Haldex Quattro system

[veeeight]

From 5' 20"

"And a four wheel drive system that can send a 100 percent of its torque to the rear axle....
... but I don't know when it does that, perhaps when you're parking or something......
... because it doesn't feel like it wants to drift away from a corner at all, not even a little bit....
..... it doesn't feel like there's any power going to the rear axle in fact"





100% torque and rear bias on a Haldex?
Nope. It just doesn't happen in reality, on the road or track, or grippy tarmac.

 

[veeeight]

from:
http://forums.vwvortex.com/showthread.php?7402722-Haldex-Mod

 

[veeeight]

from:
http://forums.vwvortex.com/showthread.php?7138012-Haldex-Difference-Between-S3-and-RS3

 

[veeeight]

Does the new TT-S give you rear bias at a press of a button, in Dynamic?

No.

http://forums.vwvortex.com/showthread.php?6943404-Haldex-Improved

http://www.ttforum.co.uk/forum/viewtopic.php?f=98&t=578337

 

[veeeight]

from:
http://www.audiaddict.net/viewtopic.php?f=52&t=498

 

[veeeight]

from:
http://forums.vwvortex.com/showthread.php?4224835-Changing-the-Haldex-bias

 

[veeeight]

from:
http://www.awdwiki.com/en/torque+split+ratio/

 

[gamegenie]

Does the new TT-S give you rear bias at a press of a button, in Dynamic?

No.

http://forums.vwvortex.com/showthread.php?6943404-Haldex-Improved

http://www.ttforum.co.uk/forum/viewtopic.php?f=98&t=578337

Good link. They too are unsure about the Haldex-V, Dynamic drive select rear bias function

I like that Audi video that talks about the new drive systems functions.


I translated it's German info points.

quattro drivetrain

Networked System for optimum traction and driving dynamics

Signal and Information Exchange
Continuous evaluation of the driving condition and calculating the optimal torque distribution

Intelligent quattro scheme
Situation-dependent distribution of traction on front and rear axle

Electro-hydraulic multi-plate clutch
Infinitely variable torque transfer to the rear axle

Electro-hydraulic multi-plate clutch
Innovative , weight-optimized pump design with centrifugal governor

Variable distribution of drive torque
Depending on driving behavior , driving situation and Audi drive select mode

All -wheel drive quattro with torque vectoring
Interplay between braking and wheel control system

quattro and Audi drive select
Dependent torque distribution for optimum driving dynamics and efficiency

quattro and Audi drive select
Switching from Audi drive select dynamic mode to mode effiency

Permanent all-wheel drive quattro in all conditions
Active Torque Control by sensitive evaluation of the driving situation

quattro and Audi drive select
Switching from Audi drive select efficiency mode to dynamic mode

 

[steeve]

Don't see any mention of rear wheel bias

 

[gamegenie]

Don't see any mention of rear wheel bias

Rear wheel power bias was directly said in the link here.
https://www.audiusa.com/newsroom/media-kits/2016/2016-tt-tts

Another published release says in Dynamic mode 'torque is distributed to the rear axle earlier and to a higher degree'
https://www.audiusa.com/newsroom/news/press-releases/2014/03/emotion-dynamism-high-tech-new-audi-tt


The only problem I have with all this information is that it's only talking about the Audi TT, TTS

Not sure A3 / S3 with Quattro and Drive Select have the same programmed haldex functions though.

 

[GreatBallsofFire]

Don't see any mention of rear wheel bias

I believe, for a good reason Say it would be a commercial/add for BMW -X-drive, I figure BMW would mention in it the first sentence, because they can (and not lying). Audi want to sound like they have it, but that's obviously only marketing, and actually close to lying (which is a bad thing to do).

 

[AL_B]

This is a subject that has run for years and years, right back to the original days of this forum!! Still enjoyable to read though.

We had this quattro / Haldex discussion when the S3 8L and the S3 8P were the "new models". Way-back-when, 2003, a member called Mutley actually emailed Haldex for some answers. The original thread was lost when this forum was migrated, but luckily I had saved the content of what was said.

Here is a link to discussion we had in 2007 and the content from Haldex as it was in 2003. Now, there's obviously been an evolution of Haldex since then, but I thought I would provide you with this information anyway.

http://www.audi-sport.net/xf/threads/new-s3-quattro.33173/#post-306089

It would be great to get a similar technical response from Haldex now, over a decade later.

Really like the sound of the Ford system though - its that sort of innovation Audi should be achieving. Vorsprung what?

AL

 

[veeeight]

Good to see the original Ulf Herlin email exchange re-surface again!

 

[GreatBallsofFire]

This is a subject that has run for years and years, right back to the original days of this forum!! Still enjoyable to read though.

We had this quattro / Haldex discussion when the S3 8L and the S3 8P were the "new models". Way-back-when, 2003, a member called Mutley actually emailed Haldex for some answers. The original thread was lost when this forum was migrated, but luckily I had saved the content of what was said.

Here is a link to discussion we had in 2007 and the content from Haldex as it was in 2003. Now, there's obviously been an evolution of Haldex since then, but I thought I would provide you with this information anyway.

http://www.audi-sport.net/xf/threads/new-s3-quattro.33173/#post-306089

It would be great to get a similar technical response from Haldex now, over a decade later.

Really like the sound of the Ford system though - its that sort of innovation Audi should be achieving. Vorsprung what?

AL

And meanwhile, BorgWarner has Acquired Haldex (2010). I am hoping the Americans are at it. Audi is the fat cat here, which is dangerous in an ever changing competitive world. Same thing with Audi small 4 wheeled (rear biased) hybrids - where are they?

 

[steeve]

It does indeed say the following....

A new quattro® all-wheel-drive system varies torque delivery percentage front to rear by measuring the coefficient of traction at all four wheels via 150 readings every 10 milliseconds, and for the first time can be controlled through the Audi drive select system. When in dynamic mode, the quattro® system has a rear-wheel power bias.

 

[veeeight]

To deconstruct the sentence above:

and for the first time can be controlled through the Audi drive select system

Yes, historically (and currently), by pressing the ESC off button, you would get the Haldex clutch to engage 100% of the time. Gen 4&5.
Now, if you select "Dynamic" in the ADS, this will change the map in the Haldex ECU, causing a different shape of the graph in post #83 (i.e.: the clutch pack will lock up sooner (rather than leaving it in FWD for longer), in more situations, according to driver intent).

Hence

In “dynamic” mode, torque is distributed to the rear axle earlier and to a higher degree

This is also true for the current S3 8V and RS3 8V.

(but to be really pedantic, you can't "distribute" torque )


However

When in dynamic mode, the quattro® system has a rear-wheel power bias.

This is not possible, for any Haldex, of any generation.



If the marketing blurb had said:

When in dynamic mode, the quattro® system has more rear-wheel power.

Then it would hold true.


Sometimes, you just have to accept that Sales & Marketing releases aren't written by Engineers.......

 

[veeeight]

To give you an idea of what different maps/calibrations can look like when pressing the ADS button to put it into "Dynamic" mode:
(this is from an older aftermarket Haldex controller)

But note:
The Rear Wheel Power curve, is NEVER higher than the Front Wheel Power curve, for any given program.

 

[h5djr]

With all this interest in how the current 'quattro' system works on the transverse engined Audi models there is an interesting article in this month's Audi Driver magazine entitled 'quattro ultra' In one sentence it says "Clearly what is needed is a 'best of both worlds' scenario - the advantages of four-wheel drive when it is necessary, but automatically switching to the more fuel-efficient front-wheel drive mode whenever possible". The article continues "The new system will only apply to the various Audi quattro models with longitudinally mounted engines, the A4, A6, Q5 etc. rather than the models like the A3, S3, TT and Q3 etc. that already have a system that automatically switches between front and four-wheel drive thanks to operation of the rear mounted Haldex coupling.

 

[veeeight]

They are a bit late to the party!

Land-Rover introduced the GKN Active Driveline in 2013 for the Range Rover Evoque!

It's mainly driven by fuel saving and economy figures, rather than any performance benefits.

Thankfully Torsen systems will still be available alongside "ultra", should customers wish to stick to "proper" quattro in their Audi



Other notable marques with GKN AWD systems:
http://www.evo.co.uk/features/15377/evo-car-technology-gkn-edrive-and-awd-disconnect

 

[h5djr]

They are a bit late to the party!

Land-Rover introduced the GKN Active Driveline in 2013 for the Range Rover Evoque!

It's mainly driven by fuel saving and economy figures, rather than any performance benefits.

Thankfully Torsen systems will still be available alongside "ultra", should customers wish to stick to "proper" quattro in their Audi



Other notable marques with GKN AWD systems:
http://www.evo.co.uk/features/15377/evo-car-technology-gkn-edrive-and-awd-disconnect

Exactly. Why suffer the additional fuel costs of 'proper quattro' when most of the time you don't need it. If you drive in a manner that does require it then purchase a car that has it.
From a personal point of view the 'non-proper quattro' in my 184 means I drive can through the lanes and corner quit a bit quicker if I choose to than I could in my previous front-wheel drive 170 and with very little penalty in fuel consumption. More than happy with my current setup.

 

[veeeight]

As you often eloquently put it Dave,

It's good to have the choice!
(until they decide not to offer Torsen anymore)

 

[Martinbanshee]

I find the Haldex system works great but it definitely can't do any better than a 50:50 split.
The propshaft going to the rear of the car spins with the front axle at all times and feeds a clutch pack on the rear axle. You only get rear drive when the clutch pack on the rear axle locks the constantly spinning propshaft to the rear axle to create rear wheel drive.
If the clutch pack locks up fully you'll get a 50:50 split, if the clutch pack partially locks you'll get more front bias e.g. 50:30 split with front bias.

 

[gamegenie]

I wonder if we only get 50/50 if the car is in Dynamic mode then.

 

[Martinbanshee]

No, Haldex clutch pack will fully lock up if there's lots of slip on the front wheels regardless of driving mode.

 

[steve111b]

Thanks Veeeight.


When the EDL is working you can go to the back of the car and smell the rear brakes and feel the heat that the EDL generated.

I got this wrong. The rear brakes were getting hot because the rear pads were dragging/sticking. Sorry to post incorrect info.

 

[Tony1982]

All I know is, the system works very well for what I need from it. If I wanted true rear wheel bias power, I would have bought another proper rear wheel drive BMW. I have in my s3 on occasion managed to get a four wheel drift / powerslide going, got my back end out and had the rear snaking out on a straight launch, granted all of which has only happened in the wet/damp and yes is quite difficult to achieve, no chance in the dry though. The haldex/quattro has proven to be very forgiving to be fair, and in the snow/ice it's been consistant in providing grip, the BMW I had was terrible in the snow by comparrison. I think there would be considerably more Audis written off due to people not being able to handle rear wheel bias if Audi were to give in to what people here seem to want. Just my 10 pence worth.

 

[veeeight]

Haldex per se isn't bad if all you want from it is straight line traction.


However it's not a system that lends itself well (in transverse engine application) to a well/good handling car.

For this, it needs to be used in conjunction with a front LSD, or modified/reconfigured to mimic a more flexible system (eg GKN).

In this respect its a bit of a one trick pony.

The Torsen application of AWD in longitudinal engines Audi's do provide more capability in more situations.

 

[GSB]

Not sure if this will help, but I'll throw it in anyway.

8 years ago, long before I bought my still-to-be-delivered S3, I owned another Haldex equipped car. I was one of the 1000 people in the UK who bought a Mazda 6 MPS when they came out. A brilliant but little regarded car...

The forums for that car were also inundated with speculation of just how much work the rear axle was doing at any given time. The arguments were long and boring, and much was made of the potential for transmission "wind-up" without a centre diff, and of course the rear axle only getting drive when the front slipped. All the speculation was ended by simple virtue of measuring and monitoring the signal to the Haldex coupling in given driving situations.

The findings on the Mazda are shown in the video. 0 volts equals clutch open. 5+ volts and the clutch is fully locked. The only time it was ever in front drive only mode was when the handbrake was on, or when doing very low speed maneuvering.

Perhaps someone would like to do a simple experiment on an S3?

HTH.

 

[h5djr]

From my experience a Haldex quattro is much better taking corners than a front wheel drive car.

 

[veeeight]

The findings on the Mazda are shown in the video. 0 volts equals clutch open. 5+ volts and the clutch is fully locked. The only time it was ever in front drive only mode was when the handbrake was on, or when doing very low speed maneuvering.

Perhaps someone would like to do a simple experiment on an S3?

In a S3 (8P or 8V) or any other Haldex VW/Audi - Haldex is dis-engaged, when the handbrake (EPB) is engaged, and Haldex is dis-engaged when the foot brake is applied.

Thus, if you are descending a snowy hill, and you *have* to apply the foot brake, the rears are de-coupled and you are back in front wheel drive.

Haldex is also disengaged at low speeds (to prevent car-park scenario wind up), and at high speed where the axle rotation difference is small (e.g.: on the motorway).

It's also gone beyond simply voltage measurements now, as the Haldex controller is CAN.

 

[GSB]

I'd have thought linking it to the foot brake like that would be liable to induce all sorts of instability... Does it really work that way?

 

[veeeight]

I'd have thought linking it to the foot brake like that would be liable to induce all sorts of instability... Does it really work that way?

Yes.

It's one of the methods of dealing with the wind-up without the centre diff.

To deal with the potential instability, the ESP system comes into play

 

[GSB]

Not sure I like the sound of that. The Mazda, a far bigger, heavier, and inherently more "stable" car than the S3 would exhibit a distinct change in attitude if you dropped the rear axle out whilst driving ( this could be done activating the handbrake switch). This would suddenly disengage the rear axle, and is not something I would recommend doing when subjecting the car to any sudden yaw moments.

Wind up really wasn't a big issue though, the only time I got it on the Mazda was with a space saver wheel on. The car would then crab along and do all sorts of undesirable things. Pulling the AWD system fuse restored order by making the car front drive only.

Incidentally, pulling the fuse on that earlier Haldex (gen 3?) would liberate as much as 2 extra mpg.... Handled like a pig though. Wouldn't corner properly, was prone to losing traction, and was basically ****** awful. AWD "made" that car, as I suspect it makes the S3.

 

[veeeight]

S3 is predominantly a FWD car most of the time (in steady state conditions)........
(fuel efficiency, economy blah blah)

Clutch pack is coupled and de-coupled automatically depending on various inputs (e.g. brake light switch, CAN messages, throttle sensor) and switches (ESP switch, ADS switch).

 

[CraigI]

From my experience a Haldex quattro is much better taking corners than a front wheel drive car.

That all depends on your experience.
I have experienced a FWD car that handles corners better than any Quattro Audi that I've driven.

 

[h5djr]

That all depends on your experience.
I have experienced a FWD car that handles corners better than any Quattro Audi that I've driven.

I'm talking about near identical A3s on exactly the same roads. The front wheel driven was a 2.0TDI - 170 A3 sportback with s-tronic, 17" wheels and 225x45 Dunlop Sport Maxx RT tyres. The quattro car was an 2.0TDI-184 A3 sportback with s-tronic, 17" wheels and 225x45 Dunlop Sport Maxx RT tyres. The only difference between them was an extra 14hp and the quattro handles much better especially on fast corners and when driving through the lanes with a lot of much tighter corners. Even my wife agreed when she first drove the car.

 

[veeeight]

Obviously, I can't take away anything that you and your wife felt during your test drives, however, the 8P and 8V forums have numerous examples of owners not even noticing that their Haldex had failed (there are no warning lights), save for the obvious wheel spinning under acceleration in the wet, and perhaps a hint of torque steer. It really isn't night and day when your Haldex fails, I've experienced it in both my 8P and 8V numerous times.

Haldex (or any AWD) doesn't give you additional grip in corners (even when it's activated), Haldex only gives you additional traction where it needs it (2 different things). I would suggest that maybe the differences you and your wife felt were perhaps due to other factors eg tyre pressures etc. (but not taking away anything from you both, you obviously felt a difference).


As for FWD cars vs Haldex cars in general - a well set up FWD car will often outperform a Haldex car when it comes to handling, even when it's down on power. Especially on B-roads & "handling" circuits (e.g. Llandaw), as opposed to "power" circuits (e.g. Knockhill).

Haldex may give you an advantage in straight line traction scenarios, but there are also downsides to Haldex (and AWD or 4WD) too. There's never such a thing as a free lunch!

FWD vs Haldex:







However - the future for "cars" (marketing led) is for more and more "crossover" type vehicles (e.g. Q2) which will have some form of part time AWD systems in them, so we expect to see more and more development in this area.

 

[h5djr]

Well as I always say, each to his own. All I know is that I can take some corners that I use a lot quite a bit quicker in my current 184 (quattro) car than I could in my previous font wheel drive 170. The main reason I purchased the quattro version was because I did not have a choice. If I wanted the 184 and s-tronic Audi only offered it as a quattro.

 

[gamegenie]

So is this guy lying?



at the minute and 57 sec mark.

 

[davc]

Who cares?

I thought this thread was dead and buried