Quattro Settings
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RSS-S3
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The Latest Haldex system in Facelift s3 ...in Dynamic mode I believe is 80-20% split .......i think .....
Flying Scotsman
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I have no definitive figures as to split but dynamic will still allow power to the rear even if oversteer is detected. For a fun ride set Quattro to dynamic and set ESC to sport by pressing quickly.
RSS-S3
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I'm not technical, but my understanding of the Haldex system in the A3/S3 is that even in Dynamic, the vast majority of the power/torque is sent to the front wheels most of the time. It's only when the system detects that it needs to send power/torque to the back, that it fires it rearward. I think 'upto' 80% is in conditions such as launch mode for example. But, I could be very wide off the mark on that one.
RSS-S3
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I found the information ages ago when reasearching into my car. Im sure it was in a audi brochure.Not that I don't trust you guys but do you have any official source for those numbers? I'm a bit curious and would like to read more about it
RSS-S3
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I think that was the RS3 ???
Not sure ...... there is so much waffle on the internet about haldex power outputs.... it could be ****** anything
Trev241
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I read this as well, I am quite keen to find out for sure. So what I wonder will Auto setting give ?
Where the hell do these numbers keep coming from?
There's so much rubbish quoted about four wheel drive systems, and Haldex in osrticular seems to suffer a great deal of Chinese whispers about its capabilities.
There's so much rubbish quoted about four wheel drive systems, and Haldex in osrticular seems to suffer a great deal of Chinese whispers about its capabilities.
Satory
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paradigital
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Posts like these don't help matters. Yes the front wheels always have to turn, but that doesn't mean that 100% of the torque being transferred to the floor isn't from the rear.
The problem with all of the info about Haldex is that firstly people don't understand exactly what it is and what it does, secondly they don't really understand how friction and thus the physics of the system works, and finally you get the fanatics that think haldex is somehow capable of delivering a massively dynamic rear biased drive in normal driving conditions when it really REALLY isn't.
Mainly because it's a USP for the car, and secondly because modern Haldex is a very tuneable beast. It can be tuned to run with a greater or lesser ramp rate, and run with a higher or lesser degree of torque transmission for any given circumstance.
Drive select offers you these options.
RSS-S3
Registered User
Well you should be able to feel the differences and then make a subjective choice depending on what you prefer. If you can't feel any difference then what the settings are technically doing is irrelevant really
@RSS-S3 Useful, thanks!, although I'm not entirely sure what the difference between the "Hydraulic multi-plate clutch" and "quattro on-demand" systems are.
The self-locking one is the classic Torsen diff system. I remember when Haldex first appeared and everyone said it wasn't "proper" quattro as it wasn't Torsen but I think that, nowadays, Torsen is a bit of a dinosaur as it has limited flexibility and, as it's a permanent system, has economy and emissions disadvantages.
The self-locking one is the classic Torsen diff system. I remember when Haldex first appeared and everyone said it wasn't "proper" quattro as it wasn't Torsen but I think that, nowadays, Torsen is a bit of a dinosaur as it has limited flexibility and, as it's a permanent system, has economy and emissions disadvantages.
The use of when needed is interesting presumably that means the front wheels have completely lost traction or are in the air the all the system can do is transfer the torque rearward lol
I interpret it as the former is always sending power to all wheels with a varying degree of bias, whereas the latter normally operates in front wheel drive only.
paradigital
Registered User
To me, the "on demand" Quattro, especially considering it's an A4 platform vehicle, is likely to be a detachable version of the TorSen system, so kind of a hybrid between TorSen and Haldex.
So when it's engaged it's full-time four wheel drive, but when it's detached it has little of the transmission losses.
****** hell, even the Audi "facts" are ambiguous to the point of uselessness.
Unless torsen have come up with yet another clever system then centre diff type systems with Torsen diffs aren't able to send "100% of power to front and rear" and never really have been.
There's a multitude of different ways of doing the same job, and all of them have advantages and disadvantages. I'll leave the technical explanations for another post, but for now consider just this;
With modern tyre and chassis technology all wheel drive is now an anachronism, about as valid now as having to pull a choke to start the engine. Audi's entire brand and reputation had been built upon, and is now utterly reliant on it though, so they've painted themselves into a corner.
Having dined out on all wheel drive rally success for nearly four decades, theyre not about to admit AWD isn't worth the bother anymore. Biting the bullet and going pure rear drive would be commercial suicide, as would going front drive, since the nearest market comparisons suddenly become ford, Vauxhall and Citroen. So Audi will continue to punt Quattro as its USP, and hide from buyers things like the R8 has a viscous coupling about as advanced as a wood burning stove, or that Quattro ultra, aka "quattro on demand" is basically a Haldex-esque four wheel drive system who's biggest trick is being able to run most of the time as a pure front wheel drive system, disconnecting the rear axle at the rear diff AND at the power take off so they don't even have the parasitic loss of the prop shaft. (It's done by moving the variable coupling up front and putting a dog clutch on one of the rear driveshafts - no torsen trickery involved)
Audi can then continue to offer "AWD" whilst still keeping emissions down and economy up. Ita a topsy turvey world in which audi needs to punt out 3 Series and C class competitors, but the only way the public will accept an A4/5 as being in the same class as those two is if some of its drive goes rearwards. The fact that it only does it a fraction of the time, the rest of the time leaving your premium saloon with pretty much the same driveline as a mondeo, is of course not widely acknowledged.
If ever there was an example of marketing departments pushing engineering in directions it doesn't need to go, then this is it.
Unless torsen have come up with yet another clever system then centre diff type systems with Torsen diffs aren't able to send "100% of power to front and rear" and never really have been.
There's a multitude of different ways of doing the same job, and all of them have advantages and disadvantages. I'll leave the technical explanations for another post, but for now consider just this;
With modern tyre and chassis technology all wheel drive is now an anachronism, about as valid now as having to pull a choke to start the engine. Audi's entire brand and reputation had been built upon, and is now utterly reliant on it though, so they've painted themselves into a corner.
Having dined out on all wheel drive rally success for nearly four decades, theyre not about to admit AWD isn't worth the bother anymore. Biting the bullet and going pure rear drive would be commercial suicide, as would going front drive, since the nearest market comparisons suddenly become ford, Vauxhall and Citroen. So Audi will continue to punt Quattro as its USP, and hide from buyers things like the R8 has a viscous coupling about as advanced as a wood burning stove, or that Quattro ultra, aka "quattro on demand" is basically a Haldex-esque four wheel drive system who's biggest trick is being able to run most of the time as a pure front wheel drive system, disconnecting the rear axle at the rear diff AND at the power take off so they don't even have the parasitic loss of the prop shaft. (It's done by moving the variable coupling up front and putting a dog clutch on one of the rear driveshafts - no torsen trickery involved)
Audi can then continue to offer "AWD" whilst still keeping emissions down and economy up. Ita a topsy turvey world in which audi needs to punt out 3 Series and C class competitors, but the only way the public will accept an A4/5 as being in the same class as those two is if some of its drive goes rearwards. The fact that it only does it a fraction of the time, the rest of the time leaving your premium saloon with pretty much the same driveline as a mondeo, is of course not widely acknowledged.
If ever there was an example of marketing departments pushing engineering in directions it doesn't need to go, then this is it.
That would make sense as the A4 AllRoad has it whereas the A4 is standard Torsen and I doubt they'd have two completely different systems on these cars.
V6 tdi allroad has Torsen, but the 4 cyl has Quattro ultra.
Ultra is at present only being used on the lower capacity (4 cyl) cars.
Its an intriguing system, but when push comes to shove, I think I'll take the old fashioned all wheel drive system that's 'on' all the time...
Audi does not pass on much info about the Haldex, but based on what I have seen I believe the normal power is 85/15 front/rear. When the Haldex is engaged it delivers 50/50 to the axles. However, the car can take that 50/50 and change things depending on what is going on with weight transfer and road surface. When you accelerate the car pitches up sending weight to the back, and the rear wheels generate more force which can make the split 35/65. Hit a patch of ice and the power can shift to 100% on either axle.
On gen. 4 cars you can engage the Haldex by selecting ESP off or selecting Sport mode. By doing this you now have full time AWD. When you coast the car will deliver 50/50 of the engine braking to the axles. This is going to reduce oversteer at the limit because when the weight shifts to the front there will be drag at the rear axle. With the normal 85/15 the weight will shift to the front and combine with the engine braking. The remaining 15 at the rear will not encounter much resistance and the momentum of the rear wheels will force the rear up. As the back end goes up the car will be prone to oversteer.
The gen. 5 cars work the same as gen. 4, so no change. The facelift S3 gets its own ESP Haldex setup (also RS3) which turns off some ESP functions when in Sport mode. The throttle is not cut which means the car can oversteer even though the ESP has not been turned off.
On gen. 4 cars you can engage the Haldex by selecting ESP off or selecting Sport mode. By doing this you now have full time AWD. When you coast the car will deliver 50/50 of the engine braking to the axles. This is going to reduce oversteer at the limit because when the weight shifts to the front there will be drag at the rear axle. With the normal 85/15 the weight will shift to the front and combine with the engine braking. The remaining 15 at the rear will not encounter much resistance and the momentum of the rear wheels will force the rear up. As the back end goes up the car will be prone to oversteer.
The gen. 5 cars work the same as gen. 4, so no change. The facelift S3 gets its own ESP Haldex setup (also RS3) which turns off some ESP functions when in Sport mode. The throttle is not cut which means the car can oversteer even though the ESP has not been turned off.
There are some really fundamental issues of understanding that are missing here. Key among which is that torque splits are marketing jargon that have almost nothing to do with real life. You cannot say whether the S3 runs 85/15 , 90/10 or 95/5 front to rear because we dont have access to the programming and we haven't measured it. What we can say is that mechanically it lacks an epicyclic centre differential, so it is unable to run with a mechanically fixed torque bias like a BMW or an RS5. The default mechanical layout is therefore fixed at 50/50. What the software does with the coupling is variable, both between models and according to all manner of other dynamic factors, including yaw rate, steering angle, which gear you are in and what the ESP system is monitoring. This dynamic adjustment of torque transfer is highly variable, and differs from moment to moment, but it's range is variable from 100%front, 0% rear, to 50% front, 50%rear. This is its fixed design range. There are many other factors to consider though that in real life will expand that envelope.
This torque spilt everyone keeps banging on about is entirely dependant upon a key factor that is consistently missed. This torque transmitted along driveshafts only exists if there is something for the driveshaft torque to react against. That reaction comes from only one place (well, two if we also account for the pseudo front Limited Slip Diff, but that's another complication we ought to ignore for the moment). That key, fundamental part of the jigsaw, is the tyres and their grip on terra firma. It takes almost no torque to spin a transmission system with no load on it, which is why your dealer testing your Haldex coupling by showing you your car on a lift with all four wheels spinning merrily away is an utterly useless test - in the same way as you being able to bench press 100kg, you can only put in the power required to lift that 100kg weight if you have 100kg to push against. So, if the rear tyres have no grip and the front tyres are sticking to the tarmac like superglued leeches then you can lock the Haldex coupling solid, weld it shut if you want, and the torque transmission will be still be 100% to the front, as there is nothing for that torque to do at the rear wheels. Vice versa, if the rear wheels are sat on something super sticky and the front wheels are in free air, then 100% of the torque goes rearward.
The issue is further compounded by dynamic weight transfer. An accelerating vehicle with a centre of gravity above its axle centrelines (i.e. - all cars) will transfer a proportion of its total mass to its rear wheels. Grip at a tyre is proportional to the torque it can transmit without slipping - more grip = more capability to transmit torque. That level of grip increases when you put more weight on the tyre. So an accelerating vehicle might reach the point where the reduction in weight at the front tyres leads the grip to fall below the point at which the torque being transmitted would cause them to slip. In a front drive car you would have wheelspin, in the Haldex car you have a locked mechanical connection that means the rear tyres are doing the lions share of the work. You won't ever see this, since with a locked system the front tyres are revolving at exactly the same speed as the rears, but despite there being a mechanical 50-50 split, the rears will be transmitting more torque because they have more grip and have no exceeded their grip (torque transmission) limitation. This is apportioned torque split, which is highly variable, has nothing to do with clever diffs, and is what really counts to a driver.
Fundamentally though it's still a 50/50 split system until some other external factor comes into play, which really isn't as often as some cynics would have you believe. The slip at the coupling which must occur to reduce torque transmission to the rear axle and thus generate a front bias will only occur when the input torque to the rear axle is greater than the torque reaction from the rear tyres. Until that point, it's fundamentally a locked system. This means that when you are pootling along at a 70mph cruise, and you are using only a fraction of the 300Nm of torque the S3 engine can muster (say - 50Nm) then (gearbox multiplication ratios aside) the front and rear axles are dealing with 25Nm each. A Haldex coupling clutch set to a very low set point can transmit this with no issues and no slip at all, so you can consider it 100% locked and thus set to 50-50.
The system layout brings with it some difficulties in the form of a phenomenon called 'wind-up' that exists in all four wheel drive vehicles with no centre diff or a locked centre diff. To relieve the stresses created in wind-up, the Haldex coupling will allow some slip when rear drive power is not actively required. This slip might amount to only 1 or 2 revolutions of the rear propshaft in a number of miles, so it's not much, but it can be very damaging when not relieved. The way to deal with it is to either open the coupling up regularly, or run it at a set point where the it will slip if the torque transmitted is greater than that determined by the ecu as being the required amount of torque being sent down the propshaft.
So what does this mean with regard to the original question - what difference does comfort-auto-dynamic have on the Quattro system?
Being an active system (forget all that rubbish you've read about the rear wheels only becoming active when the fronts have already started to slip, you're fifteen years out of date and that sort of tech is only used in the R8 now), there are a number of things a programmer can adjust to map the way the system behaves. First, you can run it in a less active mode, where it allows a great deal of slip at the coupling and gives the familiar feeling and stability of afrint drive chassis. You can reduce the ramp rates so that the couplings transition from slip to full locking is nice and steady, and engages almost imperceptibly when required. Whilst this isn't very sporting and won't give the 'feeling' of driving an AWD car, it brings with a number of advantages; it's better for fuel economy, its better for noise and vibration, and its better for tyre wear. You could even go to the extreme that Honda caught a lot of flak for on the old CRV. They fitted AWD to that car because it's what the market demanded, but they didn't want to sacrifice economy, efficiency and weight, so they fitted a system that 'could' drive the rear wheels, but in reality couldn't transmit enough torque to open a jam jar. The punter got the AWD kudos they wanted, which fell apart the minute they got to something slippery and found that even with perfect grip at the rear axle, if the fronts had no grip they were stuck.
On the flip side of the coin, you could set it so that the system achieve full locking very early, allows a greater tolerance for wind up in the transmission, hammers the coupling to full closed at the very millisecond its required to, and runs as much torque through to the rear axle as the engine can throw at it. This more aggressive stance results in feeling much more "Audi", being able to do far sillier things on roundabouts, and of course gives the buyer the sense that he's spent his cash on something discernible. It does use a bit more fuel though, and will result in a bit more noise in the form of clunks and whines. Oh, and all the transmission wind-up forces will be increasingly relieved through tyre slip, which will result in more tyre wear.
This torque spilt everyone keeps banging on about is entirely dependant upon a key factor that is consistently missed. This torque transmitted along driveshafts only exists if there is something for the driveshaft torque to react against. That reaction comes from only one place (well, two if we also account for the pseudo front Limited Slip Diff, but that's another complication we ought to ignore for the moment). That key, fundamental part of the jigsaw, is the tyres and their grip on terra firma. It takes almost no torque to spin a transmission system with no load on it, which is why your dealer testing your Haldex coupling by showing you your car on a lift with all four wheels spinning merrily away is an utterly useless test - in the same way as you being able to bench press 100kg, you can only put in the power required to lift that 100kg weight if you have 100kg to push against. So, if the rear tyres have no grip and the front tyres are sticking to the tarmac like superglued leeches then you can lock the Haldex coupling solid, weld it shut if you want, and the torque transmission will be still be 100% to the front, as there is nothing for that torque to do at the rear wheels. Vice versa, if the rear wheels are sat on something super sticky and the front wheels are in free air, then 100% of the torque goes rearward.
The issue is further compounded by dynamic weight transfer. An accelerating vehicle with a centre of gravity above its axle centrelines (i.e. - all cars) will transfer a proportion of its total mass to its rear wheels. Grip at a tyre is proportional to the torque it can transmit without slipping - more grip = more capability to transmit torque. That level of grip increases when you put more weight on the tyre. So an accelerating vehicle might reach the point where the reduction in weight at the front tyres leads the grip to fall below the point at which the torque being transmitted would cause them to slip. In a front drive car you would have wheelspin, in the Haldex car you have a locked mechanical connection that means the rear tyres are doing the lions share of the work. You won't ever see this, since with a locked system the front tyres are revolving at exactly the same speed as the rears, but despite there being a mechanical 50-50 split, the rears will be transmitting more torque because they have more grip and have no exceeded their grip (torque transmission) limitation. This is apportioned torque split, which is highly variable, has nothing to do with clever diffs, and is what really counts to a driver.
Fundamentally though it's still a 50/50 split system until some other external factor comes into play, which really isn't as often as some cynics would have you believe. The slip at the coupling which must occur to reduce torque transmission to the rear axle and thus generate a front bias will only occur when the input torque to the rear axle is greater than the torque reaction from the rear tyres. Until that point, it's fundamentally a locked system. This means that when you are pootling along at a 70mph cruise, and you are using only a fraction of the 300Nm of torque the S3 engine can muster (say - 50Nm) then (gearbox multiplication ratios aside) the front and rear axles are dealing with 25Nm each. A Haldex coupling clutch set to a very low set point can transmit this with no issues and no slip at all, so you can consider it 100% locked and thus set to 50-50.
The system layout brings with it some difficulties in the form of a phenomenon called 'wind-up' that exists in all four wheel drive vehicles with no centre diff or a locked centre diff. To relieve the stresses created in wind-up, the Haldex coupling will allow some slip when rear drive power is not actively required. This slip might amount to only 1 or 2 revolutions of the rear propshaft in a number of miles, so it's not much, but it can be very damaging when not relieved. The way to deal with it is to either open the coupling up regularly, or run it at a set point where the it will slip if the torque transmitted is greater than that determined by the ecu as being the required amount of torque being sent down the propshaft.
So what does this mean with regard to the original question - what difference does comfort-auto-dynamic have on the Quattro system?
Being an active system (forget all that rubbish you've read about the rear wheels only becoming active when the fronts have already started to slip, you're fifteen years out of date and that sort of tech is only used in the R8 now), there are a number of things a programmer can adjust to map the way the system behaves. First, you can run it in a less active mode, where it allows a great deal of slip at the coupling and gives the familiar feeling and stability of afrint drive chassis. You can reduce the ramp rates so that the couplings transition from slip to full locking is nice and steady, and engages almost imperceptibly when required. Whilst this isn't very sporting and won't give the 'feeling' of driving an AWD car, it brings with a number of advantages; it's better for fuel economy, its better for noise and vibration, and its better for tyre wear. You could even go to the extreme that Honda caught a lot of flak for on the old CRV. They fitted AWD to that car because it's what the market demanded, but they didn't want to sacrifice economy, efficiency and weight, so they fitted a system that 'could' drive the rear wheels, but in reality couldn't transmit enough torque to open a jam jar. The punter got the AWD kudos they wanted, which fell apart the minute they got to something slippery and found that even with perfect grip at the rear axle, if the fronts had no grip they were stuck.
On the flip side of the coin, you could set it so that the system achieve full locking very early, allows a greater tolerance for wind up in the transmission, hammers the coupling to full closed at the very millisecond its required to, and runs as much torque through to the rear axle as the engine can throw at it. This more aggressive stance results in feeling much more "Audi", being able to do far sillier things on roundabouts, and of course gives the buyer the sense that he's spent his cash on something discernible. It does use a bit more fuel though, and will result in a bit more noise in the form of clunks and whines. Oh, and all the transmission wind-up forces will be increasingly relieved through tyre slip, which will result in more tyre wear.
Great write up as always, thanks GSB! So, could the FL's quattro setting just an option to switch the AWD module's "Acoustic measure: Wiring logic" from "Reduced noises" to "Increased traction"? Could anyone verify this by switching the setting and check VCDS/OBD11? Wondering if setting to "Increased traction" could have negative longevity effect on the Haldex unit as well...
I've no answer to that question I'm afraid, but I know that when I have the driveline in dynamic mode, there's an audible 'clunk' from the rear end as I dip the clutch in first gear traffic, presumably from the coupling abruptly disengaging. The clunk dissapears in the other two modes.
These clunks were a fact of life in my old Mazda MPS6, which would fully engage the rear driveline without hesitation. That car would wear tyres out in 12,000 miles, struggle to better 28mpg, and would wind its transmission up into a pretzel if you put the space saver spare on. It seems that Mazda's designers were less concerned about efficiency and economy than they were about going fast. Really really fast. Probably why they also fitted a limited slip diff at the rear, and came up with a car that could, and would, get very very sideways indeed given a bit of exuberance on the loud pedal.
Of course it was very different in the early days when 'quattros' had a manual locking centre and rear diff.
I had a B2 1.8quattro ( 1985-87) and if you operated the center diff lock you knew all about it within a yard or so! You could feel the wind up through the steering wheel and the tyres would really scrub on any hard surface........... but it was fantastic off road, on icy surfaces and to an extent in the snow. With both diffs locked I did a 360 spin in a straight line in , more or less in the car's own length...........on the road...... it was v e r y scary on the highway - fortunately with nothing about. Never ran on the road with locked diffs again!
I had a B2 1.8quattro ( 1985-87) and if you operated the center diff lock you knew all about it within a yard or so! You could feel the wind up through the steering wheel and the tyres would really scrub on any hard surface........... but it was fantastic off road, on icy surfaces and to an extent in the snow. With both diffs locked I did a 360 spin in a straight line in , more or less in the car's own length...........on the road...... it was v e r y scary on the highway - fortunately with nothing about. Never ran on the road with locked diffs again!
