sailing220

Can somebody explain "stall" to me? Stall as in "a 2500+ stall," not "my engine stalled." [/align] [/align]

rford426

no idea either

Simon1

It's a reference to automatic transmissions. The stall speed is the point at which the transmission will rev to without overpowering the tires. It can probably be better explained but here's the reason why it is desirable. If you drag race and raise the stall speed of your tranny to a specific point, there is an actual diminished return it needs to be specific to your application, you can launchfrom the line at a higher RPM thus starting out higher in the power band which makes you faster.

sailing220

Thanks Simon, and how is this adjusted? [/align]

zkiller

You purchase an aftermarket torque converter.

sailing220

How much do those run (for the not-a-POS ones)? Does a shop have to do it or is it something I can do myself? [/align]

NyFordTech

This answers many ?'s about stall speed converters
http://www.protorque.com/FAQ.html#5

you need to remove the transmission to change the converter
converter is about 800$ im sure theres better prices out there dont feel like re searching
http://www.realspeedautomotive.com/histtocofor2.html

RedFire281

sailing220, don't feel like the lone ranger.lol. Stall speed is a function of the torque converter and is probably one of the most misunderstood pieces of equipment in all of automotive. A lot of people brag that they have a "stall speed converter", which displays a stunning ignorance because all automatic transmission cars have a stall speed converter - its the number that makes the difference. The converter is, to automatic transmissions, what a clutch is to manual transmissions. The whole idea behind different stall speeds is to allow the car to launch at, or just below, the point where the engine makes the most torque. That way, the engine doesn't have to build up to the peak RPM point - all of the power is already there, on tap.

Simply put, stall speed is the engine RPM level at which the torque converter "locks" and overcomes whatever resistance is present to turn the wheels - including the weight of the car, engine torque,and the brakes. Weight effects stall speed in that a lighter car produces a lower stall speed because the amount of resistance (weight) has been reduced. By the same token, a more powerful engine also lowers stall speed because increasing engine power has essentially the same effect as decreasing vehicle weight. Because each car might have differences in brake holding power, in two cars that are exactly the same weight, horsepower, etc., the one with the weaker brakes will display a lower stall speed, even if it really isn't, because the brakes will lose their grip at a lower RPM.

One of the worst mistakes is to buy a torque converter with a stall speed that is too high. This usually results in a car that gets horrible fuel economy and eats transmissions. That's because the converter is slipping all of the time, absorbing power and passing it along as heat to the rest of the transmission.

The most accurate method of determining YOUR car's actual stall speed is to launch the car at full throttle and note the RPM at which the car actually takes off. This will be quite low on cars in stock trim, maybe between 1800 and 2200 RPM., higher if the car is modified.The stall speed should be rated at about 500 - 750 RPM under your engines's peak torque While you don't want to end up with a converter with too high a stall speed, don't be too conservative because it is possible to get a converter with too low a stall speed, which will have roughly the same effect as too high of a stall speed. Know your camshaft specs; in stock trim you make most of your torque down low in the RPM range, and you probably won't need more that a 2500 RPM stall speed, if even that much. Know your car's weight; remember, lighter cars will lower the rated stall speed; heavier cars will have the opposite effect. Install good brakes because you want to be able to hold your tires still up to the point your engine produces peak torque. And also remember, high stall converters generate a lot of heat -which is the number one killer of transmissions - so get a good external transmission cooler.

sailing220

Thank you very much, RedFire281. This is exactly what I was looking for.

Are torque converters things that people actually buy (is there a clear benefit) or is it not very worth it?

Does it need a tune?
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281GT

"One of the worst mistakes is to buy a torque converter with a stall speed that is too high. This usually results in a car that gets horrible fuel economy and eats transmissions. That's because the converter is slipping all of the time, absorbing power and passing it along as heat to the rest of the transmission."

This information is not entirely valid for for modern cars. Starting the early 1980's torque converters are all equipped with a clutch that locks the converter solid at crusing speeds. This elminates most of the slippage and heat produced by a converter that has a higher stall speed.
Certainly "back in the day" one needed to be very careful about converter selection because of the extra slippage and heat this caused. With "modern" lock up converters this is a non issue.
The stock converter in the S197 GT stalls at 2450. Since the 3v engine doesn't start to make good torque until a higher rpm a huge improvement can be had by changing the converter for one that stalls at 3500. In the days before lock up converters a 3500 rpm stall speeed would as the previous poster indicates create all sorts of slippage and heat issues on the street.
Certainly a higher stall converter will cause some additional sluppage and heat but ONLY when it's being operated under a speed at which it locks, but this is a small percentage of driving. The only case where you'd probably notice it is during a night of drag racing where the converter would rarely if ever lock. For people who race a lot, drag or otherwise a higher capacity trans cooler would be a good idea, but again, many of the issues that were created by high stall converters in the past are no longer anything to worry about.