Last week, Brabus wowed us with a wildly tuned Mercedes-AMG GT63 S. The German tuner turned up the horsepower, matched it with an aggressive body kit, and slapped its Rocket badge on the back. Brabus calls it the Rocket 900, hinting at the horsepower on tap, though the name doesn’t begin to explain all the modifications made to it. A new Shmee150 video has the Brabus hitting the track before showing a thorough walkaround of the super saloon.

Brabus increased the GT63’s 4.0-litre V8’s displacement to 4.5 litres. The company paired the larger mill with a pair of custom turbochargers, which feature a larger compressor that can handle a higher boost pressure maximum. The added power requires more cooling, so Brabus installed a pair of ram-air intakes on both sides of the radiator grille. The tuned mill makes 888 bhp (662 kilowatts) and 922 pound-feet (1,250 Newton-metres) of torque, though Brabus limits torque to 774 lb-ft (1,050 Nm). That’s still a significant upgrade over the AMG GT63 S.

Gallery: Brabus 900 Rocket based on the Mercedes-AMG GT63 S

Shmee’s video opens with a quick overview of the Rocket 900 before taking it out onto the track. He checks out each of the car’s driving modes, pushing it harder and harder around the course. He also provides a listen to the exhaust, which hums through a stainless steel quad exhaust system. The video also gives a glimpse at the interior, which has several Brabus touches. The unique 21- and 22-inch wheels with their carbon-fibre aero discs are also highlighted, showing how they’re installed on the rims.

The Brabus Rocket 900 has a lot of upgrades that don’t come cheap. The one Brabus revealed last week had a price of €435,800 (about £395,500 at currency exchange rates). Only adding to the price tag is its exclusivity – Brabus plans to give only 10 GT63 S saloons the Rocket 900 treatment. This will become an automotive unicorn in no time.