Zzyzx

Personally I don't think the allroad has three open differentials. It is advertised as having a torsen center differential, with electronic front and rear.

The author basically states that the allroad is a poorly designed 4 wheel drive system.<ul><li><a href="http://www.rallycars.com/Cars/4wd_turbo_cars.html">http://www.rallycars.com/Cars/4wd_turbo_cars.html</a</li></ul>

PJD

$#%^ the author! He/She obviously has a bug up his @#$ for some reason. I realized after a couple paragraphs it was a bunch of dribble aimed at justifying his dislike of either Audi, or 4WD. For example...

-Points out a rear wheel distribution only on front spin for Audi a3, tt but no mention of the 60/40 drive split on the AR. Sorry author, but use the right data to support what you seem to want me to believe.

- Basically says ESP sucks cuz it overides the driver and prohibits fun, spirited driving. Well, if he bothered to do any research he would realize you can turn ESP off and throw the car around to your hearts content.

I didn't see much reason to read beyond this point. Basically felt the author didn't present very credible arguments so I stopped.

Besides, nobody is allowed to tell me the AR isn't the best AWD sport utility vehicle on the planet!!

Actually, the piece looked like marketing collateral from non Audi/BMW company. I'd recommend going to an unbiased source for a true comparison.

ukpik

If there were a list of the most heavily discussed issues on listservs and discussion boards, the torsen debates would be somewhere near the top.

Some years ago when I first got a quattro and subscribed to the Q-list (now www.audifans.com) I was fascinated by the endless technical and emotional discussions of various 4wd systems. The subject of the "spider bite" (a handling transient that may have affected hard-driven quattros, if I remember right) went on for months.

The discussion became so heated and arcane that a separate torsen list was established at
http://www.audifans.com/pipermail/torsen/. Here's a small taste of the traffic: http://www.audifans.com/archives/1999/11/msg00012.html.

kwh

This guy doesn't know what he's talking about when it comes to quattro. The AR, A4, A6, and A8 all use a Torsen center differential. The front and rear diffs are open; wheelspin is controlled by electronic traction control (EDL). The AR actually uses a four wheel detection logic similar to Mercedes, BMW, and Land Rover (which all use open centers) - it will brake up to 3 wheels at the same time. The EDL on other quattros is slightly less advanced and controls the front and rear independently (this may not be the case with ESP). The EDL system uses the ABS sensors and is now integrated with ESP.

April

Viscous coupling takes time to respond. Locking mechanical diffs are less refined and can be expensive to repair/maintain.

What could be more simple than using the ABS sensors in reverse to act like a limited slip ( and you only wear the brake pads, not something expensive to fix like LSD clutches ) and then having a good center diff like Torsen ? Much more flexible than most AWD systems out there.

Wir fahr'n auf der Autobahn

Hey from the A4 forum. Just dropping by and saw this cause I've read this article before.

I believe all audi's that aren't based on the A3/S3/TT/Golf/Jetta (B4 I think) use the same layout, Torsen in the center and open diffs in the front and back. The torque split is generally known to be 50/50 for the type of Torsen's that Audi uses.

Non-ESP based Audi's use EDL (electronic differential locks) which is a fancy name for traction control. If the ABS sensor sees one wheel say on the left spin faster than the right by so-and-so amount of speed, it'll apply the break to it.

ESP audis (and other companies like Benz, or DSC on BMW) have what they call stability control systems. There's a yaw sensor on the car that detects the direction its going and the position of your steering wheel. If it detects that your off course, it'll apply the ABS system accordingly and/or cut your throttle to put you back on course. Of course, this is more advanced than traction control/EDL.

The guy who wrote this article is a biased since he's looking at this from a rally perspective. When you hit things like mud, snow, sleet, rain, gravel etc etc.. its generally better to have some power to all 4 wheels, which the Haldex in the B4 platforms don't have.

If you look at the best AWD systems for the regular road survice, systems similiar to the Haldex system is the best. Read up on the Nissan Skyline GT-R and Mitsubishi Lancer Evolution 7 and you'll see what I mean. New rally cars will probably include stability control systems as long as the rules allow.

maugt

EDL is just operative at below 20mph (I think - it might be more or less), and is purely for if you're going slowly and one wheel gets stuck. At speed, the allroad is just center diff + ESP (which is only active during cornering, and brakes a wheel depending on over/understeer).

However, if you know what you're doing, its still faster to drive with ESP off because it reacts slower than you can.

Not entirely sure what the effect of ESP + EDL at &lt;20mph (or whatever the speed is) is. I suspect that there is a combination of the systems, hence the "more complicated" answers.

Wir fahr'n auf der Autobahn

but since both EDL and ESP operate on the ABS system, I wouldn't be surprised if the software was now 1 big package. They do similiar things to the brakes, just that ESP has extra sensors and is smarter.

maugt

My Jetta has it (for what good it does).

FastFast

He says that the Allroad uses a center
torsen and so on...

The Audi AWD system is by todays standard
completely obsolete for use in Rally Cars.

Some of you need to drive a real good AWD
car before coming up with BS statements
that the Audi system is better. You guys
are a joke!

Regards,
FastFast