RE: Haldex - the truth!
Discussion
kambites said:
There's absolutely nothing wrong with Haldex in principle (and never has been, really); it's just that the majority of VAG's older implementations have been rubbish.
The engineering is fundamentally ok, but the application is crap because most VAG are designed to drive like vanilla ice cream.Since that is what their buyers want too, great. Why buy a VAG for it's AWD system if you want a sporty car?
But to try up-sell the system and compare it to focussed AWD systems on truly focussed sporty AWD road cars is just going to end in failure.
Proof-read police!
"Or least that's what the makers pushing sportier cars would have us believe"
"you already know the bulk of those 300,000 last year were all-wheel drive versions of things the Nissan Qashqai."
"But there are also and more sporting models with AWD"
"Now we're talking to all manufacturers about the possible of having their cars AWD"
"The current fifth-gen Haldex can sends about 10-15 per cent of power to the rear "
"not typical a UK surface""
"Or least that's what the makers pushing sportier cars would have us believe"
"you already know the bulk of those 300,000 last year were all-wheel drive versions of things the Nissan Qashqai."
"But there are also and more sporting models with AWD"
"Now we're talking to all manufacturers about the possible of having their cars AWD"
"The current fifth-gen Haldex can sends about 10-15 per cent of power to the rear "
"not typical a UK surface""
There seems to be an awful lot of anger about a system which, to me, turns a transverse-engine FWD car into a car with something approaching 4WD. This, surely, is rather a good thing? If not for handling poise and acceleration, then at least for getting my wife's mother to the shops in some gentle sleet, which is what (IMHO) FWD cars are for anyway.
Mr Whippy said:
kambites said:
There's absolutely nothing wrong with Haldex in principle (and never has been, really); it's just that the majority of VAG's older implementations have been rubbish.
The engineering is fundamentally ok, but the application is crap because most VAG are designed to drive like vanilla ice cream.Since that is what their buyers want too, great. Why buy a VAG for it's AWD system if you want a sporty car?
But to try up-sell the system and compare it to focussed AWD systems on truly focussed sporty AWD road cars is just going to end in failure.
Mr Whippy said:
You don't have to be the end user for it to be an effective advertorial piece.
Now people will go into their VW garage or Audi garage and hear about the amazing sporty Haldex system, and that is what VAG are selling.
A decent technical appraisal independent of the marketing stuff from the manufacturers would be good.
Dave
So those VW or Audi garages wouldn't have otherwise mentioned the availability of 4WD on their models to punters walking through their doors? Now people will go into their VW garage or Audi garage and hear about the amazing sporty Haldex system, and that is what VAG are selling.
A decent technical appraisal independent of the marketing stuff from the manufacturers would be good.
Dave
I am by no means an expert, but aren't Audi rather renowned for having four driven wheels on their cars...NickGibbs said:
Yeah...not enough detail. I've explained this in the past:tomjol said:
<grumpy pedant mode>
Sigh. The Haldex myths persist.
At no point have Audi sold a Haldex-equipped vehicle which varied rear axle torque dependent only on wheel slip. This is a complete and utter myth based on a misunderstanding of how the system operates.
The clutch pack is powered ultimately by oil pressure, supplied [ETA: in the generation of vehicles mentioned below] by the rotational difference between the two axles. The amount of difference required is absolutely tiny, so there is usually plenty of pressure, the exception being from a standing start (which leads to that slip-lock-go behaviour).
However, the clutch pack is controlled by a computer, which alters its behaviour based on a whole list of things, even in the early applications i.e. original TT, S3, V6 Golfs etc:
</grumpy pedant mode>
Back on topic: People are ignorant, and therefore have no idea how to drive in these conditions. The vast majority think that the solution to wheel slip is more loud pedal. The number of SUVs I saw on the way to work this morning crabbing their way towards the opposite kerb while not achieving any forward motion was remarkable.
In other words, it's always been "pre-emptive" in most situations, just got (a lot) better over time.Sigh. The Haldex myths persist.
At no point have Audi sold a Haldex-equipped vehicle which varied rear axle torque dependent only on wheel slip. This is a complete and utter myth based on a misunderstanding of how the system operates.
The clutch pack is powered ultimately by oil pressure, supplied [ETA: in the generation of vehicles mentioned below] by the rotational difference between the two axles. The amount of difference required is absolutely tiny, so there is usually plenty of pressure, the exception being from a standing start (which leads to that slip-lock-go behaviour).
However, the clutch pack is controlled by a computer, which alters its behaviour based on a whole list of things, even in the early applications i.e. original TT, S3, V6 Golfs etc:
- Accelerator pedal position
- Brake light activation
- ABS activation
- ESP activation
- Handbrake position
- Engine speed
- Wheel speed
- Longitudinal acceleration
</grumpy pedant mode>
Back on topic: People are ignorant, and therefore have no idea how to drive in these conditions. The vast majority think that the solution to wheel slip is more loud pedal. The number of SUVs I saw on the way to work this morning crabbing their way towards the opposite kerb while not achieving any forward motion was remarkable.
Edited by tomjol on Friday 30th January 00:16
This is still PH here isn't it?Theophany said:
So those VW or Audi garages wouldn't have otherwise mentioned the availability of 4WD on their models to punters walking through their doors? I am by no means an expert, but aren't Audi rather renowned for having four driven wheels on their cars...
They were renowned when you had either fwd or rwd as primary choices, and their implementations were done without regard for efficient packaging and cost. I am by no means an expert, but aren't Audi rather renowned for having four driven wheels on their cars...Today the Quattro is just a marketing thing, and to make it work at all they need to actually have four driven wheels.
If Audi could get away with it they'd make Quattro just another name to stick on for up-selling.
In the end I'd prefer most VAG stuff to be really good and lighter, cheaper FWD, than FWD with token AWD just so it can have a fancy badge on it and have a higher list price, and probably duller dynamics.
Dave
I'm surprised that with all the multitude of settings cars have now for ride, and steering, and power, and gearbox that the 4wd cannot have a setting which allows the driver to set the percentage of the drive to the set of wheels as they wish. You could have auto, dynamic and then manual which allows 0 to 100% to any set of wheels as the driver chooses.
Isn't that the next step?
Isn't that the next step?
Gandahar said:
I'm surprised that with all the multitude of settings cars have now for ride, and steering, and power, and gearbox that the 4wd cannot have a setting which allows the driver to set the percentage of the drive to the set of wheels as they wish. You could have auto, dynamic and then manual which allows 0 to 100% to any set of wheels as the driver chooses.
Isn't that the next step?
I think if you took a standard Haldex equipped Golf (for example) and sent all of the power to the rear wheels, it would still feel FWD. What we feel a FWD is more to do with relative spring and damper rates and suspension geometry at the front and back of the car than the actual place the drive is going to. Isn't that the next step?
All very exciting: the evolution of a more lightweight and more nuanced AWD. Thanks for the explanations, PH.
In just a few short years we'll have even more to discuss as battery-electric vehicles come into the mainstream. Imagine the sophistication in torque delivery per wheel that electric motors might provide.
unsprung said:
In just a few short years we'll have even more to discuss as battery-electric vehicles come into the mainstream. Imagine the sophistication in torque delivery per wheel that electric motors might provide.
I think the Tesla P85D has full torque-vectoring capability already. 
I can only speak from experience with my Octavia Scout driven in pretty tame everyday conditions. No off roading and with standard summer tyres.
Driving across muddy farmers field where 2wd cars were getting stuck. Stopping and starting with no problems.
Driving across snow covered car parks with no drama while 2wd cars were stuck. Stopping and starting no problem.
Full throttle starts on slippy roads with nice clean takeoff.
It has a 4th Gen Haldex. I would have another.
Driving across muddy farmers field where 2wd cars were getting stuck. Stopping and starting with no problems.
Driving across snow covered car parks with no drama while 2wd cars were stuck. Stopping and starting no problem.
Full throttle starts on slippy roads with nice clean takeoff.
It has a 4th Gen Haldex. I would have another.
This article leaves out the Honda/Acura SH-AWD system that is unique and very cool. Extraordinary levels of traction and efficiency. But it also has torque vectoring to the rear wheels left and right to rotate the car, RWD car behavior. At the limit you can correct understeer with throttle.
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