Re: A4 Electronic locking diffs... (kinda long)

[George Economou <economou@tiac.net>]

At 12:25 PM 10/12/96 -0400, Andy Poling wrote:

>Now, upon reading what I've just written about the operation of Torsen
>diffs, I can't help but wonder if the center Torsen diff on my A4Q won't end
>up fighting with the EDL if, say, both wheels at one end lose traction.  I
>think the result is that the Torsen will only come into play above 25mph
>when the EDL is no longer active, but I don't know how far Audi goes with
>the EDL braking.

I don't believe that the Torsen is fighting with the EDL.  The Torsen
operates over the entire range of vehicle speed, and continuously 
transfers power to the "axle" with most traction, regardless of
whether EDL is on or off.  Since EDL can only shift power from 
side-to-side, it can provide an individual axle more total traction.
The Torsen will respond accordingly.

But, as you said, there is probably an interesting dynamic occuring.
The Torsen is torque-sensing and lag-free, and EDL is speed-sensing and
not.

>I still think the ultimate solution would be Torsen diffs in all three
>locations, front, center and rear.  Can anyone offer a reason why this is a
>bad idea?

I think that's a great idea.  The Porsche 968 equipped with a six-speed
manual has a Torsen differential option.  The all-Torsen, no-slip model
works.

One may argue the point that "ABS/open diff" can deliver a higher
percentage of power to the opposite side.  But, I'd rather have the
smooth instantaneous, robust transfer of power that the Torsens
would offer.

George

96 A4Q
86 4KS