Convert stock twins to ball bearings????
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Convert stock twins to ball bearings????
Is it possible for a machine shop to modify a stock twin turbo to use ball bearings instead of the stock bearing??
#2
gross polluter
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anything is possible with enough $$$, but I have never heard of anybody converting a turbo from oil suspended bushing to ball bearing. Why would you want to do that?
M2 makes a replacement ball bearing set, I dont know if you can maintain the sequential operation though.
Not to make this a ball bearing vs. bushing thread but there really isnt much of an advantage in ball bearing. I was looking into the subject a couple months ago and it seems the only people that say ball bearing are oh so much better are average joes that just heard it somewhere. Every web page I found that looked remotely professional said spooling is more a function of not getting a turbo that is too big. Ball bearing will spool about the same rate. The only thing I could find that really made one better than the other is that an oil suspended bushing has a much longer life.
M2 makes a replacement ball bearing set, I dont know if you can maintain the sequential operation though.
Not to make this a ball bearing vs. bushing thread but there really isnt much of an advantage in ball bearing. I was looking into the subject a couple months ago and it seems the only people that say ball bearing are oh so much better are average joes that just heard it somewhere. Every web page I found that looked remotely professional said spooling is more a function of not getting a turbo that is too big. Ball bearing will spool about the same rate. The only thing I could find that really made one better than the other is that an oil suspended bushing has a much longer life.
#3
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Originally Posted by Tom93R1
M2 makes a replacement ball bearing set, I dont know if you can maintain the sequential operation though.
However, I doubt M2 was doing the work themselves, rather sending them out for the modification. It would be interesting to find out if that's the case as the modification could still be around for those that want it by using the original source.
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I do not claim to be an expert but Brian at M2 showed me a set of the BB turbos before he made them public. All you had to do was gently blow and the turbines would start moving. Now on the stock twins its a whole different story. No matter how hard I tried to blow to make the turbines spin they did not budge one bit. The fact that you need less gas pressure to spin the turbines on the BB set has to mean something no? And I believe the ONLY reason why M2 was discouraging people from buying their BB set was because many people thought they could simply slap them on and get 400rhp right away, which is simply not true. They were not taking into account fuel, ignition, ecu, bolt-ons and etc.
#5
2/4 wheel cornering fiend
Originally Posted by Tom93R1
anything is possible with enough $$$, but I have never heard of anybody converting a turbo from oil suspended bushing to ball bearing. Why would you want to do that?
M2 makes a replacement ball bearing set, I dont know if you can maintain the sequential operation though.
Not to make this a ball bearing vs. bushing thread but there really isnt much of an advantage in ball bearing. I was looking into the subject a couple months ago and it seems the only people that say ball bearing are oh so much better are average joes that just heard it somewhere. Every web page I found that looked remotely professional said spooling is more a function of not getting a turbo that is too big. Ball bearing will spool about the same rate. The only thing I could find that really made one better than the other is that an oil suspended bushing has a much longer life.
M2 makes a replacement ball bearing set, I dont know if you can maintain the sequential operation though.
Not to make this a ball bearing vs. bushing thread but there really isnt much of an advantage in ball bearing. I was looking into the subject a couple months ago and it seems the only people that say ball bearing are oh so much better are average joes that just heard it somewhere. Every web page I found that looked remotely professional said spooling is more a function of not getting a turbo that is too big. Ball bearing will spool about the same rate. The only thing I could find that really made one better than the other is that an oil suspended bushing has a much longer life.
Ball bearings have far less internal drag than oil-film bushings. They're actually the ideal bearing setup for a turbo. It's the reason you see them used in so many low-load/high rpm applications where the absolute minimum internal drag is desired. Oil-film bushings actually suffer from drag induced by the oil film itself, due to the surface tension properties of oil. The reason you see oil-film bushings used so much with engines today instead of ball bearings is cost, their load-bearing capacity, and--as you "found on the web"-- longer overall service life.
#7
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Originally Posted by Kento
Just because you weren't able to find anything searching on the web doesn't mean that there is no appreciable performance difference between ball bearings vs. bushings. And it's easy to make a web page look "professional", but still populate it with hearsay and conjecture.
Ball bearings have far less internal drag than oil-film bushings. They're actually the ideal bearing setup for a turbo. It's the reason you see them used in so many low-load/high rpm applications where the absolute minimum internal drag is desired. Oil-film bushings actually suffer from drag induced by the oil film itself, due to the surface tension properties of oil. The reason you see oil-film bushings used so much with engines today instead of ball bearings is cost, their load-bearing capacity, and--as you "found on the web"-- longer overall service life.
Ball bearings have far less internal drag than oil-film bushings. They're actually the ideal bearing setup for a turbo. It's the reason you see them used in so many low-load/high rpm applications where the absolute minimum internal drag is desired. Oil-film bushings actually suffer from drag induced by the oil film itself, due to the surface tension properties of oil. The reason you see oil-film bushings used so much with engines today instead of ball bearings is cost, their load-bearing capacity, and--as you "found on the web"-- longer overall service life.
In my searching I could find nothing about why BB is better other than "I heard form somebody" while I did find alot of sites from professional racers including RX7.com stating they use the oil suspended bushing because it does spool up just as fast. The difference is they use the same turbo for the whole season instead of having to rebuild every couple races.
I didnt mean the page looked like it was made by a professional web page builder or not, I am smart enough to realize that any idiot can have a good looking web page.
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#8
Super Snuggles
Originally Posted by Kento
Ball bearings have far less internal drag than oil-film bushings. They're actually the ideal bearing setup for a turbo.
#9
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why would you need ball bearing for stock sequential twins??? they spool really fast already and i dont see an advantage... now if you want to run them non-sequential, thats a different story!
#10
Super Snuggles
Originally Posted by Tom93R1
In my searching I could find nothing about why BB is better other than "I heard form somebody" while I did find alot of sites from professional racers including RX7.com stating they use the oil suspended bushing because it does spool up just as fast.
A: Turbonetics created the ceramic ball bearing turbocharger for durability. By utilizing a single, ceramic, angular-contact ball bearing on the compressor side instead of the more common bronze piece, the ball bearing can absorb the thrust loading that all too often can lead to turbo failure in high performance gas applications. The Turbonetics ceramic ball bearing turbo can withstand up to 50 times the thrust load capacity, compared to a conventional floating bearing unit.
*Dual ball bearing turbos can only withstand 2-3 times more thrust loading than standard turbos.
Q: Do the ceramic ball-bearing turbos "spool up" faster than a normal turbo?
A: YES! The ceramic ball-bearing design reduces the frictional loss that occurs with a conventional floating bearing-and-thrust system turbo. The ceramic ball-bearing design allows the turbo to accelerate much quicker, thus decreasing spool-up time. In most cases we have found our ceramic ball-bearing designs require 50 percent less energy to drive the turbo.
http://www.turboneticsinc.com/faq.html#2
The difference is they use the same turbo for the whole season instead of having to rebuild every couple races.
#11
2/4 wheel cornering fiend
Originally Posted by Tom93R1
BB also have alot more mass to spin up because of that bearing.
Originally Posted by Tom93R1
Generally a similarly sized BB will not perform as will at the top end because of this.
Originally Posted by Tom93R1
In my searching I could find nothing about why BB is better other than "I heard form somebody" while I did find alot of sites from professional racers including RX7.com stating they use the oil suspended bushing because it does spool up just as fast. The difference is they use the same turbo for the whole season instead of having to rebuild every couple races.
Originally Posted by Tom93R1
I didnt mean the page looked like it was made by a professional web page builder or not, I am smart enough to realize that any idiot can have a good looking web page.
#12
2/4 wheel cornering fiend
Originally Posted by jimlab
Agreed. I've heard they also make cool sounds after you shut off the car because it takes awhile for them to spin down to a complete stop.
#13
Racing Rotary Since 1983
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ball bearing conversion for oem turbos?????
you are re-arranging deck chairs on the Titanic.
yes, they might spool faster. yes, there may be less drag
BUT
the turbos are poorly sized for additional power. at 15 psi they are running 150,000+ rpm and cavitating/superheating the charge air. sure you can major mod the ports and support systems and temporarily make 400 hp but it won't be pretty and it won't last.
in addition to the turbos being poorly sized the manifold ( 22 pounds of cast iron) bolted to the block does it's significant part as to frying the engine.
cast iron retains lots more heat than stainless steel which retains 33% more heat than mild steel. the rotary creates approximately 500 degrees more exhaust heat than a comparable piston engine. somewhere around 1600 degrees.
the manifold can't take the heat:
i'll bet there aren't any remaining oem cast iron manifolds existing that don't have large heat cracks.
the engine can't take the heat:
i believe that more than half of the rotary engine failures are substantially related to the baking effect of the 22 pound cast iron manifold.
engine builders have to love it.
so you heat the 22 pounds of cast iron bolted to an aluminum/mild steel block to a very high temperature and then you turn off your motor. the 22 pounds bakes the block for an hour or more. the mild steel and aluminum block receives the heat.
instead of screwing around w an engine killing turbo system junk it or use it for a boat anchor. bolt on 6 pounds of stainless steel (flangeplates from a single turbo) and spend the additional time and money you will save from not melting your motor at the track.
howard coleman
you are re-arranging deck chairs on the Titanic.
yes, they might spool faster. yes, there may be less drag
BUT
the turbos are poorly sized for additional power. at 15 psi they are running 150,000+ rpm and cavitating/superheating the charge air. sure you can major mod the ports and support systems and temporarily make 400 hp but it won't be pretty and it won't last.
in addition to the turbos being poorly sized the manifold ( 22 pounds of cast iron) bolted to the block does it's significant part as to frying the engine.
cast iron retains lots more heat than stainless steel which retains 33% more heat than mild steel. the rotary creates approximately 500 degrees more exhaust heat than a comparable piston engine. somewhere around 1600 degrees.
the manifold can't take the heat:
i'll bet there aren't any remaining oem cast iron manifolds existing that don't have large heat cracks.
the engine can't take the heat:
i believe that more than half of the rotary engine failures are substantially related to the baking effect of the 22 pound cast iron manifold.
engine builders have to love it.
so you heat the 22 pounds of cast iron bolted to an aluminum/mild steel block to a very high temperature and then you turn off your motor. the 22 pounds bakes the block for an hour or more. the mild steel and aluminum block receives the heat.
instead of screwing around w an engine killing turbo system junk it or use it for a boat anchor. bolt on 6 pounds of stainless steel (flangeplates from a single turbo) and spend the additional time and money you will save from not melting your motor at the track.
howard coleman
#14
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I know I am no turbo expert, I am just stating things I remember finding in a few searches.
The comment about turbo life was not based on just rx7.com. I found similar statements on many web sites belonging to serious racers. rx7.com was the only name I specifically remember. I do remember asking a few years back on the rx7club about the expected life of the M2 turbos and was told it was much shorter than the stockers because of the ball bearing design. It isnt like I am saying in a street application you will have to rebuild it weekly I am just saying you may not get the 100k+ out of a bearing that you will from the bushing. The thing about high end not being as good I admit I have only heard a few times but at least once was from a friend who rebuilds turbos for a living.
The way I understand it is ceramic ball bearings are a relatively new thing that seem to have resolved any shortcomings of the conventional ball bearing turbos. This thread looked to be more about a conventional dual ball bearing vs bushing any ways so I didnt even consider ceramic.
I am done here before I look like any more of a tool for trying to talk about something I dont know much about
The comment about turbo life was not based on just rx7.com. I found similar statements on many web sites belonging to serious racers. rx7.com was the only name I specifically remember. I do remember asking a few years back on the rx7club about the expected life of the M2 turbos and was told it was much shorter than the stockers because of the ball bearing design. It isnt like I am saying in a street application you will have to rebuild it weekly I am just saying you may not get the 100k+ out of a bearing that you will from the bushing. The thing about high end not being as good I admit I have only heard a few times but at least once was from a friend who rebuilds turbos for a living.
The way I understand it is ceramic ball bearings are a relatively new thing that seem to have resolved any shortcomings of the conventional ball bearing turbos. This thread looked to be more about a conventional dual ball bearing vs bushing any ways so I didnt even consider ceramic.
I am done here before I look like any more of a tool for trying to talk about something I dont know much about
#15
Super Snuggles
Originally Posted by howard coleman
i'll bet there aren't any remaining oem cast iron manifolds existing that don't have large heat cracks.
#19
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Originally Posted by howard coleman
i'll bet there aren't any remaining oem cast iron manifolds existing that don't have large heat cracks.
Originally Posted by jimlab
You can say that again. When we converted my car to non-sequential at about 3,700 miles on the odometer, I already had light cracking evident on the exhaust manifold and wastegate orifice.
#20
2/4 wheel cornering fiend
No offense, but this was the reason I even entered this thread...
Originally Posted by Tom93R1
I was looking into the subject a couple months ago and it seems the only people that say ball bearing are oh so much better are average joes that just heard it somewhere.
Originally Posted by Tom93R1
The thing about high end not being as good I admit I have only heard a few times but at least once was from a friend who rebuilds turbos for a living.
#21
Rotary Enthusiast
Originally Posted by jimlab
...Turbonetics-> The ceramic ball-bearing design reduces the frictional loss that occurs with a conventional floating bearing-and-thrust system turbo. The ceramic ball-bearing design allows the turbo to accelerate much quicker, thus decreasing spool-up time. In most cases we have found our ceramic ball-bearing designs require 50 percent less energy to drive the turbo..
#22
Rotary Enthusiast
My stock exhaust manifold cracked at 90K and was replaced under the extended factory warranty along with the engine. I now have another 50K on the current engine and stock twins and have done about 40 hours of track time (about 20 track days approx 2 hours track time each). So far no cracks or blown coolant seals. I'm sure it will happen eventually. I use synthetic motor oil... maybe that helps.
Going Single Turbo is tempting but I do still drive the car on the street and there is no way I can pass CA smog with a single turbo.
-John
Going Single Turbo is tempting but I do still drive the car on the street and there is no way I can pass CA smog with a single turbo.
-John
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all this talk about the cast iron manifold beingbad gives me an idea.Why not just get a stainless steel manifold made to work with the existing twins? Does the manifold have the wastegate built into it?
#24
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Originally Posted by speeddemon7
all this talk about the cast iron manifold beingbad gives me an idea.Why not just get a stainless steel manifold made to work with the existing twins? Does the manifold have the wastegate built into it?
It would probably cost less to convert to Single!
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Originally Posted by speeddemon7
all this talk about the cast iron manifold beingbad gives me an idea.Why not just get a stainless steel manifold made to work with the existing twins? Does the manifold have the wastegate built into it?