This is a write up by Alan in regards to some questions a customer was asking. I thought it might be some good info for those who might have questions, this particular post pertains mainly to race converters , but the basics are there.WARNING this is a long post!
So with out further ado i present the torque converter thread.
I wrote the first part of this as a reply to a customer who asked me some basic converter questions. The first being "what will it stall exactly and what does that mean"
it is long but should be worth the read if you are interested in torque converters or could use a little better race oriented understanding and peak inside the industry.
In the past I have dissected a bunch of different converters both on the internet and in person. It only takes me a few minutes to cut one open but explaining them takes a bit longer.
The only real way to tell the true stall is with a transbrake. Then their are variables, how is the motor running that day, air quality and fuel make big changes sometimes. This is especially true on pump gas cars. I will agree 100% that loose is consistant.
A local guy I build converters for has a 5500 stall 9.5 inch behind a small block chevy around 600hp.It is very consistant, especialy in the 1/8th. Really the car would be faster with a lesser stall but the difference is caused by the stator.
The 9.5 gm converters have an array of different pump and stator angles. Those are the components of the converter that control stall the most, pump to turbine clearance, turbine porosity and turbine to front cover distances change these things but very little The pump and stator make the big changes.
The pump has all the fins that are driven by the motor. Those fins can be directed with engine rotation to speed up the fluid, neutral or against engine rotation to slow the fluid down and increase stall. The Stator (slang for stationary reactor)controls the fluid flow back to the turbine that drives the input shaft of the transmission and ultimately the rear wheels.
The stators can be in different angles also. One way clutch operation has to be considered as well. It would be easier to explain with pictures however if the stator fluid flow is very restricted the stall will increase if the flow is a direct path it will decrease the stall. At some point of restriction it will begin to reduce torque multiplication. This will be soft on apply.
If the flow is restrictive when holding the roller clutch and free flowing when turbine speed is high enough to allow stator flow to be free you will get the best mph and a desirable 60ft. If flow is restrictive the entire time you will get much higher stall and soft launch. With any combinations eventually the pressure has to overcome the turbine and push it.
The stator rotation is greatly controlled by turbine speeds. With a spragless unit the converter will stay in high stall and this is why they are not good for street cars, unless very low stall. It is a delicate balance many engineers spent plenty of hours getting just right. Some are better than others to say the least.
The biggest failure within any race converter is ballooning usually caused by people who want to buy a very inexpensive converter and convince themselves it is enough for the combination. Off the shelf summit and jegs converters seem to have the biggest problems with this because the companies only stock those types. That is mostly because they cost little of nothing to build except time.
The break down of cost. If summit is selling the unit for $400 then they probably bought 100,000 dollars worth of them at $150-$200 a piece. To pay someone 2-4 hours to build it the company has to build it very inexpensively. No furnace brazed parts, cheap equipment bearings instead of torrington bearings. A simple bolt pattern ring welded onto a stock gm 9.5 front cover a 3-4 inch piece of roundstock machined down to pilot size and welded on, usually another piece of the same round stock welded to the turbine, bored and broached without hardening of any form. Completely stock stator from a fwd gm 9.5 core. and a $8 hub.
Less than $50 in parts everytime. Those cores go about $3 a piece and cheaper if you buy them a few thousand dollars worth at a time. Building units inexpensively and durable is difficult but rarely possible. Better units will have billet steel front covers, my favorite being the drog forged casting process sonnax uses however those machined out of good grade billet steel are equally as good, just a bit heavier.
Furnace brazing the turbine and pump is one of the biggest costs because finding people who can do it properly, shipping the heavy parts back and forth, accepting a certain amount of damaged parts that you will pay for and they will be thrown away, it adds up. The cost of metals increasing drives this cost up nearly every time they get sent in.
Good quality turbine and impeller hubs aren't cheap either. On those I prefer the hardened 300m material but the sonnax heat treated parts are also very good. Figure $100 for a set of hubs, one that connects to the input shaft and one that drives transmission pump.
Stators can be the most expensive parts of all, The steel stators are very nice but only available for opel 8 inch parts. I call it 9 inch because it physically is closer .This is what most older racing converters are built from, at least the good ones that are still working after a couple years.
Aluminum stators from the fwd gm core can be adapted to hold a better roller clutch, most aftermarket converters under about $600 will use the stock stator from the core that was used. Good stators can be at cost over $300 when you include a nice high element style or diode style one way clutch, quality steel or aluminum stator caps,bearings,hardeneds inner and outer races and even spiral wound snap rings to prevent snap ring failure.
The only converters that do not come from cores at this time are opel 8 inch and they are just exact copys from gm's dies. All other converters are built from some sort of core. I hear people all the time tell me their converter guy builds all his converters from new parts, No he doesn't.
Stamping pumps and turbine bowls then staking in the fins accurately in the first place is a multi million dollar setup cost. Brand new tooling can only pay for itself to the big companies like Ford,GM and Chrysler many foreign and converters are built from those stampings as well, but most foreign car companies share Jatco parts, toyota and honda make their own. Nissan makes some of their own, All korean cars pretty much use the same basic stuff.
Converters are not that simple their are many many things to consider when buying one. Do you want the fastest 60ft or the highest mph. Usually the goal is to find a combination that gives you the best of both but there is always a give and take. It is completely a hydraulic system so many things will change it mildly.
Often 2 different people in the same car will give you 2 different stall numbers that seems to be true.. Usually the best way to rate a converter is by multiplication numbers. Converters can range from 1:1 to 3.17:1 being the highest I know of. If the multiplication is high you will hit the wheels with the most torque on launch.
Getting high multiplication will reduce your mph. Stall number isn't everything. A converter builder will usually consider the combination to build a unit that works for it and then take an educated guess at stall speed. Stall speed is an effect it is not an exact science. Results may vary, experience is the only way to get them right.
Almost every major city has at least 1 or 2 transmission shops that have purchased equipment to build their own converters and as the economy gets worse those places do more and more stuff to keep a float.Others do it because of their love for racing. Not all will be good with racing but if you can find one local to you that is talk to him.
It gets expensive shipping converters back and forth to get things right. A guy who knows what he is doing will have no problem cutting your converter open in front of you and explaining to you what it has, doesn't have, needs, or just tell you the honest truth that it is a piece of junk.
I give that news to people all the time and half the time they doubt me because of it. The truth hurts, people don't want to think they paid good money for junk, especially when they can't tell the difference. When dealing with someone local you can get a real warranty, and after warranty service.
It is hard to guarantee a race converter, you sell it to people who are doing their best to break it.Without experience you will fail quickly trying to guarantee them.As the consumer if you can see it for yourself an understand it a little better you can begin to figure out what you need and what will benefit your combination the most, not just stall speed. A converter is so much more than a number! Lockup changes everything too, but does not matter to most racing.
Alan
Last edited by DirtyD0g; 11-17-2011 at 09:25 PM.
So with out further ado i present the torque converter thread.
I wrote the first part of this as a reply to a customer who asked me some basic converter questions. The first being "what will it stall exactly and what does that mean"
it is long but should be worth the read if you are interested in torque converters or could use a little better race oriented understanding and peak inside the industry.
In the past I have dissected a bunch of different converters both on the internet and in person. It only takes me a few minutes to cut one open but explaining them takes a bit longer.
The only real way to tell the true stall is with a transbrake. Then their are variables, how is the motor running that day, air quality and fuel make big changes sometimes. This is especially true on pump gas cars. I will agree 100% that loose is consistant.
A local guy I build converters for has a 5500 stall 9.5 inch behind a small block chevy around 600hp.It is very consistant, especialy in the 1/8th. Really the car would be faster with a lesser stall but the difference is caused by the stator.
The 9.5 gm converters have an array of different pump and stator angles. Those are the components of the converter that control stall the most, pump to turbine clearance, turbine porosity and turbine to front cover distances change these things but very little The pump and stator make the big changes.
The pump has all the fins that are driven by the motor. Those fins can be directed with engine rotation to speed up the fluid, neutral or against engine rotation to slow the fluid down and increase stall. The Stator (slang for stationary reactor)controls the fluid flow back to the turbine that drives the input shaft of the transmission and ultimately the rear wheels.
The stators can be in different angles also. One way clutch operation has to be considered as well. It would be easier to explain with pictures however if the stator fluid flow is very restricted the stall will increase if the flow is a direct path it will decrease the stall. At some point of restriction it will begin to reduce torque multiplication. This will be soft on apply.
If the flow is restrictive when holding the roller clutch and free flowing when turbine speed is high enough to allow stator flow to be free you will get the best mph and a desirable 60ft. If flow is restrictive the entire time you will get much higher stall and soft launch. With any combinations eventually the pressure has to overcome the turbine and push it.
The stator rotation is greatly controlled by turbine speeds. With a spragless unit the converter will stay in high stall and this is why they are not good for street cars, unless very low stall. It is a delicate balance many engineers spent plenty of hours getting just right. Some are better than others to say the least.
The biggest failure within any race converter is ballooning usually caused by people who want to buy a very inexpensive converter and convince themselves it is enough for the combination. Off the shelf summit and jegs converters seem to have the biggest problems with this because the companies only stock those types. That is mostly because they cost little of nothing to build except time.
The break down of cost. If summit is selling the unit for $400 then they probably bought 100,000 dollars worth of them at $150-$200 a piece. To pay someone 2-4 hours to build it the company has to build it very inexpensively. No furnace brazed parts, cheap equipment bearings instead of torrington bearings. A simple bolt pattern ring welded onto a stock gm 9.5 front cover a 3-4 inch piece of roundstock machined down to pilot size and welded on, usually another piece of the same round stock welded to the turbine, bored and broached without hardening of any form. Completely stock stator from a fwd gm 9.5 core. and a $8 hub.
Less than $50 in parts everytime. Those cores go about $3 a piece and cheaper if you buy them a few thousand dollars worth at a time. Building units inexpensively and durable is difficult but rarely possible. Better units will have billet steel front covers, my favorite being the drog forged casting process sonnax uses however those machined out of good grade billet steel are equally as good, just a bit heavier.
Furnace brazing the turbine and pump is one of the biggest costs because finding people who can do it properly, shipping the heavy parts back and forth, accepting a certain amount of damaged parts that you will pay for and they will be thrown away, it adds up. The cost of metals increasing drives this cost up nearly every time they get sent in.
Good quality turbine and impeller hubs aren't cheap either. On those I prefer the hardened 300m material but the sonnax heat treated parts are also very good. Figure $100 for a set of hubs, one that connects to the input shaft and one that drives transmission pump.
Stators can be the most expensive parts of all, The steel stators are very nice but only available for opel 8 inch parts. I call it 9 inch because it physically is closer .This is what most older racing converters are built from, at least the good ones that are still working after a couple years.
Aluminum stators from the fwd gm core can be adapted to hold a better roller clutch, most aftermarket converters under about $600 will use the stock stator from the core that was used. Good stators can be at cost over $300 when you include a nice high element style or diode style one way clutch, quality steel or aluminum stator caps,bearings,hardeneds inner and outer races and even spiral wound snap rings to prevent snap ring failure.
The only converters that do not come from cores at this time are opel 8 inch and they are just exact copys from gm's dies. All other converters are built from some sort of core. I hear people all the time tell me their converter guy builds all his converters from new parts, No he doesn't.
Stamping pumps and turbine bowls then staking in the fins accurately in the first place is a multi million dollar setup cost. Brand new tooling can only pay for itself to the big companies like Ford,GM and Chrysler many foreign and converters are built from those stampings as well, but most foreign car companies share Jatco parts, toyota and honda make their own. Nissan makes some of their own, All korean cars pretty much use the same basic stuff.
Converters are not that simple their are many many things to consider when buying one. Do you want the fastest 60ft or the highest mph. Usually the goal is to find a combination that gives you the best of both but there is always a give and take. It is completely a hydraulic system so many things will change it mildly.
Often 2 different people in the same car will give you 2 different stall numbers that seems to be true.. Usually the best way to rate a converter is by multiplication numbers. Converters can range from 1:1 to 3.17:1 being the highest I know of. If the multiplication is high you will hit the wheels with the most torque on launch.
Getting high multiplication will reduce your mph. Stall number isn't everything. A converter builder will usually consider the combination to build a unit that works for it and then take an educated guess at stall speed. Stall speed is an effect it is not an exact science. Results may vary, experience is the only way to get them right.
Almost every major city has at least 1 or 2 transmission shops that have purchased equipment to build their own converters and as the economy gets worse those places do more and more stuff to keep a float.Others do it because of their love for racing. Not all will be good with racing but if you can find one local to you that is talk to him.
It gets expensive shipping converters back and forth to get things right. A guy who knows what he is doing will have no problem cutting your converter open in front of you and explaining to you what it has, doesn't have, needs, or just tell you the honest truth that it is a piece of junk.
I give that news to people all the time and half the time they doubt me because of it. The truth hurts, people don't want to think they paid good money for junk, especially when they can't tell the difference. When dealing with someone local you can get a real warranty, and after warranty service.
It is hard to guarantee a race converter, you sell it to people who are doing their best to break it.Without experience you will fail quickly trying to guarantee them.As the consumer if you can see it for yourself an understand it a little better you can begin to figure out what you need and what will benefit your combination the most, not just stall speed. A converter is so much more than a number! Lockup changes everything too, but does not matter to most racing.
Alan
Last edited by DirtyD0g; 11-17-2011 at 09:25 PM.
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