Quattro?

[JRMSLINEA4]

Is the split 50/50 all the time? Thanks, Joe.

[Glassnpowder98]

I'm pretty sure that what I'm about to write is correct... But if I'm wrong, someone feel free to correct me!

The quattro system is set up so that it is normally 50/50. However, our differential is a 2:1 ratio so that it can transfer power to the wheels that have the most grip. From what I saw on the Stasis website, I'm pretty sure that it can transfer 66% of the power from front to back and vice versa.

Here is what I saw... I'm pretty sure the S4 and A4 use the same diff.
"Looking for more rear drive bias in your Audi? Tired of front wheel spin?
Put power to the ground more effectively with the STaSIS high-bias center Torsen for your manual transmission Audi. Converting from the stock 2:1 ratio to the STaSIS 4:1 ratio enables an increase from 66% to 80% in torque distribution. Use your all wheel drive to its fullest potential and extract the most from your quattro driveline.

Tuning the center differential provides one of the most significant performance gains available to the Quattro owner. The standard torsen center differential in the Audi S4 provides a 2:1 torque distribution capability. This enables the end of the car with traction (generally the rear) to deliver twice the torque being delivered by the least tractive end of the vehicle (generally the front). For high performance street cars, we recommend a bias ratio of 4:1. This is the same bias ratio that Audi has provided in the stock RS4 driveline."

[whartung]

All Audi performance models (S and RSs) starting in 2006 have a 40/60 front/rear quattro bias. The 2005.5 S4 is the only B7 to retain the older quattro standard of 50/50

[Glassnpowder98]

^^ So you're saying the B7 A4's have a full time 50/50 split and don't have the ability to transfer power?

[Zebman]

^^ So you're saying the B7 A4's have a full time 50/50 split and don't have the ability to transfer power?

They can but it's the 2:1 (safety oriented) vs. the 4:1 (performance oriented).

[Alkemix]

is the power distributed through the diff. or through ABS?

[Zebman]

The manual says that it's distributed by the brakes, and states that you don't want to sit on a slippery surface with ESP on and continually try to keep going as it will unneccesarily wear on the brakes.

[Glassnpowder98]

So, in reality it is "reducing" power instead of transferring it? I think you might be talking about how the ESP works and not how the differential works when entering and exiting a turn. I can see the ESP using the brakes to straighten the car out in a slide... Also, from experiences that I've had when ESP kicks in, it shuts down power all together, so it won't even have the ability to transfer power.

I am pretty sure that the differential is 2:1 and will transfer power to the rear wheels when exiting a turn (because they have the most grip). It makes no sense for the car to engage the front brakes when exiting a turn to ensure that more power is going to the rear wheels... I don't know much about differentials and how they work, but my previous statement is pretty common sense...

[davis449]

ESP and torque shifting by the diff. are two completely different things.

[Zebman]

I'm talking about snow/ice driving, which is what our cars are better at. If the rear wheels spin, the brakes pulse on the rears, which sends the power to the front. And ESP doesn't necessarily have to kill power (via opening the DV). ESP works on the track as well, coordinating the brakes in a way we never could, although its goal is to keep handling neutral which is no fun. :)

I'll be honest; mechanically, I have no idea how our awd acts. I'm thinking that it's all open and just sends the power through the path of least resistance, which would be through the wheels with less grip. Again, i'm just guessing, I have no real idea.
P.S. If the rear wheels were given power exiting a turn, wouldn't that just make understeer worse?

[Clown4]

that's what I think as well~
just day before yesterday,
went mountain speeding with some people,
when entering the turn(sharp left), I put even more gas,
then during the turn and while exiting, I can feel the power
was transfered to the right rear, and some to the right front,
pushing the car to rocket out the turn.


I'm just wondering though... for fun driving(when there's no snow) and performance driving...
do most of the guys here drive without the esp, or with the esp?
I always have the ESP on... unless i wanna do some donuts in the snow...
having esp on... i can enjoy quattro more than worrying about sliding away

I am pretty sure that the differential is 2:1 and will transfer power to the rear wheels when exiting a turn (because they have the most grip)

[F.An]

power is shifted by the diff and the diff is like a gearhouse transfering the power using the resistance the wheels are making (its easier to turn a wheel on ice then on tar). The ESP (electronic stability program) uses the brakes to make the car go around a bend and the TCS (Traction controle system) uses the ECU to gut the ignition to reduce power going to the transmission... Think i got it right..

[F.An]

I'm just wondering though... for fun driving(when there's no snow) and performance driving...
do most of the guys here drive without the esp, or with the esp?

Drifts = ESP off
Driving = ESP on

[Alkemix]

I know Torsen is for Torque Sensing. I hope someone who knows definitively could answer, but glassnpowder, i think you might be right that our diff. does mechanically deliver a power bias outside of ABS, which is then also supplemented by the ABS system, which ALL TOGETHER make our quattro system.

I am only confused because I have heard the same thing that our A4's were 50/50 power distribution as well... but why would they call it that, if it was capable of creating a power bias of 2:1. That's 66/33 no? So, maybe this is more of a question about semantics or defining what is meant by the 50/50 that we always hear about.

EDIT: I just saw F.An's post after i finished my post. Almost answered the question, but still need an expert.

[Glassnpowder98]

P.S. If the rear wheels were given power exiting a turn, wouldn't that just make understeer worse?

More power to the rear wheels actually helps to induce oversteer and helps the car rotate around a turn. Having power go to the rear wheels is ideal because when you are on the gas, inertia is putting more weight on the rear tires making them have more grip (exiting a left hand turn, the wheel that will have the most traction will be the right rear. Second most will be the left rear, third right front, fourth left front). On the other hand, front wheel drive or a front wheel bias differential is going to be pulling the front of the car through the turn more. This does not let the car rotate around the turn and it causes understeer. All of the power will be given to the two wheels that have the least amount of grip. The claimed "perfect" setup is a 4:1 differential that provides 80% of the power to the rear wheels and 20% to the front wheels. This allows the car to rotate just enough to get the car through the turn. The 20% to the front wheels pulls the car just enough through the turn so you can get on the gas earlier than a RWD car and not have to worry about oversteer or spinning out.

I can vouch that those statements are 100% accurate because I paid attention during the classroom sessions at the Audi Club track day. However, I'm not quite sure how our torque transferring diff works because I'm not as familiar with the mechanical side of things... I just drive it like I stole it!

[Zebman]

Ok I see. My thinking was that, mid-turn and exiting the turn your front wheels are still turned in the direction of the turn, and if you were to have the rear wheels put down more torque, it'd start pushing the car straight if the fronts lost traction.

[Glassnpowder98]

Because of the power being delivered to the rear tires and the coefficients of the different frictions between the front and rear tires (I don't know if that's the right term but I'm trying to sound smart), your rear tires are going to break loose and start spinning long before enough power is put down to start pushing your front wheels. This will obviously cause oversteer and make you slide sideways. What a lot of people will do is add toe-in to help the car stay hooked up and turn better (toe-in is when your rear wheels are pointing in like this from a top view above the car / \ ). Imagine you are making a left turn again... Toe-in helps because your right rear wheel is already pointing towards the direction you want to go. The only negative with toe-in is you will wear your tires down faster and lose some straight line stability.

Back to front wheel drive and exiting a turn... Your coefficients of friction are going to be combined. Think about it, your front wheels are trying to do two things at the same time. They are trying to laterally change the direction your car is moving as well as put down the power that your engine is making (your rear wheels are just along for the ride). This is when you will start understeering because your tires cannot provide the necessary grip to turn and put down the power at the same time. This is why our 2:1 ratio quattro tends to understeer. Because the car is so heavy, it takes more friction to turn the car. When you add that 33% of the engines power to the front wheels, it is going to break traction and pull the front of the car. That's why a 4:1 ratio helps to properly balance a car through the turn and not pull too much on the front of the car... reducing understeer.


P.S. I see you're in West Virginia. You should definitely try to make it out to Summit Point the next time the Audi Club is there. You will definitely learn a lot and have a blast!!

[Zebman]

All I can say now is, $700 + core for a STaSIS 4:1 differential... that is so incredibly tempting.

[a4dc89]

the stasis differential sounds like a really cool idea.

would that mean more bind up on tight turns like how my car drives now or less?

One of our members (Papachristou) has a video on youtube with the 4:1 differential http://www.youtube.com/watch?v=vy6EUhO4sb0

[wflan]

Quattro is a full-mechanical system (except the TT/A3 platfrom, which uses a different sort of differential) that redistributes torque based on which wheel(s) has the most traction. The fact that it's mechanical, not electric means that there doesn't need to be wheel slippage for it to step in. The 50/50 is the default torque split under normal, full traction situations, which changes when one+ wheel has less grip.

ABS and ESP start to operate once the electric systems detect a wheel slipping/not behaving properly (I think its sensitivity is 1/6th of a turn) and use computers to alter how braking is done.

The center differential is the only torsen one in the quattro generation we're talking about with the others being open ones. Electronic Differential Lock will put the brakes on a wheel that would otherwise be spinning freely, transferring torque. This is especially useful because old quattros had issues where they'd get stuck if one wheel were in the air due to a quirk in how the differentials worked.

The Haldex system electronically distributes torque, with over 90% going to the front in normal conditions and is able to do 100-0 split in either direction. This is what's used in VW 4Motion and the A3/S3/TT.

wiki!

info on torsen differentials

[JRMSLINEA4]

Quattro is a full-mechanical system (except the TT/A3 platfrom, which uses a different sort of differential) that redistributes torque based on which wheel(s) has the most traction. The fact that it's mechanical, not electric means that there doesn't need to be wheel slippage for it to step in. The 50/50 is the default torque split under normal, full traction situations, which changes when one+ wheel has less grip.

ABS and ESP start to operate once the electric systems detect a wheel slipping/not behaving properly (I think its sensitivity is 1/6th of a turn) and use computers to alter how braking is done.

The center differential is the only torsen one in the quattro generation we're talking about with the others being open ones. Electronic Differential Lock will put the brakes on a wheel that would otherwise be spinning freely, transferring torque. This is especially useful because old quattros had issues where they'd get stuck if one wheel were in the air due to a quirk in how the differentials worked.

The Haldex system electronically distributes torque, with over 90% going to the front in normal conditions and is able to do 100-0 split in either direction. This is what's used in VW 4Motion and the A3/S3/TT.

wiki!

info on torsen differentials

Good write up thanks.

[Quattro]

hello =)

[bsrpilot44]

hello =)

Ahahhahaah

[eskimopunk]

do most of the guys here drive without the esp, or with the esp?
I always have the ESP on... unless i wanna do some donuts in the snow...
having esp on... i can enjoy quattro more than worrying about sliding away

i've found that having the esp on during hard cornering makes you go slower cos you can't push it to the edge. And the manual says to always have the esp OFF when in the snow

[wflan]

i've found that having the esp on during hard cornering makes you go slower cos you can't push it to the edge. And the manual says to always have the esp OFF when in the snow

nononono

ESP is mildly aggressive and uses brakes to correct things so if you're going fast enough to intentionally slip and/or slide, then having it off would be better, but in slippery or unpredictable situations, you DEFINITELY want it on. I hear that there are a few situations where you want some wheelspin, like (rocking out of being stuck ??) but it's damn useful and you want it there to make the best of an unexpected slipup, which happens most often when there's stuff like snow... I'll check the manual, but I'd be flabbergasted if it said to turn it off once the roads got hairy.

[eskimopunk]

nononono

ESP is mildly aggressive and uses brakes to correct things so if you're going fast enough to intentionally slip and/or slide, then having it off would be better, but in slippery or unpredictable situations, you DEFINITELY want it on. I hear that there are a few situations where you want some wheelspin, like (rocking out of being stuck ??) but it's damn useful and you want it there to make the best of an unexpected slipup, which happens most often when there's stuff like snow... I'll check the manual, but I'd be flabbergasted if it said to turn it off once the roads got hairy.

no it makes no sense to have it ON dwhen you're driving in the snow. imagine you're driving in the snow and you turn just a little bit too hard around a corner on a mountain or something and the esp puts the brakes on to try and stop it - it just makes it worse because it doesn't know you're in the snow so you'll probably just slide worse and won't be able to correct it by using the gas because the esp is controlling everything.
I'll try it out if it snows here tonight or tomorrow and if it doesn't im driving up to colorado so i'll try it there too.
oh and i almost crashed in the rain a few months ago with the esp on because i turned to fast on a left arrow and the esp kicked in and sent me straight towards the corner, and i almost hit it. If it was off then i could've just counter-steered and corrected it.

thats what's making sense for me

[Glassnpowder98]

I'm not too sure if ESP will help you in the snow or not. I like to have it off because I have gotten pretty good at feeling when the car is beginning to slip or purposely making the car slip. With ESP on, it ruins the fun...

I know of one accident that was caused by ESP. Another member on here was driving some back roads and came into a right then left S-turn. The back end of the car started coming out during the first turn and the ESP kicked in. It got him straight, however when he tried to make the immediate left turn, I guess the car thought he was overcorrecting the initial slide and he continued going straight and into the guard rail. He was using a headrest video camera mount and you could see him trying to turn the wheel to the left and nothing happens... So, there are times where ESP can hurt you. However, I'm sure 99% of the time it will help an inexperienced driver. At least they give you the option to turn it off!

[eskimopunk]

i think the more you drive your car hard the more you like the esp off cos you have more control. I think if you raced two identical a4's together or did separate runs with drivers that had a feel for the vehicle, one with esp on and one with it off, the one with it off would probably be a little faster round a track

[wflan]

off would def. be faster, but in my snow experience (living in Colorado) esp does help. Our cars understeer and ESP is meant to make it a lot more neutral. I checked the manual from an A6 and they def. didn't say to turn it off once it got slick. I have seen how it seems like it doesn't help, but if you're out of traction and you crank the wheel, going sideways doesn't necessarily mean turning. As far as I've driven, it helps most of the time.

[4RingRook]

hello =)

Hilarious.

[whartung]

off would def. be faster, but in my snow experience (living in Colorado) esp does help. Our cars understeer and ESP is meant to make it a lot more neutral. I checked the manual from an A6 and they def. didn't say to turn it off once it got slick. I have seen how it seems like it doesn't help, but if you're out of traction and you crank the wheel, going sideways doesn't necessarily mean turning. As far as I've driven, it helps most of the time.

Don't quote me, but i believe ESP is intended to be off in only heavy snow. The logic on this is that heavy snow will cause wheel slippage, which ESP will counter by apply brakes and cutting engine power, resulting in the car coming to or near a halt. In the heavy snow, you need to maintain momentum, and as such ESP off is sometimes recommended. That is not intended to mean you should drive around a crowded town the first time snow comes with no ESP. Its intended more for if you're driving on an unplowed, empty road, in deep snow, which I promise from experience, having ESP off helps.


Also, the only thing I'm saying in terms of the AWD splits, is 2006 and up S4s, RS4s, S5s, and S6s (i believe) have a sitting distribution of 40/60 front/rear, while my car and all the S4s before it have 50/50.

[barkerd427]

All of the B7 A4's have 50/50 and the RS4 has 40/60. Also the reason that you would want ESP off in heavy snow, not light snow, is because you will stop faster without it. When you stop in heavy snow a mound of snow will build up in front of your tires which will help you stop, but if ESP is on it will since a skid and intermittently apply and release the breaks which will break the mound up and increase stopping distances. Finally, for that bogus story about the guy wrecking into the guard rail, ESP can not stop you from turning the car if you are actually in control of the vehicle. He may have still been skidding and the car just wasn't responding to his inputs.

[Glassnpowder98]

^^^ Are you being serious? Where have you heard of these "mounds of snow?" Last I heard, the ABS system is what senses the wheels sliding under braking, not ESP. You can't turn the ABS system off (unless there is some way through VAG-COM). If you've been around for the past 15 or so years, you would understand that ABS pulsating the brakes and preventing them from locking up is far superior in any situation than the wheels locking up... Even if they are plowing snow and creating "mounds" in front of your tires.

And for the "bogus" story... Like I said, he has it on video. You can clearly see the car start to slide around the first right hand turn and then it straightens out. The ESP light is still flashing when he turns the wheel to the left. The car finally responds but it's too late for him to hit the apex and he rides the guardrail. It's not like ESP made him go straight into the guardrail, but the car wouldn't turn for a split second while ESP was doing it's thing and that ended up not allowing him to make the turn while still on the road. Hence, him riding the guardrail for the last half of the turn...

[audidrver]

^^^ Are you being serious? Where have you heard of these "mounds of snow?" Last I heard, the ABS system is what senses the wheels sliding under braking, not ESP. You can't turn the ABS system off (unless there is some way through VAG-COM). If you've been around for the past 15 or so years, you would understand that ABS pulsating the brakes and preventing them from locking up is far superior in any situation than the wheels locking up... Even if they are plowing snow and creating "mounds" in front of your tires.

And for the "bogus" story... Like I said, he has it on video. You can clearly see the car start to slide around the first right hand turn and then it straightens out. The ESP light is still flashing when he turns the wheel to the left. The car finally responds but it's too late for him to hit the apex and he rides the guardrail. It's not like ESP made him go straight into the guardrail, but the car wouldn't turn for a split second while ESP was doing it's thing and that ended up not allowing him to make the turn while still on the road. Hence, him riding the guardrail for the last half of the turn...

link to vid

[Glassnpowder98]

I saw the video at a local meet on his camera. I don't think he has or wants to put it online due to insurance reasons and the like... I'll PM him and see if I can get him to chime in.

[bloodstar57]

Would just like to chime in and say that the ESP can be partially turned off. The ASR(traction control) can be turn off while the ESP is still functioning. What a lot of you are talking about when the car is taking power away from you is the ASR. Turning this off while still having the ESP on will allow you to rotate the front by get the rear wheels to spin a bit. This gives you the best of both worlds because you can use tire slippage and have the ESP monitor if things get a bit out of hand. However i have found that the ESP even with the ASR turned off can be pretty intrusive in my driving style. Also with the stasis Diff i would suspect that performance driving would improve because the 80% is only on demand; when the power needs to be in the rear it can put 80% of there as apposed to 66%. This means on the drive out off a turn you are putting power down the most effective way.

Now is the 40/60 split on the newer audi's on a constant basis; under all driving conditions 60% is going to the rear? However does this mean that when the Torsen diff senses the need for power to the rear, it sends only up to 60% to the rear? If this is true does it mean that b7 a4's and those with a 50/50 and stasis diff will still retain the 50/50 split under normal condition but when needed 80% can be transferred to the rear?

[a4dc89]

ESP saved me in my old car on solid ice, i was able to prevent a collision with a tree. Anything but a computer would not have been able to apply the correct braking to the right wheel to stop the understeer.

The people on here who believe ESP off will help them in the snow are dead wrong. In fact, some cars and probably our cars will store in the ECU in the event of an accident whether or not the ESP was turned on. I have heard stories where the insurance will not cover the claim in such a case

Not to say that there are certain situations where ESP can be counterproductive but it is usually a good thing

[Jim@STaSIS]

Well I’m no engineer but I can try to eschew a few obfuscations concerning ye ‘ol center diff! some great reading here on torsens: http://en.wikipedia.org/wiki/Torsen

in a very small nutshell a differential, by definition, allows wheels to spin at different speeds. if, in a simple example, you're turning left, the outside wheel travels farther than the inside wheel for the car to go a given distance [bigger circle and all of that]. allowing that speed "differential" is gives these little gems their name. esp and and asr are essentially electronic controls over existing devices - and apply brakes, limit throttle, etc when sensors see things starting to go pear-shaped. the differential is different as it is a mechanical device, like a little transmission. note that the tt/a3 uses a totally different system [haldex].

the audi torsen center diff [used through the b7 chassis, the b8 car's is entirely different and vastly more complex] essentially takes the output from the transmission and decides how much power to send to the front and rear ‘axles’ [each of which use their own differentials to account for L/R diff action] at a ratio of UP TO 2:1 [it’s variable, this is important]. Thus if you have a 300hp car, and 300/3=100, the center diff can send up to 200hp one way and 100hp the other way. With our 4:1 modification in the same 300hp car the maximum differential would be 240 and 60, since 300/5=60. Essentially what you're doing is giving the diff more to work with, it makes a big difference in daily driving and a HUGE difference in traction-limited situations like you find on a racetrack. It makes no noises and there is no binding as it is still a fully functional diff. Seamless really in its operation. And no, the 'washer mod' is NOT the same.

Also, it's really a misnomer to think of the torsen as a "50/50" split [marketing propaganda notwithstanding]. if it were a true 50/50 there would be no difference in F/R power split and thus no need for a 'differential'. this is essentially what happens when you weld the planetary gears in the diff together. the r8 has no center diff and is true 50/50, it never varies the split. when you're driving down the freeway at a steady speed there is no significant load/traction difference and the diff isn't varying the power split [no differential action], so it's 50/50. however once you start turning, accelerating and braking the wheels all want to go different speeds and have different loads and traction levels. this is where the diff becomes 'active' in its distribution of power. To put it in simple terms the split is 50/50 when the loads are static, but varies when the load gets dynamic. The cool thing is that it varies in response to the dynamic loads. the real beauty / genius of the torsen is that it actually sends power to the wheel with MORE traction rather than less, which is how most open diffs work. It’s also why your camry wants to spin the tire on the ice when the other tire is on pavement.

Bad camry. No doughnut.

[Glassnpowder98]

Haha finally someone credible chimed in! Thanks for that info... Hopefully a Stassis 4:1 diff will be purchased in the not to incredibly distant future. I'm still unsure if I want to make the a4 into a track mobile once it's paid off or if I'm going to throw my money into an E36 325is for a rear wheel track mobile. But a 4:1 diff definitely would make the a4 a more viable option for the track! If only it would also shed about 500-800 lbs off the a4...

[Jim@STaSIS]

heh i don't know about 'credible' but i'll take it! nothing we do will turn your car into a race car - there's nothing worse than driving to work in a race car. drinking coffee is hard when you've got 9 trillion pound springs and clients hate it when they can hear your clackity control arms over your conversation. we take racing theory and technology and apply it to these cars to make them more fun, more dynamic and engaging but every bit as liveable and useful.

this is the owners daily: http://forums.audiworld.com/a4b7/msgs/110497.phtml