Press Release
Birth of a sports legend
The BMW M3 made experts and car buffs wax lyrical right from the very beginning, before the car even made its official appearance. For it was back in summer that 1985 car magazines all over Germany published their first reports on an “over-the-top 3 Series� based on the E30 model series and boasting exceptional performance data: 200 horsepower, a top speed in excess of 230 km/h or 143 mph, and acceleration to 100 km/h in 6.7 seconds.
Obviously, the connoisseur immediately realised that the fastest BMW 3 Series the world had ever seen was about to make its appearance. In reality, however, well over a year was still to pass before the first car testers and customers were able to take their seat in a BMW M3.
The BMW M3 project had started a few months before at BMW Motorsport GmbH. The legend has it that Eberhard von Kuenheim, at the time the Chairman of the Board of Management, gave the go-ahead for a particularly sporting and dynamic engine in the BMW 3 Series in a talk with the Technical Director of BMW M GmbH, Paul Rosche. So the order to develop such an exceptional power unit quite literally came right from the top.
A high-performance power unit after just two weeks of development. Rosche and his team were however well-prepared when they received the green light to build this exceptional power unit. For Rosche, incidentally also the “father� of the turbocharged engine which helped Nelson Piquet bring home the Formula 1 World Championship in 1983 in his BMW Brabham, had already checked out the “bits and pieces� he needed for the engine: The new power unit was based on the crankcase of the four-cylinder already featured as a highly refined and dynamic two-litre in large-scale production, with its engine block already rendering an invaluable service in the World Championship engine.
The decision in favour of a four-cylinder and against the six-cylinder introduced in the BMW 3 Series in the meantime was taken not only to save weight, but also and above all for technical reasons: The longer crankshaft on the large engine started to vibrate much earlier at increasing engine speeds than the crankshaft in the four-cylinder. Hence, the responsible designers made the crankdrive on the BMW M3 so stiff that it was able to run even at speeds of 10,000 rpm and more – an increase in engine speed by approximately 60 per cent over the four-cylinder built in regular series production. And at 6, 750 rpm, maximum engine speed of the road-going BMW M3 was significantly below the critical limit, offering adequate margin for ongoing development.
The cylinder head also came from series production, as it were, with the engine specialists opting for the four-valve cylinder head of the six-cylinder and then simply “cutting off� two combustion chambers. This was possible without any major complications due to the same distance between cylinders in both versions, which obviously made things easier. The last step then required was to increase engine capacity to 2.3 litres.
After an incredibly short development period of just 14 days, the first prototype engine was ready to go, proudly bearing the abbreviation “S14� in a slightly modified version and destined to write history in both motorsport and series production.
The only bad news for Paul Rosche in this development process is that he was not able to integrate a turbocharger in the engine for reasons of homologation, since the “fathers� of the BMW M3 had planned the car from the start also as a Group A racing car, which required production of at least 5,000 units in 12 successive months. And that made it quite clear that the BMW M3 had to be a road-going car suitable for everyday use, making it impossible to give the car a technically very demanding and sophisticated turbocharged power unit.
Powerful and clean all in one.
While focusing particularly on the power and performance of the new engine, the responsible engineers also had other important developments in mind. One point was that the four-cylinder in the BMW M3 was to pave the way into the future also in terms of emission management, forming a perfect team with a fully controlled catalytic converter – a combination quite unusual back then in the mid-80s, when the catalyst still tended to increase fuel consumption and reduce engine output.
A further potential drawback was that unleaded gasoline, obviously a must for an engine with a catalytic converter, did not have the reputation of being particularly good for a high-performance power unit. And last but certainly not least, the quality of fuel in Europe varied significantly from one region to another – again not good news for the reliable operation of such an engine.
But again, Paul Rosche and his team found the solution: They modified the engine and reduced its compression ratio from 10.5 : 1 to 9.6 : 1. As a result, the power unit featured in the BMW M3 did not develop any destructive knocking effect even in response to fuel with a varying octane rating.
And a truly sensational factor at the time was that even this reduction of engine compression and the integration of a catalyst meant a reduction in engine power by only 5 hp down from the regular 200 horsepower.
