[s-cars] EDL Vs. Manual Diff Lock

[Keith Maddock]

Great summary Wayne!

Jeremy, my personal suggestion is to buy a 95.5 with EDL and then install a Torsen.

A locker is the best  for ultimate traction but only usable in very specific circumstances.  In all other circumstances, you're stuck with a open diff.

Both EDL and Torsen work all the time (S6 EDL cuts off above 40mph I have read), and the synergy you get with the combination of both is about as good as you could get for our cars.

I have a good technical paper from the ZexelTorsen boys that describes well the benefits of Torsen with EDL, I can forward to anyone interested.

Cheers,
Keith "EDLBoy by day, TorsenBoyJunior by night" Maddock

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


>>> "Wayne Dohnal" <dohnal at hevanet.com> 20:13:51 15.01.2003 >>>
>Can anybody discuss the pros and cons of each? Trying to decide if it's
>worth it to go for a 95.5 S6 Vs. a 95
>Jeremy Hull

Keith Maddock has discussed this at length in the past.  If you can find his
posts in the archives that would be the best.  I'll try to hit the meat of
what he said, but he works with this stuff and explains it the best.  The
only Pro of EDL is that it automatically engages.  So if you hit some
slippery stuff unexpectedly, it's there to help you when you might not have
engaged the diff lock.  It's also cheaper to manufacture, since all of the
hardware is already there for ABS.  It's only 'a simple matter of
programming' which, of course, is free (sorry, Keith, I couldn't resist).

Once the diff lock is engaged it is superior.  If one wheel has zero
traction, all of the torque on the axle will go to the other wheel, the
ideal situation.  With EDL a maximum of 50% of the axle's torque will go to
the wheel with traction, while you're heating up the brake pads on the
slipping wheel with the other 50%.  But you will never achieve even 50% of
the torque to the wheel with traction because the EDL must let the slipping
wheel rotate some to test if it slipping or not, resulting in further
inefficiency.

I'm amazed how fast my S4 will accelerate on packed snow with the diff
locked.  And it does it in a straight line, too.  But I can't help feeling
that most people would rather have the sport steering wheel than a locking
rear.

Wayne Dohnal
1994 S4

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