BMW's current six-cylinder diesels use a sequential dual turbo setup with small and large blowers to provide quick response and better top-end power. The new engines may use an electric motor to spin up the turbo more quickly allowing the use of a single turbo for reduced weight and complexity.
Aerodynamics will also be a major focus of the new 3 with the expected inclusion of front wheel air curtains. Ducts in the lower front bumper will route air out just ahead of the front wheels, creating a virtual wheel skirt. The high velocity over the wheels will prevent air coming around the sides and spilling around the wheels, one of the major sources of drag.
Other areas of improvement will include weight reductions, the incorporation of hybrid drive technologies, low-power climate control systems and eight-speed automatic transmissions. All that and more could be in showrooms as early as 2012.