3 liters, 3 turbos, and 423 ponies: AC Schnitzer’s diesel ACZ4 does our kind of math

Diesel engines are typically associated with high-torque work trucks and fuel-efficient commuter cars, but in the right hands, they have impressive performance potential.

Perhaps the best example of this came last year, when the English-built Trident Iceni Diesel wowed with its claims of 0 to 60 mph in 3.7 seconds and a 2,000-mile tank range.

German tuner AC Schnitzer is looking to further prove the capabilities of diesel engines with the ACZ4 5.0d.

The car starts out in life as a BMW Z4, but the 2.5-liter inline-six has been yanked out. Replacing it is the 3.0-liter diesel unit from the X5 M50d, the same that features not one, not two, but three turbochargers.

Under the hood of the X5, the six-pot makes a stout 381 horsepower and 545 pound-feet of torque, but AC Schnitzer cranked it up to 423 hp and a whopping 619 lb-ft. It’s so powerful, in fact, that the Aachen, Germany company had to swap out the rear axle for the one featured in the old V8 M3.

AC’s modifications didn’t stop there, though, because the Z4’s stick shift has been swapped out for an 8-speed auto with “pedal sports shift.” Put it all together and you’ve got a 0 to 60 mph time of 4.5 seconds, making it one of the quicker diesels you can find.

Unfortunately, you can’t buy one. The 5.0d is billed as a one-off concept, which explains the radical bodywork. Outside of the stylized decals and orange soda wheels, the car wears a carbon fiber roof, carbon fiber rear skirt, and carbon fiber trunk lid. It also equips fully-adjustable racing suspension, a performance braking system, sports exhaust, and a revamped interior.

AC Schnitzer says that despite the SUV-sourced powerplant, the car weighs only 3,238 pounds, some 200 less than stock.