[cdeslandes]

So what is pre-torqued semi-LSD? Do both wheels lock up and spin at the same speed? Is it a Helical based locking differential or a clutch pack?

Or did lexus take the cheap route and is using individual corner brakes to stop the spinning?

It's a clutch-type LSD that couples the two wheels with a spring. At first, the two wheels are locked up by clutches applied by the spring. If you apply too much power or lose traction (wheel on ice...) you WILL spin a wheel, but the opposite wheel will still get some torque (equal to the torque needed to overpower the coupling spring).

Only a specific amount of torque is "guaranteed" to a wheel. By opposition, a "true" LSD can apply a high percentage of the total torque (or even 100%) to the wheel with traction.

That, and they have traction control that applies individual brakes, too.

 

[SilverF16]

Thanks for the technial explanation. Now, in practice, how does this work?

With VDIM turned off, If I round a slow corner, and floor it, will I paint 2 strips of rubber or just one? How is this design different from the standard clutch pack LSD?

 

[Badman Forever]

from the few times i've launched w/ trac off from a stoplight.. i've been told by the people behind me that there were 2 even tire track marks.

 

[METEORO]

from the few times i've launched w/ trac off from a stoplight.. i've been told by the people behind me that there were 2 even tire track marks.

yup tried it, two solid marks. But when you really need it, coming out of turns, it does not work as well. You easily reach its limits, and it acts almost like an open diff.

I think Lexus' idea was to use it to control wheelspin before VDIM engaged, it was never their intention for it to b used as a true LSD.
And for that job, then yes it does the job.