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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Turbocharger VSR Balancing information-



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      11-22-2014, 06:40 PM   #1
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Turbocharger VSR Balancing information-

All,

It has came to our attention that there is some confusion in the arts of turbocharger balancing methods so we felt we'd take a moment to share our viewpoint on VSR balancing. We will not be discussing intricate details in the arts of proper VSR CHRA balancing, but wanted to give more of a high level overview of what it entails.

Being concerned about providing customers the best possible quality in each and every turbocharger we took delivery of a new VSR balancing machine this past summer and have been very pleased with this machine to say the least.

We all know that performance is great but what makes it even better is reliability. The bottom line is that consumers need turbochargers they can count on, one that has been bench tested to perform, and it needs to be done prior to shipping. This could save countless amounts of headaches and costs down the road.

For those who may not know VSR stands for Vibration Sorting Rig. This is an expensive and delicate piece of equipment that gives visibility of a CHRA's performance under conditions they are subjected to when bolted to an engine. During bench testing the final assembled CHRA is bolted to a fixture and is injected with pressurized/heated oil and then a large supply of air is applied to propel the rotor through the entire operating RPM range that the unit will be subjected to in application (ie. 0-170k RPM). The entire RPM range is plotted on a graph along with a vibration intensity measurement at each point during acceleration of the rotor, and calculations are performed to help the operator determine where the rotor components can be lightened by very minute grinding techniques to lessen the mechanical vibration.

This essentially is a way to determine whether a turbocharger is assembled correctly and allows the VSR operator to have ultimate control over the balance of the turbo cartridge assembly. As one can imagine, "vibrations" in mechanical components suggest that the device is imperfect and subject to larger wear in shorter amounts of time. Large amounts of vibrations mean poor performance, slow spool, oil consumption, audible noise, and at times a quick failure. A smooth operating unit that does not vibrate means exceptional lifespan, quick spool, low oil consumption, and superb performance. It is also worth mentioning that no amount of "robust" hardware can compensate for a poorly balanced center section.

VSR's also indicate how well each CHRA is balanced by comparing the performance to a predefined OEM threshold. OEM thresholds are typically very high which can be acceptable for non high performance, but can lead to short turbocharger life if or when they are pushed harder than what they were intended.

Also keep in mind that even IF a cartridge was VSR'd, it doesn't mean that it was done proficiently. Ideally each CHRA will be at balanced to what we refer to as "the balance floor", "flatlined", or at least very close to it. The report shows the performance and illustrates to what caliber the CHRA was precisely balanced. They can not always be absolute perfection and it should not be expected, unfortunately, but turbocharger manufacturers should be diligent in achieving as close to perfection in each unit as possible.

Beware of manufacturers who do not have the cutting edge technology employed, as ultimately the product could suffer in reliability especially when pushed to the products outer limits. Some manufacturers maintain that they utilize the technology but they do not. CHRA performance and analysis reports should be provided to confirm.

As always many things can cause a turbocharger to fail, sometimes outside of their control… but this is an absolute safe way to ensure the product is built to exceptional standards.

Below is a sample of a VSR report for visual reference.

Thanks,
Rob

PS- Would like to take a moment also to give a big thank you to Jesse @ Pure Turbo for helping us along and furthering the understanding in the art of VSR balancing!
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      11-22-2014, 07:02 PM   #2
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Tks Rob. Will you be providing the reports with future RB deliveries?
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      11-22-2014, 07:06 PM   #3
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Quote:
Originally Posted by Aerotest View Post
Tks Rob. Will you be providing the reports with future RB deliveries?
Yes sir and we have for the past 4 months.
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      11-22-2014, 08:04 PM   #4
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Originally Posted by Rob@RBTurbo View Post
Yes sir and we have for the past 4 months.
Good stuff, Rob!

Neil
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      11-22-2014, 09:43 PM   #5
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Useful info as usual Rob
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      11-22-2014, 10:40 PM   #6
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Good stuff!

Since balancing is a bit of a cumbersome process, curious what sort of limitations you invoke on static versus group couples.

To everyone else not well versed in balancing, the old way of doing this is lets say the compressor and the turbine both had a "high spot" or heaviest part of them at 12 o'clock. This means they'd both be exciting a 1-per-rev that would be quite high. In this case, however, the group couple would be zero. Now many people would just rotate one of the wheels 180* to "balance" them out. The static value of vibration, which is the chart like Rob posted, would read very very low, BUT, the group couple is now extremely high, with a very high phase angle. The turbo would measure well but would not last long.

What's a group couple? Well, hard to write it, easy to understand, again, imagine two wheels on a shaft. Each of the wheels has a "heavy spot" 180* out from each other. Under rotation, they're going to try to bend the shaft. This plays hell with turbine engines, turbos, you name it. Actually, turbos are a lot more sensitive to this than turbine engines but I digress...

The phase angle is just the angle between the two wheels' heavy spot. Rule of thumb is the smaller the phase angle, the better off you are. I know the rules of thumb for turbine engines and I know what Garrett strives for as well.

So put it all together, you want to component balance everything (meaning balance them by themselves), then assemble them such that the group couple is within tolerance, THEN remove material/etc to get static within reason. If you just get static good and ignore everything else, I'll bet you a ham sandwhich and a grape soda that your turbos will have short, unhappy lives no matter how cool your graph looks.

Cool info Rob, nice to see this getting posted for the further education of consumers.

High group couple won't show up in a simple vib trace. It's calculated. I'm sure Rob has ways of dealing with this. I know what Garrett does and Honeywell, since I've done this operation many times for turbine engines -same same.
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      11-23-2014, 12:34 AM   #7
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Great post. Agree on most everything. But the chart is not static, it's a dynamic representation of the entire group of components (each of which is individually balanced prior to strategic grouping/assembling). In short the VSR will see (and plot) imbalance of each plane and show them as out of phase as they appear dynamically, if they exist, and the operator then has the ability to correct one plane (or in some cases both planes at their discretion).

With this machine the operator can achieve what one can not come close to with the typical industry balancing standards, which many shops still utilize and consider acceptable. While VSR'ing, the operator can see that improvement not only make the graph more appealing visually- but there are very distinctive improvements as well. Improvements such as duration cycle of testing is dramatically improved (ie. Spools faster), audible sound of the rotor acceleration is much more pleasant, and finally of course the unit is making very low amounts of mechanical vibration.

Thanks,
Rob
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      11-23-2014, 12:50 AM   #8
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Glorious. That should make a significant contribution towards people being able to boost the piss out of things and not trash turbos.
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      11-23-2014, 10:57 AM   #9
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Quote:
Originally Posted by MDORPHN View Post
Good stuff, Rob!

Neil
Quote:
Originally Posted by mike@x-ph.com View Post
Useful info as usual Rob
Thanks sirs!

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Originally Posted by C.Pop View Post
Glorious. That should make a significant contribution towards people being able to boost the piss out of things and not trash turbos.
100% concurrence.
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      11-24-2014, 01:10 AM   #10
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All fine and dandy, but how did you end up determining 1.5 and 0.5 for OEM and Hi-Perf thresholds respectively? Where do these numbers come from? So far they look like they've either been arbitrarily selected or "cherry picked"...
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      11-24-2014, 05:01 AM   #11
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Quote:
Originally Posted by vasillalov View Post
All fine and dandy, but how did you end up determining 1.5 and 0.5 for OEM and Hi-Perf thresholds respectively? Where do these numbers come from? So far they look like they've either been arbitrarily selected or "cherry picked"...
It is hard to see from the picture or understand entirely without experience using the VSR. But if you look at the top of the picture there is a more "bold line" (which is a bold green line on the VSR's monitor). This is predefined by the OEMs for the particular rotor assembly (ie. GT15, TD04, etc) that you maybe balancing. So when you select the exact rotor assembly (using the VSR's database) it tells you what the OEMs find as the upper acceptable threshold and gives that indication on the chart. These figures are determined mainly by rotor sizes, weights, and RPM ranges.

Of course the smaller the rotor assembly, the "tighter" the OEM threshold, as smaller rotor assemblies are known to spin much faster and being much lighter tend to inherently induce much less of vibrations overall. Typically the smallest of the turbos have an OEM upper threshold set at .5 grams.

This information along with the combined VSR experience of us and others (ie. and VSR'ing other known new Hi-Po turbos), we well know what is is good and what is not.

Quite frankly we even go much better than the .5 grams, on these turbos we are typically dynamically averaging between .1-.2grams as we take much time with them to ensure they are be best that they can be. This is the result of taking any amount of time necessary to achieve great results, it is not always easy to get them.

As stated prior even if some do VSR balance it doesn't mean they are achieving good numbers, but the supplied reports should give you an idea of how diligent the manufacture is to obtain the best possible results. Also high speed balancing may still not be enough, you really want to see dynamic balancing (i.e. balanced through the entire RPM range).

This thread is just to help provide some insight and information on VSR balancing, as we know it is something that is not talked about much or understood by many.

Rob

Last edited by Rob@RBTurbo; 11-24-2014 at 05:08 AM.
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      11-24-2014, 07:24 AM   #12
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Rob,
On another note are you planning on making an RB+ turbo upgrade with larger compressors?
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      11-24-2014, 07:53 AM   #13
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Rob,

Thant makes more sense now. Thanks for the explanation.
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      11-24-2014, 09:59 AM   #14
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Quote:
Originally Posted by Aerotest View Post
Rob,
On another note are you planning on making an RB+ turbo upgrade with larger compressors?
After development and testing we decided those options were not in the best interest of the consumer due to other gaping N54 system deficiencies, primarily in the plumbing. So to ensure the best reliability, power potential, and general engineering/developmental turbocharger practices we felt it was best to hold back on product sales until it is developed correctly as a system (rather than a unit in a system) and tests properly.

Quote:
Originally Posted by vasillalov View Post
Rob,

Thant makes more sense now. Thanks for the explanation.
No problem and you are welcome.
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      11-24-2014, 02:14 PM   #15
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Very cool! Thanks for sharing!!
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      11-24-2014, 09:48 PM   #16
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Quote:
Originally Posted by Rob@RBTurbo View Post
After development and testing we decided those options were not in the best interest of the consumer due to other gaping N54 system deficiencies, primarily in the plumbing. So to ensure the best reliability, power potential, and general engineering/developmental turbocharger practices we felt it was best to hold back on product sales until it is developed correctly as a system (rather than a unit in a system) and tests properly.
With VTT intakes and Hot side charge pipe. Not sure what plumbing is lacking. Maybe your balancing is causing performance issues. Nice to see your buying good equipment. But this is nothing new.
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      11-24-2014, 10:19 PM   #17
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Quote:
Originally Posted by Ingeniator
Quote:
Originally Posted by Rob@RBTurbo View Post
After development and testing we decided those options were not in the best interest of the consumer due to other gaping N54 system deficiencies, primarily in the plumbing. So to ensure the best reliability, power potential, and general engineering/developmental turbocharger practices we felt it was best to hold back on product sales until it is developed correctly as a system (rather than a unit in a system) and tests properly.
With VTT intakes and Hot side charge pipe. Not sure what plumbing is lacking. Maybe your balancing is causing performance issues. Nice to see your buying good equipment. But this is nothing new.
Why would you imply the intakes and hot side cp are going to solve any problems? Has anyone tested them? I think Rob is doing his due diligence here to ensure he delivers a quality product. On the other hand we need to take someones word the intake and CP are going to increase the flow. Without 3d modeling to test the flow characteristics it could actually make things worse. The problem is if it doesn't increase power on the dyno, it will go back to R&D and spend another 3 years in development while a group buy sits holding the bag for the new R&D.
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      11-24-2014, 10:29 PM   #18
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Quote:
Originally Posted by Give_Em_The_DD View Post
Why would you imply the intakes and hot side cp are going to solve any problems? Has anyone tested them? I think Rob is doing his due diligence here to ensure he delivers a quality product. On the other hand we need to take someones word the intake and CP are going to increase the flow. Without 3d modeling to test the flow characteristics it could actually make things worse. The problem is if it doesn't increase power on the dyno, it will go back to R&D and spend another 3 years in development while a group buy sits holding the bag for the new R&D.
How about you look up Cv of a 2" line and tell me it won't flow more than stock. As for Rob you couldn't get the lego pieces to work and don't know why. So you say your set is broken when you just can't read the instructions. As for VSR it means shit if you don't know how to use it. What accuracy are the probes. The unit is usually milli-gram inches not grams and .1/.2 grams is a lot of imbalance. Also for the benefit of the community like the OP was about imbalance is the same at slow rotor speeds the force is just less. So don't look behind the curtain kiddies. It is just an old man not a wizard.
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      11-24-2014, 11:22 PM   #19
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Quote:
Originally Posted by FCobra94 View Post
Very cool! Thanks for sharing!!
You are welcome bud.

Quote:
Originally Posted by Ingeniator View Post
How about you look up Cv of a 2" line and tell me it won't flow more than stock. As for Rob you couldn't get the lego pieces to work and don't know why. So you say your set is broken when you just can't read the instructions. As for VSR it means shit if you don't know how to use it. What accuracy are the probes. The unit is usually milli-gram inches not grams and .1/.2 grams is a lot of imbalance. Also for the benefit of the community like the OP was about imbalance is the same at slow rotor speeds the force is just less. So don't look behind the curtain kiddies. It is just an old man not a wizard.
Thanks for the feedback and more so for keeping the thread up top where others can actually learn some meaningful information and be educated consumers.
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      11-25-2014, 01:24 AM   #20
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Quote:
Originally Posted by Give_Em_The_DD View Post
Why would you imply the intakes and hot side cp are going to solve any problems? Has anyone tested them? I think Rob is doing his due diligence here to ensure he delivers a quality product. On the other hand we need to take someones word the intake and CP are going to increase the flow. Without 3d modeling to test the flow characteristics it could actually make things worse. The problem is if it doesn't increase power on the dyno, it will go back to R&D and spend another 3 years in development while a group buy sits holding the bag for the new R&D.
Some people don't care about facts. It's amazing how far they will go out of their way to make a complete @ of themselves only to jump ship when things fall apart. Sounds like another pipe dream to me...
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      11-25-2014, 02:15 AM   #21
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Hey Rob, any group buy or discounts for christmas? Please
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      11-25-2014, 10:34 AM   #22
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Quote:
Originally Posted by Ingeniator View Post
Nice to see your buying good equipment. But this is nothing new.
Neither is road force balancing, but 99% of the people actually using those machines daily don't have a clue about: what they do, how they do it, or what they're actually capable of. Doesn't mean that you, as a consumer, can't learn more about the process in order to understand what to look for when looking for a shop to do quality work.
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