BMW M12

The BMW M12/13 turbo was a 1,499.8 cc four-cylinder turbocharged Formula One engine, based on the standard BMW M10 engine introduced in 1961, and powered the F1 cars of Brabham, Arrows and Benetton. Nelson Piquet won the FIA Formula One Drivers' Championship in 1983 driving a Brabham powered by the BMW M12/13 turbo. It was the first Drivers' Championship to be won using a turbocharged engine. The engine also powered the BMW GTP and in the 2.0-litre naturally-aspirated form, the successful March Engineering Formula Two cars. BMW engineers estimated the engine produced around 1,400 hp at maximum boost, however the BMW engine dynamometer could not go beyond 1,280 bhp.

Formula 2
As BMW M12/7, the engine design since the 1960s became one of the most successful in racing. Starting with the European Touring Car Championship, it was also used in Formula 2, expanded to two-litre and fitted with four-valve heads, producing over 300 hp. In the Deutsche Rennsport Meisterschaft, a 1,400 cc variant (with a 1.4 handicap factor equal to 2,000 cc) was turbocharged by Paul Rosche according to FIA Group 5 rules. At well over 350 hp from the beginning, it rendered the normally-aspirated engines in the two-litre category useless. After some development, power, driveability, and reliability improved, especially in the IMSA car, and BMW began to think about entering F1, where a handicap factor of 2.0 required 1,500 cc engines.



Formula One
During the season, the Brabham team, then owned by future F1 boss Bernie Ecclestone, used both the older Cosworth DFV V8 engine as well as the turbocharged BMW M12 in selected races in a development program. The BMW proved to be fast in its first year in Formula One, though its reliability, with turbocharging still in its infancy, was lacking. Reigning World Champion Nelson Piquet recorded the first win for the engine in F1 when he led home Brabham teammate Riccardo Patrese (in the Cosworth-powered car) at the 1982 Canadian Grand Prix.

In, Brazilian driver Piquet won his second Formula One World Championship driving a Brabham BT52 powered exclusively by the M12, which by that year was producing approximately 850 bhp in qualifying trim and 640 bhp for the races. Piquet, who won the Brazilian, Italian and European Grands Prix that year, won the championship by just two points, ahead of Renault's Alain Prost (Renault had pioneered turbocharging in F1 in, but would never win the World Championship in the original turbo era (1977-1988)). Piquet was the first driver to win a World Championship in a turbo-powered car.

The main advantage of the inline-four M12 over its V6 Ferrari and Renault opposition was that, with one fewer turbo, two fewer cylinders, and eight fewer valves, the BMW engine had lower frictional losses and, therefore, produced less waste heat. This allowed Brahbam's lead designer Gordon Murray the luxury of designing the BT52 with smaller radiators, which meant better aerodynamic efficiency and thus better straight-line speed. The BT52 was notable for its very skinny, short sidepods, especially compared to the Renault, giving it better penetration through the air on circuits with long straights.

and, by contrast, were lean years for the M12. The engine was generally regarded as the most powerful in F1 at the time, producing approximately 1100 hp in qualifying trim by 1985, and Piquet took nine pole positions in 1984 alone. However, the engine's mechanical reliability and durability under full workload suffered severely, with engine blow-ups and turbo failures becoming common occurrences. Furthermore, with FISA imposing a maximum fuel limit of 220 litres per race (refuelling was allowed in 1982 and 1983), the four-cylinder BMW suffered from high fuel consumption which often led to drivers running out of fuel, and continued to suffer from poor reliability. Consequently, Piquet scored only three wins - the 1984 Canadian and Detroit races, and the 1985 French Grand Prix. These proved to be Brabham's final wins in Formula 1.

For, the M12 was upgraded into the M12/13/1. (Bore 89.2 mm X Stroke 60 mm) 374.95 cc and 350 PS per cylinder 933.46 PS/litre. This version was claimed to have produced a maximum output of 1400 hp at 11,000 rpm, and about 850-930 lbft of torque in qualifying trim, which would make it the most powerful engine ever to race in Formula 1, turbocharged or otherwise. At the time, there was no way to accurately measure horsepower figures over 1,000, and so claimed output figures were generally accepted from the engineers' theoretical calculations; for example, 0.1 bar of turbo boost was rated to be worth approximately 20 hp). During the 1986 Italian Grand Prix at Monza, Gerhard Berger's BMW-powered Benetton B186 recorded the highest straight line speed by a turbocharged Formula One car when he was timed at 352.22 km/h. In fact, the top five cars through the speed trap at Monza (Berger and teammate Teo Fabi, Brabham's Derek Warwick and Riccardo Patrese, and the Arrows of Thierry Boutsen) were all powered by the BMW M12.

Brabham tilted the upgraded engine sideways by 72° for use in the extremely low BT55, but the concept proved unsuccessful, most likely due to cooling issues in the tight compartment. Instead, Benetton, with the more conventional B186, were the leading BMW users in 1986, with Berger scoring his and the team's first (and the BMW engine's last) win at the Mexican Grand Prix.

BMW announced their withdrawal from F1 at the end of 1986, but that they would continue to honour their contract and supply, Brabham, with their tilted M12s for 1987. Arrows team boss Jackie Oliver, with support from the team's primary sponsor USF&G, brokered a deal to continue the use of the upright BMW engines under the name of its subsidiary Megatron, Inc., founded by long-time F1 aficionado John J. Schmidt. The engines were serviced from Switzerland by Arrows' long time engine guru Heini Mader, a former mechanic of Jo Siffert.

Megatron
Rebadged as Megatron, the BMW engines were used by the Arrows team for the and  seasons, as well as Ligier in 1987. By 1988, Arrows were one of only six teams still running turbocharged engines, and the Megatrons were the oldest turbo engine still in use in Formula One, Ferrari having introduced a brand-new turbo engine the previous year.

The Megatron programme ended after 1988 as a result of rule changes that banned turbocharged engines from 1989 onwards, with Eddie Cheever scoring the old BMW engine's last podium finish with third place in the 1988 Italian Grand Prix at Monza. This race was also significant as it marked the first time Heini Mader had solved the problems caused by the FIA's boost limit valve, which limited turbo boost pressure to 4.0 bar in 1987 and 2.5 bar in 1988. By moving the valve closer to the engine, the problem of the turbo not delivering enough boost had been solved, and the Arrows A10B was among the fastest cars on the long Monza straights, faster even than the all-conquering McLaren-Hondas into which designer Steve Nichols had effectively incorporated elements of Gordon Murray's low-line Brabham design as well as featuring a more powerful V6 engine.

With turbos banned from the season, the Arrows team reverted to using 3499 cc, naturally aspirated Ford DFR V8 power plants.

The M12's major shortcoming as a Formula One engine was its lack of throttle response due to turbo lag. Unlike the V6 and V8 turbocharged engines which ran with twin turbos (one for each bank of cylinders), the inline-4 BMW engine, like the other four-cylinder turbo engines used in F1 such as the Hart 415T and the Zakspeed 1500/4, only used a single turbocharger. The twin-turbo setups of the "V" engines eliminated much of the turbo lag. However, with only a single turbo, the BMW M12 suffered from approximately 2 seconds of turbo lag, meaning drivers often had to start accelerating through the apex of a corner. The power from the turbo was described by many (including Piquet and Berger) as coming on like a light switch which often induced sudden oversteer. Consequently, the BMW was usually seen at its most competitive at power circuits such as Kyalami, Imola, Paul Ricard, Silverstone, Hockenheim, the Österreichring and Monza. On tighter tracks such as street circuits like Monaco and Detroit which required greater acceleration and less top speed, the BMW-powered cars often lagged behind their major rivals.

Formula One record
World Championships: 1 (Nelson Piquet in a Brabham in )

Wins: 9 (Piquet 7, Riccardo Patrese 1, Gerhard Berger 1)

Pole positions: 15 (Piquet 12, Teo Fabi 2, Patrese 1)

Fastest laps: 14 (Piquet 9, Patrese 2, Berger 2, Fabi 1)

Complete Formula One Championship results
(key) (Results in bold indicate pole position; results in italics indicate fastest lap) * Ineligible for points.