Quote:
Originally Posted by tranzformer
Great video. I enjoyed it. A few issues:
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2) I thought a torsen was a mechanical? What is this about a mechanical as an option?
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Quote:
Originally Posted by Dimman
+1 on the confusion.
I think I generally understand the different differentials (open, clutch pack, viscous, torsen, and locker), but the term 'mechanical' is new to me. I also associate 'mechanical' with the geared torsen. Plus going back to the Supra it gets more confusing with upgrades. For instance the Mk3 Turbo came with a clutch-pack LSD. The Mk3 JDM Twin-Turbo R got an upgrade to a torsen unit. But the heavy-duty racing unit from TRD was a clutch pack.
I just don't see this 'mechanical' diff as a locker, so a clutch pack like Kaaz or OS Giken (and old TRD) aftermarket ones? But I would use 'friction' over 'mechanical' for my description...
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Hi everybody,
actually I read since month in your forum about the great GT 86 /BRZ, which will sure be my next car!
Yesterday I suddenly thought, I should join the forum, as maybe I can assist a little in this question to reduce the confusion about the LSD.
Apologies for my English, I am not a native speaker.
Basically you are right, both, clutch type LSD and Torsen LSD are "mechanical".
However, Chris Harris asked, if this mechanical one is for drifting people, and Tada-san replied: "And for racing people".
I think this makes it pretty clear: The only useful upgrade from a Torsen LSD to improve the performance on a race track is a mechanical clutch type LSD. And somehow the clutch type is indeed more "rough mechanics" than the Torsen, as clutch packs may show wear over the time.
For those interested in more details, here a little overview.
(Feel free to add more info!)
Bascially there are two main groups of LSDs:
- LSDs, that react on different torque
- LSDs that react on different revs (revolutions/min)
Torque sensing LSDs are the best choice for sports cars and track racing cars.
Rev sensing LSDs are the best choice for low grip like snow, mud.
1.) Torque sensing LSDs:
Clutch type LSDs:
Highest level (and therfore first choice for race track cars) are clutch type LSDs.
As a consequence of torque, a ramp creates power to compress clutch packs, resulting in friction and torque transfer.
The more flat you choose the ramps, the higher the friction, the higher the torque transfer between the axels.
The more clutch packs you add, the higher the friction and torque transfer and the faster the response time of the LSD.
These type of LSDs react extremly fast.
However, the clutch packs will wear over the time. In intense professional race track use they may need exchange every season. For usual street use the may be fine for a whole car life.
Despite wear nearly all professional race teams use clutch type LSDs due to their fast response time and high flexibility to change the setup.
You can have clutch type LSDs with or without preload: Preload ensures a certain minimum locking to enhance traction on snow (although it may increase understeer slightly).
You can choose between 1-way, 2-way, 1,5 way. Actually they may be delivered with alread two different ramps, so changing the setup is possible without exchanging parts.
A very popular maker in Europe is Drexler. You will find Drexler LSDs in many professional race cars.
http://www.drexler-drivetrain.com/ar...ferenzial.html
Torsen LSDs (Torsen = torque sensing) are also used in some race cars, e.g. some Caterhams, Radical SR3, etc.
The principle is to make use of helical shaped gears: These will not only start to turn, but be pushed at the same time with their axle into their bearings, which creates friction
Benefit: More or less no wear!
Drawback: No preload possible, so not toque transfer, if one wheel is hanging in the air or standing on ice. Response time is said to be clearly slower than Clutch type LSDs. Less flexibility for the setup: Once you have a your LSD, there is hardly an option to change the setup.
If you need it the hard way, please find here all the technical details
:
http://www.torsen.com/files/Traction...ol_Article.pdf
Important makers are e.g. Gleason or Quaife (
http://www.quaife.co.uk/)
2.) Rev sensing LSDs
Visco:
Perforated wheel packs rotate in a viscous solution, that increases viscosity with higher temp. Reacts very slowly. No option for sports cars.
Visco-Lok:
Rev differences activate a little pump, that builds up pressure in a fluid to compress clutch packs. I am pretty sure, that BMW uses this type in the current M3 (E90/E92, as well as the E46 and the E60 M5). Good for winter times, not first choice for race tracks. I am not absolutely sure, but I would expect this type to open and close all the time during a drift, as it needs rev differences to create a locking effect, but the rev difference is elimnanted as soon as the LSD locks. The slow response time should therefore open and close movement in turn. But not absolutely sure about this point.
http://www.gkndriveline.com/drivelin...visco-lok.html
You may note, that BMW uses in their race cars Drexler LSDs, not their own ones (see the Drexler logo below on the rear fender)
In addition there are today some LSDs, that are activated in an non-mechanical way using an electric motor.
These would be indeed "non-mechanical" clutch type LSDs.
http://www.zf.com/corporate/en/produ..._gear_em.shtml
I hope, this helps a little - at least some of you - to overcome confusion
By the way: My car is equiped with a tailor-made Drexler clutch type LSD, and I can only say: Brilliant!
Cheers
ChrisH