Torque converter

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Mopar Tim

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Hello all. I know how a torque converter works, what I want to learn is how a different stall speed converter works. I thought stall speed was just a way to convey how fast the engine could idle without engaging the driveshaft. I could use a little education. Thanks:burnout:MT
 
The stall speed refers to the maximum engine speed that can be achieved when raising the speed of the engine with the trans in gear and the brakes locked. It is essentially the amount of slip built into the converter. The idea is the higher the stall speed the more the engine speed can be raised to get more torque applied to increase the speed of take-off from a stop.
 
and it can vary depending on engine torque and vehicle weight, and I think most aftermarket units are overrated-actually less than advertised
 
The stall speed refers to the maximum engine speed that can be achieved when raising the speed of the engine with the trans in gear and the brakes locked. It is essentially the amount of slip built into the converter. The idea is the higher the stall speed the more the engine speed can be raised to get more torque applied to increase the speed of take-off from a stop.

This is a pretty good lay mans explanation and I'll only add to it. Since the science of it is way more complicated.

The stall speed refers to the maximum engine speed that can be achieved when raising the speed of the engine with the trans in gear and the brakes locked.

This is mostly correct in a way. The engine speed is raised without a serious engagement or drive of the wheels. Once the converter reaches the stall speed it is rated for, and that is very variable for each converter no matter what they rate it at, the car starts to move . Do note that it can and will move before the stall speed is reached. It just lacks power.

Even with the brakes on, the car can be pushed forward before the rated stall RPM is reached. Though, when it is reached and gone beyond, it's light them up city.

It is essentially the amount of slip built into the converter. The idea is the higher the stall speed the more the engine speed can be raised to get more torque applied to increase the speed of take-off from a stop.

The part in bold. This is a really good description.

The second part is also really good and a basic dead on. Heres the idea in another way to help understand it. Your cam and engine start to make nice power at lets just say.... 2000. The cam operates in the 2-6K range. If you delay the strong engagement of the trans and let it slip a little bit to quickly get to that 2K RPM area, the car doesn't get bogged down with the weak engine torque and bog or stall out. The higher stall allows the engine to get into it's power area and then the converter starts to work.
Your off the line performance increases because of this.

Now lets step it up to a more radical ride. Lets pretend we have a Duster with a very powerful engine and a big cam. This set up doesn't start to work until 4500/4700 RPM. Thats a lot of RPM to wait until you get moving from a dead stop. But since the starting line is where you launch from, you bring the RPM's up past the converters stall, and for Ha-ha's, we'll say it is a 5000 stall, with your trans brake activated, you hit the button to take off releasing the trans brake and into first you go.

You could launch at 5500 or 6000. (Everything is dependent on everything on where you launch from RPM wise.) Everything goes at once. "Launch" is the perfect word here. Like a rocket, everything engages at once and off you go. But your in your power band. Where you want to be.
And that is dependent on everything else. EVERYTHING
 
just google torque converter stall speed...lol
 
Stall speed is a function of engine rpm. The more torque an engine makes, the higher the rpm the converter will stall, or lock up at, and transfer that torque to the transmission.


There are two types of stall speed-foot brake stall and flash stall.
 
i just pull our my mopar service manual and it is all right there in black and white......
 
think of a converter as one fan blowing air at another .At some point it will move enough air to turn the other fan and this would be the stall speed.If you change the pitch of the fan blades in either fan the speed that the second fan starts turning at will change.
...Now rev up the blowing fan quickly and it will spin a bit faster before the second fan starts to turn because it will slip briefly until the air starts turning the other fan...this would be the flash stall speed.
In a transmission the prime mover would be oil rather than air...
 
i just pull our my mopar service manual and it is all right there in black and white......
I wont ask any more stupid questions. damn you are rude. And nowhere in the mopar service manual talk about how stall speed relates to engine performance. I did say I know how torque converters work. :wack:MT
 
OK, I wanted to ask this before but waited till all the stuff was mentioned above.

After launch, how much effect, if any at all, does the torque converter have on the RPM drop from first to second and second to third? I was under the impression that those variables could be adjusted somewhat by a custom torque converter shop. I have heard a few cars at the strip that seemed as though the converter was slipping a little at the gear changes keeping the RPM up in the torque band. Is that the torque converter or something else I am missing?
 
I wont ask any more stupid questions. damn you are rude. And nowhere in the mopar service manual talk about how stall speed relates to engine performance. I did say I know how torque converters work. :wack:MT

comon Tim it was a joke..of course a service manual will not cover stall..the issue was covered very well.. i enjoyed the read also..... not near as bad as saying to google it...:violent1:
 
OK, I wanted to ask this before but waited till all the stuff was mentioned above.

After launch, how much effect, if any at all, does the torque converter have on the RPM drop from first to second and second to third? I was under the impression that those variables could be adjusted somewhat by a custom torque converter shop. I have heard a few cars at the strip that seemed as though the converter was slipping a little at the gear changes keeping the RPM up in the torque band. Is that the torque converter or something else I am missing?

As i understand it.. all effects are gone because you are in your power band and past the "flash" rpm... its in full pull mode.. as for the slippage sound... might be "loose" clutches applying? Maybe a tranny builder will chime in...
 
unless it is a lock up converter...ALL torque converters have some amount of slippage in them....after each gear change the engine should fall back on to the stall speed of the converter....which will depend on the torque out put of the engine...
 
unless it is a lock up converter...ALL torque converters have some amount of slippage in them....after each gear change the engine should fall back on to the stall speed of the converter....which will depend on the torque out put of the engine...

so thats the "slipping sound we hear at the track? I agree sometime it sounds really bad slip other times more of a lag then gone... i suspect a not so powerful build with too much of a converter will cause the long slip? and a correct converter stall matched well should have no slip or lag?
 
IMO, if you want a good explanation of stall speed and how it works, look up sites like edge racing converters, ATI, Dynamic Converters, Ultimate Converters and see what they have to say as they build them every day. Might get a clearer picture of what it really does vs a bunch of gobbly-gook and smart alec answers.
 
IMO, if you want a good explanation of stall speed and how it works, look up sites like edge racing converters, ATI, Dynamic Converters, Ultimate Converters and see what they have to say as they build them every day. Might get a clearer picture of what it really does vs a bunch of gobbly-gook and smart alec answers.

That takes all the different views out of it... I like hearing different views and thoughts and seeing what different eyes see... there are no smart alec answers just good ole discussion thats all...now Im going to go drive my dart to get some KFC and put the slippage to the test with my 2800 stall... all this talk has me wanting to feel and listen more attentively....
 
Thanks for the info. Sometimes I get too thin skinned. Sorry. I know more now then I did before. :burnout:MT
 
Actually Cracked a is answer is the best, go to the pros.
But on the short & quick, the above works well enough.
 
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