AC Schnitzer's goal of making bad decisions into a viable business model consistently delivers. The latest bit of evidence is this BMW Z4 with the M50d's diesel shoved into the nose and tuned to put out 620 lb-ft of torque. That should do.
AC started with a lowly Z4 sDrive 23i, ripping out the 2.5-liter six and mounting the triple-turbo, 3.0-liter inline-six diesel from the M50d X5/X6 siblings. In stock form, it's outputting 381 hp and 546 lb-ft of torque, but AC turned up the boost to a properly bonkers 430 HP and 620 lb-ft of twist.
That grunt is set to an 8-speed slush box and a limited slip differential cribbed from an E92 M3. Couple that with the metal roof being replaced with a carbon fiber unit, a lightweight exhaust, carbon fiber body work and seats, the whole package comes in at around 3,200 pounds – about 300 pounds less than stock – resulting in a claimed 0-60 run of around 4.5 seconds.