Few could have guessed that a small, rather basic and decidedly unromantic sounding four-pot could rewrite the Formula One record book, but that’s precisely what BMW achieved with the M12/13 – ‘The Megatron.’ It helped usher in one of F1’s finest eras, one colloquially known as ‘The Battle of the Boost.’ Here’s how the unassuming little four-banger was transformed from a mass market road car-hauler to a multiple championship winner.

The engine that gave rise to the 1500bhp M12/13 was both resolutely production based and decidedly old hat by the time BMW top brass gave its F1 programme the go-ahead in late 1980 – the M10. The iron blocked, alloy headed four-pot had been developed to power the company’s road car range twenty years previously, though it had been designed with versatility in mind from the outset; able to be re-bored for capacity from 1600 to 2000cc and therefore ideal for motorsport applications such as this. 

The BMW M10, the unassuming mass production engine which formed the basis of its maker’s 1980s F1 success

Still there were many in the motorsport world who scoffed at the notion of BMW, a relatively small car maker with a modest motorsport CV at the time, taking the fight to established outfits like Lotus, Ferrari and Tyrell. 

That’s not to say that F1 was still the sole preserve of the Cosworth DFV V8 or the Ferrari V12 as the ‘70s gave way to the ‘80s, because it wasn’t. Renault had pioneered forced induction from 1977 onwards, and while it had struggled for both drive-ability and reliability (Le Regie’s F1 cars were unkindly referred to as ‘yellow teapots’ for a period, and for good reason) the potential for supremacy in terms of outright power was plain to see.

Paul Rosche with his all-conquering creation

Nocken Paul Knocks

BMW was no stranger to forced induction versions of the M10, even before it entered the F1 fray in 1982. The hero of this piece, one Paul Rosche, had pressed ahead with the concept with a 1.4L version of the engine for the firm’s Group 5 E21, and while a tricky car to drive for anyone other than a Hans Stuck or an Eddie Cheever, there was no denying it power. 

Rocshe was also the architect of BMW’s Brabham success, at least in terms of engine development. He’d acquired the nickname of ‘Nocken Paul’ – ‘Camshaft Paul,’ clear evidence of how well he understood the relationship between cam and valve, and no one knew more about boosting the venerable M10. He was therefore charged with the development of BMW’s first F1 engine, a unit slated to power the Brabham BT50 of 1982 and soon known as the M12/13.

Am early M12/13, probably destined for Piquet’s Brabham BT50

Blockbuster

That season saw Brabham effectively hedge its bets by running both a conventional, DFV powered car and, for team leader Nelson Piquet, an M12/13 one. The engine itself was a classic case of a motor being greater than the sum of its (modest) parts: the iron block, 1499cc engine had an 89.2mm bore and 60mm stroke, a compression ratio of 7.5:1, made use of Bosch electronic fuel injection and made use of either a KKK or a Garrett turbo. It could rev to 11,500rpm, and would in time make as much as 1200bhp. 

The BT50 proved fast but fragile, not to mention fond of spitting flames and eating turbos for fun

1982

The M12/13’s first F1 season was a mixed bag, with between 700 and 800bhp (race and qualification) available for Piquet’s BT50. This was comfortably more than the NA DFV powered rivals and compared favourably with turbocharged opposition from Renault…but it was also maddeningly unreliable. Turbo failures blighted Piquet’s year and meant he retired more races than he finished, but he was able to demonstrate the unit’s potential with a win in Canada, his only one of the season. 

Gordon Murray’s greatest M12/13 powered Brabham, the BT52

1983 

This marked the high watermark of the BMW-Brabham relationship, and also the M12/13 at its most competitive. It’s also when we can begin discussing another Retropower Hero and a personal friend of ours, Gordon Murray. Murray had been ensconced at Brabham for some years by 1983 and had already designed a championship winning car, the of ground effect BT46, but his 1983 challenger was a true gem even by his own lofty standards – the BT52. 

In common with all Murray’s most successful designs, the BT52 was a work of art in terms of its packaging. Ultra-skinny, somewhat stumpy sidepods housed equally diminutive radiators, only made possible by the M12/13’s compact dimensions and single turbo, in marked contrast to the twin-turbo V6s powering the Renaults and Ferraris. 

You can click through to learn more about the BT52 and its championship season here, but suffice to say that the combination of Murray-penned Brabham and Rosche fettled engine proved the one to have, and Piquet pipped Renault’s Alain Prost to the title (the first won by a turbocharged engine) by a scant 2 points. 

The ill-fated ‘low line’ BT55

1984-1987

Piquet and Brabham proved unable to repeat their success in the seasons which followed owing to a mix of unreliability and, increasingly, improved performance from their rivals, most notably Honda’s V6. The BMW unit was still among the most powerful on the grid and proved good enough to give Piquet three more wins (Brabham’s last), but it was also temperamental and thirsty.

Gordon Murray’s solution, or at least attempted solution was the radical ‘low line’ Brabham BT55 of 1986, and another car we’ve covered here before. The concept involved redesigning the M12/13 (now dubbed the M12/13/1) once more, this time canting it over by a full 72 degrees so that it could be housed within the incredibly low chassis. This would allow for a ‘clean’ flow of air over the rear wing and a corresponding increase in downforce. 

Disassembled view of the BT55’s specially canted-over M12/13/1

The concept was sound, so much so that it was proven in the all-conquering McLaren MP4/4 two years later, but the realisation left much to be desired. The BMW engine simply didn’t like being tilted at such an extreme angle, whereupon it suffered from a litany of issues including oil surge, poor throttle response and overeating issues, out of the reach of much of the air feed it needed to perform as it once had. The result was that the ‘low line’ Brabham failed to trouble the podium all year, the team scoring just two points over the course of the 1986 season.

Megatron: so-so engine, superb name

1987-1988 – Megatron 

BMW pulled out of F1 at the end of the 1987 season but the M12/13 lived on, though it was now known a new (and almost impossibly cool) moniker – Megatron. It was very much a final flourish for the engine, with forced induction set to be banned from the 1989 season onwards. It was still a competitive enough unit for both Arrows and Ligier though, even if its inline-four, single turbo arrangement meant it was better suited to power circuits like Silverstone and Hockenheim rather than the twists of Monaco. 

It was only fitting that it fell to Eddie Cheever, the man who’d done much to convince BMW of the worth of its turbocharged M10 in the Group 5 DRM days, to claim the engine’s final podium, 3rdat the Italian Grand Prix of 1988. 

Derek Warwick attempts a novel corner entry in his Megatron powered Arrows A10B, 1988

Taking the Piss

The M12/13 is one of those motorsport engines which has more than a few folk tales and rumours associated with it, most of them centred on boost and power. Rocsche once stated that he didn’t know precisely how much power his engine made as the BMW dyno only went up to 1000bhp, but that he reckoned 1400bhp was probably a close approximation – or at least as close as he could get! This was doubtless true of the qualifying engines running 5.4BAR in 1986 but not in 1982 or 1983, where Piquet and co could call upon ‘just’ 800bhp at 3.2BAR in qualifying sessions. 

Most famously of all, BMW’s motorsport engine blocks were drawn from high mileage cars, sometimes showing six-figure mileages, and were creatively ‘seasoned’ before being shipped to Brabham and Benetton. This saw the old blocks left outside and exposed to the elements for months at a time while also being periodically urinated upon by BMW employees, the latter apparently having a nitriding effect on the iron blocks. 

It should also be stressed that the full fat, 1200bhp M12/13 was a short-lived affair, both in terms of its career and the lifespan of each of the individual engines. Such figures could only be achieved by screwing both boost and fuelling ‘to eleven,’ and the motors (effectively ‘qualifying grenades’) would last a handful of laps before detonating in spectacular fashion.

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