[s-cars] Of EDL and switches...

[Keith Maddock]

Disclaimer:  The below comments are purely my thoughts from experience with EDL in general and do not represent first hand experience with Audi/Bosch EDL systems.  They are offered to add some general facts to the discussion, and I welcome any experience that may counter the statements below.

While I don't have first hand experience with the Audi/Bosch EDL, I have no reason to think that the EDL wouldn't also activate on the front axle.   There is nearly zero additional cost for a double EDL (front and rear) vs. a single EDL (rear or front only) system.  (The cost being a few extra lines of code in the software, and a small amount of extra development time).  Doesn't make sense to NOT have it, but we all know common sense doesnt always rule.

So if this is the case, the addition of front EDL is one advantage point of the EDL cars over the locker cars....

Triple EDL (front, rear, and center) is also possible but adds a higher degree of complexity to development, but is currently only used in truck-type vehicles with three open diffs (X5, M-Class, Sequoia, 03+ Yukon/Suburban/Escalade (the latter set being my paycheck the past 2 years) )  Triple EDL may be used across a torsen center in the future, but this is of course only heresey....

WRT to the EDL speed limit, I can again only offer conjecture based on industry experience.  All the Bosch literature I have read points to their EDL functionality having a double phaseout.  Above a certain level (we'll say 40 mph for now), the thought is that single-wheel EDL activations can cause stability concerns.  So, above this level (up to a complete cutoff speed, say 60-70mph perhaps) the EDL will control a single wheel spinup by applying both rear brakes evenly (obviously a stability priority over acceleration here).  Now, I will say that all these publications are all regarding 2WD vehicles, I dont know if they do a similar 2-wheel activation on the AWD cars, or just turn the whole thing off, since a single wheel spinup is less of a concern on a AWD vehicle than a 2WD, especially RWD vehicle.

Keith "More EDL banter forthcoming" Maddock
93 S4 ohne EDL, torsen center (Oregon)
95 968CS ohne EDL, torsen rear (here)


****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> Russ Panneton <russ at panneton.name> 19:33:40 01.11.2002 >>>
I'm almost positive the EDL operates on the front wheels, too.  I've felt and
heard the front brakes pulsing sometimes when I start out on glare ice.

Russ (8300', 11F and looking out over 12" of new powder!)

On Fri, 1 Nov 2002 08:17:29 -0500, Robert Pastore <rpastore at animalfeeds.com>
wrote:

>All Urs4/s6's have open diff's front and rear.   On the pre-EDL cars, you
>can lock the rear diff to dig your way out of being stuck, up to 15MPH.  At
>that point, the lock is automatically disengaged and the rear reverts to an
>open differential.  On EDL cars, the ABS system applies rear brake to limit
>the speed differential between the wheels.  I think EDL can function up to
>40mph, then the car reverts to straight open differentials.
>

--
Russ Panneton                          russ at s-cars.org
Nederland, CO              "Too bad ignorance isn't painful"
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