Can someone explain how a non/lu stall works?

[faststkr]

Say you have a 3200 non/lu converter. In effect how does the 3200 rpm come into play.
does the converter slip untill 3200 then catch and how does it work in relation to not have a cluth? thanks.

 

[TurboBurge]

The non lock up aspect has nothing to do with stall speed at all. The lock up clutch is a clutch inside the T/C which when engaged creates a direct link between the engine and transmission (acting somewhat like a clutch on a manual). From the factory the clutch typically locks up at cruising speeds to aid fuel economy. You can alter the lock up parameters in the chip. Some guys also run a jumper and manually lock up the T/C to improve 1/4 mile MPH. Some guys prefer the non lock up due to personal preference and cheaper cost.

 

[BJM]

Stall speed is easy to measure, plant your feet on both the gas and the brake and see what the tach reads while the engine is churning away and quickly heating up the transmission which must dissipate the power as heat.

How does it work?

If you hold the output side of the torque converter still while applying a known torque to the input side (the shell you see) the speed will rise until a fixed value is reached where the drag of turning the coverter equals the input torque. The speed at which this occurs depends on the design of the internal fins on the impeller, stator, and turbine components in the coverter.

Add more torque to the converter and the speed will rise again until equilibrium is reached at a new higher speed. A curve can be plotted of resisting torque versus input speed (all done while holding the output side still).

If you take an engine torque vs speed curve and plot on top of it the torque coverter curve described above the two line cross at the stall speed. At speeds higher than the crossover point the engine has less torque than what the converter needs to push its speed up so the engine sits at the crossover point. This is why for a given converter a bigger engine has a higher stall speed than a smaller engine. The bigger one has more torque and can operate further of the converter's curve.

 

[faststkr]

Can you brake it down for a brother, like whats happenening (inside the converter) say when you ride around with a 3500 non/lu stall under 3500 and then over 3500rpm.

 

[BJM]

The 3500 RPM is only a number that applies during the stall condition, car not moving, engine reving like crazy against the brakes. Once you are moving the output of the converter is turning as is the input side. A good converter will "lock up" to the point where the output is turning ~90-95% of the input speed at fairly slow speeds, well below the stall speed. Remember the stall speed is at WOT while stopped. Once both shafts are turning the behaviour changes.

To answer your question, at 3500 above or below, nothing actually changes. Also none of this has anything to do with it being a lock up style or not. The lock up style has an actual clutch to remove all of the slip so that input and output speeds are identical which saves gas. People here force it to lock up for the purpose of improving strip times and speed something the factory never originally intended. Forcing it to lock up will wear it out sooner. Its a trade off.