The MB dealer was telling me that the quatro disengages at 80 KM/hr. Is this true?

Do not trust any technical explanations from whoever told you that, going forward.

quattro is a marketing term covering several AWD technologies. In the A6, it is accomplished with a Torsen center differential, that is a purely mechanical system that is always active at all speeds.

which uses the ABS sensors and brakes in reverse to slow a spinning wheel and thereby fake the open differentials at either end of the car to sending power to other wheels, does disengage at 55mph to prevent you from cooking the brake pads.

At those speeds you're either wailing on the track or if it's slippery enough to need EDL, should be going slower than that;-)

You can tell him that on their AWD (4Matic) they cannot use their new 7 speed Automatic. It is only a 5 speed and their front suspension is different than their RWD car....

I dumped my M-B 4matic for my new A6. The A6 is superior in just about every way, but the M-B 4matic system works better in snow and ice than the quattro does.

Quattro and 4 Matic both use brake applied EDL to exqualize traction right to left on each axle. That leaves the center diff as the major difference. The Mercedes uses a non-lockable open planetary diff with rear torque bias. The A6 uses a torque biasing Torsen normally running 50/50 split and able to bias torque to the axle with better grip.

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the 1st gen 4-Matic only engages until certain MPH and disengages. no knowledgable person who's into AWD bought those. in the 2nd gen 4-Matic MB used fixed split AWD that won't disengage. quite dumb, i believe. it's easy to fish tail 2nd gen 4-Matic on the slippery stuff. the other MFR using fixed split is BMW. it's bit funny that neither MFRs have ever raced AWD vehicles.

(for the record, the 1st gen AWD BMW is pretty good, except the drive shafts going through the oil pan bit.)

with exception of Gulf-based Audis (TT/TTS and A3), all Audi quattros are full-time and cannot be disengaged regardless.

There is a cul-de-sac in front of my house. I could never get the M-B to fishtail or wobble going around that. The A6 will fishtail with the back end breaking out. The same kinds of differences showed up in normal driving in the snow. The M-B was more refined in its application of ESP than the A6.

You guys may not like to hear it, but those are the facts. Heck, I wish it wasn't true, but I've got to be honest about it. Even my wife commented on it.

Maybe the A6 didn't have ESP?

Also, I believe that ESP is a DaimlerChrysler trademark--check the fine print on you C6 brochure. If I remember correctly, the new A6 is using ESP version 8. If MB is involved with the development, maybe they're on version 9 or so.

April suggested earlier this winter that the MB ESP system might be more aggressive than the A6. I think she may be right. Whatever the reason, it was a challenge to get the MB to slide much. It's not much of a challenge with the A6. I'm not knocking the A6--it is good in the snow. But the MB was very impressive in this regard--moreso than I thought it would be when I got it.

Hey, the MB is better in this one feature. The A6 is better in every other way. ;-)

MB's ESP wont let any slipangle occur.

RB

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The A6 ESP must be configured to allow for sportier driving.

It makes sense.

Getting a little loose is nothing to worry about.

You're right. Quattro does allow oversteer. It doesn't redistribute torque instantaneously so you can throttle steer the rear end to a certain extent.

same snow tires-different snow;-)

The test indicates that the A6 quattro can get through a snow slalom baster than the E320 4matic.

That to me tells me it's a better AWD system for snow as tested at the same time on the same snow by the same drivers.

I appreciate your experience but it's not a reliable result for the rest of us!

And remember the faster it can go, the further you are from the cars limit when you're not pushing it fully - to me that defines "better"

Food for thought.