Haldex Quattro system

[veeeight]

ESP Off, Lift off mid-corner, this is the result.

I think a little bit of poo must have come out:



quattro is good, but it won't help in these situations!

 

[snowfree52]

the same happened to me on a trackday several years ago with my S3. 2 tyres came off the rim ...

I didn't poop though

 

[dbm]

Just come across this. Check out ~1:20 in:

 

[steve111b]

I like the commitment that the TTS driver displays. Great car control. Nice find.

 

[danilotto]

Reading the user manual I found no istance of some warning lights / DIS messages that show if the Haldex device fails.

Yesterday I notice, accelerating on a slippery surface (wet stone road with train rails) that the ESP light blinked on the dashboard. Do you think it could address an Haldex malfunction?

 

[veeeight]

Reading the user manual I found no istance of some warning lights / DIS messages that show if the Haldex device fails.

Correct, there is no indication that Haldex has failed

Yesterday I notice, accelerating on a slippery surface (wet stone road with train rails) that the ESP light blinked on the dashboard. Do you think it could address an Haldex malfunction?

This is normal, if ESP is working.

 

[kanecullen89]

It's normal for esp to intervene slightly with haldex when accelerating hard or on a slippery surface.
I would only be worried about a haldex fault if the fronts are slipping excessively for more than a very short period of time. Best way to test is find some grass (somewhere you're allowed to mess it up), turn esp off and floor it. See if just the front slip or if the rears kick in too

 

[danilotto]

Yes but I though it is very difficult to have wheels spinning (and ESP light blinking) with haldex transmission.

 

[kanecullen89]

It is but it's known that under very hard acceleration or less than desirable road conditions the front wheels still may slip a small amount before the power is transmitted to the rear.
The haldex is a reactive system so the system will only transfer power to rear when slip is detected.
There will obviously be excessive slip if there is a haldex fault.
The torsen diff quattro is preferable (but more expensive) and that's a proactive system that is fully mechanical and has a default 60:40 rear:front split and can send more power to rear whereas haldex can only send a maximum of 50% to read. This system is used on a4 and above quattros

 

[veeeight]

If you have crap tyres, it will slip even if you have Haldex or Torsen !

But

A flashing ESP light does not necessarily mean you are wheel spinning. A flashing ESP light means the ESP Program has been activated.


^ A slight correction - Gen 4 & 5 Haldex have the ability to be proactive, they can achieve full clutch pack lockup without slip having to happen first, based on ECU inputs. Previous generations (Audi application) needed slip to lockup.

 

[scherzkeks]

The haldex is a reactive system so the system will only transfer power to rear when slip is detected.
There will obviously be excessive slip if there is a haldex fault.
The torsen diff quattro is preferable (but more expensive) and that's a proactive system that is fully mechanical ...

This is not really true anymore. Haldex Gen 4 (facelift S3 8P) and Gen 5 are proactive. The clutch pack is controlled by the ECU, and requires no driveline slip to lock up. On launch/acceleration, the cars are programmed to lock the clutch pack meaning you have 50/50 mechanical split. Also, when you actually accelerate, the front gets lighter and the weight shifts to the rear, creating slip in the front diff (not wheel spin). So on a dry road on launch, some 60-70 percent of torque ends up on the rear axle when you accelerate.

Furthermore, in other conditions in which heavy dynamic weight shift occurs (cornering), or the road surface varies, rear torque bias can again be induced. This is not the same as overdriving the rear axle, but does reduce load on the front tires and ensure that the car remains fairly neutral, and most certainly plays a role in increasing ultimate grip and improving dynamics. A FWD car will wash out earlier than a Haldex or Torsen, when the AWD cars are driven properly, and a comparable RWD will be slower on corner exit.

Finally, since the ECU can lock the clutch pack at any time, this means that the Gen. 4 and 5 cars can be programmed to act very much like Torsens when you are really on it. Being electro mechanical, they can transfer power faster than a purely mech. system and they have the benefit of saving fuel when you don't need lots of rear axle engagement. In fact, with the revised EDS on each axle, this system is very similar to what the current Polo WRC is using (but obviously more road-car friendly) -- a 50/50 split with LSDs on each axle.

I don't understand why some posters rant about Haldex not behaving like "RWD." Audi's mech. systems don't either. Torsen works to equalize axle speeds and restore traction to a slipping axle. The latest mech. systems have a slight rear mechanical bias, but this does little to alter their basic character of neutrality and stability. I'm curious to drive the latest Golf R/S3, because with the latest EDS e-diff technology, I suspect they handle very much like my S4 with sports diff.

 

[snowfree52]

so why do the front wheels spin if (from standing) you turn the steering wheel (at an intersection) then mash the throttle

(happened with winter tires couple of times)

 

[steverobertsbbc]

Is this thread only relevant to the S3 or do the standard A3 quattro 8Vs have the same Haldex system? Gen 5?

 

[h5djr]

Is this thread only relevant to the S3 or do the standard A3 quattro 8Vs have the same Haldex system? Gen 5?

It relevant to all 'quattro' A3/S3s as they all use the same system.

 

[veeeight]

when the AWD cars are driven properly, and a comparable RWD will be slower on corner exit.

The recent Evo M135i vs S3 test has shown this not to be the case.

the Gen. 4 and 5 cars can be programmed to act very much like Torsens when you are really on it. Being electro mechanical, they can transfer power faster than a purely mech. system and they have the benefit of saving fuel when you don't need lots of rear axle engagement.

The key words here are "can be programmed". They aren't.

As for an electro mechanical system transferring power faster than a purely mechanical system - this shows your lack of understanding of how a Torsen system works.

Saving fuel when you don't need engagement? Are you now saying that Haldex is a part-time system, something you dispute earlier? You're not very consistent in your assertions and beliefs.

because with the latest EDS e-diff technology, I suspect they handle very much like my S4 with sports diff.

No. Just no.

Maybe in your mind and your world, but in real life and this universe, No.

 

[kanecullen89]

I don't understand how the haldex system can ever be as fast reacting as the torsen fully mechanical system.

The haldex system waits for sensors to pick up certain figures to tell the electronics that slip has occurred or will occur then electronic side has to tell the mechanical hardware to pump the fluid into the clutch pack to create the friction required to send part of the drive to the rear.

The torsen simply automatically senses a difference in torque and the power is diverted to the appropriate axle. All mechanically and instantly

 

[Broken Byzan]

Torsen is proper quattro /end

 

[steve111b]

In 2011 I had the opportunity to drive a TT, S4, A6, and A8 on a skid pad and track in winter conditions. I found no difference between the Haldex and Torsen cars. For me, the worst car was the A8 and other drivers also mentioned this fact. The conclusion about the A8 was it was simply too heavy (and big). Last Fall I drove a TT/S and S5 on a wet track. I had more success (and fun) with the TT/S. I never felt comfortable in the S5. Other drivers called the TT/S nimble and I would agree with that description.

 

[kanecullen89]

That's more of a chassis thing though. The TT is a purpose built platform to perform well on track. It's not much of a family car. The other cars are designed primarily as family and executive cars with a large engine and 4wd added.
I think it would be strange if you didn't find the TT as the best performer regardless of the awd system

 

[Flibble]

I don't understand how the haldex system can ever be as fast reacting as the torsen fully mechanical system.

The haldex system waits for sensors to pick up certain figures to tell the electronics that slip has occurred or will occur then electronic side has to tell the mechanical hardware to pump the fluid into the clutch pack to create the friction required to send part of the drive to the rear.

The torsen simply automatically senses a difference in torque and the power is diverted to the appropriate axle. All mechanically and instantly

It can't be as fast reacting, but the ECU could pre-charge the clutch pack before slip has occurred (e.g. using throttle and gearbox info to determine that fast acceleration is required), so rather than reacting, it is already locked before slip occurs.

 

[h5djr]

It can't be as fast reacting, but the ECU could pre-charge the clutch pack before slip has occurred (e.g. using throttle and gearbox info to determine that fast acceleration is required), so rather than reacting, it is already locked before slip occurs.

Here is the description of the system from Volkswagen site. VW 4-Motion is the same as the Audi system on transverse engined models.

The Haldex coupling on our 4MOTION permanent four-wheel drive system enables the driving power to be distributed variably between the front and rear wheels. It also ensures the effectiveness of electronic systems such as the anti-lock braking system, traction control or electronic differential lock. To achieve this, additional information is taken into account via a computer. Its control system balances not just traction and the resulting differences in speed between the wheels, but also further variables such as handling conditions and drive torque. This enables better interaction with the electronic systems and improves the distribution of driving power with regard to directional stability and safety. The computer uses data from the wheel speed sensors and engine management to react in the best way to the situation.

 

[S3Alex]

This is not really true anymore. Haldex Gen 4 (facelift S3 8P) and Gen 5 are proactive. The clutch pack is controlled by the ECU, and requires no driveline slip to lock up. On launch/acceleration, the cars are programmed to lock the clutch pack meaning you have 50/50 mechanical split. Also, when you actually accelerate, the front gets lighter and the weight shifts to the rear, creating slip in the front diff (not wheel spin). So on a dry road on launch, some 60-70 percent of torque ends up on the rear axle when you accelerate.

Furthermore, in other conditions in which heavy dynamic weight shift occurs (cornering), or the road surface varies, rear torque bias can again be induced. This is not the same as overdriving the rear axle, but does reduce load on the front tires and ensure that the car remains fairly neutral, and most certainly plays a role in increasing ultimate grip and improving dynamics. A FWD car will wash out earlier than a Haldex or Torsen, when the AWD cars are driven properly, and a comparable RWD will be slower on corner exit.

Finally, since the ECU can lock the clutch pack at any time, this means that the Gen. 4 and 5 cars can be programmed to act very much like Torsens when you are really on it. Being electro mechanical, they can transfer power faster than a purely mech. system and they have the benefit of saving fuel when you don't need lots of rear axle engagement. In fact, with the revised EDS on each axle, this system is very similar to what the current Polo WRC is using (but obviously more road-car friendly) -- a 50/50 split with LSDs on each axle.

I don't understand why some posters rant about Haldex not behaving like "RWD." Audi's mech. systems don't either. Torsen works to equalize axle speeds and restore traction to a slipping axle. The latest mech. systems have a slight rear mechanical bias, but this does little to alter their basic character of neutrality and stability. I'm curious to drive the latest Golf R/S3, because with the latest EDS e-diff technology, I suspect they handle very much like my S4 with sports diff.

Not seeing any mention of the 100% rear torque bias here....


Also,you talk of programming the clutch....which software company is providing this?

 

[kenny_boon]

so why do the front wheels spin if (from standing) you turn the steering wheel (at an intersection) then mash the throttle

(happened with winter tires couple of times)

Definately notice this. Used to Torsen and it really launches and so much so if silly back end will squirm doing that. The S3 definately allies fronts to spin before any significant rear push when on lock

 

[kanecullen89]

It can't be as fast reacting, but the ECU could pre-charge the clutch pack before slip has occurred (e.g. using throttle and gearbox info to determine that fast acceleration is required), so rather than reacting, it is already locked before slip occurs.

That's a good point and I'm sure it is quick at reacting when it's precharged etc.
When on the move, as the first bend is approached fairly normally but spirited, the system will still be running front bias (not full locked sport style mode), it will take for the fronts to slip, abs to detect this, send the signal to the haldex controller then the controller to send the signal to release the fluid and then for the mechanical clutch to lock.
I understand this all happens very very quick but the same scenario on torsen is a lot more simple.
Car is driven spirited but not extreme. Default split is 40:60 front:rear. Front axle begins to slip, this is instantly picked up mechanically by the torsen diff seeing a torque difference, worm gears send more power rearwards. No electrical assistance, purely mechanical.
I can't see how the previously stated comment that haldex is as quick/quicker to respond than torsen is possible in any way shape or form

 

[Fiddie]

Someone knows if Haldex race systems allows rear wheels spins quick than front? I'm waiting for V Gen Haldex Race.

 

[kanecullen89]

Someone knows if Haldex race systems allows rear wheels spins quick than front? I'm waiting for V Gen Haldex Race.

Are you talking about race controller?

If so then no, it will still only ever allow max 50:50 split. This is a hardware limitation due to the way the haldex system is connected to the drive

 

[dbm]

I can't see how the previously stated comment that haldex is as quick/quicker to respond than torsen is possible in any way shape or form

I don't personally know whether the haldex is quicker than a torsen, however the electronic system means that it can predict slip based on the car controls. It monitors speed, acceleration and angle of steering to anticipate the possibility of understeer and act before any occurs.

 

[S3Alex]

Are you talking about race controller?

If so then no, it will still only ever allow max 50:50 split. This is a hardware limitation due to the way the haldex system is connected to the drive

Nicely put.

I know someone of course who will argue that up to 100% rear bias is possible,if you have the front axle in a complete slip(i.e.no grip at all) condition.

For his benefit,the Haldex,due to it's position in the drivetrain,will,as you rightly say,under any normal conditions,be unable to supply that sort of rear bias.

 

[Fiddie]

Are you talking about race controller?

If so then no, it will still only ever allow max 50:50 split. This is a hardware limitation due to the way the haldex system is connected to the drive

Maybe in older generations. Gen V allows to send 100% to rear wheels. I think it would lock haldex system to rear wheels.

At the moment, there are not V Gen race controller.

 

[kanecullen89]

Maybe in older generations. Gen V allows to send 100% to rear wheels. I think it would lock haldex system to rear wheels.

At the moment, there are not V Gen race controller.

No I'm sorry but that's wrong. This is what we've been discussing this whole thread. Gen V is the same as the others, just a slightly different way of delivering the oil to lock the clutch.
The principle is exactly the same and the gen V, as with the rest of haldex, can only split a maximum of 50:50

 

[Fiddie]

That's I've found in Netcarshow about V Gen (Golf R article)

Fifth-generation Haldex coupling

Permanent 4MOTION all-wheel drive has always been a trait of the Golf R. The latest generation 4MOTION system is now being used in the fourth-generation Volkswagen Golf R. This all-wheel drive system is coupled with a 6-speed gearbox that has a reinforced clutch and short-travel shifting. Another optional feature is automatic shifting with a 6-speed dual-clutch gearbox (DSG) that also offers manual shifting as an alternative.

The 4MOTION all-wheel drive system of the Golf R, further perfected by enhancements such as the Haldex 5 coupling, is activated even before any wheel starts to slip. This eliminates nearly all traction losses. The system achieves this by using an advanced control function based on specific driving conditions. When operating under a relatively low load or when coasting, forward propulsion comes primarily from the front axle, and the rear axle is decoupled. This basic drive layout saves fuel. However, the rear axle of the Golf R can be variably engaged in fractions of a second whenever necessary. This is done via a Haldex coupling, which is activated by an electro-hydraulic oil pump.

Situation-based power distribution

A control unit continually calculates the ideal drive torque for the rear axle and controls how much the multi-plate clutch should be closed by activating the oil pump. The oil pressure increases the contact pressure at the clutch plates in proportion to the torque desired at the rear axle. So, the amount of pressure applied to the clutch plates can be used to vary continuously the magnitude of the transmitted torque. The wheels of the 300 PS Golf R are prevented from spinning even when driving off and accelerating, because the control unit regulates the torque distribution as a function of dynamic axle loads. Activation of the Haldex 5 coupling is based primarily on the engine torque demanded by the driver. In parallel, a driving status identification system within the all-wheel drive control unit evaluates such parameters as wheel speeds and steering angle. If necessary, nearly 100 per cent of the drive torque can be directed to the rear axle.

Source:
Volkswagen Golf R (2014)

 

[S3Alex]

The point about your article is that the only situation in which 100% of the torque can be sent to the rear wheels is that where the front has zero grip.

 

[Fiddie]

That's the reason I think next race controller could block rear wheels independently the grip situation.

 

[S3Alex]

That's the reason I think next race controller could block rear wheels independently the grip situation.

You have to remember where the Haldex clutch is situated.

It's after the transfer case so it can at best lock and direct whatever torque is not going to the front wheels rearwards.

 

[veeeight]

Gen V

The mechanical drive is only capable of a 50:50 split.
So whatever speed the front wheels spin at, the rear wheels will spin at.


If the front of the car is lifted in the air, with the front wheels spinning in the air,
most of the dynamic torque avaliable can be at the rear wheels. In this unique situation, it can be near 100% at the rear wheels, but you have to subtract the frictional losses going through the front half of the drivetrain. Which may leave you at around say 95% at the rear wheels.

The main difference between Gen 4 and Gen 5 is the deletion of the accumulator, and a revised pump with integral "centrifugal"(!) pressure control valve. Which means the pump speed determines how much or how little pressure is available to clamp the clutch pack. All other mechanical limitations remain the same.

 

[steve111b]

ESP = ESC. They are an "umbrella" terminology, for a host of other technologies, eg: ABS, EDL, ASR/TCS, EBD etc.
ie: ASR one part of the technology that encompasses ESP.

You are correct in stating that when you press the ESP OFF button, it only de-activates some features of ESP, not all of them. In your car it will disable ASR/TCS, but not ABS, EDL or EBD.

It will also override the Haldex ECU input signals to say, "go into permanent AWD mode" - and the clutch pack will engage.

The electronic diff (front) (EDL) will remain active up to 50km/h in quattro cars, and 25km/h in FWD cars, even when ESP is disabled.

Last winter I tried to sort out a problem I had driving on snowy roads at highway speeds. This winter I have found a solution. I turn on the Haldex. Works great. Veeeight I bow to your magic.

Even at lower speeds I have noticed better performance (snowy roads) with the Haldex turned on. So yesterday I tried a test. Drove at 40 km/hr, turned in, and watched to see what would happen. First pass (8P, winter tyres, snow covered, Haldex off) I released the throttle at 40 km/hr turned after a pole and just held on. I needed a light touch of the brakes to avoid hitting a snowbank. I stopped in front of a barrel. Next pass I turned on the Haldex (ESP off) and turned in at the pole once again. This time the car turned sooner, came to rest well before the snowbank (no brakes at all), and contnued turning well past the 90 degree angle of my first pass. The barrel was a car width away. The tracks from my second pass were completely inside the tracks of my first pass.

From the driver's viewpoint the car felt better with the Haldex on. The motion of the car, without the visual reference points (barrel, tracks), made it clear that the car was performing better with the Haldex on. There was also an odd sensation as the car turned the last few feet. I will need to try some more tests to figure that out.

 

[GreatBallsofFire]

Ford RS apparently have a very nice 4 wheel system with rear wheel bias and as far as I know it is a Haldex. As far as I know, the RS have the motor in the same direction as in the A3 - hence my question, when can we expect to see this apparently brand new Haldex system in the Audi A3? It is really cool and if Audi isn't take up the challenge I guess thy will be passed by RS, or what do you think?

 

[davc]

The new focus RS does not have a haldex system. It uses a system from British company GKN, called Disconnect Twinster.

Maybe VAG should consider putting this system in their cars as it blows Haldex into the weeds.

 

[gamegenie]

What about when you put your 8V drive select mode in Dynamic? Audi says the vehicle will drive with a rear wheel bias.

 

[veeeight]

No.