Wondering...

I drove a 740 wagon -- base model, manual tranny, no frills -- for 11
uneventful, reliable (though slow) years before moving up (way, way up) to a
Saab 9-5 Aero wagon. While I love the Aero on dry pavements, it's a
challenge to handle on wet, snowy or slick roads, it has a very busy, often
noisy suspension, and the FWD on this high-hp car creates some major torque
steer... making this car a challenge to handle on anything other than pretty
straight roads.

My other car is a '98 Audi A4 Quattro 4-door. I really love the AWD, and
wish the Saab had it.. The Audi's suspension is light years better than the
Saab's, and the A4 is far nimbler (though far less brutish under a heavy
right foot).

So, among other possibilities, I'm considering a move back to Volvo when the
Saab lease expires... anyone have any thoughts on the V70 Wagons, esp. the
"R" model? I've only read about it thus far, but it sure sounds as though it
has everything the Aero has, plus the Volvo AWD system. Comments?

 

I believe one of the differences between Volvo AWD and Audi AWD is that
Volvo is a front wheel drive until AWD is required. Audi splits the power
50/50
under normal driving. This was true of my 1990 Quattro. Someone please
correct me if I am incorrect in this assumption as it applies to the latest
Volvo and Audi models.

Jack

 

The big difference with the Haldex system (Current Volvo, VW, et al) is
this matter of division of power. Haldex is a computer controlled
clutch pack appended to the rear differential of a basically FWD
vehicle. If the computer (via AWD sensors) detects slippage, front vs
rear, the clutch is engaged instantly (as in 1/6 of a wheel
revolution!).

In the older systems with silicon "clutch" there was at least some power
to the rear wheels at all time. Any slippage at the coupling caused it
to begin lock-up with increasing slippage that raises of the temp of the
fluid, which causes the coupling to progressively lock - this applies to
the initial ('98 until ??) Volvo system and to the VW "Synchro" system.

Audi's Quattro system has always appealed to me, though I've never owned
one - for a variety of reasons. The Audi's "heart" is the Torsen
torque-dividing differential at the point of power input. While totally
mechanical, it allows variable division of power front/rear. This seems
a very elegant solution to me.

I've never had occasion to inquire into the systems used by BMW, MB,
etc. The Haldex seems to be the coming thing - inexpensive, yet
effective. It is being evaluated by most of the U.S. manufacturers at
this time. Visit the Haldex website to get the full story.

bob noble
Reno, NV, USA

 

I believe that the transverse engined Audis use the same Haldex system
as Volvo - the car is front drive until wheels slip, then power is added
to the rear. The longitudinal engined ones have the Torsen center diff
(earlier versions had an electrically lockable open diff), which sends
some power to front and rear all the time.

 

I am getting kind of tired correcting this... A car with Haldex is not
FWD, even if you are just crusing at constant speed. In such a
situation, it is more biased towards front (most of the torque goes to
the front), but that is not necessarily negative. Think of the fuel
that you save... Immediatly when you press the gas pedal, a larger
percentage of the torque is transfered to the rear. What I mean is
that the Haldex doesn't wait until it detects slip before increasing
its torque transfer, and the torque transfer is there when you need
it.

The torsen is good as well, while the visco is an inferior system. An
advantage of the Haldex is that it is no disaster if you have
differently worn tires front/rear, and it is also possible to change
only 2 tires (no need to change all at once as you have to with most
AWD systems).

Yes, cars from the VW group (including Audi) that have transverse
engines do have Haldex AWD system.

/Staffan