[s-cars] Of EDL and switches...

[Keith Maddock]

Taka,

Volvo AWD is also a Haldex coupling and now recently they are starting to use a very similar GKN device in some applications.

All VAG transverse engine AWD systems are Haldex, there is now a 2nd generation Haldex out which offers more consistent control. (by adding a pressure sensor so they can do closed-loop control of the hydraulic pressure that activates the clutch)

All Subaru automatic transmission vehicles are also a electronic controlled clutch coupling.

In addition Ford, GM, and Dodge/Jeep "Auto 4WD" heavy truck systems are also clutch-based couplings (with clutch locking capability) that are usually disconnected in A4WD mode.  These systems are housed within the transfer case, rather than a rear-mounted unit like the Haldex/GKN.

Most of the car-based SUV's also use some sort of a coupling that is normally open until slip. Ford Escape, Saturn VUE, Aztek, DC minivans, on and on and on....

These systems are desirable because they are easy to electronically tune to give the vehicle the desired torque transfer characteristics. Additionally, they can be decoupled in a short amount of time by the DSC system if wants to make a brake intervention to correct oversteer or understeer.

The big difference with these systems is that they are NOT a differential.  When they are "off", there is no connection between the front and rear axle.  The allow progressive locking of front to rear, so can only transfer 100% torque to the passive axle at full lockup, but many of the systems on smaller SUV wanna-bees don't have enough clutch power to even do this.   But, for most suburbanites, this is sufficient to get to soccer practice.

Cheers,
Keith

****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> <t44tq at mindspring.com> 15:49:04 04.11.2002 >>>
So it's only Volvo AWD and MBZ 4Matic that are
nearly totally biased front and rear, respectively,
until slippage occurs? Oh and VAG's Haldex iteration
is the same way.

Taka

-----Original Message-----
From: Keith Maddock [mailto:Keith.Maddock at trw.com]
Sent: Monday, November 04, 2002 9:27 AM
To: t44tq at mindspring.com; 'J. Khang'
Cc: s-car-list at audifans.com
Subject: RE: [s-cars] Of EDL and switches...


Taka,

The viscous center diff of my 93 Subaru Legacy with manual trans was
advertised as a 50/50 F/R torque split in stable conditions.  In
comparison, the auto-trans version of these cars used a electronically
controlled clutch coupling which had a 90/10 F/R torque bias in stable
conditions.

Keith "The Subie was great, but the Audi is so much nicer**" Maddock

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.408 / Virus Database: 230 - Release Date: 10/24/02


_______________________________________________
S-CAR-List mailing list
S-CAR-List at audifans.com
http://www.audifans.com/mailman/listinfo/s-car-list