Quote:
Originally Posted by JohnnyGrey
You guys can't quantify TC losses like that. The reason it's called a torque CONVERTER is because it converts some of the RPM on the input shaft to additional torque on the output shaft. It doesn't do this as efficiently as a set of gears, but the power loss isn't as dramatic as the apparent RPM loss. You gain some torque at the wheels.
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Yes, that's true some of the time, but I doubt that it's true when I'm climbing that hill at 32 MPH. I know that when the car is stopped and the throttle is applied, the torque converter can at least double the torque in most cases. It has something to do with the stator redirecting fluid flow inside the torque converter. As the car goes faster, at some point the overrunning clutch allows the stator to turn with the rest of the torque converter. When that happens, there is no more torque multiplication, so any slippage is just generating heat and not contributing to additional torque. I took a look at the "HowStuffWorks" web site. It says that the stator will begin freewheeling at about 40 MPH. I think that this is for a heavy load in high gear. At lighter loads the stator should freewheel at lower speeds. There is probably a formula to calculate when the torque converter is multiplying torque. It probably happens when the output speed of the torque converter is less than a certain fraction of the engine speed. What that fraction is I don't know. There is probably some variability according to the type of torque converter.
Here is where I read the basics of the torque converter.
HowStuffWorks "The Stator"