For 20 years the BMW M3 has been the by-word for race-bred on road excellence in a compact car.
Over three generations, the legend has gone from strength to strength, beginning as a four-cylinder two-door coupe and flowering into a mighty six-cylinder naturally aspirated Coupé, Sedan and Convertible, the envy of the world.
As popular with fast road drivers as it was successful on track, the M3 legend was born of humble beginnings but has grown to a position of majesty.
Much copied, never matched in its purity of performance, function, and understated yet distinctive styling, the M3 today is as much in demand by enthusiasts as ever, as critically acclaimed as never before, and undoubtedly the benchmark for a plethora of would-be rivals.
Powered by a 252 kW, 3.2-litre high-technology, high-revving straight-six engine, now shared with the just launched Z4 M Roadster and the soon-to-arrive Z4 M Coupé, the 2006 M3 celebrates its 20th birthday in trade-mark understated style.
How the legend was born
The sentence has become a legend: “Mr. Rosche”, said the BMW Chairman sometime around the beginning of the 1980s, almost as an aside to his engine designer, “we need a sporty engine for the Three Series.” Eberhard von Kuenheim knew exactly who he was motivating to take action:
Paul Rosche was not only the engineering managing director of M GmbH, he was also the father of the turbo engine which had powered Nelson Piquet to victory in the 1983 World Championship, driving a Brabham BMW. And as far as Rosche was concerned, a sporty car had to do one thing: win. That was when the M3 was born.
Basic engine drawn from Formula 1
However, the designers of the sports engine weren’t exactly standing there empty-handed. The right ingredients for the projected engine were available, the mission was simply to put them together in the right way. The crankcase of the four-cylinder engine was available as a basis. This was being installed as a solid two-litre engine in volume production. Paul Rosche had long since found out about the potential really contained in the grey cast-iron housing.
It was this block that was to form the foundation stone for the champion engine of Formula 1
Four cylinders didn’t simply mean less weight and high torque for blue riband performance, but also offered ideal specifications for the projected sports engine. BMW had already introduced the six-cylinder era in the 3 Series.
But no matter how smooth and powerful the running of the in-line engine was, it had one major disadvantage for racing given the technology available at the time. As the engine speed increased, the length of the crankshaft meant that it started to vibrate much earlier than the short four-cylinder shaft. The designers therefore designed the crankshaft drive of the M3 as stiff as possible so that it could achieve in excess of 10,000 revolutions per minute.
By comparison, at that time the four-cylinder of the 318i delivered its maximum output at 5,500 rpm. The engineers were already aiming for a rated speed of 6,750 rpm for the road version of the M3, i.e. they left plenty of scope upwards.
Development goal: Group A racing car
Potential for records: The first engine fires after just two weeks development
The engineers then increased the capacity even further to 2.3 litres and the first prototype was now ready. Paul Rosche: “Whether you believe it or not – we had created an outstanding four-cylinder engine for the 3 Series within the space of two weeks. Under the development name S14, this engine was to generate headlines in sport and in volume production over the years to come. One Sunday, I drove to von Kuenheim’s flat and gave him the car for a test drive. When he came back he said: ‘Good, I like it.’ And that’s how the M3 came into being.”
Fast and clean: Adopting a Catalyst barely slows the M3
However, the engineers weren’t only working on performance. The emissions of the M3 engine were also supposed to be geared to future requirements. That’s why the four-cylinder was from the start developed in such a way that it could easily be supplemented by a controlled catalytic converter. The function was by no means a simple task. In the mid-1980s, catalytic converters tended to reduce power and make engines less fuel-efficient.
Another factor was that unleaded petrol didn’t exactly have the reputation of being the ideal fuel for high-performance engines. The quality of the new fuel varied too much in Europe to meet this specification. In order to err on the safe side, the team headed by Paul Rosche adapted the engine and reduced the compression from 10.5 : 1 to 9.6 : 1.
On the one hand, this resulted in the engine not reacting to variations on the octane number with unpleasant knocking. On the other hand, the reduction in compression plus installation of the catalytic converter in the exhaust system only resulted in a loss of 5 of the standard 200 bhp.
Goal achieved: Full throttle at Nardo
Although the design engineers were pleased with the superior performance, they also spent some sleepless nights. The north loop of the Nürburgring was particularly hard on materials and what was blown into the manifold here by the four-cylinder wasn’t digested so easily by the exhaust system – the pipes were continually fracturing. It transpired that the cause was unplanned growth in the exhaust system. High temperatures at full load meant that the high-performance system became so hot that it expanded by up to 25 mm and became distorted within its mounting. A simple set of different washers solved the problem.
The drivers from BMW Motorsport GmbH immediately proved the point. On the high-speed test track in Nardo, Italy, they drove an M3 three times at full throttle over a distance of 50,000 km. The exhaust system withstood the test just like the rest of the car.
M3 goes fast even standing still
On the BMW exhibition stand at the Frankfurt Motor Show in autumn 1985, the M3 was presented to a more broadly based public audience for the first time. Even without a special paint finish, it was not difficult to distinguish the car from the other 3 Series vehicles. The boot lid was crowned by a wing across the width of the car.
Aprons all round indicated the refined aerodynamic work that had been carried out on the bodywork of the 3 Series. Anyone who spent long enough making comparisons discovered that the C-column was slightly wider and had a flatter taper in order not to interrupt the airflow over the edge of the roof and at the same time direct the airflow more effectively onto the rear spoiler.
Thick cheeks had sprouted over the wide wheels of the M3, the flared wheel arches came to an end in a striking edge below the edges of the wings. There was no question about it – the M3 looked fast even when it was perched on an exhibition stand.
Plastic parts save weight
Anyone who got that close was inclined to pat the new sports car on its chubby cheeks to see whether the bulging wheel housings had simply been attached, or whether they really had been pressed out of sheet metal. And they were impressed. The entire bodywork including the wings and the bonnet were made of metal. A lightweight plastic had been used for front and rear bumpers, and side sills and boot lid including spoilers in order to keep weight down. The M3 weighed in at 1,165 kilograms without payload on the scales and hence remained a sporty lightweight with only 5.8 kg for every 1 bhp.