In defense of lower powered cars at high speeds:
[quote name=Nick Adams' date=' Vehicle Development Manager for the Fed. Elise
On Limited Slip Differential]
The Elise was always designed from the outset to work without an LSD. We have recently started to offer an LSD as an option on the Toyota engined cars, primarily in response to market demand from the Autocross enthusists in the USA, who need one to be competitive when accelerating away at full throttle from very slow, tight corners in first or second gear.
In this type of competition they do not tend to run high speed (100mph +) corners and therefore the increase in understeer on this type of corner which you get with an LSD is of little negative consequence to them and they therefore are better off with an LSD.
In our experience an Elise or Exige equipped with an LSD is at a disadvantage to one without an LSD on a typical European race track. On top of that the LSD bluntens the steering feel and repsonse of the car which we don't like.
If you want an LSD then by all means fit one, but please understand that there are negative as well as positive effects. In the instance you describe, instead of spinning the inside wheel as you accelerate away at full throttle (which can be easily fixed by modulating the throttle! Very Happy ) a car with a 2:1 LSD like the obne we supply will provide twice the torque to the outside wheel as it does to the inside one. This will increase the slip angle of the outside wheel and the car will tend to oversteer heavily on corner exit, requiring a reduction in throttle if you are not to spin.... It isn't much quicker, honest.
The optional diff we supply is a Torsen unit, the aftermarket unit supplied by Motorsport is a plate diff, with a similar 2:1 bias and no preload so in terms of action it mimics the Torsen closely.
I know this only applies to light, low powered cars, at higher speeds, but there is something to be taken from this excerpt. non-open type differentials do tend to bring the car back to a straight line under full traction in the middle of a corner. With the rear suspension designed NOT to lift the inside wheel (soft or no rear sway bar) in theory good traction can be had, and a limited slip type differential is not necessary.
Of course, in practice, and in the world of high powered zcars, everything is opposite