How Torque Converters Work
The more you understand about how things work, the better off you will be in making decisions on performance upgrades. Torque converters are often misunderstood. They are complex parts in an even more complex system - the automatic transmission. A clutch and torque converter have few similarities. They do perform a couple of similar functions. They both allow you to come to a stop and not stall your engine. The other is that a clutch and a torque converter both connect the transmission to engine power. That's about where the similarity ends.
The outside cover of a torque converter has to be strong to maintain rigidity under stress from torque. Inside the converter is a turbine and a stator. The turbine connects to the input shaft from the automatic transmission. When the turbine moves, the vehicle will move. Stators are used to multiply torque. They are a unique component.
As the engine turns at increasing RPM's, the torque converter pumps more and more fluid through it causing the turbine to turn faster. This leads us to stall speed, which most performance enthusiasts are interested in. Stall speed is the RPM that the impeller of a torque converter has to spin to overcome a given amount of load and begin moving the turbine. Or, you can say stall speed is the RPM that the torque converter must spin to build enough fluid force on the turbine to make a car move at full throttle.
Making a small car move with one engine/torque converter/transmission package is easier than making a heavier car move. Weight of a vehicle comes into play as to an actual stall speed. Engine load (torque) varies between engines and the given torque curve for your particular engine.
There are even more factors that can effect a torque converter and the stall speed. Given this basic knowledge, you can see that the torque converter is just one piece of the whole car when it comes to stall speed and power transfer. Choosing the best torque converter for your application depends on several factors: Weight of the vehicle, Knowing the amount of engine torque at _?_ RPM, application/driving needs and more. If your engine makes the most torque at 3,200 RPM, a 2,000 - 2,400 stall speed torque converter will probably not be the best choice. You want to match the engine's max torque to the torque converter, because modern torque converters multiply torque. If the torque converter and engine are well matched, the max torque from the engine is multiplied to give you maximum torque at the rear wheels.