Re: Carrera 4 & diff designs

[u3109@calv1.cray.com (Mike W. Young)]

[snip]
> 
> the idea of using the viscous coupling as _the_ center differential, thus
> providing part time, automatically engaging 4wd was audi's, who then
> rejected it and gave it to vw.  lots of cars today use this simple
> concept, from minivans to the diablo VT to the latest carrera 4. 
> 
[snip] 
> also it hindered ABS operation.  recall that mitsubishi was not able to
> provide a VC rear diff _and_ ABS for a few years.  porsche, who was in a
> blitzkrieg mood at the time came out with computer controlled clutches in
> the 959 and original carrera4, also going on record about the evils of the
> viscous coupling. 
> 
> they were in good company.  mercedes also used CCC's over VC's.  it is
> thus supreme irony that the latest C4 uses a simple minivan style VC after
> building the most sophisticated 4wd system (in the 959) for reasons that
> are completely understandable.. to retain the rwd 911's feel. in
> retrospect i think it was a good decision.

VC also reduced the weight of the Carrera 4 drive train, and increased
performance since the car no longer carries around the "Unwanted dinner guest".

Quattro is a 400 lb weight penalty in the 90 however great a benefit it is, 
and I recalled Porsche reclaimed 200 lbs by switching to VC. Thats alot of
hardware to remove. It also facilitated a price reduction because the
Carrera 4 is using fewer parts,and is easier to assemble.

I *personally* think somewhere in the equasion, the old Carrera 4 drive 
train did not work very well with the new rear suspension, or upset the 
balance of the 993 chassis. I have read that they wanted to keep the RWD 
balance of the car, but that should have been just as possible with the 
old system. Porsche worked hard to develop the old system, and dropped it
after only a single iteration. This is not a normal Porsche move.
They are the incremental improvement car company. Perhaps its just that
they were not convinced their design was any benefit over a more simple one. 
Just an uninformed guess. 
 
> 
> i guess the lesson to be learned is that technical perfection is not
> necessarily a good thing.  a 911 with all quirks expunged is no longer a
> 911.  an audi without a 5 cylinder engine is ...(fill in the blanks)..  no
> wonder many enthusiasts are shunning the latest cars with honda style
> steering and quiet refined engine.  if audi is trying to ape the lexo
> barges, what do they have to offer the customer _over_ the lexo-barges? 

Those damn fickle customers, I guess Audi should just build what they like 
and learn to sell it, instead of following fashion. Remember the days
when they set the fashion trends?

Anybody else remember when a Toyota Cressida could be mistaken for
a 4000, or notice it was not long after the '88 body change that Honda
used even more Audi styling cues?
The ultimate compliment.

Audi was Quattro, before it was cool.

> one only has to drive one of these so called "perfect" japanese cars to
> really get a feel for "perfection"..a driving experience that is utterly
> detached, distant and cold.  it is as perfect as talking to a computerised
> telephone answering system that doesn't have bad moods or makes any
> mistakes.  it makes the high costs of audi ownership worth it for me. 
> 
> eliot
> 

Yeh, What he said!



Mike

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        Michael W. Young                 Americas East Technical Support Group
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