This Mercedes-AMG S63 Cabriolet is easily one of the fastest drop-tops out there, courtesy of its heavily modified engine.

Since this is the pre-facelifted version of Merc’s flagship, Posaidon had to work with the old twin-turbo 5.5-liter V8 instead of the new twin-turbo 4.0-liter V8 that powers the latest iteration.

Anyhow, in order to make it put out 1,005 PS (991 hp / 739 kW) and 1,400 Nm (1,033 lb-ft) of torque, the displacement has been increased to 6.3 liters and German tuner also worked on the turbochargers, air intake, main bearing line and compression ratio, among others.

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Thanks to the extra 420 PS (414 hp / 309 kW) and 500 Nm (369 lb-ft) of torque produced by the engine, this Mercedes-AMG S63 Cabrio goes from naught to 100 km/h (0-62 mph) in just 2.9 seconds. That’s an entire second faster than the stock pre-facelifted AMG S63 Cabrio, and will eventually max out at 350 km/h (217 mph).

Posaidon isn’t limiting the tuning package to the range-topping convertible from AMG’s lineup, as they’re also offering it for other cars equipped with the same engine, such as the 63 versions of the E-Class, CLS, ML and G-Class.

As for the actual cost of the upgrade, we have a feeling that it’s anything but cheap. But since the German tuner hasn’t said anything about the price, potential customers will have to contact the company themselves to see how much they have to pay to make their AMGs deliver more than a thousand PS.