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MINIUSA's awarding winning marketing is at it again… this time pertaining to the new and highly anticipated limited slip option. What they do is break down the option to make it easily understood. First for the engineering major and then for the rest of us. Here's an excerpt from the flyer currently at US MINI dealers:
For The Engineering Major:
A Limited Slip Differential (LSD) is a modified or derived type of differential gear arrangement that reduces wheel spin, especially when cornering at high speed by allowing for some difference in rotational velocity of the output shafts. Limited Slip Differential (LSD) does not allow the difference in speed to increase beyond a preset amount. By limiting the velocity difference between the pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.
For The Rest of Us:
The Limited Slip Differential (LSD) reduces wheel spin while cornering at high speeds to maintain:
- Go-kart like handling.
- Optimum traction between tires and pavement.
So there you go. Now the next time someone asks you what a limited slip does… tell them to grab one of those handy flyers at the dealer or point them right there.
You can check out the flyer here [via Sean Bartnik's weblog].
<p>Shaweet! Now if they would just release info on who makes the LSD and what model it is hehehe.</p>
<p>Also on bottom of flyer, if it was the same one I had seen.
They explained that their LSD was not a drug.</p>
<p>So how much of a difference will the LSD make? Should I be sad I have an early '05 model without the LSD? Would I notice a big difference or even a small difference if I were to drive a later model '05 with LSD?</p>
<p>Just curious.</p>
<p>Yeah, love the hippie reference at the bottom. MINI marketing is pure genius – just got my package in the mail the other day with my unofficial owners manual and accompanying paraphernalia – makes me want to go buy another one just for fun!</p>
<p>O.k. let me get this right, LSD only works on front and rear wheel drive cars!?!?<br />
Does this also work on AWD cars as well? Sorry for the stupid question but I would really like to know. Thanks.</p>
<p>Works very well on AWD cars. The optimum set up for an AWD car would be to have three LSDs. One for the front wheels, one for the rear wheels and one between the front and the rear! Not very many AWD cars have this arrange ment though. Pretty expensive. Most try to implement similar effects electronically.</p>
<p>NREYES here is an excerpt from the Subaru web site. This must come close to the best setup ever for an all wheel drive. The car is the STI.</p>
<p>Driver Controlled Center Differential (DCCD) AWD: Exclusive to the WRX STi. Features both manual and automatic modes, uses an electronically managed multi-plate transfer clutch in conjunction with a planetary gear-type center differential to control power distribution between the front and rear wheels. Normally, DCCD splits power 35% front and 65% rear. DCCD also features a helical-type limited-slip front differential and mechanical limited-slip rear differential.</p>
<p>My comments as an engineer, sure to raise others. An LSD compensates for reduced traction at one wheel of an “axle”. Vehicles under hard lateral acceleration will tend to reduce the weight on the inside wheels as centrifugal force tries to roll the vehicle over to the outside. If enough weight is transferred from the inside wheels to the outside wheels, the inside wheel could slip when increasing torque is applied (acceleration). A LSD will resist this.</p>
<p>Under hard braking as well as hard cornoring, the inside rear wheel of the vehicle is the most unloaded, so an LSD has very high value in a RWD car. Maybe not so much value for a FWD car. However there is really no negative other than cost to having a LSD.</p>
<p>It also can produce better acceleration on limited traction surfaces, such as water on crosswalks without traction control kicking in and reducing the throttle or blipping the brake of the wheel that is slipping.</p>
<p>I don't differentiate between electronically controlled limited slip units and pure mechanical units, they all try to produce the same result, reduced torque to the wheel(s) with reduced traction and more torque to the wheel(s) with more traction.</p>
<p>Pete – on the other hand if you are cornering or braking in a RWD car where one of the rear wheels would beneift from a LSD, then I would think that you're not on the throttle. Acceleration out of a tight turn is right on, tho.</p>
<p>So is there any final word on whether the LSD will be offered as a retrofit by MINI on pre-2005 Cooper S models?</p>
<p>Final word… hmmm… I haven't heard enough to call it definitive but everything I've heard is that it is not retrofittable.</p>
<p>I'm wondering if the reason Mini is saying no to it being retrofittable is due to the cost. That's going to be a whole bunch of labor and I have a feeling there would be a huge backlash against them. Until I hear from my Service Manager that they are not retrofittable (contrary to the marketing stance) because of a physical difference, I'll be standing by my opinion that it's a cost issue.</p>
<p>I have layman's question – How will LSD interact with traction control and stability control? Are they best switched off? And how significantly do they differ in real world? I think I understand it's a matter of braking vs. torque rerouting, but I'd love to hear from a knowledgable source. Thanks!</p>
<p>As another engineer – there is a downside to an LSD besides cost, two actually:</p>
<p>Turning radius usually goes down, because the whole point of a differential is to allow the outside wheel in a turn to spin at a different rate from the inside. If you're making a tight turn, you could imagine how the wheels would want to be more then 30% differing in speed. Not the biggest issue on a MINI I suspect, but an issue.</p>
<p>Weight – its an extra thing, so its going to weigh more. Again not a large issue, but if you're the performance minded type (The only people who Need an LSD anyway) you probably care.</p>
<p>I was really hoping to see a gear based LSD more like the Quaife. Clutches wear out over time, you could say these are life long clutches but they will wear out over time. At 500 bucks it's a nice option but I have my concerns long term. With that said my 05 will get a quaife fitted at some point.<br />
Having driven many FWD car's with and without LSD it's really night and day</p>
<p>for 500 bux it's a deal with the Quaife around 1100 plus about the same for install! guess when the clutches wear out i will pop in a quaife but till then……</p>
<p>Is it clear that it's a clutch-type lsd and not a viscous-coupled unit?</p>
<p>The SCCA autocross folks class the MCS very favorably, with an lsd, it should be the class leader.</p>