AC Schnitzer is a company that specialises in tuning BMW Group cars. This time instead of offering a fully-tuned car, AC Schnitzer is announcing the availability of an after-market limited slip differential (LSD) for BMW 1 and 3 Series as well as MINI cars.
The LSD basically works to ensure the rear-wheel-driven vehicles have as much traction as possible in order not to slip out of control. If it detects that one side of the driving axle is about to slip it sends up to 75 percent of extra power to the opposite wheel.
MINI is front-wheel-driven so its LSD improves steering behavior to make it more direct. It also helps to reduce understeer which is common with FWD cars.
Source: AC Schnitzer