Quote:
Originally Posted by Coupes33
I agree Tim that the RB Classics were worn and definitely required rebuilding. It was on that basis that I sold them. Even with all that wear, they didn't smoke and still performed ok with 11.3s runs before removal. Your rebuild sounds like it has gone well. I hope they work well for you.
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Yep you were 100% accurate in your description of them prior to sale. I knew what I was getting.
Quote:
Originally Posted by Rob@RBTurbo
T1M,
Hopefully they machined your entire compressor cover for the wheel as the billet and OE contour profiles are not really the same. Even then not sure how the entire profile would align, it is likely it is not ideal and some areas would be out of tolerance. FWIW all of our 15T billet wheel setups are machined ONLY from fresh uncut housings, whereas any returned "RB Classic" 15T cast wheel housings we machine for only larger wheel setups.
Also it would seem your shop would've provided a VSR trace per each rebuilt turbo which specifies these results- care to share? Reason asked is that we have never heard of an assembly dynamic VSR balance level of 0.0184g as it just is not obtainable. Perhaps you have a decimal off however, that would make more sense. Either way you trust them and if not they are close and that is all good, but as has been discussed in this thread the biggest problem is the labor in it all.
About the balance check of the used unit- it really just depends on what the results were in actuality and also what the results of the unit would've been when new. As these units were from 2012 with the VSR function outsourced, we honestly do not believe they were ever even as good as the 0.389g even from day 1. We'd be willing to bet that most of our outsourced balancing, knowing what we know today, was probably closer to 0.5-0.9g max levels as that is what is very easily obtainable and "quick". At any rate if they got better over time, that is great but just not likely whatsoever. Likewise most of the aftermarket turbos we see, even new, are in the 0.5-0.9g max range. So not sure if we have some decimals off, or what exactly it is that has broken down with the communication path with your shop- but 0.389g max is actually really good for even a lightly used and balanced to perfection when new unit let alone a much older heavily used/tracked turbo that was likely never balanced to perfection in the first place.
Regarding the off-axis cover: Just so you know there is only about ~0.3mm clearance between the wheel and housing. So the point is if there was even ~0.3mm the off axis would not only be EXTREMELY visually obvious, more importantly the wheel would not even spin in the housing which obviously would be instant turbo death. So we believe there could be some "misinformation" or "miscommunication" going on with this entire point- we use high quality machinery/tooling and our tolerances for a part like this would be at most 0.03mm, MAYBE 0.05mm if there is some error such as debris caught in the tooling or perhaps too much clamping force is used... BUT even that would be visually noticeable to a trained eye when it comes to wheel symmetry. In short these figures would have to have been very largely exaggerated.
For reference here is a VSR trace of the last unit we balanced last night just to give you an idea of the actual values- FWIW anything around 0.1g is very very good.
Rob
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Stock covers were machined to use instead. If one side of the cover was machined out to centre the compressor in the snout I was told the tolerance on the other side was apparently too large. When I received the turbos from the original owner and was testing it the compressor could touch the housing I found it coils on one side but could not on the other, which seems to support the claim? Either way it was corrected and the builder was happy with the compressor to housing clearance after he machined the stock covers.
I didn’t ask for balance traces, just asked what the balance figures were. I know it’s become an N54 turbo marketing point now to give customers confidence in the items as it was common knowledge the classics and perhaps other brands turbos back in the day weren’t well balanced but in other markets where this was never a problem (GTR’s, Evo’s etc) they’re not commonly supplied with turbos.
It would stand to reason that if the VSR balancer reports to 5 significant figures and 4 decimal places, ie: it reports to one ten thousandth of a G, that the 3rd and 4th significant figures are within its measurement range and well above the limit of detection. Ie: if it can report 0.0614 and the 4th decimal place is accurate - the machine is sure it’s 4 and not 3 - the 2nd and 3rd decimal places, being one one hundredth and one one thousandth of a G, respectively, would be well over 2 standard deviations from the LOD and therefore accurate. Hence mathematically speaking 0.0184 G isn’t outlandish as it’s still reporting to one ten thousandth of a G. I’m not a turbo engineer or manufacturer though so I’m just looking at this from a math point of view.
In any case I’m happy with them and the given the cost, time and inconvenience of buying items like this out of the US especially when failures occur, I think it makes a lot of sense to utilise local companies where possible.