Considering it has a twin-turbo 4.0-liter V8 engine producing 603 horsepower, the Mercedes-AMG S63 Cabriolet isn't begging for more power. Posaidon seems to disagree, however, because the German tuner has turned the droptop Mercedes into one of the most powerful four-seat convertibles in the world.

It's based on a pre-facelift S63, which means it originally had a twin-turbo 5.5-liter V8 engine with 577 horsepower and 664 pound-feet on tap. Posaidon has increased the displacement to 6.3 liters and there are now new steel bushings for the cylinders along with an updated main bearing line, a tweaked compression ratio, and reinforced valve springs.

The turbochargers have also been tweaked and Posaidon has fitted the convertible S63 with a custom air kit, sports air filter, and a new radiator. To cope with the extra power under the hood, the ECU, differential locks and the seven-speed automatic transmission have all been modified. The result of all these modifications is a luxurious convertible with room for four that is almost as powerful as the mighty Project One hypercar.

Incredibly, the engine now produces an earth-shattering 1,005 hp and 1,033 lb-ft, enabling the S63 Cabriolet to sprint from 0-62 mph in just 2.9 seconds before it reaches an electronically limited top speed of 218 mph. The current S63 Cabriolet can do the same sprint in 3.4 seconds and top out at 186 mph.

Posaidon is offering the substantial power upgrade for Mercedes-AMG models fitted with the twin-turbo 5.5-liter V8 to give cars such as the older generation E63, ML63, GLE63 and G63 a new lease of life.