compared to the journal bearing.

Here is where the bb shines. Gear changes and respool as the journal bearing shaft will slow down significantly faster while the bb will retain alot of its shaft speed during shifts making respool very quick compared to the journal bearing.

Thats about the only advantage to a BB turbo really.

**Its been dyno proven that there is only a 2-300rpm difference in spool time given the same size turbo just one being a journal and one a bb. Again proven.**No no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no.

That is not how boost onset works. That is not how turbo lag works. That is not how turbo bearings work.

It might be time for my to make another new thread...