I have never heard of a LSD with problems. I have heard of electrical problems though.

 

Yeah, a mechanical LSD is pretty simple. It's basically an open diff with some friction discs in there.

I personally went with the DTC... but ultimately that's because it's the only option for the Cooper.

 

as i stated before the QIAIFE mechanical LSD carries a LIFETIME guaranty even in racing applications, mini dont use the quaife rather a cheaper less effective alternative, the quaife is all gears so there is NO clutch plates to wear, the quaife WORKS at all speeds and is not compromized by electronic controls, with a few exceptions being a mechanical lsd with computer control integrated such as the excellent evo and sti subie a quaife is superior performance and unmatched reliability

 

Looks like all gears to me.
http://www.motoringfile.com/2004/12/..._differential/

 

Hmm... I'll have to find where I read that it was a friction plate style and that people tracking their cars have been wearing them out to the point of them acting "open".

Must have been a different thread. I'll look around.

 

I would doubt that the Mini uses the "friction plate" style LSD. First, everything else is computer controlled, so why "go dumb" with the diff?

Second: the only way to get an open diff to act as a limited slip diff without wheel speed input would be to used the friction pads to partially couple the two drive shafts together at all times. While this would give some of the desired limited slip performance we want, it also means the diff is trying to act as a closed diff whenever the car makes a normal turn. In additional to the continual wear the diff's friction pads would experience, the "locked" effect of the diff would adversely effect the car's normal turning performance, which is against the Mini's basic engineering.

Mini's being really tight on technical details, but my guess is their LSD is an adjustable friction type, with a servo adjusting a mechanism that controls the coupling friction between the axles based on wheel speed and engine power data.

Also, reading the article linked above, the article's drawing is of a notional open diff, with nothing in the way of slip limiting mechanisms.

 

From the pfd below, it seems that the SuperLSD (the factory MINI LSD) is a strictly mechanical LSD with no electrical inputs or outputs regarding engine power, wheel speed, etc.

http://www.gkndriveline.com/drivelin.../Super_LSD.pdf

So, it may be "dumb", but I don't believe it uses any sort of input or sensors from wheel speed or engine parameters.

On the other hand, the DTC w/ eLSD (and other related systems) DO use such inputs. When the computer senses that one wheel is spinning faster than the other (I'm sure there is a lower limit to this ratio to avoid problems with normal turning), it applies braking to the faster-spinning wheel.

The SuperLSD from GNK does not, however. It is a strictly mechanical LSD, so it does TECHNICALLY "interfere" under simple turning. However, having driven other vehicles with friction-based mechanical LSD's, it's not a problem under normal conditions. They are designed to have an effect when one tire is spinning at a notably higher speed, not just a little higher as in turning. It's not as if we're talking about a true locker here, where one tire will actually skip around turns because it is truly directly connected to the other wheel.

I think the Cooper S buyers are in a unique situation here, in that they can opt for DTC, which includes an almost exclusively electronic way of controlling non-matching wheel speed, or they can opt for the SuperLSD, which is entirely mechanical.

 

great posts!

Ken: Isn't the ELSD system functionally the same as a friction plate LSD? I mean one usues an internal plate, and the other uses the front rotors, and both get the same job done in the end?

Assuming the ELSD is programmed smartly, it wouldn't suffer from mechanical-only disadvantages like wheel hop or plain not-working in very low friction like rain or snow, so in that respect: +1 for the electronic system.

Also, it seems like you overwhelm the front brakes if it's being used for both cornering acceleration and braking. I'm thinking aggressive driving for several minutes on very twisty roads. +1 for the mechanical system?

Interesting stuff!