"A flat sports car with a mighty diesel under the bonnet? Who does that? AC Schnitzer does. And they know what they are doing." That was the verdict of Auto Bild sportscars in its 03/2015 issue. The ACZ4 5.0d was a one-off concept car based on the BMW Z4 (E89), built at a customer's request and at the same time as a technology carrier for AC Schnitzer's product development.
The core of the conversion was the engine. The M50d unit, used by BMW in models such as the 5 Series (F10/F11), was tuned and transplanted into the Z4. It produced 430 hp and 840 Nm, compared with 381 hp and 740 Nm as standard. The rear axle and differential lock came from the BMW M3 (E92), and the manual gearbox made way for an eight-speed automatic with paddle shifters.
The ACZ4 5.0d sprinted from 0 to 100 km/h in 4.5 seconds and only reached its top speed beyond 300 km/h. In the Auto Bild sportscars test it lapped the Sachsenring in 1:37.22 minutes, which made it the fastest diesel on that circuit. A new engine look and a modified instrument cluster were also part of the extensive conversion.
Power was only half the equation. Carbon fibre parts replaced the folding metal roof and the boot lid, saving 90 kg on their own. A lightweight silencer weighed 4 kg instead of 23 kg, and forged Type VIII wheels in 9.5J x 19 with 265/30 R 19 tyres saved another 25 kg. In total 131 kg came off, so despite the much heavier M50d engine the car weighed just 1,469 kg.
The adjustable RS coilover suspension lowered the body by 30 mm and was tested on the Nürburgring Nordschleife and on public roads, paired with a lightweight high-performance front brake system. A carbon front spoiler, two carbon sport wings, bonnet vents, a two-piece rear spoiler and a carbon rear apron insert shaped the look. Inside, orange painted trim and carbon racing bucket seats with an embroidered ACZ4 5.0d logo were made especially for the car.
Key facts
- Tuned M50d diesel with 430 hp and 840 Nm
- 0 to 100 km/h in 4.5 seconds
- Top speed beyond 300 km/h
- 131 kg lighter, 1,469 kg in total
- Sachsenring lap in 1:37.22 min
