[s-cars] EDL fails (but my new 22's worked great!)

[Mark Strangways]

Nice Keith,

Makes me want my 5000 centerlocker :)

Mark
----- Original Message ----- 
From: "Keith Maddock" <keith.maddock at gmail.com>
To: "Taka Mizutani" <t44tqtro at gmail.com>
Cc: <s-car-list at audifans.com>
Sent: Tuesday, March 01, 2005 7:37 PM
Subject: Re: [s-cars] EDL fails (but my new 22's worked great!)


> Torsen on a 92-95 (non-EDL) car really doesn't buy you much when
> you're stuck in deep snow.  Generally here (at least part of ) your
> problem is that you have one wheel with nearly zero traction.
>
> For simplicity's sake just consider the rear axle (which is quite
> dominant on an 18% grade anyway...)
>
> With an open diff (IE broken locker on 92-95's), the most torque you
> can transmit (for any appreciable amount off time) to the wheel with
> traction is the same as the wheel without traction.
> Zero Traction on one wheel, zero traction on the other wheel: STUCK.
>
> With a torsen (retrofitted 92-95), the most torque you can transmit
> (for any appreciable amount off time) to the wheel with traction is 4
> times the amount as the wheel without traction.
> Zero Traction on one wheel, zero traction on the other wheel: STUCK.
>
> With EDL and an open diff (95.5) , the most torque you can transmit
> (for any appreciable amount off time) to the wheel with traction is
> the same as the wheel without traction.  However EDL tricks the diff
> into seeing a brake application as traction.  So you can get torque on
> the "good wheel" up to the lowest value of:
> A) max brake torque EDL will apply (or can apply if your brake pad is
> on fire from doing this...)
> B) 1/2 the engine torque.
> C) surface traction available (Mu * Normal Force!)
> Zero Traction on one wheel, up to 1/2 engine power on the other wheel:
> SOMETIMES STUCK.
>
> With EDL and a torsen, you are nearly golden!  It's the same as above
> but the limiatations of torque to the "good wheel" are now the lesser
> of :
> A) 4x Max brake EDL will (or can) apply
> B) 4/5 the engine torque
> C) surface traction available (Mu * Normal Force!)
> Zero Traction on wheel, up to 4/5 engine power to the other wheel:
> RARELY STUCK
>
> With a locker, you are completely golden.  100% of the torque can go
> to the good wheel.
> Zero Traction on one wheel, up to full engine power on the other wheel:
> NEARLY NEVER STUCK
>
> Of course of both rear wheels don't have much traction, you'll be
> fairly stuck anyway on a 18 percent grade with 9.5" of snow,
> regardless of what rear axle bits you've got...
>
> In this case consider that with the center torsen, your front axle
> torque is limited to 4x rear axle total traction.  If rear axle
> traction is zero, front axle traction is zero.
> STUCK :-)
>
> Cheers,
> Keith
>
>
>
>
>
> On Tue, 1 Mar 2005 18:27:53 -0500, Taka Mizutani <t44tqtro at gmail.com> 
> wrote:
>> I don't agree with that statement at all- Torsens do not work as well
>> as lockers in low traction situations, just a lot more friendly
>> driving on the street and turning.
>>
>> Too bad there is no Audi application for the new Eaton diff-
>> electronic locker that is a Torsen LSD when not locked.
>>
>> Taka
>>
>> On Tue, 01 Mar 2005 13:54:21 -0500, Serge Filanovsky
>> <s6serge at verizon.net> wrote:
>> > on 3/1/05 10:04 AM, LL - NY at larrycleung at gmail.com wrote:
>> >
>> > > IMHO, wouldn't have needed the shovel if I had diff lock.
>> >
>> > Or a torsen rear diff.
>> >
>> > Serge Filanovsky
>> >
>> > 95.5 S6 Avant
>> >
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