Anytime the words “world’s fastest” and “most powerful” are mentioned, a lot of people immediately look for the source of these words. In this case, it’s German tuner Brabus that’s doing the boasting when it announced its new program for the Mercedes-AMG S63 Cabriolet, appropriately called the Brabus 850 6.0 Biturbo Cabrio.

So why exactly was this AMG S63 christened as the world’s fastest and most powerful cabriolet? For that, we have to look at the sweeping changes the tuner made to the car’s 5.5-liter bi-turbo V-8 engine. The process was complicated, but in the end, Brabus was able to increase the V-8’s output from the standard 577 horses and 664 pound-feet of twist to an enormous 838 horsepower and 848 pound-feet of torque.

The result is nothing short of impressive, but it’s also not the only notable thing about this particular program. Just as important are the upgrades down on the periphery, including the new aero kit, the customizable interior, and the fresh offer of new wheels, which is an underrating of the entire tuning experience given how important they are in the overall makeup of the tuned AMG S63 Cabriolet.

Other tuners have also developed programs of their own for both coupe and cabriolet versions of the AMG S63. But Brabus is probably the only one that is confident enough to lay the “world’s fastest” and “most powerful” claim for its program. That speaks to the kind of confidence the tuner has in its own abilities, something that nobody has questioned in a long time.

Continue after the jump to read the full review.

Exterior

The AMG S63 Cabriolet was the recipient of a host of aerodynamic upgrades that have been installed to help improve the car’s stability in light of the massive performance upgrades given to its 5.5-liter, twin-turbo V-8 engine. Brabus put particular emphasis on the front and rear of the car with a front spoiler that attaches to the front bumper and a carbon rear spoiler installed on the trunk lid to help improve downforce on the front and rear axles. Tailor-made carbon surrounds were also used to surround the large side air intakes in the front bumper. Likewise, a carbon diffusor was added to the rear section of the AMG S63 Cabriolet, not to mention the carbon attachments for the side air outlets in the rear. On the cosmetic side, the German tuner is including naked carbon covers for the exterior mirrors.

Moving to the wheels, Brabus opted to give the program a new set of Monoblock wheels. The wheels are available in different sizes - 18 inches to 22 inches - but for this particular program, Brabus opted for a set of its own 21-inch “Platinum Edition” forged wheels that can be fitted with 9Jx21 tires in the front and 10.5Jx21 tries at the back.

Interior

True to form, Brabus is also offering a series of interior refinements for the AMG S63 Cabriolet. The highlight of the interior is the customer’s ability to customize it with premium materials like fine leather and carbon fiber that can be personalized in a variety of colors. The carbon fiber offering is used to replace the production wood inlays and trim strips in the interior. The German tuner is also offering aluminum components that can be used to replace the stock door pins, pedals, and paddle shifters. Last but not least is a new speedometer that comes with a top speed of 250 mph. This speedometer is essential to the overall tuning package, especially with the work Brabus put into the AMG S 63 Cabriolet’s V-8 engine.

Drivetrain

First, let’s look at the Mercedes-AMG S63 Cabriolet in standard configuration. This open-top bad boy comes with a 5.5-liter bit-turbo V-8 engine that pumps out 577 horsepower and 664 pound-feet of torque, allowing it to sprint from 0 to 62 mph in 3.9 seconds to go with a top speed of 186 mph. Impressive, right?

Now, this is where it gets interesting. The noted Merc tuner first bored out the block and increased the V-8 engine’s displacement from 5.5 liters to 6.0 liters. From there, it fitted a bevy of new components, including a new crankshaft, connecting rods, cylinder heads, forged pistons, turbochargers, intake module, and an exhaust system. Combining all of this up, the tuner was able to increase the V-8’s output to a ridiculous 838 horsepower at 5,400 rpm and 1,069 pound-feet of torque between 2,500 and 4,500 rpm. That said, the tuner capped the peak torque at 848 pound-feet to maximize the long-term potential of the heavily modified V-8 engine.

The performance numbers speak for themselves as the AMG S63 Cabriolet, with Brabus' upgrades in tow, is now capable of sprinting from 0 to 60 mph in just 3.5 seconds and from 0 to 124 mph in just 9.4 seconds. The car’s top speed also increased to 217 mph, but once again, Brabus opted to cap it at that number to keep the tires in proper working condition.

Chassis and Suspension

Further improvements in handling and stability come courtesy of a lowering module that Brabus itself worked on. This kit is specifically calibrated to lower the ride height of the AMG S63 Cabriolet by about 0.60 inches.

Pricing

Brabus didn’t divulge the pricing details for the program but it did say that customers are free to buy the AMG S63 Cabriolet with the kit already installed or have their cars fitted with the kit. Seeing as the actual donor car costs around $180,000, it would be reasonable to think that the total cost of the program, including the donor car, will amount to about $250,000.

Competition

Mercedes-AMG S63 by Mansory

Since there aren’t that many programs for the open top version of the AMG S63, allow me to instead look at what other tuners have done with the coupe version of the luxury performance car. Mansory is one of the tuners that had a program available after it was launched at the 2016 Geneva Motor Show. That program came with its own share of exterior and interior upgrades, but the engine upgrade is what I’ll focus on. Mansory didn’t increase the V-8’s displacement, but it did add a host of new components to the engine, including a new turbocharger and a compressor system. The result is 985 horsepower and 1,034 pound-feet of torque, enough to help the AMG S63 push to 60 mph in just 3.2 seconds. Unfortunately, the car’s top speed still stands at an electronically limited 186 mph.

Read our full review here.

Mercedes-AMG S63 by G-Power

G-Power is another tuner that has worked on making the AMG S63 fiercer and more intimidating. The tuner accomplished that by using its own Bi-Tronik 5 V1 power upgrade, which helps the bi-turbo V-8 increase its output to 705 horsepower and 738 pound-feet of torque. It’s not as much as what Brabus and Mansory were able to get out of their respective programs, but it’s still good enough to have a 0-to-60-mph time of 3.8 seconds to go with a new top speed of 205 mph.

Read our full review here.

Conclusion

Is there really anything else to say here? Brabus is known for building programs that usually result in cars that are described as the world's-fastest-this or the world's-fastest-that. It's not surprising that the German tuner known for its insane Mercedes programs has developed another program that follows the same blue print. Everything about this kit speaks to the kind of tuning talent and admittedly demented mind that Brabus has for Mercedes models. I love it!