Audi 4WD Systems

[NorrS2]

Guys

Help settle a bet!

A mate of mine has an Audi TT and used to have a 4Motion Golf V6.

Now I know that the 4WD system on the Golf & TT are the same yes?

He says that the TT & golf is not in permanent 4WD but only goes into 4WD when the traction control senses slipage on the front wheels. He also claims that a guy at his work has a new A4 1.8T quattro that has a button that disengauges the 4WD as it has the same system as his.

I know the these systems are not as per URQ S2 etc, but I thought that the current Audi 4WD systems were still permanent 4WD.

Who's correct

Cheers

[dan_b]

AFAIK, and I stand to be corrected, but I think that the 4WD system used in the Golf/TT platform is a clutch-based system that uses electronically controlled/engaged clutches to distribute torque between the front and rear axles. I was of the understanding that this system was set up to always supply torque to all 4 wheels but to varying amounts. I'm sure though that it being electronically controlled that you could retro-engineer a control system to fully disengage it and make it fully 2wd - but why would you want to?

[S2 Ant]

Not sure entirely how it works, but i know things like S3's that use the Haldex system are rolling roaded, FWD only, so its def not permanent 4wd on the newer cars by any means, altho how it applies the power split i dont know

[Nuvo]

For a definitive answer look at the item titled "When is a quatrro not a quattro?" on page 23 of this months Audi driver. Sorry no time to quote what is written at the moment.

Nuvo

[Jamo]

******* both are both perm 4wd mate!

The 4 Motion use a Torsen Centre diff and the TT uses a Haldex.

Haldex details

http://www.audi.com.sg/glossary/h/haldex.htm

Torsen details

http://www.audi.com.sg/glossary/t/to...fferential.htm

[AndyP]

I heard from a very well respected Audi technician the other day that the Titties are definatley NOT permenant 4WD.
I will stand correction on this but he is usually a very reliable source of info.

Bry, you were there, what was Ben saying about Titties and 4WD??

Andy

[rotoryboy]

but i know things like S3's that use the Haldex system are rolling roaded, FWD only,

This is because they disconnect the propshaft

[NorrS2]

Wey hey! Unless I'm reading anything wrong, It appears that the TT has a Haldex system because the engines are transverse but none the less both systems are permanent.

Thanks guys - i've just won a tenner

Well done that man the Audi site states the word "permanent" on both systems

[4WheelDrifter]

Disconnecting the Haldex for RR runs isn't a good idea. The Haldex would overheat. Not good. I've heard of a BTDT on this.
It should be treated as permanent 4WD.

The FWD theory wouldn't explain the power oversteer either.

Transverse quattro = Haldex.
Longitudinal quattro = Torsen.

For example:

[bcdesigns]

They (on S3) just remove the fuse and go for dyno just with front wheels, ive seen it :S

[4WheelDrifter]

They (on S3) just remove the fuse and go for dyno just with front wheels, ive seen it :S

Yes. It's that easy.

[Keeper of The Kitten]

If the removal of a fuse is all it takes to disconnect the rear drive it clearly isn't a "permanent 4wd" system.

My understanding of the term "permanent 4wd" would assume a full time mechanical link to all four wheels. A system which can be electronically disconnected appears to be using some form of electro-static or electro-hydraulic clutch.

That is very different from a mechanical Torsen type differential which certainly cannot totally disengage drive output on one end or the other - hence Torsen applications are permanently connected to both outputs.

__MDC__

[Fat Audi 80]

If the removal of a fuse is all it takes to disconnect the rear drive it clearly isn't a "permanent 4wd" system.

My understanding of the term "permanent 4wd" would assume a full time mechanical link to all four wheels. A system which can be electronically disconnected appears to be using some form of electro-static or electro-hydraulic clutch.

That is very different from a mechanical Torsen type differential which certainly cannot totally disengage drive output on one end or the other - hence Torsen applications are permanently connected to both outputs.

__MDC__

Yes - Exactly what he said!

Which is why I don't really regard Haldex as "Quattro" and have turned into a "real" quattro snob!

[BRY]

I heard from a very well respected Audi technician the other day that the Titties are definatley NOT permenant 4WD.
I will stand correction on this but he is usually a very reliable source of info.

Bry, you were there, what was Ben saying about Titties and 4WD??

Andy

MR Ben said;
"They are not really four wheel drive, they only engage the rear wheels when the traction control senses that the fronts have gone awol"
Don't know / care enough about them TITies to fathom it all out; he seems to know his stuff though - MR Ben.

[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?