Can anyone explain how 4 motion works?

How exactly does the 4motion system work? I know Haldex is an electro-hydraulic multi-plate clutch which automatically sends more torque towards the rear wheels.


So does that mean its 2wd until the front wheels lose grip which would then mean it engages the propshaft to the rear wheels and that provides 4wd?


Further into it while the rear wheels are moving without any torque being transmitted to them would you really count the extra friction of rear shafts etc as transmission loss or only friction?


Hope you get where i'm coming from here, any light thrown in to this would be great thanks.

 

PhatVR6 knows a thing or three about this sort of stuff....

 

Some blerb on the site.
http://www.haldex-traction.com/default.htm

I'm interested to know how it all works

 

Like you've not been testing it to the limit in the R32 over the last couple of years, Gary!

 

Testing it and understanding it's workings are two totally different things Stella

Just been reading this and it proves my theory of what the faint hissing was we heard as we were tearing round the Nurburgring in Claire's R32, was the pumps working for the Haldex. Could hear it on the slower corners.

Good info here.

Edited by: GVK

 

Ah cheers for that Gary!


I was under the impression that until the fronts started to slip it was 100% front wheel drive. Also found out that the only way 100% of the power can be put to the back wheels would be to have the front wheels in the air

 

can I also add that when you have the builders in at work and they deposit loads of wet mud all over the concrete car park then having a haldex equipped car is immense fun!

 

So what is the 4wd system in the Rallye and how does that work?

 

Rallyes use the older Synchro system which was a viscose coupling

Edited by: GTD.

 

so, if you were to chop into a 4motions front abs with a signal generator, you could boot it off the line with full front breaks and 100% rear thrust

go on, somebody try it, it sounds like it would work lol

 

Cheers for that, always nice to know how everything works.

 

The net result of the way that Haldex works is that you have to
aggravate it to make use of it. Nothing really happens if you drive as
if you've got front wheel drive.

 

what about rewriting the software to a full time 4x4?

 

I've heard its possible, but not seen any evidence first hand...



Haldex is never going to be a match for proper torsen diff'd quattro
with proper diffs, equal length shafts, and industrial strength. That
said its the best compromise 4wd I've driven; I find quattro very
boring to drive on dry tarmac, haldex is more lairy and sideways
without the unpredicatable behaviour of viscous coupled setups like
syncro and vauxhall's stuff

 

you don't NEED full time 4wd...that's the whole point of it...it comes in when you need it, and turns off when you don't.

 

Vag tuner market a haldex controller to alter the characteristics towards oversteer...

It's a maximum 60-40 split front/rear isn't it?

 

This ?

http://www.eiptuning.com/eip/haldex_popup.html

 

i've driven a mk2 with haldex and selectable 2wd/4wd, was amazing the difference in how much extra power the car will take with the 4wd system operating compared to 2wd.

i knew there would be a difference in corners or slippery surfaces, but even on dry tarmac in a straight line you could feel a massive reduction in torque steer etc.

VAG do tend to use the terms Syncro, 4Motion and Quattro pretty much willy-nilly (think that's the first time i've used that term on here

Audi used Quattro to describe their original setup - which was a torsen diff, then on the TT they use Quattro to describe the Haldex system, which vw call 4 motion, except some 4Motion VWs actually are Torsen (so they are Quattro) and some later Syncro VWs actually use Haldex IIRC

soooo

as a general rule

Syncro = Viscous Coupling
4Motion = Haldex
Quattro = Torsen.

except when 4motion is torsen, quattro is haldex etc...

 

That's the one GVK