New garret bb turbo noise ??
Discussion
After running out of holsets to try I splashed out on a new gt3076 with billet wheel and metal bearing cage . Carefully primed it and made sure everything was spotlessly clean when building it up . Spun over on the starter with the drain pipe off to make sure it was flowing and run it for a couple of mins . Thought I could hear something through the air filter which is at head level so shut it off and could hear a noise as it spun down .
Can't feel any notches as such but this doesn't sound right to me especially as it cost the thick end of 2k
http://youtu.be/25rShhuBUnw
Can't feel any notches as such but this doesn't sound right to me especially as it cost the thick end of 2k
http://youtu.be/25rShhuBUnw
mighty kitten said:
I found another clip on YouTube with the same noise and a few comments saying the same thing . I took it off and syringed some light oil through onto a white cloth and its spotless . Il see what Owens make of the clip in the morning before going any further .
Get it on the car and get it boostin !It's worth noting that the "ball bearing" in a turbo charger is really quite unlike say a ball bearing for a slow speed (<20krpm) shaft for example. Because the peripheral speeds are so high for typical automotive turbochargers (shaft spinning at ~180krpm) the ball bearing system used is almost a hybrid of a dynamically lubricated plain bearing and a ball raced bearing. It uses significantly larger clearance between the rolling elements and their races, in conjunction with a controlled oil film provided by the lubrication feed. That lubrication feed should supply enough oil to allow a dynamic film to build up, supporting, centering, and crucially "damping" the orbit of the shaft (the shaft doesn't actually just turn purely about it's mass centroid, it actually orbits around that point, depending on rotational speed transversing several different "modes" and orbital paths. This is why having "just enough" oil is quite important for a ball bearing turbo, where too much can actually harm the bearing system performance. Basically, you need just enough to cool the bearing system and replace the oil centrifuged out of the races, but no more.
The upshot of all that^^^ is that when there is no oil, flow (engine off) the bearing system of the turbo can feel really quite horrible to the "spin it with your finger test. Because there is no preload in the bearing system the bearings can feel both "loose" and "notchy" at the same time, as tiny irregularities in the form of each rolling element and the races create discontinuities in the drag and orbit.
The upshot of all that^^^ is that when there is no oil, flow (engine off) the bearing system of the turbo can feel really quite horrible to the "spin it with your finger test. Because there is no preload in the bearing system the bearings can feel both "loose" and "notchy" at the same time, as tiny irregularities in the form of each rolling element and the races create discontinuities in the drag and orbit.
blade7 said:
I believe when converting to a BB turbo a restrictor is often needed in the oil feed.
Most such turbos now come with the restrictor built inI'd say a lot of the noise is also down to the fact tge balls run in the inner/outer shell with no cage, so the balls do move about and can contact each other.
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