The Bespoke AMG Supercharged V8 at the Heart of the Mercedes-Benz SLR McLaren

The story starts in Detroit, at the 1999 North American International Auto Show, where Mercedes-Benz unveiled the Vision SLR concept inspired by the 300 SLR Uhlenhaut Coupe from 1955. Presented as "Tomorrow’s Silver Arrow," in reference to the nickname earned by the aforementioned race car driven by the likes of Sir Stirling Moss or Juan Manuel Fangio, it was met with a positive reaction by the public, so the carmaker released a roadster version a few months later and ultimately decided to continue to start a limited production run.

At the time, Mercedes owned 40% of the McLaren Group, a partnership that saw the two companies winning the 1998 and 1999 Formula One constructors’ and drivers’ championships, so the British manufacturer was also enrolled on the SLR project.

With McLaren F1 creator Gordon Murray leading the design team, the Vision SLR was extensively reworked, becoming more aerodynamically efficient and technologically advanced.

The powerplant was the brainchild of the experts at AMG. It started out as a 5.4-liter M113 K V8 with slight modifications on the concept cars and was extensively improved for the final production versions, earning the M155 SLR engine code.

It retained the all-aluminum construction, displacement, and SOHC three-valve per cylinder configuration of the unit that powered the flagship 55 AMG performance models at the time yet featured many exclusive upgrades. The most evident is the heavily reinforced closed deck engine block which was fundamentally different from the open deck design of the M113 K. Furthermore, the compression ratio was slightly lowered from 9:1 to 8.8:1 thanks to the redesigned forged pistons and high strength forged conrods. The rev limit was also improved to 7,000 rpm, as opposed to 6,500 rpm.

Other notable improvements included more aggressive camshafts, an optimized exhaust system, a bigger 80-mm (3.14-inch) throttle body, or a dry-sump lubrication system. Combined with the engine’s inherent compact size, the latter feature allowed Murray and his team to mount it in a lowered position, completely behind the front axle, which significantly improved weight distribution and balance.

The Lysholm-type twin-screw supercharger was optimized to rotate at a maximum of 23,000 rpm and produced 13 psi (0.9 bar) of boost. The compressed air was then cooled using two large intercoolers, each with a dedicated water pump.

With all these upgrades, the M155 SLR generated 617 hp (460 kW) and 575 lb-ft (780 Nm) of torque, directed to the rear wheels via an AMG SPEEDSHIFT R five-speed automatic, a version of Mercedes’s 5G-Tronic transmission specifically built for this exclusive grand tourer.

After four years of arduous development work, the production-spec Mercedes-Benz SLR McLaren was unveiled on November 17, 2003, followed by the 2006 722 Edition, a beefed-up 641-hp version that honored Stirling Moss’s 1955 Mille Miglia-winning 300 SLR. A year later, the SLR Roadster was introduced along with the 722 S Edition.

The most exclusive and breathtaking version of the SLR was the Stirling Moss unveiled at the 2009 North American International Auto Show. Drawn up by Korean designer Yoon Il-hun, the speedster was the ultimate homage to the legendary British driver. It featured the most powerful iteration of the M155 SLR engine, which produced 651 hp (485 kW) and propelled the car to 62 mph (100 kph) from a standstill in 3 seconds. It was produced in 75 units and was only available to existing SLR owners for a price that exceeded $1,000,000.

This model also marked the end of the SLR production after a total of 2,157 units, all of which were assembled at McLaren’s Surrey plant in the UK.

While the Mercedes-Benz SLR McLaren became one of the most popular supercars of the 2000s, its bespoke hand-built AMG engine will be remembered as one of the best supercharged V8s ever developed in Europe, not to mention one of the best-sounding of all time.