Billed as a one-off concept, the model is based on the Z4 sDrive 23i and features the tri-turbo 3.0-liter six-cylinder diesel engine from the M50d.

AC Schnitzer has unveiled their insane ACZ4 5.0d.

Billed as a one-off concept, the model is based on the Z4 sDrive 23i and features a carbon front spoiler, carbon fiber front fenders and a ventilated hood.  The car has also been equipped with a carbon fiber roof, a carbon fiber rear skirt, a carbon fiber boot lid and 19-inch lightweight forged alloy wheels - among other things. 

The interior largely carries over but the company has added carbon fiber racing seats, painted trim and aluminum pedals.

Under the hood, the 2.5-liter six-cylinder engine has been replaced by the tri-turbo 3.0-liter six-cylinder diesel engine from the M50d.  It produces 430 PS (316 kW) and 840 Nm (619 lb-ft) of torque which enables the model to accelerate from 0-100 km/h in 4.5 seconds before hitting a top speed in excess of 300 km/h (186 mph).

Speaking of performance, the car has also been equipped with an adjustable racing suspension, high performance brakes and a lightweight sports exhaust system.  The model also has an eight-speed automatic transmission and a limited slip differential from an E92 M3.

While the ACZ4 5.0d isn't for sale, AC Schnitzer says the model would cost €113,965 ($120,733 / £81,835) in its current configuration.

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AC Schnitzer ACZ4 5.0d unveiled with a 430 PS tri-turbo diesel engine