NAC: Miata Torsen

[Lawrence C Leung]

FYI,

Torsen/Quaife - Mechanical planetary gears, self proportions torque to
balance out  output shaft speeds, hence it really isn't limited slip, but
within the limits of the torque applied, NO slip. There is no sliding
parts in the system. By the way, other than the normal gear faces, this
is a non-wear part.

Haldex - Hydraulic (or is it Electric or electro-hydro, list help here?)
self proportioning. It does wait for a driven wheel to slip before it
reacts, but it is self-proportioning. It is also a non-wear part. Uses
hydraulic pressure generated by shear in the fluid to activate  (can you
say, Torque Converter in reverse?). Slip reaction can be electronically
assisted (Subaru Autobox cars). Slip is entirely within the fluid.

Detroit Locker - Locked halfshafts. Both wheels turn at the same speed,
NO MATTER WHAT. Wear occurs at the tire/road interface, and in the driver
trying to compensate for slip/grip, slip/grip of the driven wheels. Most
noticable when watching old Detroit iron going (lurching?) around a
corner at lower speeds going, (tire noise) chirp, chirp, chirp until the
path of the car straightens out. Quattro 1 cars (MAC) acheive this by
activating the Diffy Locks, and Porsche used them (okay, in effect, they
just welded the spindles) in 935, 936, Late 917, and early 962 GT race
cars. At the speeds they were running, the tires had so little grip
anyway (due to speed, not to actual grip), so it was deemed a
differential wasn't needed anyway. And different forms of LSD's
(including the planetary systems) were deemed too unreliable for a 24 hr
endurance racer. If a planetary set-up overheated, it could disintegrate.
A hydraulic set-up could leak, or overheat, loose lube and seize. If the
welded diff failed, it just becomes an open diff, as the weld was the
weak link (purposely). The car races on, with albit less grip. 

Limited Slip Diff (LSD)- Detroit style. Positraction is a trademark of
one of the Detroit Big Three, Just don't recall if it was Ford or GM. -
Open diff, with clutch plates pre-loaded so that at a pre-defined torque,
the clutches slip. This IS limited by the pre-load. It means, at maximum
slip conditions, the wheel with grip will transfer the pre-scribed amount
of torque set by the pre-load (even if the engine is putting out a ton),
the other wheel just spins merrily away! This IS a WEAR part! (the
clutches). 

Each serves almost the same function, except the LSD. 

On Tue, 23 Jan 2001 16:57:31 EST RyanWeath at aol.com writes:
>I am certainly no expert, but I believe that Quaife, Torsen, Halex, 
>Detriot 
>Locker, etc, are all various trademarks of different systems of 
>"limited 
>slip" (aka posi-traction, perhaps also a trademark) differentials of 
>one type 
>or another.  They accomplish the same task (splitting power between 
>the 
>wheels that grip using some sort of a clutch/lock/etc), in different, 
>
>patented ways.  
>
>A Torsen diff is an option on the miata because stock it comes with a 
>NON 
>limited slip rear diff (Aka around turns you will be able to light up 
>the 
>innner tire as the outer tire grips) which is a lame, very poor 
>handling way 
>for a sports car to be.
>
>There is some website floating around that outlines the various 
>changes in 
>audi diffs throughout the years (manually lockable, electronicaly 
>lockable, 
>torsen, etc).  Currently most (all?) new audis use the halex system, 
>not 
>torsen diffs.  In fact, I think that Torsen equipped Audis don't have 
>3 
>torsen diffs, only one or two of them is a torsen model. . me thinks. 
>. 
>
>I'm sure there are many out there that know far more about this 
>subject than 
>I .. feel free to correct me and/or fill in the blanks.
>
>-Ryan
>'91 CQ
>Chicago, IL