Audi 4WD Systems

[Henka]

Yes, the difference in speed between the axles will send a signal to the Haldex unit to start engaging the rear wheels.

Anyone saying that an A4 has a button that disengages the 4wd needs to see a doctor. Anyone claiming that Haldex is as good as the original Quattro system with a Torsen center either needs to get back on the pill OR needs to start taking pills.

[Fat Audi 80]

Yes, the difference in speed between the axles will send a signal to the Haldex unit to start engaging the rear wheels.

Anyone saying that an A4 has a button that disengages the 4wd needs to see a doctor. Anyone claiming that Haldex is as good as the original Quattro system with a Torsen center either needs to get back on the pill OR needs to start taking pills.

[4WheelDrifter]

I'm not sure which is better. Haldex seems to work ok to me.
Now. Where are those pills?

[BRY]

I'm not sure which is better. Haldex seems to work ok to me.
Now. Where are those pills?

You are used to driving a metro and other front drive thingys

[4WheelDrifter]

People in glass houses.......

[bcdesigns]

i think the biggest diference is that torsen can give more power on rear wheels, and haldex not, at least 50% on front...

And the electronic ESP, etc, etc of haldex cars doesn't let him do donuts for example...

But it is smoother, eat less power to the engine, and it is lighter i think.

[quattroTurbo]

Haldex in the Golf, TT and S3 is not quattro. It is part time 4wd designed for the Golf 4. It is front wheel drive until the front wheels spin a few degrees (usually under 1 foot). The reason it is called quattro is for marketing reasons - who's going to call it a TT Haldex or TT Synchro - quattro makes more sales.

The new proper quattro equipped Audis (logitudinal engine) still use Torsen differentials, and their quattro systems are very similar to that of the S2. There is no push button to disengage 4WD, what **** would say that.

[4WheelDrifter]

Ok. So if I put a Haldex quattro car up on axle stands, then drive on, will just the front wheels drive? Or all four?

Ok. Here's the answer. Sent in on a postcard. All four are driven.

[Keeper of The Kitten]

Nobody said that Haldex doesn't drive all four wheels. The argument was as to whether it is a permanent 4wd system.

Saying "it drives all four wheels" is a bit like the old wive's tale about how you can identify a limited slip diff by jacking the wheels off the ground and seeing if they turn in the same direction!

When all four of my wheels are on the ground (!!) they all roll forwards as I drive along. Even if I am driving the Micra, the rear wheels do that. They are linked to the motion of the front wheels by the road surface.

That doesn't make it permanent 4wd though!

Anyone see the new RS4 bit in Autocar? Standard torque distribution is 60% to the rear, with up to 85% available at the rear. A 10% shift compared to the old Quattro system!

__MDC__

[Jas11n]

Doesn't a tuner (MTM I think) make a "chip" that will turn the haldex into a permanent 50/50 drive? seem to have read that somewhere but can't remember.
It all comes down to the definition of "permanent AWD"
Torsen distributes power to all four wheels 100% of the time, ie at any given time, the rear wheels and the front wheels are being driven.
Haldex distributes power to all four wheels only when needed.
I'm not knocking the Haldex mind, it works well given the size and engine configuration of the TT and A3/S3.

[4WheelDrifter]

When all four of my wheels are on the ground (!!) they all roll forwards as I drive along. Even if I am driving the Micra, the rear wheels do that. They are linked to the motion of the front wheels by the road surface.

WTF? Micra?

I think Jas is right. It's all down to the definition.
All I know is when you RR a Haldex equiped car it should be treated as a 4WD car. I've never tried RRing a 2WD Micra on a 4WD RR, so I'm not sure about that.

I find if you pile on the speed round a corner, the A3 will tend to break traction at the rear. Which seems strange for a mostly FWD car. Perhaps it's over sensitive to front wheel speed changes, then overdoes the shift in rear drive. I don't now. There's something strange going on there. I wish the S2 was more like that.

[charlie]

Having owned both driven systems i can confidently say;

Haldex:
- it's a swedish invention which is alot lighter and more compact
about 100 kgs compared to Torsen.
- It's normally 95% to front wheels, 5% to rear
- It uses an electric engaging clutch which is activated
when either front wheels start to spin as read by ABS sensors
- Their is software that allows u to have 50/50 split at all times
or can be fine tuned to any % ur heart desires.
- Can transfer up to 95% of power to rear wheels
-very quick and instantanious transfer rate compared to Torsen
_ very dangerous to dry quickly in snow
_ same system used by Volvo S70, V70 , AWD.

Torsen:
- Derived from TORgue SENsing and is controled by torque output
of engine ( not ABS sensors or bhp)
- Slower to react than Haldex.
_ consumes more power than Haldex
- only effective only effective when powering through corners
i.e slow in, fast out. with practice you can get your back end out
using the pendulam technique.
- slowing down using gears still engages 4wd system but dipping clutch
or braking disengages 4wd system in order for ABS to be active
- alot safer to drive in snow and more fun its just a shame audi
dropped the ABS switch found on 3B cars

[porkkis]

- Can transfer up to 95% of power to rear wheels

BS. It can never transfer more than 50% to the rear axle as the unit is at the rear axle!

[RIX]

Doesn't a tuner (MTM I think) make a "chip" that will turn the haldex into a permanent 50/50 drive? seem to have read that somewhere but can't remember.
It all comes down to the definition of "permanent AWD"
Torsen distributes power to all four wheels 100% of the time, ie at any given time, the rear wheels and the front wheels are being driven.
Haldex distributes power to all four wheels only when needed.
I'm not knocking the Haldex mind, it works well given the size and engine configuration of the TT and A3/S3.

alot off tuners have this,it´s sometihings that makes the haldex work faster and it cost around 10000dkr,it´s developed by haldex/in sweden.
i looked at it when i had my S3.

Regards
RIX

[bcdesigns]

yep, i that is correct i think, but even that iwas truth, audi doesn't is like bmw that have almost 50:50 weigth distribution, RWD with all the weigth on front will be a little dangerous/funny