Re: AWD Alfa 164 Q4 [was: 5 bangers galore]

[Eliot Lim <eliot@u.washington.edu>]

On Fri, 11 Nov 1994, Ljubisa D. Stevanovic wrote:
> I would actually very much appreciate if you, or anybody else, is
> willing to share (point to) any good article written on the subject.

there were lots and lots of articles written about the 959 during its
time.  very very few magazines (least of all the american ones) truly
understand awd technology, which is why till this day a lot of people
are still spreading incorrect facts.  the most common item of
confusion is that people don't seem to realize that the viscous
coupling can be used in two very different ways: as a limited slip
device with a conventional diff and as a automatic drive engaging
device/differential.  magazines that don't know the difference 
would simply use the buzz word "viscous coupled" 4wd without
mentioning whether it is a full time or part time system.  they
would also attempt to disguise their ignorance by sprinkling a
lot of technical mumbo jumbo which amounts to nothing.

of the british magazines, performance car understands it the best and
they also happen to be the biggest enthusiasts (in the english
language press) of awd.  i must admit i did not understand the extreme
subtlety of the 959's variable torque split system for years.

> I guess I was confused with these four initial torque-split numbers. 
> How exactly is this "initial" defined by Porche; after all, as you said, 
> starting (parking lot) setting is 0-100 in all cases.

the 4 settings on the stalk are: dry, rain, snow and off-road (!!!)
dry starts out with a 40-60 split, rain 50-50.  the idea of
increased front drive for rain is because there will be less
weight transfer before wheelspin on a wet surface.

i don't know what the difference is between snow and off-road.  my
guess is that off-road probably has smaller tolerances for speed
differences before the center and rear differentials lock.  (or maybe
off-road simply locks both center and rear while snow locks only
center.. sounds familiar??)

i also believe that the snow setting locks the center diff, so none of
that fancy computer controlled torque splits happen any more, it will
vary torque in the same fashion as a 4000Q with a locked center diff.

> With continuously
> variable, microprocessor-controlled, torque-split with many input
> parameters, it doesn't make sense to talk about specific differential
> ratios (e.g. 50-50, 20-80, etc.) 

one could talk about constant speed torque splits.  e.g. travelling
at constant speed with "dry" one knows for a fact that the split
is 40-60.

>I suppose that if one chooses "rain"
> button, a computer map with one set of weights controls the torquesplit, 
> while "dry" button down-loads a different map with weights giving a car 
> more rear bias. Does this make sense? 

yup.
 
> I came across a couple of articles on the 164 Q4; one in Autoweek (Jan.
> 10, 94) and one in British Fast Lane mag. (Jan. 94). Both say that the
> car has "most sophisticated (and complicated) 4wd system to ever appear
> in a production road car." 
	^^^^^^^^

the 959 was hardly a production road car.  also, it is not clear to me
if these rags have driven or studied the 959.

i have also not read any comparison tests between the alfa and the
lancia delta integrale.. i would pick the lancia because of its
impeccable breeding and rally heritage.  too bad audi quit the
racing business.


eliot