How Quattro Works?

[Vinnie981]

So today I got stuck in the snow in my 2000 Audi A6 4.2L. It got me thinking how the quattro system truly works in my year car. Heres a sample pic : Using it as reference to my car.



Ok the the wheels circled in Green where touching the ground when I got stuck. The Passenger front was on the ground along with the drivers rear.


The wheels circled in Red where not. The drivers front was just freely spinning when in gear a idle. The passenger rear was the same way but not as bad.


Now heres my question. When I hit the gas in Drive or Reverse the tires in red (that are not touching the ground) were spinning hardcore, but the tires in green that were touching the ground were not moving what so ever. Like NO POWER was being delivered to them. Why is that? In my eyes that seems ass backwards. Im sure I would have got out if the tires touching the grou actually moved, but they didn't. It just kept spinning the two that were not even having any contact with anything. In the end my brother in his Subaru had to pull me out. Embarrassing

[Sparkstack]

Because friction.

We don't have locking diffs. Any wheel in the air (or with zero traction) will stop you moving as all power will go to that wheel.

If you lose a drive shaft same result. You ain't going anywhere.

[Vinnie981]

well...i remember that happening on my a6 3.0. my front drivers side axle broke and the car went no where. Said i was doing 60mph sitting still. lol

well thanks for your explanation. Is there differential upgrades to stop this from happening.

[Racin2redline]

Well the main downfall with Quattro is the lack of a mechanical limited slip differential. Audi replaced there locking unit (the button on the center console in older cars ) with a electronic system (EDL) which basically applies the brakes... Clearly not nearly as effective.

I understand how the system works and why the power is transferred a certain way.. I'm just not qualified to explain it lol.. Basically the power is following the path of least resistance

[Vinnie981]

just for the record my car does NOT have ESP and is a tip

[ENDEE666]

I have heard of LSD upgrades. There was a thread about it recently that sparked some interest with me-

http://www.audizine.com/forum/showth...LSD-installed-)

[rollerton]

Yeah..that's a tough spot! The way it's intended the brakes are supposed to attempt to LOCK the wheel(s) that spin to transfer power to the ones that aren't. It's amazing how great Quattro works - UNTIL you have one wheel completely free. Then you're hosed. I've thought about this before...and I wonder if a solution would be to install an individual 'line-lock' for the front / rear brake systems.
So~ if you have one wheel spinning in the rear you lock the down the brakes to the rear and it essentially transfers all the power to the front~but there is the Ebrake for that...right?
Vice versa if you have a wheel spinning up front. I don't know..? Can't be that simple.

[Vinnie981]

well it seems that all the LSD upgrades are for MT and not AT. I might need to do that 6 speed swap

[G0to60]

Here's a video on how differentials work. It's from Toyota but the concept is the same. Part two of the video talks about mechanical and electronic limited slip differentials.

[rogersb6]

Seems like the real problem is that two wheels were free at either end of the car, not allowing the central LSD to kick on. It only works when there is a torque differential between front and rear, with equal power going to front and rear (since each has a wheel slipping) torque is equal, so the mechanical system alone fails.

The Quattro system makes up for that problem by letting the traction control apply the brakes on the corner(s) that are slipping so that the torque can be redistributed to those wheels with grip.

[Vinnie981]

The Quattro system makes up for that problem by letting the traction control apply the brakes on the corner(s) that are slipping so that the torque can be redistributed to those wheels with grip.

Is that ESP? Or does the abs module do it? My car does not have ESP. And I though ESP only killed down the motor and didn't affect the brakes in any way. Im guessing the abs module does what you talking about than. And in that case my ABS and BRAKE light are on because my module needs rebuilding. I need to fix that

[ddillenger]

Is that ESP? Or does the abs module do it? My car does not have ESP. And I though ESP only killed down the motor and didn't affect the brakes in any way. Im guessing the abs module does what you talking about than. And in that case my ABS and BRAKE light are on because my module needs rebuilding. I need to fix that

Yeah, then your EDL lock is disabled

[Racin2redline]

Is that ESP? Or does the abs module do it? My car does not have ESP. And I though ESP only killed down the motor and didn't affect the brakes in any way. Im guessing the abs module does what you talking about than. And in that case my ABS and BRAKE light are on because my module needs rebuilding. I need to fix that

You said your cars a 2000 right? I have a 2000 parts car that had no abs problems when I took it apart if you want the module for cheap. Pm me

Edit - not sure if it's the same between a 4.2 and 2.7 but we can check

[Vinnie981]

You said your cars a 2000 right? I have a 2000 parts car that had no abs problems when I took it apart if you want the module for cheap. Pm me

Edit - not sure if it's the same between a 4.2 and 2.7 but we can check

its not the same....i was going to take it from my 2002 audi a6 3.0l but my 4.2L has bigger brake line connections.

[Vinnie981]

Yeah, then your EDL lock is disabled

so if I fix my module then my EDL will work? what is EDL?

[ENDEE666]

EDL = Electronic Differential Lock. But I am not sure if you have it or not in a non-ESP car. I really don't know, and I have never seen a non-ESP A6 Quattro. I thought the two went hand in hand. Only non-ESP I saw was also non-Quattro..

[Vinnie981]

pic of my 2000 Audi A6 C5 4.2L ABS Module......

[rogersb6]

Is that ESP? Or does the abs module do it? My car does not have ESP. And I though ESP only killed down the motor and didn't affect the brakes in any way. Im guessing the abs module does what you talking about than. And in that case my ABS and BRAKE light are on because my module needs rebuilding. I need to fix that

I acctually don't know much about the differences between ESP and traction control, but I can tell you that with the ESP light on on my dash (this is an RS6 dash in an AR) and under 40mph the Traction control lets the car get sideways and allows wheel spin without applying brakes. But if the car has TC and Traction control enabled and the car oversteers, then the brakes apply to bring the car back into straight again. It's pretty fantastic to witness from behind the wheel. Pretty harsh too. On understeer only the throttle cut seems to be applied, I haven't noticed any brake system activity for that.

[Vinnie981]

EDL = Electronic Differential Lock. But I am not sure if you have it or not in a non-ESP car. I really don't know, and I have never seen a non-ESP A6 Quattro. I thought the two went hand in hand. Only non-ESP I saw was also non-Quattro..

ESP was not a full on option until 2002

In 2000 and 2001 Audi A6 C5 4.2L it was available but only for special ordered cars. And was big bucks. Im still wondering if I can retrofit the ESP system from my 2002 Audi A6 3.0L into my 2000 Audi A6 4.2L

[rogersb6]

This might be some good material for Electronic stability systems: http://www.volkspage.net/technik/ssp/ssp/SSP_204.pdf

I haven't read through it yet, so I'm not sure if it's applicable to this situation.

[LINDW4LL]

As others have pointed out, this is the flaw of open diffs.

EDL should have transferred power to the wheels on the ground by braking the free-spinning wheels.

[ddillenger]

Trust me, you're not missing much without EDL.

What you need is enough power to scare the ground into submission.

That, or some wavetrac differentials.

[Vinnie981]

Trust me, you're not missing much without EDL.

What you need is enough power to scare the ground into submission.

That, or some wavetrac differentials.

wavetrac only makes them for manual transmission. Which you are aware I don't have

[ddillenger]

You can get one for your rear diff.....

[Vinnie981]

This might be some good material for Electronic stability systems: http://www.volkspage.net/technik/ssp/ssp/SSP_204.pdf

I haven't read through it yet, so I'm not sure if it's applicable to this situation.

very interesting

[Vinnie981]

You can get one for your rear diff.....

linky link?

[ddillenger]

http://advancedautomotion.com/shop/p...roducts_id/244

[Vinnie981]

think i just shit my self with that price tag lol

[Vinnie981]

someone fix my ABS MODULE lol. guess I'm gonna just have to send it to module masters

[ddillenger]

I told you I'd fix it sir. Send it with the rest of my shiz....

Also, I have wavetrac front and rear along with a 4:1 center diff. THEMS is pricetags worthy of a shat.

[V1nny]

http://advancedautomotion.com/shop/p...roducts_id/244

is this just a superficial similarity, or this LSD is built and works a lot like Type III torsen differential?

[Racin2redline]

is this just a superficial similarity, or this LSD is built and works a lot like Type III torsen differential?

It does look like that. Wavetrac LSDs are bad ass. You can literally break an axle and it will still transfer 100% of power to the other wheel

[rollerton]

There are TWO kinds of traction control that VAG used on these 10 year old cars- there's "ESP" :which is the "Electronic Stability Program" ? and "ASR" which is "Anti-Slip-Regulation" .
If I understand it correctly ASR is the one that cuts engine power when you lose traction.
ESP is the one that applies ABS to transfer torque.

I don't think any of our C5's use ASR, but just ESP. And it's a good thing too because if you think ESP is nonsense that ASR is total bullshit. My 03' 4mo Passat had both, but..I don't remember a button to turn off ASR. My 01' GTI had both buttons I think and was FWD.

[G0to60]

Yeah, ASR is pretty much crap. My wife's 20th GTI only has ASR and all it does is cut the power. It's really annoying when you are trying to get going.

I have a question about ESP. I know that you can turn it on and off by just pressing the ESP button, but I have read that you can get a different program if you press and hold the ESP button for ~10 seconds. We are only now getting snow here so I haven't been able to test any difference but is this true?

I tried to find it in the owner's manual but they don't mention it. I'm reading through the ESP link posted now.

[4ringAR]

Tl;Dr

One wheel in air, all power to that wheel because there is zero resistance and front and rear diffs are open style.

Center diff is torsen lsd. Lsds are worthless if a wheel has zero resistance, it just acts like an diff. Wavetrac is different and locks. Maybe I'll expand this post later. But I am on my phone.

[Scotty@Advanced]

is this just a superficial similarity, or this LSD is built and works a lot like Type III torsen differential?

Like all torque biasing diffs, wavetracs have gears that distribute torque, however it also have clutches that behave like an LSD in zero torque situations. And if you price these things Wavetracs are some of the lest expensive diffs on the market. Quaife's cost upwards of 2 grand, and Guards diffs are even more.

[8520]

I still need to figure out if I'm able to delete esp in my allroad. I hate it. My 2000 A6 didn't have it and it was MUCH more fun to drive.

Need to fix my axle first though, as I don't think I can recode it for non-esp with an abs light on.

[19dabeast85]

Your car would handle that situation fine if it had ESP. It would also handle it fine with an lsd in the rear end. In all honesty you only every need a front lsd under extreme conditions (racing, offroading) A rear lsd guarantees you at least 3 tires are always pulling.....MUCH better than just two and a whole lot better than fwd or rwd with open diff=one drive wheel looses traction you're screwed.

I have purposefully put my Allroad in a situation just like yours where I completely unloaded opposite corners going diagonally up a steep hill.....I heard frictional grabbing/slipping as the car braked the two non-traction wheels and the car never stopped moving up that hill and onto the flat road at the top. Cool deal!

ESP also cuts power output, drive on the snow with it on and then with it off. You can floor it on snow, the wheels will slip for a second, then power gets cut dramatically as you SLOWLY accelerate....even with the pedal to the floor!

It's amazing how quickly ESP responds......I had to get somewhere QUICKLY recently and it was raining AND I have dangerously low tread depth. Driving 80-90 on backroads straights, slowing to 65-70 on turns and for puddles.....even still I felt ESP kick in about 3-4 times pulling the rear end back in line. I could have wrecked it driving faster, but knowing my limits, ESP let me drive closer to the limits safely!

ESP will NOT let you turn-drift though....for that you just turn off ESP, play the power and turning just right and when you completely break the rears loose, the center diff transfers VERY little power to the front since there's very little traction at the rear and you can drift fairly easily even on dry pavement! lol! Even with ESP off it doesn't take too long on dry pavement for the rears to gain enough traction that the center diff can multiply the torque used by the rears (2x,3x,4x depending on your center diff) and send it to the fronts letting you shoot out of a turn like a bolt of lightning! Fun times with the Allroad!

A rear wavetrac is on my list of future mods! The Allroad should have come with one factory. It's really not horribly prices relative to comparably functioning diffs and since I can do the installation myself no shop fees!

[redneck truck]

When you're stuck in a situation like this, provided you haven't lost an axle, hitting the brake pedal rapidly will slow the spinning wheels and transmit more torque to the other wheels. Worked in my Frontier on ice, even with its 1wd.

[Vinnie981]

^Thanks will try that if it ever happens again. Hoping it doesn't lol