I can't provide any advice about tuning, since I am just getting into this myself. But the Torque Converter Clutch (TCC) is the mechanism that, at a programmed point, locks the torque converter up so it ceases to be a torque multiplication/hydraulic device and becomes a mechanical link like a regular clutch.
The torque converter has a certain amount of slip built into it. In the early ones, this allowed use of low numbers of gears. My '57 Chevy 210 Delray has a Powerglide with two gears.
The engine's power is used to basically force fluid from a set of vanes on the outside of the converter to a set of vanes attached to the inside of the converter. As the speed of the engine increases, the force applied to the fluid as it is flung off by the vanes increases. At some point, inertia is overcome, and the inner set of vanes begin moving along with the outers. By the way, the outer vanes are attached to the case, and from there to the "flywheel" of the engine (called a "flex plate" for an automatic).
At lower speeds, the hydraulics work to amplify (or multiply) the torque at the lower end of the RPM range. Your engine may be producing 100 lb-ft of torque at a relatively low speed, but due to the effects of the hydraulics, it becomes 110, 120, 130, or so lb-ft of torque at the input shaft of the transmission. Which is attached to the inner set of vanes in the converter...
Okay. Worked well. Still does. In fact, the higher the "stall speed" of the transmission, the higher the RPMs of the engine will be before the converter becomes, effectively, a solid mechanical device due to the hydraulic force. So higher stall speed converters help automatic trans cars launch more forcefully, since the torque is multiplied by the converter.
But, at road speeds, the converter will not achieve a hydraulic "lock." They slip slightly, since you aren't really applying a huge load at freeway speed. So, in the late 1970s, the TCC was introduced. At a specific speed and set of conditions, the converter locks up through application of electronic impulse, removing the fuel mileage loss experienced in, say, my 1969 Shelby. At road speed, if I vary the throttle, the RPMs will vary disproportionately to the change in vehicle speed. I may need to add 200-300 RPM to see any increase in vehicle speed.
There are lots of arguments for and against the TCC. It increases mileage and reduces heat generation, since it eliminates the need to push lots of trans fluid around to achieve lock-up, and avoide slipping. On the whole, a good thing.
But it can lock too soon, creating a situation where you could use the benefits of the torque multiplication effect, but can't get it because the TCC is locked. On an old Dodge Magnum my mother had in the early 1980s, the clutch failed in the locked position, and you couldn't engage gears - it was like trying to shift a manual trans car without being able to disengage the clutch.
I'm guessing the TCC Duty Cycle has to do with how early/late the clutch locks up. Beyond that, I can't guess. My 1999 with the A4 does pretty well, but I need to play with the shift points. That's another set of parameters. Set too low, and you "hunt" gears (that's the term GM used relative to my 1984 Trans Am with the A4 trans, back then). You shift up and down, because your shift points are low, but the throttle position keeps kicking you back into lower gears due to slight foot position changes. Set too high, and you wind out in all the gears all the time, and if the PCM Torque Management (TM) is turned off (or even down), may bark the tires at most or all shifts.
Sounds cool but, as a 20 year old college student with a recent Shelby GT500 (A3 trans), it created problems. The factory shift kit in that car made for hard shifts, and if the pavement was wet, you got chirps and barks at any shift. To the point that, after turning onto my girlfriend's residential street and chirping the tires during an almost-closed-throttle shift, the local constabulary felt a need to follow me into her driveway, then hit the lights and siren.
Her father was service manager at the dealership that maintained the police cars and, on hearing what had happened, gave John Q. Law a quick lesson on torque multiplication, wet pavement, wide tires, and being a jerk.
So the long and short of it is that the TCC is useful at highway speeds, and to reduce wear at cruise regardless of speed. But you want it out of the way when you are engaging in "spirited" driving. In fact, on some of the early TCC cars, I'd heard of owners removing the fuse or disconnecting the wires so the TCC wouldn't engage.
Doesn't help with the parameters, but may help explain why they're there...
Corvette Store
Can anybody point me to information about transmission tuning???
