QUATTRO_PEARL

I'm sure there are countless videos like this all over the net.

http://x3.xbimmers.com/forums/showthread.php?t=445809

or
http://www.youtube.com/watch?v=HvqQu...layer_embedded

So what gives, what's up with this version of quattro?

I'm wondering if Audi will ever sponsor their own event...

Rafale

Yes have seen this.
Got me to do a lot of research last night. This has actually been a known fact for a long time and a lot of debates have gone one several years back on BMW forums.
To summarize it:
The Audi Torsen system is purely mechanical and "gives up" when an axle has no resistance. It will therefore put all the torque to the path of lowest resistance and spin the wheels.
The BMW system is based on a "freewheely" differential which relies on electronic sensors to apply brakes on the spinning wheels. Kind of like the ESP. By doing this it forces the torque to the other Axle which does have traction. X-Drive can direct up to 100% of the torque to one Axle while Torsen can "only" direct 75% at the most. This has nothing to do with this video but it was another selling point for the X-Drive.

In reality you rarely find yourself with a full axle having absolutely no traction so this roller test is sort of an extreme case. Comments from on the Bimmer forums hinted that the Quattro system was more intuitive and "natural" while the X-drive is more like an electronic gizmo. One guy even said he could get out of the rollers by taping on the brakes to apply resistance to the spinning wheels and get the differential to work again, transferring torque to the other axle. Long story short it is really a BMW marketing campaign and there is nothing new about it. This test is just a test and nothing else. It did show one weakness of the Torsen differential but it is behaving as designed. In real life situation the Quattro feels safer although not designed to go hard core off road, it is perfect for the snow and what you would expect to do with a crossover...

Rafale

Also look at this other TV review.

http://www.youtube.com/watch?v=vAHPM...layer_embedded

QUATTRO_PEARL

Thanks both of you for the reply and information. I was wondering if BMW had pulled one over on Audi as they sometimes jab at the other in comparisons. So Xdrive must be similar in function to the Subaru Symmetrical awd system. I have seen videos of that, sponsored by them of course. So my next question is.... The RS5 reviews talk about some things Audi has added to the Quattro system(Crown Gear), does anyone know how it would compare to the current Quattro system, offered in the S4(Sport Differential), or is it the same?

RS5

http://www.youtube.com/watch?v=_09y0...eature=related

Subaru


http://www.youtube.com/watch?v=2OzK-...layer_embedded

QUATTRO_PEARL

To reply to myself...I just watched the vide on the Sport Diff, it only works side to side on the rear wheels..unlike the Crown Gear which works front to back.

So when this Crown Gear filters down the Audi gene pool, it should be more comparable to what Xdrive & Subaru & SH-AWD are at the moment, since it can send more torque where it's needed, improving on the current quattro/torsen system.
Cool.

kleinbus

Xdrive is controlled with multi dics clutch like Haldex and there is no differential gearing in it, meaning if electronic control is disabled, Xdrive is just rear wheel drive as there is no middle differential gearing, just freely rotating multidisc clutch.

Subaru (like Audi) haves mechanical awd's and multi clutch awd's (Audi A1, A3, TT).

Honda / Acura SH-AWD is multi clutch system and not comparable mechanical drives. This system is based on front wheel drive and is incapable to convey continous power to rear as the power distribution is via multiclutch which doesn't have enough pressure to create 100% lock inside the multidisc coupler ( meaning 50/50 split for front and rear).

This Supersuper thingie is superfunky as it haves planetary gear on front of rear differential that allows rear differential rotate 15% (or so) faster than actual drive shaft. In theory nice and impressive but in reality if the multiclutch is the weak link on system then there is no power to spin those rear wheels otherwise I could take one and go do donuts on parking lot (I did it with my Audi)

All multidisc couplers have safety feature to control the temperature and electronics will release the clamping power when it gets too hot (rarely happens in normal driving unless owner plays on snow and slippery surfaces)

The Torsen differential that Audi used under license, was invented by American Vernon Gleasman and was build early days by his company Gleason Corp. The company was sold to Zexel Corp (majority owned by Bosch Corp) and these days it is owned by Japanese JTEKT Torsen North America.

Gleason Torsen is based on worm gears while new design by German company and what Audi seems to start using is crown gear.

I saw somewhere nice illustration from both but it is somewhere....

CrustyNoodle

http://www.youtube.com/watch?v=tDdB6scffPM

http://www.youtube.com/watch?v=V7-qxXB4y30&NR=1

The most interesting of all....

ESP on VS ESP off


http://www.youtube.com/watch?v=rI6tP...eature=related