Haldex question

[imported_velcrobix]

I know A3/S3 quattro's have most of the power going to the front wheels during 'normal' driving conditions but does anyone know to what extent (eg 80/20).

Also, is it possible for the car to put more power to the rear than the front in the right conditions or is 50/50 the most that it will apply power to the rear wheels?

 

[mattyboy199]

my mate who works for Audi said its 60 to the front & 40 to the rear

 

[jcs356]

I thought it was 80:20.

AmD do a Haldex controller unit for about £500 which alters the bias more to the rear, but I don't know how much.

 

[colinra]

The following came direct from haldex after a member of this forum asked some questions about the S3's quattro system:

There are situations where near 100% torque transfer to the rear axle
occur. An example is if the front wheels are on ice and the rear wheels are
on tarmac. In that case the front wheels have (almost) no grip. In that
case, the Haldex coupling will transfer all torque to the rear axle and
prevent front wheel spin. On uniform surfaces however, the coupling can not
transfer all torque to the rear axle.

 

[S3_MCD]

[ QUOTE ]
I thought it was 80:20.

AmD do a Haldex controller unit for about £500 which alters the bias more to the rear, but I don't know how much.

[/ QUOTE ]

I believe that it fixes it to a perm 4 wheel drive - 50:50

There was a group buy going on a while ago.... not sure whether it was here or on the TT forum?

 

[imported_velcrobix]

Cheers for the response...

The haldex controller does not create a 50/50 distribution, it just shifs the torque between the wheels faster with greater bias towards the rear than standard.

Here is some info... haldex info

 

[jojo]

Guys, the Haldex is basically a clutch that engages the rear 'drive', the front wheels are permanently driven, so when the Haldex coupling/clutch is engaged to maximum, then the 'drive' between the front and rear axles is 50/50, so the power distribution is 50/50 at most. It is impossible to have a rear bias power distribution with this setup, but as suggested by Colinra a few posts above, in the event where the front wheels have no grip - lets say the fronts are off the ground - then all the available power would be transmitted through the rear wheels, with the fronts spinning away... hope that makes sense...

The standard Haldex system will only engage when it senses a loss of grip up front(15 degrees difference in rolling radius between the 2 axles I think?) or when full throttle is pressed, but there is a slight delay for all this to happen. The uprated Haldex controller will engage the Haldex clutch/coupling before the power is transmitted to the axles, so kinda locks the wheels into permanent 4WD when medium to full throttle is applied.

 

[ianhg]

getting a haldex controller fitted today, then some more track day action in a few weeks, il let you know what i think of the difference

 

[imported_velcrobix]

Look forward to hearing what you think of it ianhg. Have considered getting on for myself.

 

[ianhg]

no probs il let you know

 

[dunk]

there are 2 types of aftermarket haldex controller -

the first is the switch type - you choose either normal or locked 50:50 - generally not a good idea

the second is the later and created by haldex themselves - it responds to throttle velocity as well as throttle position and tries to move torque to the rear on big or sudden throttle inputs prior to the wheels actually slipping - this is the current non-switched uprated haldex controller available for about £500 or so.

does it make a difference for road use - probably not, but it can stop the initial bad understeer when you floor the throttle on a roundabout - the system sends more torque to the rear earlier and so you tend to drift all 4 wheels rather than just the front running wide

is it an effective mod for the money - almost certainly not for the road even with 345hp plus - maybe for the track? i never tried mine on the track so cant say.

 

[DuncS3]

Have to say I agree with you dunk re the Haldex Controller - I have been on track with mine and as I have said before, my car is very neutral with no oversteer - and I'm not talking driving miss daisy either.

Neuspeed ARBS are a much better mod imo

Dunc

 

[ianhg]

Hi chaps, im getting mine for the track as im only a few mins from a great track with regular track days,its on the track a week on sunday so il write a report on that aswell as road usage,

 

[Ryanc]

hmm,interesting.Was thinking of going for one of these.

 

[ianhg]

group buy group buy, shame im getting it this week

 

[madvw]

hopefully not too OT.

thinking about these.. could they be a mod that actually saves wear and tear on your haldex?

For example, the uprated haldex ECU engages rear wheels earlier before the torque delivery (than the standard ECU) when flooring it.
In my mind, that means that the uprated ECU puts less strain on the haldex as its engaging at a time when there is less torque to be tranferred. On a standard ECU, it would be transferring at a time when most of the torque has already arrived.

just a thought.. of course, there is the argument that you would be using the haldex more, so it would even out..

 

[ianhg]

interesting thought there mad.

 

[Ryanc]

been told rear arb's makes more of a difference,but better than the 50:50 controller that melts the haldex clutch.

 

[ianhg]

blimey 50:50 all the time!
arbs going on this week too, so i wont get the full feeling of just the haldex controller