drbobvs

OK a torque converter converter converts the flywheel power to my auto trans right? WHAT IS THE DIFFERENCE BETWEEN TORQUE CONVERTERS? What is "Stall speed" and why is it important? How does different stall speeds affect your vehicle and how do you choose?
Knowledgable people need only reply. Thanks in advance.


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chubrock

a torque converter has two "fans" in asealed container, one "fan" is attached to the trans, the other to the crank of the motor. Inside the converter is liquid, as the crank turns one fan the fan attached to the tranks is forced to move, well not forced but almost. Im not quite sure what the stall number means but i know it has something to do with how much grip it has or something like that

dkano

I've been meaning to ask about torque converters also, since I have an auto and have read on different forums that a tall torque converter will help an auto get into the 12s. The part that confused me was that I think I read somewhere that if you get the TCI 3000 it means that you have to rev the car to 3K RPMs for the car to start moving or something to that effect. Doesn't that mean that you're going to have to accelerate the car a whole lot more just to move an inch, like when you're stuck in traffic. I might just be mistaken so I would really appreciate it if someone could clarify that for me.

monkeydude3

I don't think that's the case... I think stall means where it firmly starts to engage... under normal conditions I believe it still drives the same. When you bury the pedal, and hold the brake, a 3000 stall would mean it revs to 3000 rpm...


I'm not sure, I have a manual... I know a few guys with older muscle cars that are autos


George

Phantom_Captain_13

two second search reveals:

http://auto.howstuffworks.com/torque-converter.htm

ren274u

great link, but it didnt explain stall speed, and the question about it above. anyone else know?

Professor Wizard

Lets see if the Professor can help.... Stall Speed is simple, yet confusing...


Stall is the speed at which the converter will hold the engine speed and not allow any further gain in RPM. (i.e., the engine "stalls"). That is to say, if you go WOT with your wheels locked, the engine would not go any further in RPM then the stall speed at which point it would either stall/die or just lug out at that RPM, unti you release the brakes. The Stall speed rating on your converter is the RPM at which the power transfer is most efficient. Below the Stall Speed - lots of slip - at and above the stall speed - near lock transfer.

The simple answer - you want a converter with a stall speed just below your “Sweet Spot� of Horsepower output RPM for maximum performance, however that wouldn't work very well for everyday driving as your engine would overrev every time you want to take off..

The more complicated answer involves as much the engine then the Torque Converter. The speed at which stall occurs with a given converter is a function of engine peak torque. The stall speed on a given converter will not be the same coupled to a tame small block engine when compared to a big block with all of the muscle features added.

When comparing stall speeds it is important to account for the engine that drives it. True converter stall can best be determined when a Transbrake is used. Testing for stall value by locking the wheel brakes generally does not produce a true stall value because the engine power can often cause wheel turn by overpowering the brakes, but it will give you a general idea.

Selection of the right stall speed for your vehicle should be matched to the engine peak torque, engine torque curve shape and vehicle weight. In general, the stall speed selected for your converter would be 500 to 700 rpm below the peak torque. This speed allows the margin for application of the torque reserve on takeoff. When selecting stall speed without having prior experience to go by, it is better to conservatively estimate the engine torque speed than it is to over estimate it. If you over estimate the torque output you will have a converter with a stall speed too low, making your car slow off the line and have slow ET. A properly selected stall speed will give you better launch and better ET. Within the converter, stall speed is balanced off against inefficiency after launch. Getting desired stall at the expense of performance after launch is just as costly as improper stall speed to begin. The optimum converter has careful selection and design of changes to the impeller, turbine and stator.

Stall speed should be matched to engine performance, the car weight, tire size and gear ratio. Proper selection of stall spec will make for quicker launch, better 60 ft. time and better ET. It is very important that these parameters be specified when ordering a converter to assure satisfaction.

While stall speed is very important it is by no means the only consideration when selecting a converter. Torque multiplication at launch and high-end efficiency are equally important. Stall speed can be attained in many ways that cripple the converter in other ways. Stall speed can be obtained at the expense of looseness at low speeds and loss of performance at higher speeds after launch. You want a converter that produces the right stall without sacrificing performance down the street or down the strip.

Stall speed is also affected by the torque converters efficiency ratios. Some brands are very efficient, and will stall the engine earlier in the RPM curve, while others are not as efficient, so there is always slip requiring a lower stall speed to get the HP to the wheels. Finding the correct stall speed will require a bit of experimenting depending on make/model of converter as well as engine performance statistics.

757GT

Stall speed= stock are cars have 2450 stalls. That means that if you hold your foot on the brake and your other foot on the gas it will rev to 2450 without spinning the tires. By coming off the line at a higer rpm supposing you get traction you will cut much better 60 ft times and it will get you a lower e.t. If you just take off normally it will not rev up to the top stall speed before it goes. Usually the number is a little higher than what it will actually do. Like the one in mine is the stock 2450, mine starts to turn the tires over after 2300 rpm. Coming off the line higher in the rpms puts you in the power band even quicker. Usually to get the good times with the stall you need drag radials, you come off the line that high on street tires and usually nothing but spinning will happen. Hope this helps. If not pm me and I will try to explain it better.

EDIT- Professor Wizard, you beat me to the punch, you explenation is much better than mine.

hawgman

More info can be found here

chevykiller

I was going to answer his question but thank goodness I read through the other posts first and saw wizard's response. It is not possible to explain any better than that. Well put, professor!!

On a side note, it is a good idea to use 2 tunes with seperate settings on your converter. One for street and one for the track on drags or slicks. Obviously as pointed out by 757GT.