The German tuner IMSA takes on AMG and Brabus at their own game, and the result is epic!

The Mercedes AMG GT has been around since 2014 and since then, many special versions have been introduced. As the second Mercedes model, completely developed by AMG, performance is plentiful, but that never stopped companies like Brabus and even AMG from developing more hardcore variants like the AMG GT Black Series, AMG GT-R, AMG GT Track Series, and others. Among the creators of hardcore Mercedes AMG GT models is another German tuner that goes by the name IMSA, and they may have produced the closest thing to an AMG GT-based race car for the road that’s also capable of making AMG and Brabus models sweat a bit.

In the world of high-end, sports cars, it is easy to dismiss IMSA as just another tuner, but the truth is, the specialists, based in Brueggen, Lower Rhine have been going mad with various Mercedes models for well over a decade. This becomes even more apparent when you look at what they have done to the Mercedes AMG GTS. You probably know that just like its predecessor, the SLS AMG “Gullwing”, the AMG GT is competing in the GT4, GT3, and GT2 classes of the FIA racing series. With that said, out of all modified and special editions of the German sports car, the IMSA RXR One Super GT is the closest thing to the actual competition models.

IMSA has taken the standard, 2017 AMG GTS, which packs 510 horsepower (380 kilowatts) and 479 pound-feet (650 Nm) from a 4.0-liter, dry-sump, twin-turbo V-8 and has “re-engineered” it comprehensively, by lightening and balancing the factory crankshaft and installing new, forged pistons with bespoke forged, H-section connecting rods. Every engine modification is bespoke, including the new intake, which runs from the nose of the car and delivers air individually to each cylinder bank.

There are also modified turbochargers and dual-row intercoolers as well as larger throttle bodies. The cylinder heads have been CNC ported, polished, and gas-flowed. Speaking of gasses, the IMSA RXR One comes with a bespoke, Inconel exhaust system, which results in a lower gas temperature, allowing the use of higher boost pressure. The end result is an output of 860 horsepower (641 kilowatts) and 752 pound-feet (1,020 Nm).

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The seven-speed, dual-clutch automatic has been beefed up to reliably handle the extra power. A competition-grade clutch pack and a forged driveshaft have been added, as well as upgraded cooling for the transmission, differential, and engine. The twin turbochargers, themselves, have a dedicated water-cooled circuit. According to the tuner, the performance modifications are enough to allow the "Merc" to sprint from 0 to 62 mph (100 km/h) in 3.3 seconds, on to a top speed of 217 mph (350 km/h). And that's with a huge wing on its back.

As you can see from the images, the German tuner has not limited itself to modifying the engine and transmission. IMSA has put the AMG GTS on a radical diet, which includes extensive use of carbon fiber. The result is a weight reduction from 3,626 pounds (1,645 kg) down to 2,857 pounds (1,296 kg), meaning this is the lightest road-going version of the Mercedes AMG GT.

The chassis has been revised, and a roll cage has been fitted for added safety and rigidity, similar to other track-focused variants like the AMG GT Black Series or the Mercedes AMG GT Track Series. The factory, double-wishbone suspension has been revised and now features forged wishbone mounts with Rose joints as well as forged wheel hubs and longer driveshafts to cope with the wider track. There are also fully-adjustable springs and shocks that are bespoke for the model and feature a wide spectrum of adjustability for any road or track.

The package is completed by IMSA Racing lightweight forged alloy wheels 12x20 inches at the front and 12.5x21 inches at the rear, wrapped in Pirelli P-Zero Trofeo R tires that measure 305/30ZR20 at the front and 315/30ZR21 at the rear. Behind them are upgraded, carbon-ceramic brakes with high-performance brake pads meant for extensive track use.

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IMSA has turned its eye on the car’s aerodynamics. The new carbon-fiber body kit is 110 mm wider at the front and 130 mm wider at the rear. The new body has been computer designed with the latest software and as the tuner states, it “achieves the optimal balance between drag, downforce, and purposeful appearance.

The car certainly looks like it belongs on the racetrack as the wider body incorporates additional air ducts as well as making the usual ones bigger. The front fascia features a Mille Miglia-inspired grille like on the car’s racing version while the massive, new rear diffuser necessitates relocating into the rear bumper, above it. Last but not least, there is the obligatory, “bench-style” rear wing. The interior of the car is as equally inspired by motorsports. While it retains the standard car’s amenities, more “naked” carbon fiber can be seen and in addition to the roll-cage, new, IMSA-exclusive carbon-fiber racing seats have been installed, with six-point harnesses.

We know we are stating the obvious here, but the IMSA RXR One Super GT does not come cheap. The German tuner commands a premium price tag of $400,000. To put things in perspective, a standard, 2023 Mercedes AMG GT Coupe can be had for $118,600. IMSA also states that the 860-horsepwoer RXR One Super GT will be built in limited numbers although the exact figure has not been quoted. Moreover, with the Mercedes AMG GT being completely replaced by the AMG SL, this may be the last direct descendant of the legendary 300SL and 300SLR Gullwing models, or at the very least, the last one that doesn’t feature hybridization.

Dim’s fascination with cars began when he was just six. Born into a family of car enthusiasts and racing drivers, he started learning basic mechanics and driving from an early age. While he loves writing for any car, Dim is most interested in exploring obscure and forgotten cars as well as finding the best deals on the enthusiast car market. His passion took him to car restoration in the Malta Classic Car Museum, where he briefly worked on a 1964 Jaguar E-Type and an Alfa Romeo Junior. In Malta, he also graduated Media and Communications, which further improved his skills as an automotive journalist. Dim is always ready to get behind the wheel of any car and tell you all about it later.