Re: U/S Torsen

[Eliot Lim <eliot@u.washington.edu>]

> during development of the syncro, they had to install a disengager
> so that the VC would not cause rear wheel lockup, something caused
> by its exponential characteristics.
> 
> then they realized that the disengager didn't know the difference
> between overrun and reversing, thus you only had 2wd for reversing.
> 
> at this point my memory fades, i don't remember how they got around
> that, but the fact that they had to engineer all these extra bits
> to accomodate an uncooperative device to me makes it "ugly".

following up to my own post, i believe the solution to keep 4wd
engaged during reverse is to tap off the reverse light switch.
wouldn't a full time system be far more simple and elegant?

here is another instance of "ugliness" of VC systems.  the wildly
successful WRC lancia delta integrale used a center VC diff.
they programmed the engine computer to apply a little throttle
during braking so that the VC wouldn't lockup the rear wheels.

i still don't completely understand why VCs have this effect, but the
various solutions to this problem is well documented.

remember that there are two completely different ways of deploying
VCs in a 4wd system:

1) part time automatically engaging 4wd, where the VC acts as the
center diff as well as the "transfer case"

2) full time 4wd with the VC acting as a limited slip device for
the conventional diffs.

both have their share of problems, which can be overcome.  i still
prefer to have systems that don't generate problems in the first
place. 

the torsen's biggest weakness from what i can gather, is strength.
the computer controlled clutches require hydraulic pressure to operate
which is fine if you have a slushbox but far more costly if you don't.


eliot