Designed by Paul Rosche, the legendary engineer behind Bavaria’s most successful engines, such as the S70 / 2 V12 of the McLaren F1, the architecture of the M12 dates back to the 1960s, a decade in which several racing versions of the M10 four-cylinder were used in various competitions used.
In 1973 such a version with the code name M12 / 7 was developed especially for Formula 2. The 1,991 cc (2.0 liter), 300 horsepower engine installed in a March Engineering 732 would win its first race, then seven more and finish the season in first place. That would be the first of six F2 championships won by M12 / 7-powered racing cars from 1973 to 1984.
In the late 1970s, BMW also competed in the US IMSA series, but fought against rivals Porsche and their turbo boxers. To solve this problem, McLaren’s North American subsidiary was hired to build a turbo-charged variant of the M12 / 7.
At home, engineers were also working on a similar design for a new Group 5 racing car to replace the iconic 3.0 CSL. The E21 3 Series, nicknamed the “Flying Brick”, ended up using a 1.428 cc (1.4 liter) turbo mill derived from the F2 unit. Unfortunately, neither was very successful for the German manufacturer, but both M12 versions laid the foundation for the most powerful Formula 1 engine of the original turbo era and probably the most powerful in the history of the competition.
The year is 1981, and although Renault had been using turbos in the world’s most famous open-wheel series for years, the naturally aspirated Ford-Cosworth DFV was still the best powerplant ever. However, the French team’s turbo V6 became a real threat and helped them take third place in the constructors’ championship. During the season, numerous teams used experimental turbo engines in training seasons, including Brabham (officially Parmalat Racing Team) who tested the new BMW M12 / 13.
The four-cylinder was built around a cast iron block shared with the stock M10 and featured a Bosch electronic fuel injection system and a large KKK turbocharger that allowed it to deliver up to 850 horsepower in qualifying.
Legend has it that the blocks used for the M12 / 13 came from various BMW models with an M10 engine that had traveled over 100,000 km (62,137 miles). The theory was that a used one was basically tried and tested, so any casting defects could easily be pulled out.
To make it even more outlandish, Rosche reportedly ordered his engineers to leave the blocks out for several months, exposure to the elements, and instructed staff to urinate on them. Yeah, I know that sounds crazy, but ancient swordsmiths used urine to extinguish the steel blades, so if the rumors are true, Rosche’s madness had method.
Despite these rumors, the engine showed a lot of promise during the 1981 tests. Brabham’s lead driver Nelson Piquet managed to win the drivers’ title that year with a DFV, but the team eventually decided to drive BMW units part-time at Piquet’s car for 1982. A single win and multiple reliability issues ensued, but engineers continued to fine-tune the engine they wanted to use full-time in 1983.
Output of 1,280 PS (950.) kW) in qualifying specification and 850 PS (630 kW) for the races, the 1,499 ccm (1.5 liter) was built into the Brabham BT52 lengthways. Unlike Ferrari or Renault, which used twin-turbo V6 engines, the M12 / 13 had one less turbo, fewer cylinders and valves, so it generated less heat. This enabled Gordon Murray of Brabham to design the BT52 with smaller radiators and a leaner body, which gave the car an aerodynamic advantage.
The reliability problems persisted throughout the 1983 season, but mostly in the unit that powered Riccardo Patre’s car. Even so, Brabham finished the year in third place, while Piquet took his second drivers trophy, ousted Renault’s Alain Prost with two points and became the first person to win the title in a turbo car.
Used in the following years by Brabham, ATS, Benetton and Arrows, the M12 / 13 never managed to repeat the success of 1983. In 1986 BMW finally withdrew from Formula 1 and continued to deliver the engine to Brabham in 1987. This year Swiss manufacturer Megatron brought in the rights for its design and made Ligier and Arrows renamed units available. The latter was the last team to use the M12 in Formula 1 in the 1988 season.
Basically a year-long miracle of success, this German masterpiece was the most powerful F1 engine ever, but its exact performance has been the subject of decades of debate. In qualifying it is said to have run 1,280 (1983) and 1,350 hp (1986), but according to Paul Rosche’s calculations it produced well over 1,400 hp.
Peak performance aside, Gerhard Berger and his Benetton B186 with M12 / 13 drive earned a place in the history books by reaching 352.22 km / h (219 mph) at the 1986 Italian Grand Prix in Monza. This was the fastest straight-line speed ever recorded by a turbocharged Formula 1 car, an achievement that has since been surpassed. The current record holder is Valtteri Bottas, who reached 372.5 km / h (231.461 mph) in 2016.
In the video below, posted on YouTube by hardwarenoob0815, you can watch Berger shredding the Adelaide Street Circuit behind the wheel of the B186, considered by many to be the fastest F1 car ever.
