Read something interesting in the service book

[PaulBelsham]

It says you have to change the Haldex oil every 20,000 miles, then says TT & S3 Quattro - no mention of the S4, RS4 or any other quattro car for that matter.

Does this mean the TT & S3 are the only cars to use the Haldex, and if thats the case, why ?

 

[RichA3Turbo]

[ QUOTE ]
Paul_Belsham said:
It says you have to change the Haldex oil every 20,000 miles, then says TT & S3 Quattro - no mention of the S4, RS4 or any other quattro car for that matter.

Does this mean the TT & S3 are the only cars to use the Haldex, and if thats the case, why ?

[/ QUOTE ]

Yep, A3 Quattro/S3/TT are the only Audi's to use the Haldex system... A4/S4/S6/Rs4/RS6 all use permanent 4wd system so is purely mechanical.

Rich

 

[ben]

TTs and S3s are technically a Golf Mk4 under the skin i.e. same floorplan with transverse engine. They use the Haldex system just like Golfs. Other Audis use Audi's own Quattro system. I think the main difference is Haldex is a viscous coupling were Quattro is mechanical (I could be wrong tho)

heres the haldex site:

http://www.haldex-traction.com/

 

[marksyms]

That is correct, only the "small" quattros use Haldex. The bigger cars are full-time maechanical four wheel drive.

It's probably a power/weight/size/cost thing and the Haldex was the most appropriate solution for the A/S3 and TT.

 

[PaulBelsham]

So do you think the Haldex system offers more road holding/control then a full time 4WD setup what is it a 60/40 split on A4's etc....

 

[marksyms]

The fulltime 4wd is almost certainly superior to the Haldex system but you can't have it on the A/S3 and TT so it's a bit irrelevant really.

 

[603ELO]

True quattro system on bigger Audis is a more substantial system that is normally 50/50 split but can vary either way through the central torsen diff (torque/sensing). This coupled with modern electronics that apply brakes etc make for a very sophisticated system.
S3 / TT system is more of a compromise and is generally a 2wd system that will introduce drive to the rear if front traction is poor.
I only have an A3 1.8t at present but have owned quattros in the past. Have driven them in the snow and it is quite amazing to feel the constant shifting of traction.

 

[AlexStanley]

Does that mean that Quattro in the bigger cars has more of an efficiency overhead if it's permanent 4WD?

 

[PaulBelsham]

Very interesting this, I had absolutely no idea this was the case. I always thought the Quattro system was something really impressive due to the Haldex.

Does any one know how the Quattro system differs from other 4WD systems, such as the one Subaru uses ?

 

[marksyms]

The "clever" thing in the original "legendary" Quattros was not the Haldex but the Torsen diff that is still used in the bigger cars.

As far as I know the 4wd systems in the Scooby and Evo are conventional mechanical 3 diff systems that can shift power to whichever wheel has traction much as the Torsen systems do.

 

[lost_it]

Do they have some sort of electronic locking system or torsen middle diff..
else they will transfer drive to the wheel that is least loaded (IE with the least traction)

 

[acf8181]

so to sum up...the bigger audi's and scooby's have 'proper' 4wd, where as smaller audi's are basically 2wd but every now and then 4wd?

 

[Mutley]

http://www.audi-sport.net/ubbthreads/showflat.php?Cat=1,10,15,105,200,900,1000&Board=technical&Number=25855&page=0&view=collapsed&sb=5&o=&fpart=1

/ubbthreads/images/graemlins/beerchug.gif

 

[paulbinks]

the full time quattro 4wd system is used on all longditudinal mounted applications but the TT and S3 are both transverse mounted engines so to make 4wd posible the haldex system was adopted.
I have owned 4 of the conventional quattro systems including 2 of S2's and now have an S3 and both systems have the safety net of understeer but the original torsen system was also quite nose heavy too which could be entertaining on the limit. /ubbthreads/images/graemlins/jawdrop.gif

 

[LYRAC]

What a well questioned and answered post congratulations to all. I will read with avid interest.