RENNtech tuning company is well-known for its special programs built around Mercedes-Benz cars. This time, it has turned its attention towards this gorgeous Mercedes-AMG GT 63 4-Door Coupe, and created a project called “Monster.”
The car started from the AMG GT 63 platform, then received the firm’s RIIIx package plus extra changes chosen by company founder Hartmut Feyhl.
The drivetrain stays based on the Mercedes-AMG twin-scroll M177 BiTurbo V8, though nearly every major support system around the engine changed. Stage II turbochargers from RENNtech use larger inducer and exducer wheels together with a dedicated core assembly aimed at lowering rolling resistance and reducing lag. Carbon fiber air boxes feed the engine, and the intake system uses a filter area enlarged by 30 percent. High-pressure fuel pumps support the full package.
Exhaust work follows the same route. Stainless-steel downpipes connect to free-flow 200 cell catalytic converters, then continue into stainless-steel performance mufflers developed for the AMG GT63 chassis. Blow-off valves, a heat exchanger, ECU programming, Transmission Control Unit programming, and Powertrain Control Unit programming complete the hardware and software package.
Numbers rise sharply depending on fuel. With 100 octane, output reaches 1196 HP and 927 LB-FT. On 93 octane, the same car delivers 965 HP and 817 LB-FT. Acceleration from 0 to 60 mph takes 2.3 seconds when running on 100 octane fuel.
RENNtech also states a 0 to 100 mph time of 5.5 seconds. Quarter-mile performance stays under 10 seconds. Road testing, dyno sessions, and track development shaped the calibration, with ignition, injection, and boost pressure revised during repeated validation work.
The company says one goal stayed unchanged during development: preserve control and comfort while chasing peak output. A hand-held suspension module appears in the package, along with an exhaust valve module linked to driving behavior.
Visual changes remain focused but clear. The body carries exposed carbon fiber elements, and the red exterior uses contrast stripes over the hood. The rear wing extends well beyond factory specification, while the front section receives deeper aerodynamic surfaces and dark trim pieces around the grille and lower intakes.
Inside, the center console carries RIIIx branding, a reminder that this car goes beyond a standard catalog build. RENNtech calls the result the final stage of its AMG GT63 four-door program and places the project among street-legal four-door builds developed at its base in Stuart.
The company presents the car as a single finished example rather than a production series. In practical terms, one GT63 received the full list at once, and the result sits well beyond ordinary AMG territory.
