Use of Quattro

[youngd]

Hello, I was just wondering how you's use the quattro system (b8 3.0tdi tdi system mechanical 4wd) looking on videos on YouTube some people say to usr half throttle etc, some say none at all. What do yous do to make it operate at its best?
Thank you

[QUA77RO]

My understanding is that quattro works by shifting power so you must be on the throttle otherwise you are relying on electronic nannies not the quattro system.

Neutral throttle would be the bare minimum required to keep quattro engaged and distributing power. Once you lift off throttle, you are no longer giving the system power that it can shift around as needed to maintain forward progress. At that point, you are relying on the computers/sensors to trigger ESP.

[dscline]

It's a completely passive system, you don't have to do anything special. Unlike some systems that leave the rear or front wheels "disengaged" until wheel spin is detected, Quattro is a full time system with purely mechanical differentials. The distribution of power between the front and rear is much like the distribution of power between the left and right wheels in any car. The only difference is the center differential is a torsen type instead of a conventional differential. Torsen differentials tend to lock once an imbalance of torque occurs between each output (in this case, a difference in torque between the front & rear). But that generally doesn't happen unless a wheel looses traction. Under normal conditions it pretty much behaves much like any other differential. The torsen differentials in the B8 is designed to split torque 60/40 rear/front, so from that perspective you can treat it a little like a RWD car (you might be able to bring the tail out a little in a sharp turn with a heavy foot), but with power being applied to all wheels all the time, it's still going to remain relatively neutral regardless of what you do.

[b6onboost]

^ This.

[Comp4k]

That's the secret of the Quattro system, it's always operating at its best.

[LINDW4LL]

I always keep my foot in the gas in heavy snow. The Torsen diff will make up for wheel speed differences even if your foot is off of the gas, however if you apply throttle it is always actively distributing torque to the wheels with the best traction.

Basically you will do much better if you give it throttle versus coasting. Also ESP off is always a must.

[B-Time]

Wait for bad weather, turn off traction control, then drive it like I stole it.

[amz]

I was wondering this myself so I spent an afternoon researching the Quattro system as a whole, and this is what I've figured out. Please correct me if I'm wrong on any count:

There are three main diffs in the car, F, R, and C. The Center diff is the Torsen diff and is responsible for sending power to the front or rear axles, depending on where traction is. In normal circumstances, it will be a 40/60 F/R split. The Front and Rear differentials are open, using EDL instead of a mechanical differential. An open differential will divert power to the path of least resistance under normal circumstances. As a wheel starts to slip, it becomes the path of least resistance (spinning freely in the air is much easier then pushing a 1600kg car!) which is when the traction control module kicks in and applies the brakes (I believe it uses the ABS system, someone correct me?) to brake the slipping wheel. The slipping wheel then becomes the path of most resistance, so the open diff will transfer power to the wheel with grip.

You cannot turn off the Torsen differential, it is a mechanical fixture of the drive system, responsible for diverting power to the Front and Rear of the car. You can, however, turn off traction control (and stability control, read up on the implications before trying it!!), which means power will NOT be sent to the left or right sides of the car. For straight-line performance, many people will turn off the stability control and traction control systems.

One thing to note: If you do start to slip, as long as your traction control is on don't be afraid to give it power. Quattro will sort itself out, including automatically limiting the throttle while 'getting a grip' on things (I made a funny...)

[QUA77RO]

It's a completely passive system, you don't have to do anything special. Unlike some systems that leave the rear or front wheels "disengaged" until wheel spin is detected, Quattro is a full time system with purely mechanical differentials. The distribution of power between the front and rear is much like the distribution of power between the left and right wheels in any car. The only difference is the center differential is a torsen type instead of a conventional differential. Torsen differentials tend to lock once an imbalance of torque occurs between each output (in this case, a difference in torque between the front & rear). But that generally doesn't happen unless a wheel looses traction. Under normal conditions it pretty much behaves much like any other differential. The torsen differentials in the B8 is designed to split torque 60/40 rear/front, so from that perspective you can treat it a little like a RWD car (you might be able to bring the tail out a little in a sharp turn with a heavy foot), but with power being applied to all wheels all the time, it's still going to remain relatively neutral regardless of what you do.

Have you ever driven your A4 at the limit?...or on ice? There is NO WAY that the B8 A4 has a 60:40 torque split (R:F). Everyone who is also misquoting that figure, failed to read Audi's small print. Audi states that the split varies across models. Further documentation from Audi states that the 60:40 R/F split is for "S" models with the R8 getting an even more rearward bias of 80:20 R/F. I have never seen a torque split given for the A4 but would venture that it is just the opposite... 40:60 R/F split. At the limit, it takes significant suspension modifications to reduce the B8 A4's natural tendency to understeer. Inducing oversteer in even a modified B8 S4 is difficult but doable more due to the torque vectoring rear sport diff though...an option that unfortunately we didn't get for A4's in the U.S... I watched a MotorTrend test driver get frustrated as hell that he couldn't get the tail out of either a stock or modified B8 S4 while attempting to get some "slideways" shots. Quattro requires serious hoonage to get the tail out

I always keep my foot in the gas in heavy snow. The Torsen diff will make up for wheel speed differences even if your foot is off of the gas, however if you apply throttle it is always actively distributing torque to the wheels with the best traction.

Basically you will do much better if you give it throttle versus coasting. Also ESP off is always a must.

^This

[B8_Jim]

Have you ever driven your A4 at the limit?...or on ice? There is NO WAY that the B8 A4 has a 60:40 torque split (R:F).

I don't think I've seen audi say what the system does at the limit - but their press info for the B8 A4 release does quote the torque split "for normal driving conditions" :

"Both gasoline FSI engines are available with the quattro permanent all-wheel drive, which is optional on 2.0 TFSI or standard on 3.2 FSI. Under normal driving conditions, this distributes the forces at a ratio of 40:60 between the front and rear axle. This emphasis on the rear end perfectly harmonizes with the overall dynamic character of the new A4. If needed, the self-locking center differential transfers the majority of the torque to the axle with the better traction. As in the past with all North American models, all A4 Avant models always have quattro as standard equipment."

[treginginco]

Check this out:
https://www.youtube.com/watch?v=USRGroq25Hc

And this:
https://www.youtube.com/watch?v=JykT6ovtC_Q

[dscline]

Have you ever driven your A4 at the limit?...or on ice? There is NO WAY that the B8 A4 has a 60:40 torque split (R:F).

That is simply what Audi claims. I certainly have no way of measuring it. Though I can tell you after driving my B5 for over 14 years, and now my B8 for over 2, I can tell a difference. Like I said, with the B8 if you really get on it in a sharp corner, you might be able to break the rear lose a LITTLE if you really romp on it. I could never really sense the rear moving out any in that kind of situation with the B5. The B8 really does feel like it has some bias towards the rear vs. the B5. If it's less than the 60/40 ratio Audi claims, I'm not going to split hairs over it.

Everyone who is also misquoting that figure, failed to read Audi's small print. Audi states that the split varies across models. Further documentation from Audi states that the 60:40 R/F split is for "S" models

I'd be interested in seeing that documentation. I have a hard time believing they'd use a different center differential in the S4 vs. A4. To what end? Sure, the S4 has the OPTION for the sports differential in the rear, but why would they claim 60/40 on the A4/S4 models, then do something different?

I have never seen a torque split given for the A4 but would venture that it is just the opposite... 40:60 R/F split.

I don't know how you've missed it, it's been mentioned quite a bit ever since they introduced it. It's listed in the brochure, among other places, as 60/40 rear/front, with no differentiation between the A and S models.

[milito-reloaded]

When you are bloqued anywhere and you cant avance because wheels spin, turn of the ESP and try again. Once you start moving turn off again the ESP for a safe driving. If you feel the car has difficulties to continue ahead or If you want a racing driving, you must keep ESP turned off.

[QUA77RO]

I don't think I've seen audi say what the system does at the limit - but their press info for the B8 A4 release does quote the torque split "for normal driving conditions" :

"Both gasoline FSI engines are available with the quattro permanent all-wheel drive, which is optional on 2.0 TFSI or standard on 3.2 FSI. Under normal driving conditions, this distributes the forces at a ratio of 40:60 between the front and rear axle. This emphasis on the rear end perfectly harmonizes with the overall dynamic character of the new A4. If needed, the self-locking center differential transfers the majority of the torque to the axle with the better traction. As in the past with all North American models, all A4 Avant models always have quattro as standard equipment."

Don't confuse "at the limit" with going fast. I'm referring to the "limit" of available grip which can just as easily be exceeded at 5 MPH on ice.

As for the brochure quote, I invite you to check the link I'll provide below.

That is simply what Audi claims. I certainly have no way of measuring it. Though I can tell you after driving my B5 for over 14 years, and now my B8 for over 2, I can tell a difference. Like I said, with the B8 if you really get on it in a sharp corner, you might be able to break the rear lose a LITTLE if you really romp on it. I could never really sense the rear moving out any in that kind of situation with the B5. The B8 really does feel like it has some bias towards the rear vs. the B5. If it's less than the 60/40 ratio Audi claims, I'm not going to split hairs over it.


I'd be interested in seeing that documentation. I have a hard time believing they'd use a different center differential in the S4 vs. A4. To what end? Sure, the S4 has the OPTION for the sports differential in the rear, but why would they claim 60/40 on the A4/S4 models, then do something different?


I don't know how you've missed it, it's been mentioned quite a bit ever since they introduced it. It's listed in the brochure, among other places, as 60/40 rear/front, with no differentiation between the A and S models.

I daresay that the difference between the B8 and B5 chassis weight distributions have more to do with your perception of a "difference" than any difference in the quattro torque split. The B8 has gotten much closer to the ideal 50/50 weight distribution than the old B5. Avants are almost dead even with the extra 250 lbs over the rear wheels.

Anyway, I, like you, hate B.S. so here's a link to Audi's B8 A4/S4 brochure (specifically the quattro section)

http://viewer.zmags.com/publication/...67#/70d55067/8

On page 9, you will find all the general advertising blather that you guys are quoting. But somehow you missed it... at the end of the first sentence at the top of the second column, we find a notation (1). If you look at the small print at the bottom of page 8, you will find notation (1) where it states:

Torque split ratio will vary from model to model

I'd take the notations as more "true" than the advertising copy that raves on about all the "uberness" that is Audi... The notation was added by the lawyer that said "we can't be so liberal with the truth in the brochure without a disclaimer."

If you have a MT B8 A4/S4, then you can buy a center diff that actually gives a rear bias and is amazingly effective.

[drob23]

I think you're looking into this a little too far and confusing the nominal torque split with how the vehicle handles. I bet that quote was more to deal with A3 "quattro" systems which aren't really close to the same thing. An AWD cars tendency to understeer doesn't have to do *only with the F/R toque split*. You can make a RWD car understeer with the proper suspension setup/weight distribution. The S and RS cars are often said to have "removed understeer" by means of the active rear diff, which has nothing to do with F/R. The gen 5 version of the quattro center diff was

"Starting with the B7 Audi RS4 and the manual transmission version of the 2006 B7 Audi S4. It was adopted in the entire S4 lineup in 2007.[1] and become the standard fitment on all quattro Audis with longitudinal engine layout until replaced in the 2010 RS5.

System type: Permanent asymmetric four-wheel drive.

Torsen type 3 (Type "C") centre differential, 40:60 'default' split front-rear, automatically apportioning up to 80% of the torque to one axle using a 4:1 high-biased center differential. With the aid of ESP, up to 100% of the torque can be transferred to one axle."

I won't provide any more sources than wikipedia because this is pretty common knowledge. There is no conspiracy here to market incorrect knowledge. Changing the nominal torque split of the center diff is not a very hard thing to do, and makes sense to send more to the rear because that's where weight transfer goes when accelerating (or going up a hill) and aren't the wheels steering the car.

[dscline]

I'd take the notations as more "true" than the advertising copy that raves on about all the "uberness" that is Audi... The notation was added by the lawyer that said "we can't be so liberal with the truth in the brochure without a disclaimer."

I'm sorry, I'm just not following what you are suggesting. What would they be being liberal with? It's not like they have anything to gain by fudging the numbers, like claiming an engine produces 300HP when they're providing an engine that's really only capable of 250HP. The torque split in a torsen differential is really just a gearing choice within the differential. It's not like there's significant cost differences for different split ratios. The version of Quattro used in the B8 uses the Torsen T3 center differential, which is available in nominal torque splits from 65:35 to 35:65. Why would Audi choose, for example, 45:55, then claim 40:60? I don't understand why you think they would specifically choose a differential that is available in a range of torque splits, produce documentation with specific numbers of what torque splits they chose, and not be truthful about it. If there was any reason to hide the "real" proportion, why divulge it at all? Why not just say it is biased to provide more torque to the rear wheels, without saying what the number is? Personally, I think the more likely reason for the disclaimer is because the nominal 40:60 split is just that: nominal. It may not be perfectly accurate. I work for an HVAC manufacturer, and we have products available in various nominal tonnages. But in reality, the actual capacity of a model may not be EXACTLY the nominal tonnage. One 4 ton model might produce 3.9 tons, and another 4.1. It's not anything intentionally deceptive, it's just how things shake out when you combine various compressors, fans, and coil configurations. They aren't available in infinite configurations. It might take a gear with 29.5 teeth to produce the exact split you're looking for, but you can't have a half tooth. Since the amount of traction (and therefore torque) applied to each wheel will also vary based on how much weight is on the wheel, I could see the actual numbers varying based on the configuration of the car.

If you have a MT B8 A4/S4, then you can buy a center diff that actually gives a rear bias and is amazingly effective.

I'm not aware of any center differential options on the A4, or even S4. The only such option I know of is the rear sport differential in the S4. I guess I'm not following what you're saying here.

[dracolnyte]

http://viewer.zmags.com/publication/...67#/70d55067/8

On page 9, you will find all the general advertising blather that you guys are quoting. But somehow you missed it... at the end of the first sentence at the top of the second column, we find a notation (1). If you look at the small print at the bottom of page 8, you will find notation (1) where it states:

Torque split ratio will vary from model to model

I'd take the notations as more "true" than the advertising copy that raves on about all the "uberness" that is Audi... The notation was added by the lawyer that said "we can't be so liberal with the truth in the brochure without a disclaimer."

If you have a MT B8 A4/S4, then you can buy a center diff that actually gives a rear bias and is amazingly effective.

that page was strictly referring to quattro awd system, not specifically the A4/S4 models, so it includes the A3/TT haldex quattro
please do your research before obnoxiously claiming other people's information as false and arguing your own perception as a fact

[rampantandroid]

So I'm confused here some, then: correct me where I go wrong:

THere are 3 differentials in my B8.5 A4: Front, center and rear. The torsen pushes power between front and center, and then the front and rear differentials pushpower left or right?

Is AMZ's summary correct? If one rear wheel brakes, then won't the torsen push ALL power to the front wheels since that will have less resistance than the rear wheels?

[dscline]

THere are 3 differentials in my B8.5 A4: Front, center and rear. The torsen pushes power between front and center, and then the front and rear differentials pushpower left or right?

Conceptually yes, but in reality, the torsen differential is actually a combo unit that does the front/rear split as well as the front left/front right.

Is AMZ's summary correct? If one rear wheel brakes, then won't the torsen push ALL power to the front wheels since that will have less resistance than the rear wheels?

Yes, if a wheel loses traction and spins, the system will brake it to help direct torque to the other wheel on the same axel. The torsen handles the front/rear torque distribution.

[LINDW4LL]

Torque split is 60/40 rear. I'm not sure why QUA77RO is disputing that.

[drob23]

Torque split is 60/40 rear. I'm not sure why QUA77RO is disputing that.

Yea this is one of the dumber 'butt dyno' + 'random asterisk' jumping to conclusions things I've seen.

[QUA77RO]

I'm sorry, I'm just not following what you are suggesting. What would they be being liberal with? It's not like they have anything to gain by fudging the numbers, like claiming an engine produces 300HP when they're providing an engine that's really only capable of 250HP. The torque split in a torsen differential is really just a gearing choice within the differential. It's not like there's significant cost differences for different split ratios. The version of Quattro used in the B8 uses the Torsen T3 center differential, which is available in nominal torque splits from 65:35 to 35:65. Why would Audi choose, for example, 45:55, then claim 40:60? I don't understand why you think they would specifically choose a differential that is available in a range of torque splits, produce documentation with specific numbers of what torque splits they chose, and not be truthful about it. If there was any reason to hide the "real" proportion, why divulge it at all? Why not just say it is biased to provide more torque to the rear wheels, without saying what the number is? Personally, I think the more likely reason for the disclaimer is because the nominal 40:60 split is just that: nominal. It may not be perfectly accurate. I work for an HVAC manufacturer, and we have products available in various nominal tonnages. But in reality, the actual capacity of a model may not be EXACTLY the nominal tonnage. One 4 ton model might produce 3.9 tons, and another 4.1. It's not anything intentionally deceptive, it's just how things shake out when you combine various compressors, fans, and coil configurations. They aren't available in infinite configurations. It might take a gear with 29.5 teeth to produce the exact split you're looking for, but you can't have a half tooth. Since the amount of traction (and therefore torque) applied to each wheel will also vary based on how much weight is on the wheel, I could see the actual numbers varying based on the configuration of the car.


I'm not aware of any center differential options on the A4, or even S4. The only such option I know of is the rear sport differential in the S4. I guess I'm not following what you're saying here.

Woah. I'm not saying that it is some kind of conspiracy. Just some CYA wording for brochure material that is used across a product line which has models with different torque splits. That and some marketing hype that is way OT...

Oh and since you asked about it, here's a link to a high bias center diff for MT B8 Audis. Makes me wish avants had been available with a MT.

http://www.stasisengineering.com/products/differential/differential-high-bias-torsen-center-a4s4a5s5

that page was strictly referring to quattro awd system, not specifically the A4/S4 models, so it includes the A3/TT haldex quattro
please do your research before obnoxiously claiming other people's information as false and arguing your own perception as a fact

Agreed! ...that the pages in question are actually used by Audi in brochures for all models.
Arguing is a waste of time but I'm happy to debate the issue.
As for doing my research...you should know me better than to think I hadn't done my research.
I don't think that I've put forth any "perception as a fact" but if I have feel free to call it out.
I hadn't thought of Haldex since it is not quattro. Was Audi claiming it was? Maybe they were and I missed it.
I thought the more obvious newer models would be the RS5 with it's new crown center diff design or the R8 and the different splits across those quattro models...

Torque split is 60/40 rear. I'm not sure why QUA77RO is disputing that.

Yea this is one of the dumber 'butt dyno' + 'random asterisk' jumping to conclusions things I've seen.

I'm just clueless. I should probably just pull my head out of my ass now.
I see things much more clearly. Thank you.

[Burrito]

Im trying to un-see what Ive read here.

[rampantandroid]

Conceptually yes, but in reality, the torsen differential is actually a combo unit that does the front/rear split as well as the front left/front right.


Yes, if a wheel loses traction and spins, the system will brake it to help direct torque to the other wheel on the same axel. The torsen handles the front/rear torque distribution.

Ahh, ok. So then, if I lose all traction on the rear wheels, can it divert all of my power to the front? Or does it just brake the rear wheels to try to stop them from spinning out of control?

Thanks!

[LINDW4LL]

Ahh, ok. So then, if I lose all traction on the rear wheels, can it divert all of my power to the front? Or does it just brake the rear wheels to try to stop them from spinning out of control?

Thanks!

It can't send 100% of the torque to the front. 66% I believe.

[drob23]

Ahh, ok. So then, if I lose all traction on the rear wheels, can it divert all of my power to the front? Or does it just brake the rear wheels to try to stop them from spinning out of control?

Thanks!

The gen 5 quattro center diff isn't self locking, it can at most create a ratio of 4-1 I believe (60-40 F/R to 20-80 F/R), so it will unfortunately act like an open differential when one of the axles is on a frictionless surface (or in the air). The abs system can remedy this, but it'd debatable how effective this is, and more importantly, how long it takes the abs system to detect this situation (there are inherent limitations in sensing these conditions). This is how they get quattro cars to fail those roller tests - they long press to the esc button to turn off all traction control, and stick one axle on rollers.

The self-locking crown center diff introduced on the 2010 RS5 quattro gen 6 system fixes this problem.

[dracolnyte]

So I'm confused here some, then: correct me where I go wrong:

THere are 3 differentials in my B8.5 A4: Front, center and rear. The torsen pushes power between front and center, and then the front and rear differentials pushpower left or right?

Is AMZ's summary correct? If one rear wheel brakes, then won't the torsen push ALL power to the front wheels since that will have less resistance than the rear wheels?

the front and rear are open diffs. so if you have ESP off and one wheel slips, it will just keep slipping because it thinks it is going through a turn. but if both wheels on the same axel slips then thats when the mechanical diff kicks in. I have seen a video where an A4 on a slope wasnt able to send power to another axel because one wheel was slipping



that is the limitation of quattro, just front and rear torque split. maybe the sport diff is better?