Good news for diesel fans – BMW has a new quad turbo engine in the pipeline. Yes, that’s four turbos, two low-pressure units feeding two high-pressure units to pressurize a three-liter inline six. That should be good for 394 horsepower and 561lb-ft of torque, while returning an increase of five percent fuel efficiency over the old three-turbo motor. The four-turbo unit will debut in an upcoming 750d x-drive sedan, and will reportedly also make an appearance in performance-oriented “M” models, such as a new m550d sports sedan and even SUVs based on the X5 and X6.