Engine Drivetrain 1st Gen Cooper S Torsen vs salisbury LSD

In daily driving and even in rain, snow, ice there will be no noticeable difference. What tires you have will mean much more in those conditions.

The only time the torsen style diff is VERY noticeable (it's noticable other times but the differences are minor) is if you get a wheel mostly or completely off the ground. Then you have an effectively open differential.

 

I'm surprised there wasn't enough information in this thread to answer your question.

I think if you are not having a problem with loss of traction in adverse conditions, or you are not experiencing an uncomfortable pushing sensation through corners while under throttle, then neither type of differential will make a difference for you. If your application is street only regardless of conditions, and your MINI has at least DSC, cost & fluid change intervals are the main differences.

 

Jonathan you are asking a loaded question. The easy way to answer this question is that Salisbury type differentials add to the understeer on corner entry because the clutches have to unlock by overcoming the force of the springs on the clutches. Torsen differentials act like open differentials if a wheel gets unloaded. This condition mainly exists on corner exit, especially on off camber turns. If all you are asking is which is best in getting through the snow, and you are not concerned with control at speed, there isn’t going to be much difference. I would describe this as the technical answer, but I do not think that is what you are asking. We normally talk about handling in terms of the car alone. Handling cannot really be considered without considering the control system. The control system in this case is the driver. What do you sense when you drive a car? What conveys control when you drive a car? Drivers are very sensitive; we can feel very small changes in toe settings. These two types of differentials will feel different as well. Race teams will change out the type of differential for different tracks. I have seen two drivers on the same Indy Car team run different types of differentials. To me and this could be different for you, a Torsen feels like an open differential going into a corner off the gas. They add a little oversteer on the gas. A lot of people would describe this as tightening up the corner. Salisbury differentials add a little understeer going into the corner on or off the gas. The clutches have to break loose to unlock the rear. Coming off the corner, if both wheels are loaded there isn’t any difference. What conveys control to you when you turn into a corner, and the car is transitioning before taking a set?

 

Things are twisted a bit. The OS Giken 1.5 way LSD does not add to understeer, it can allow it if the MINI drifts through a corner with weak throttle input; it does encourage oversteer (as much as a MINI is capable of) under strong throttle. Its numerous plates provide a smoother transition, and it is engineered for quicker release (if healthy) than other clutch type differentials. The Torsen types (Ford, Quaife), the R53 OEM is not a Torsen type differential BTW, encourage understeer. A quote from GRMS "It (Torsen type) promotes understeer in tighter corners that eventually leads to wheel spin as the inside tire becomes unloaded." Both characteristics can be compensated for with suspension modifications and throttle control on our front wheel drive MINIs. Neither characteristic is severe enough to cause a problem.

 

Interesting. I was under the impression that the OEM LSDs in the MINIs were a Torsen-type. What sort is in the R53? Clutch-type or Viscous?

Of course that leads to the selfish question: I have one of the mechanical LSDs in my R56. What sort is that?

 

I agree with you about the OS Giken not being a traditional Salisbury differential, and that isn’t want I said. OS Giken has a design to minimize the effect of the clutches unlocking. I also agree that the differences are small and different driving technics and other suspension choices can compensate or accentuate the short comings. Most of what I wrote deals with driver vehicle interaction. The point is that some drivers prefer certain types of setups, and other drivers do it differently. There isn’t one answer. I believe you should check on the design of the MINI supplied LSD. I also do not believe the Grass Roots article you are referring to is inconsistent with what I said. I wasn’t being as specific about corners and set up. I specifically said both types feel the same off a corner if the wheels aren’t unloaded.

 

The MINI mechanical LSD GKN Driveline : Automotive Driveline Components : Super LSD

In marketing literature previewing the R56, the mechanical LSD is referred to as a "Super LSD", the same as it was in 2005, so I would assume from that wording (marketing releases are not always accurate), the early R56 shares the R53 LSD design, although I've not seen the mechanical R56 LSD.

From the information I've been able to find, it employs a cone friction ring on each end, which would place it in the clutch type category. For illustration purposes only, figure 8b here, shows friction rings in this type of LSD more clearly. Note the Korean article's prototype example uses Belleville springs rather than a center coil spring.

 

Interesting. Previous to looking over the article I assumed that a "torsen" or torque sensing style LSD was like what the Helical LSD is. Looking there and at the GKN "Super LSD" I can see clearly I was mistaken. Good to get some mechanical detail.

IIRC The LSD in the latest version of the Civic Si is a Helical unit. If so, that is a helluva unit in a pocket rocket.

Keith, thanks for posting this stuff. Very cool.

 

A Torsen style differential like the Quaife and the Torsen T-1 have helical gears, so you were correct there, the off-the-shelf Torsen T-2 for the SVT Ford Focus and MINI has parallel gears, close enough to be partially correct. The internal gearing creates thrust forces rather than relying on spring or hydro mechanisms.

 

I stand corrected if MINI used the GKN Super LSD. That was not my understanding. If you found a reference in a MINI product brochure, that is better information than I have. I have not seen a MINI LSD before. I agree with you that the GKN Super LSD would act like a clutch type differential if the springs are installed. The literature suggests that the coil springs are optional. If the coil springs are not installed the side gears have no pre load and it would not promote understeer entering the corner. If the unit had the springs installed wouldn’t you have to overcome the spring to spin the wheel if only one side is jacked up? I am not aware of any car company that installs a differential with any preload in a front wheel drive car. The unlocking forces can be detected, and most people would find them objectionable. The OS Gikin unit may have tamed or eliminated the harsher characteristics, I have not used one. You brought up the Grass Roots article, and I agree it is useful even though the testing was on a MX-5. You quoted the article about losing traction off the corner when a wheel gets unloaded. I will refere you to the part of the article that talks about the Torsen turning in better. “ This time the car responded more eagerly to steering inputs; When asked to change direction, it did so with some authority. And by the way the car was faster, that day, on that course, with that driver, with the Torsen. There are small but detectable differences between different types of LSD. The good and bad characteristics can be tamed or accentuated by the rest of the suspension. Driver preference has a lot to do with it.
Paul Van Valkenburgh and Mark Donahue both wrote that LSD did not mater. They believed at the time (1970s) that the difference in radius between the inside and outside wheels was less than the slip angle of the tires. They both promoted using a locked differential for racing. Times change but these are small affects. Small affects win races, but giving the driver what he wants and getting his brain hooked up to the gas pedal is what is really important.