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stall speed Vs. stall ratio ...?

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Post  rmcomprandy January 26th 2014, 11:48 am

I had a long discussion with a top engineer at hydro-matic last evening and after further thought I kinda under stand but, I need more info about "stall ratio" ...

I now understand that a given torque converter can multiply flywheel torque at a certain RATIO, which is mostly determined by the stator and fin angles. And, that as the "lock-up" increases, (without assist of an internal clutch), the ratio of torque improvement will go DOWN...
It was explained to a number of us there that OEM's could run a higher stall ratio, (as high as 2.2 to 1 to get more power driving the wheels), now-a-days because of the internal LOCK-UP CLUTCH but, to get any real lock-up without the internal clutch that the stall ratio might suffer all the way down to 1.7 to 1 or so..

Where do the different high performance and racing torque convertors fit into this equation...??? Especially given the different "stall speeds" of the different types.


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Post  cool40 January 27th 2014, 2:53 pm

Dang Randy, why didn't you ask this brain teaser in the p-51 thread? You could'a killed it on the first page! Lol
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Post  dfree383 January 27th 2014, 5:45 pm

Hummmmm......... study 
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Post  supervel45 January 27th 2014, 11:59 pm

Just a wild quess Randy. I would say the ratio would (is) be lower, because the race convertors are a smaller diameter. It would seem they would loose internal leverage to the input shaft, just like a short breaker bar compared to a long one, but instead of doing it mechanically, it is done with fluid manipulation. The power (at the wheels) is gained by the engine operating at a Higher RPM at the Takeoff. The less surface area of the fins, probably comes into play, along with heat and fluid viscosity also. Like I said just a wild guess. Think of a lock up convertor like a standard clutch. Once it is locked there is no torgue increase. After it is locked up in second gear there is no torgue manipulation, because it is 1/1 ratio from then on. All of it torque manipulation is off the line in first gear, from a standing start. The math used by the designers (engineers) for the ratio's, might not be what we are used to dealing with either, and may have a different meaning in terms of what we are used to dealing with in the field? If the engineer wrote the theory on paper it would probably take three pages and diagrams to explain? Ask the engineer about the GM Hydromatic experiment with a variable speed torque convertor for the TH400 in the 60's, and why it did not work out? I am interested in this also, as there is not much information about it.

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Post  rmcomprandy January 28th 2014, 12:34 pm

supervel45 wrote:Just a wild quess Randy. I would say the ratio would (is) be lower, because the race convertors are a smaller diameter. It would seem they would loose internal leverage to the input shaft, just like a short breaker bar compared to a long one, but instead of doing it mechanically, it is done with fluid manipulation. The power (at the wheels) is gained by the engine operating at a Higher RPM at the Takeoff. The less surface area of the fins, probably comes into play, along with heat and fluid viscosity also. Like I said just a wild guess. Think of a lock up convertor like a standard clutch. Once it is locked there is no torgue increase. After it is locked up in second gear there is no torgue manipulation, because it is 1/1 ratio from then on. All of it torque manipulation is off the line in first gear, from a standing start. The math used by the designers (engineers) for the ratio's, might not be what we are used to dealing with either, and may have a different meaning in terms of what we are used to dealing with in the field? If the engineer wrote the theory on paper it would probably take three pages and diagrams to explain? Ask the engineer about the GM Hydromatic experiment with a variable speed torque convertor for the TH400 in the 60's, and why it did not work out? I am interested in this also, as there is not much information about it.

I did mention the "switch pitch stator" and he said its demise was all about money and what was ADEQUATE to do the job at hand.
He also said that fuel economy, (CAFE numbers), emissions constraint and efficiency drive the whole OEM vehicle industry. He even mentioned some diesel applications with TWO stators in the torque converter.

This whole conversation got started just trying to understand why Super Stock guys have 2 or three different converters for different tracks and elevations which all share the same stall speed but, are changed because some are quicker in the 60ft, some are faster in the middle of the track and some lock up harder but, outside they all look exactly the same; it seems that the stator is the ONLY difference.
We're talking about HUNDREDTHS of a second here and I personally am trying to get a real education about it. He mentioned that "stall ratio" is probably a main reason.

How is it controlled and what can be done in a RACING torque converter to help it or help lock-up...? SWAY the "teeter toughter" so to speak.

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Post  supervel45 January 28th 2014, 1:58 pm

Thanks Randy. It is a fasinating subject and tease's the mind for sure. I try not to think about it to hard, and it is very difficult to articulate in a blog. I would talk to the convertor builder's and see what they allow, if they will talk? If you talk to him again, ask him how much temp. and fluid viscoticity changes the ratio if any?I almost mentioned the Chevy guys in the SCJ thread, and deleted it before posting. They also liked the fact that the square ports where taller and some had the Holley flange instead of the Q-Jet, and some of the Q-Jet manifolds where taller also, than the base (passenger)ones. Do you remember the Clutch TH400's, they where a pretty neat idea? The Ford C-5's with the centrifical lockup convertor was another good idea on paper that failed in practice.

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Post  steven gregoire January 30th 2014, 6:47 pm

thats why i make a point to avoid engineers
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Post  rmcomprandy January 30th 2014, 11:46 pm

supervel45 wrote:Thanks Randy. It is a fasinating subject and tease's the mind for sure. I try not to think about it to hard, and it is very difficult to articulate in a blog. I would talk to the convertor builder's and see what they allow, if they will talk? If you talk to him again, ask him how much temp. and fluid viscoticity changes the ratio if any?I almost mentioned the Chevy guys in the SCJ thread, and deleted it before posting. They also liked the fact that the square ports where taller and some had the Holley flange instead of the Q-Jet, and some of the Q-Jet manifolds where taller also, than the base (passenger)ones. Do you remember the Clutch TH400's, they where a pretty neat idea? The Ford C-5's with the centrifical lockup convertor was another good idea on paper that failed in practice.

Most companies in the aftermarket won't really like taking any time talking about the real intricacies of their product technicalities unless you are buying something and I don't really blame them.  Their time is certainly better spent making money because that is what they do for their living.
There is just no way to "go to school" and learn about this sort of thing without actually being involved within it.

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Post  dfree383 January 31st 2014, 9:20 am

I agree randy, you need to learn when the chance arrives.
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Post  ultimatelenny January 31st 2014, 9:36 am

rmcomprandy wrote:
supervel45 wrote:Thanks Randy. It is a fasinating subject and tease's the mind for sure. I try not to think about it to hard, and it is very difficult to articulate in a blog. I would talk to the convertor builder's and see what they allow, if they will talk? If you talk to him again, ask him how much temp. and fluid viscoticity changes the ratio if any?I almost mentioned the Chevy guys in the SCJ thread, and deleted it before posting. They also liked the fact that the square ports where taller and some had the Holley flange instead of the Q-Jet, and some of the Q-Jet manifolds where taller also, than the base (passenger)ones. Do you remember the Clutch TH400's, they where a pretty neat idea? The Ford C-5's with the centrifical lockup convertor was another good idea on paper that failed in practice.

Most companies in the aftermarket won't really like taking any time talking about the real intricacies of their product technicalities unless you are buying something and I don't really blame them.  Their time is certainly better spent making money because that is what they do for their living.
There is just no way to "go to school" and learn about this sort of thing without actually being involved within it.

You are correct Randy, most companies will not elaborate on this subject as it gets very involved and very confusing. The formula you are speaking of was hit on by GM Hydramatic quite a few years back when there were differentiating this formula, called the 'K' factor. This was the helpful in determining approx. stall speeds with pump size, pump fin angle, stator fin count, angle and length, turbine fin count. This formula worked great when working with one engine, ratio, weight ,etc, in a controlled factory setting, but when you start changing any of these fixed combinations, the "K" ratio changes along with stall and ratio. Today , with the ever changing technology and combinations in a racing applications, we have to be ever changing also with trying different style pumps, turbines and most important, stator design and important , stator design and development. Most companies today are always testing different pump, turbine and stator combinations in a lot of different size cores to achieve what every converter builder has been trying to accomplish since the beginning, as much stall as possible to leave as hard as possible and much efficiency possible for lock up, every automatic racers dream! I have been doing this for almost 35 tears, and I am still amazed at how much I learn every week, with the ever changing engine, chassis and tuning technology that is out there. I hope this helps a little, but like I stated, this is something that changes from combo to combo, and I know that with converters, one size and style does not fit all.
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Post  whitefield January 31st 2014, 12:02 pm

Good info ! thanks  Cool 
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Post  rmcomprandy January 31st 2014, 1:23 pm

ultimatelenny wrote:
rmcomprandy wrote:
supervel45 wrote:Thanks Randy. It is a fasinating subject and tease's the mind for sure. I try not to think about it to hard, and it is very difficult to articulate in a blog. I would talk to the convertor builder's and see what they allow, if they will talk? If you talk to him again, ask him how much temp. and fluid viscoticity changes the ratio if any?I almost mentioned the Chevy guys in the SCJ thread, and deleted it before posting. They also liked the fact that the square ports where taller and some had the Holley flange instead of the Q-Jet, and some of the Q-Jet manifolds where taller also, than the base (passenger)ones. Do you remember the Clutch TH400's, they where a pretty neat idea? The Ford C-5's with the centrifical lockup convertor was another good idea on paper that failed in practice.

Most companies in the aftermarket won't really like taking any time talking about the real intricacies of their product technicalities unless you are buying something and I don't really blame them.  Their time is certainly better spent making money because that is what they do for their living.
There is just no way to "go to school" and learn about this sort of thing without actually being involved within it.

You are correct Randy, most companies will not elaborate on this subject as it gets very involved and very confusing. The formula you are speaking of was hit on by GM Hydramatic quite a few years back when there were differentiating this formula, called the 'K' factor. This was the helpful in determining approx. stall speeds with pump size, pump fin angle, stator fin count, angle and length, turbine fin count. This formula worked great when working with one engine, ratio, weight ,etc, in a controlled factory setting, but when you start changing any of these fixed combinations, the "K" ratio changes along with stall and ratio. Today , with the ever changing technology and combinations in a racing applications, we have to be ever changing also with trying different style pumps, turbines and most important, stator design and important , stator design and development. Most companies today are always testing different pump, turbine and stator combinations in a lot of different size cores to achieve what every converter builder has been trying to accomplish since the beginning, as much stall as possible to leave as hard as possible and much efficiency possible for lock up, every automatic racers dream! I have been doing this for almost 35 tears, and I am still amazed at how much I learn every week, with the ever changing engine, chassis and tuning technology that is out there. I hope this helps a little, but like I stated, this is something that changes from combo to combo, and I know that with converters, one size and style does not fit all.

Lenny, I appreciate your time.
I am guessing that the "bolt together" converter was originally used for actual testing all kinds of stators fin count, thickness, angle and through window. (All terms I recently was made aware of, LOL).
Stator specifics seem to be the most changed and track tested.
I was trying to kinda understand what stator changes would affect "stall ratio" and that part of the scenario and what is done to satisfy a specific kind of finished need.
Then, (of course), there is the pump fins and angle of discharge along with the turbine components making this a constantly changing circle.

Years ago I ran, only one of two in the country, GT-1 road race cars with an automatic transmission. No governor but, even still had a vacuum modulator to soften downshifts with a normal shift pattern; just manual.
We had our TH400 trans' completely done at Hydra-Matic development, (this guy at the dinner was the person in charge), and/but using other transmission parts and doing things like furnace welding one internal planetary gear inside another machined internal gear housing, they made us two 1.96/1 - 1.34/1 - 1/1 finished drive ratio transmissions.

The special converter they made us was light and a very tight 9 inch unit with a low stall speed for its size and the lock-up was really phenomenal. He just mentioned to me last week that the stator in that converter was simply a production OEM stator with every other fin removed.
Now, given how my mind works, I gotta believe that the "stall ratio" was not very high.




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Post  ultimatelenny January 31st 2014, 2:41 pm

I agree with you, very tight converter, low ratio. GM , ford guys will want to kill me now, did a lot more R&D back in the day to develop the high perf part of their converter deal. Using the 9" core, easier to spin up(engine acceleration) which would equate to higher stall, but keeping the pump tight and creating more flow between the pump and turbine by eliminating windows, or vanes from the stator tells me that they were well ahead of the curve on trying to get the perfect balance, high stall with good lock up. Converter theory remains the same even today, we just have a ton of more technology, data, and a better array of cores and parts to work with. The advance in data acquisition in the past few years has been one of the most revolutionary tools when it comes to converter tuning and development, the more data the better. Even if some data is thought to be insignificant, it will help every individual combination to fine tune the converter to that specific combo, again, one size doe's not fit all.

PS - oops, sorry for rambling
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Post  Larry T February 1st 2014, 1:36 am

lenny,do you have away to test the converters you build to get the data you are talking about?let's say I ordered a converter you build it i put it in and its too tight.when you get it back and do your thing to it do you have data to go by before and after the fix?
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Post  ultimatelenny February 1st 2014, 11:18 am

Larry T wrote:lenny,do you have away to test the converters you build to get the data you are talking about?let's say I ordered a converter you build it i put it in and its too tight.when you get it back and do your thing to it do you have data to go by before and after the fix?

Hi Larry, if you had a trans dyno that would utilize a converter behind it , you could get a static stall check, but you would be getting what it would flash to behind the power source you were using. I have seen and used engine type dyno's and electric motor type, so this is not helpful in the racing world where the combos and variables are endless, therefore stall is indigenous to the torque applied in one individual combo.
There is no set formula, or chart, to give you the right piece in each combo, because every combo is different. I rely, as well as everyone in the business,on many years of experience with every possible combo under the sun, to start with all the info on a customers set up. I would then choose what core style, pump angle, stator fin number and degree and turbine to target the exact stall he would need in THAT particular combo, according to many similar combos done in the past. This personal style approach increases the chances of getting the right piece the first time, as opposed to getting a converter off a mass produced shelf. Now here's where the second part of your question comes in, after running the converter and getting some seat time, tuning and data on the converter, we can look at the data, and hopefully we get it right the first time. If the data shows we can improve on it, whether a little too loose or tight, I will take it and move it exactly where it needs to be, given the data. 99% of the time these are very small adjustments, but make all the difference in the world in keeping the engine in it's happy place. Hope this helps a little
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