Throughout the years, carmakers who sought to develop high-performance engines for their sports cars have chosen to go with the twelve-cylinder design because of their smooth operation. While other configurations require counterweights or balancers to reduce vibrations, V12 powerplants are inherently well-balanced.
The first such engine built by Mercedes-Benz for road car use was the M120 introduced in 1991. Still, unlike other manufacturers who have been using V12s to power their sports cars for decades, the German manufacturer chose to fit it inside a luxury sedan, the 600 SE.
However, it made its way under the hood of the R129 SL a year later and throughout the years, it grew in displacement and performance thanks to the experts at AMG. Thus, it became the M297 at the heart of the 1997 CLK GTR race car, its street-legal version, and many track-oriented Pagani Zonda models.
The M120 was eventually replaced by the smaller, less powerful, and notoriously unreliable M137 that was only produced from 1998 to 2002 when Mercedes decided that it would be a good idea to introduce forced induction to its twelve-cylinders. That is where the company’s first bi-turbo V12, the M275, comes into play.
Like its predecessors, it used an all-aluminum construction, but its block was drastically redesigned and reinforced to increase durability and cope with the added boost pressure. It borrowed the single overhead cam (SOHC) cylinder head design from the M137, but it was also heavily revised to improve performance and reliability.
The first version was a 5.5-liter that debuted in 2003 on the 600 series S, CL, and SL models. It was fitted with fracture-split forged steel conrods, two Borg-Warner K24 turbochargers with integrated manifolds, and air-to-water intercooling.
Depending on the model, its output ranged from 493 hp (368 kW) to 510 hp (380 kW) and 590 lb-ft (800 Nm) to 612 lb-ft (830 Nm) of torque. That same year, the manufacturer also offered a slightly modified version of this 5.5-liter dubbed M285 on the Maybach 57 and 62. It made 550 hp (410 kW) and 664 lb-ft (900 Nm) of torque.
However, this engine would become even more spectacular once AMG engineers got their hands on it. The first Affalterbach variant, called M275 AMG, was released in 2004 in cars like the S 65 or CL 65, as well as the S trims of the two Maybach models introduced a year later.
Engineers increased the bore and stroke from 82 mm×87 mm (3.23 in×3.43 in) to 82.6 mm×93 mm (3.25 in×3.66 in). Consequently, the displacement also grew from 5.5 to 6.0 liters. It featured reinforced pistons, larger fuel injectors, higher intake valve lift, and longer opening intervals, along with larger turbochargers.
In standard form, it could produce up to 603 hp and 738 lb-ft (1,000 Nm), while the peak boost stood at 22.1 psi (1.52 bar). Legend has it that it could deliver close to 900 lb-ft (1,200 Nm) of torque, but AMG decided to limit this figure to maintain reliability.
The most feral version was fitted to the SL 65 AMG Black Series, which could make 661 hp (493 kW) and 738 lb-ft (1,000 Nm) of torque. It accelerated to 62 mph (100 kph) from a standstill in just 3.8 seconds, shaming many supercars of the era.
In 2012, Mercedes decided that the future development of this V12 will be exclusively managed by AMG. Therefore, both the standard and high-performance versions of the M275 were extensively upgraded, becoming the M279 and M279 AMG.
They received new forged pistons and forged crankshaft made from high-grade quenched, tempered steel, new camshafts with even more aggressive profiles, hollow-stem sodium outlet valves, a new ECU, and ignition system. These upgrades led to even better reliability, but even more importantly, fuel economy and emissions were exponentially better.
The AMG unit was the first one to hit the streets in 2012 on the SL 65. It then powered other 65 models, and it’s still in use today on the Mercedes-Maybach S 680. It is equipped with new turbochargers, redesigned exhaust manifolds, new wastegate ducts, and new cylinder heads with optimized flow. At its highest, it could spit out 621 hp (463 kW). The standard M279 was used from 2014 to 2020 on the S 600 and S 600 Maybach and could deliver 523 hp (390 kW).
Moreover, these engines were now mated to a seven-speed automatic instead of the older, five-speed variant.
The M275 AMG also served as the base design for the most powerful V12 ever to be assembled in Affalterbach, the M158. This engine was built exclusively for Pagani Automobili and their gorgeous Huayra supercar. It featured a dry-sump lubrication system, smaller twin-scroll turbos for reduced turbo lag, a bespoke ECU developed by Bosch, and a titanium exhaust system. The output was rated at 720 hp (537 kW) on standard models, whereas in the Imola, the most powerful street-legal Huayra, it went up to 827 hp (616 kW).
Since Mercedes-AMG currently focuses on electrification, the M275 engine family will go down in history as the German manufacturer's last line of twelve cylinders. It will also be remembered for its unmistakable low-pitch growl that soothes the heart and soul of even the most demanding gearhead.
However, it made its way under the hood of the R129 SL a year later and throughout the years, it grew in displacement and performance thanks to the experts at AMG. Thus, it became the M297 at the heart of the 1997 CLK GTR race car, its street-legal version, and many track-oriented Pagani Zonda models.
The M120 was eventually replaced by the smaller, less powerful, and notoriously unreliable M137 that was only produced from 1998 to 2002 when Mercedes decided that it would be a good idea to introduce forced induction to its twelve-cylinders. That is where the company’s first bi-turbo V12, the M275, comes into play.
The first version was a 5.5-liter that debuted in 2003 on the 600 series S, CL, and SL models. It was fitted with fracture-split forged steel conrods, two Borg-Warner K24 turbochargers with integrated manifolds, and air-to-water intercooling.
Depending on the model, its output ranged from 493 hp (368 kW) to 510 hp (380 kW) and 590 lb-ft (800 Nm) to 612 lb-ft (830 Nm) of torque. That same year, the manufacturer also offered a slightly modified version of this 5.5-liter dubbed M285 on the Maybach 57 and 62. It made 550 hp (410 kW) and 664 lb-ft (900 Nm) of torque.
Engineers increased the bore and stroke from 82 mm×87 mm (3.23 in×3.43 in) to 82.6 mm×93 mm (3.25 in×3.66 in). Consequently, the displacement also grew from 5.5 to 6.0 liters. It featured reinforced pistons, larger fuel injectors, higher intake valve lift, and longer opening intervals, along with larger turbochargers.
In standard form, it could produce up to 603 hp and 738 lb-ft (1,000 Nm), while the peak boost stood at 22.1 psi (1.52 bar). Legend has it that it could deliver close to 900 lb-ft (1,200 Nm) of torque, but AMG decided to limit this figure to maintain reliability.
In 2012, Mercedes decided that the future development of this V12 will be exclusively managed by AMG. Therefore, both the standard and high-performance versions of the M275 were extensively upgraded, becoming the M279 and M279 AMG.
They received new forged pistons and forged crankshaft made from high-grade quenched, tempered steel, new camshafts with even more aggressive profiles, hollow-stem sodium outlet valves, a new ECU, and ignition system. These upgrades led to even better reliability, but even more importantly, fuel economy and emissions were exponentially better.
Moreover, these engines were now mated to a seven-speed automatic instead of the older, five-speed variant.
The M275 AMG also served as the base design for the most powerful V12 ever to be assembled in Affalterbach, the M158. This engine was built exclusively for Pagani Automobili and their gorgeous Huayra supercar. It featured a dry-sump lubrication system, smaller twin-scroll turbos for reduced turbo lag, a bespoke ECU developed by Bosch, and a titanium exhaust system. The output was rated at 720 hp (537 kW) on standard models, whereas in the Imola, the most powerful street-legal Huayra, it went up to 827 hp (616 kW).
Since Mercedes-AMG currently focuses on electrification, the M275 engine family will go down in history as the German manufacturer's last line of twelve cylinders. It will also be remembered for its unmistakable low-pitch growl that soothes the heart and soul of even the most demanding gearhead.