The BMW Z4 roadster is exclusively offered with gasoline engines, which is probably why tuner AC Schnitzer decided to experiment and fit it with a massive diesel unit.

The AC Schnitzer ACZ4 5.0d is a one-off vehicle based on the BMW Z4 sDrive 23i, but with a major change: instead of the standard gasoline engine, it features an M50d diesel unit – the same triple-turbocharged 3.0-liter straight-six that is used on the BMW M550d.

The engine has been upgraded and fitted into the ACZ4 5.0d, with output and maximum torque figures increasing from 381PS (375hp) and 740Nm (546lb-ft) to 430PS (424hp) and 840Nm (619Nm).

Besides the new engine, the ACZ4 5.0d also features the rear axle gear and limited slip differential from the BMW M3 (E92), while the standard manual gearbox has been replaced with an 8-speed automatic with paddle shifters.

Needless to say, these modifications have a strong impact on the car’s performance, with the AC Schnitzer ACZ4 5.0d sprinting from 0 to 100 km/h in just 4.5 seconds and reaching 300 km/h (186 mph). It is also capable of lapping the Sachsenring circuit in 1:37.22, making it the fastest diesel-powered car on the respective track.

Besides mechanical upgrades, the ACZ4 5.0d also features lightweight construction, including the folding roof and the boot lid made of CFC. These modifications alone account for a 90kg (198lbs) weight reduction. Furthermore, the standard silencer has been replaced by a lightweight silencer, saving 19kg (41.8lbs).

A further 25kg (55.1lbs) are saved by the AC Schnitzer forged alloys Type VIII. In total, with a few further measures, 131kg (288.8lbs) have been saved, with the car tipping the scales at 1,469kg (3,238lbs), despite the significantly heavier M50d power plant.

According to AC Schnitzer, the “ACZ4 5.0d is a concept vehicle not for sale, which was produced to customer specifications and at the same time acted as a technology platform for AC Schnitzer product development. In its current form, the vehicle would cost € 113,965.”

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