BMW's Future Quad-Turbocharged Engine to Make Over 400 HP - autoevolution
Quad-turbo BMW M550d xDrive is ultimate diesel Q car | CAR Magazine
In for an engine rebuild: my BMW M550d Touring. Factory specs: tri-turbo diesel, 0-60 mph in 4.6 s. My engine's additional spec: leaking cylinder head. : r/Justrolledintotheshop