First we need to understand one thing about the RS,Ford and GKN have replaced the traditional diff with twin clutch packs., explains Ray Kuczera, GKN’s vice president of global product technology.Both packs are mounted to the 'rear drive unit', fancy talk for axles and subframes,The second clutch pack then decides if it will split drive equally or not between the two rear wheels.The second clutch pack is responsible for 'Drift Mode'. The software overspeeds the outside rear wheel to induce oversteer, which is monitored by ESC and ABS to make sure you're driving the car and not the other way around.explains Kuczera.Kuczera went on to add that"It [Focus RS] allows you to do much more extreme manoeuvres than a standard car,"It’s much more like a rear-wheel-drive car, especially when you’ve got drift mode engaged,"Our only question is what does overspeeding the outside wheels to induce sliding do to fuel economy? Just kidding...