Stall speed function

[odd boy]

Hi,

any one can explain what is stall speed, what is it for, and what it does with tuning

[joecar]

Are yo talking TC (traction control) or TC (torque converter)...?

[sorry, I couldn't help myself with the acronyms...]

[odd boy]

both,TC (traction control) & TC (torque converter) and in general, if possible.

[joecar]

The same term is used in two completely different mutually exclusive contexts (the term is overloaded):

TC (traction control):
if engine speed falls below stall speed during traction control mode, then PCM relaxes traction control... this is as best as I can understand this, and it is lacking... comes into play when traction control kicks in at low speeds when you do not want to lose engine momentum, for example when rocking back/forth when stuck in snow (...what is snow...?); I don't know that it has anything to do with the engine stalling but I may be wrong.

TC (torque converter):
stall speed is the engine rpm at which the TC couples... the force of the fluid on the turbine overcomes the drivetrain "load", and the turbine "couples" to the impeller, that is the turbine starts to catch up; you can test stall speed by holding the brakes HARD while you go WOT in gear (stationary)... the motor will spin up to the stall/coupling speed and one of 2 things will happen:
- the motor won't spin any higher being held back by the drivetrain "load",
- the motor overcomes the brakes and the drive wheels spin profusely;
In both cases the "slipping" torque converter is multiplying engine torque by something like 2 to 2.5 times and generating huge heat (e.g. 400 lbft engine torque is seen at trans input shaft as 1000 lbft... this will overcome brakes);
stall speed has to be matched to torque band (i.e. to cam), and has a dependency on torque levels (same TC will stall higher on a higher torque motor).

[odd boy]

thanks

[odd boy]

what changes I need to do?

[joecar]

what changes I need to do?

For traction control stall speed: I don't know.

For torque converter stall speed: after installing a higher stall ("looser") torque converter, you may find the engine rpm hitting the rev limiter on WOT shifts (or blowing past your desired shift rpm)...
you will need to do the following:
- firm up the shifts via tables for shift pressure, shift time, shift torque reduction;
- lower the WOT MPH and RPM upshift points to get the shift actual rpm to be what you desire (and not hit the rev limiter); when you do this you may have to also adjust the WOT MPH downshifts to be lower than the WOT MPH upshifts.

[odd boy]

thanks aloooooooooooooooot