The BMW M3 CSL - In Detail

Press Release

The BMW M3 CSL - In Detail

The roof of the M3 CSL is built at BMW’s Landshut Plant BMW builds this carbon-fibre -reinforced roof itself at the Landshut Plant, where, at the home of BMW’s lightweight technology experts, specialists acting as highly competent system suppliers make the roof of the M3 CSL out of several layers of this expensive material. The in-house suppliers at the Landshut Innovation and Technology Centre (LITZ) therefore not only contribute their particular skill and competence in this way, but also ensure fast and flexible action in implementing the most sophisticated innovations in lightweight technology. Even parts and components normally quite insignificant within the body structure as a whole were carefully considered for any possible reduction of weight. Focusing on the floor of the luggage compartment, for example, the engineers at BMW M opted for a paper-honeycomb-sandwich structure. The through-loading facility, in turn, made of steel on the “standard� M3, is made of a sandwich endless-glass-fibre mixture of thermoplastics and foam on the M3 CSL. And the rear window is made of extra-thin glass. The body shell of the M3 CSL is still made of steel panels varying in stre ngth and thickness quite simply because in some cases it hardly makes sense to replace steel by another material. Here, therefore, steel continues to prove its qualities and advantages also in terms of stability. A top performer with outstanding agility It goes without saying that a car as thrilling as the new M3 CSL requires the right kind of chassis and suspension. After all, the driver should really feel the agility of this car, agility should be an important part of the CSL driving experience. So in developing this dynamic suspension and chassis system, the engineers at BMW M again focused on motorsport, which is no surprise considering the very long list of racing wins and achievements by BMW touring cars in more than four decades. The most important parameters in this context are of course the wheel suspension as such, the steering and brakes – and the tyres also play a very important role in providing a supreme standard of driving dynamics on the road. The significant but very tempting challenge the engineers at BMW M were happy to accept was to leave the outstanding chassis and suspension of the M3 unchanged in its basic philosophy, but to thoroughly refine many features and the general set-up in view of the change in weight. In this process of optimisation starting at a very high level, each individual component was put to the test in every respect, being carefully examined for every possible improvement. Now the result is a chassis, which from the very beginning simply feels different from the “regular� chassis in the BMW M3, offering an even higher standard of precision and agility on the road. The same precision as a racing car To provide this kind of experience, the front springs are one winding shorter and both the spring and damper rates have been re -tuned all round in view of the car’s lighter weight, both the compression and rebound strokes being modified in the process. Like the front track control arms on the “standard� M3, the rear track control arms are now also made of aluminium and come with ball instead of rubber bearings for even better lateral dynamic guidance (uniball joints). In all, these improvements give the M3 not only uncompromising directional stability under all conditions, but also extremely good cornering qualities with very little body sway. And at the same time they significantly reduce the weight of all chassis and suspension components. This new dimension of agility is borne out in particular by the modified steering of the M3 CSL. Benefiting from an even more direct overall transmission ratio of 14.5:1 (versus 15.4:1 on the M3), the rack-and-pinion steering provides much more direct response and steering behavior and offers cutting-edge precision in bends. Any comparison with a racing car is by no means exaggerated and it is fair to say that only very few road cars are able to offer the same kind of dynamic driving experience of the highest, most puristic standard. A fast car needs fast brakes Driving at high speeds, the lucky man or woman at the wheel of the M3 CSL also needs fast – that is highly efficient and professional – brakes. So it is no surprise that the M3 CSL comes with particularly strong brakes taking action very quickly and forcefully whenever required. At the front the grey-cast-iron brake discs are somewhat larger in diameter than on the standard M3 (M3 CSL 345 x 28 millimetres (13.58 x 1.10´´ ) versus the “standard� M3 with 325 x 28 millimetres (12.80 x 1.10´´ ), whilst at the rear the brake discs on both cars measure 328 x 20 millimetres (12.91 x 0.78´´ ). The brakes themselves feature BMW M’s proven compound system with single-piston swing calipers. To minimize the thermal load transmitted from the brake discs to the brake housing, which might impair the service life of the cross-drilled and inner-vented discs, the discs are connected with the aluminum brake housing by steel pins in floating design. For use on public roads the M3 CSL comes with conventional brake linings, for driving on the race track or in motorsport events BMW M is able to supply special brake pads for racing offering particular strength and resistance. This gives the new M3 CSL a brake system of the highest calibre not only reflecting the car’s truly outstanding performance, but also providing brake response and stopping power previously regarded as quite impossible. In practice this means that the driver applying the brakes all-out and under appropriate conditions at a speed of 100 km/h will bring the M3 CSL to a standstill in less than 34 metres (111 feet) and within 2.5 seconds, with maximum average retardation of more than 11 metres/sec2. Last but certainly not least, the ABS anti-lock brake system featured as standard on the M3 CSL has been re-tuned to reflect the change in overall performance and the higher frictional coefficient the tyres are able to provide. Very special wheels and tyres for a very special car Clearly, the M3 CSL comes on very special aluminium wheels as another exclusive touch, with 8½-inch rims at the front and 9½-inch rims at the rear. These new, specially developed 19-inch wheels also help to save weight, the four wheels and tyres on the M3 CLS weighing eleven kilos less than the 19-inch wheels available as an option on the M3. The Michelin Pilot Sport Cup tires have also been developed especially for this outstanding car. Measuring 235/35 ZR 19 at the front and 265/30 ZR 19 at the rear, these tires provide an exact match for the M3 CSL, again contributing to the car’s optimum grip and road holding. Similar in design and structure to genuine racing tyres, these special road-going tyres, thanks to their very heat-resistant rubber compound, make a very significant contribution to the M3 CSL’s excellent driving characteristics. They are designed and conceived for ultimate performance in the dry and offer a far greater potential in longitudinal and lateral acceleration, and in their steering precision, than comparable production tires. Indeed, this sporting performance is borne out at very first sight by the asymmetric tread with its large share of negative tread elements. The purchaser of an M3 CSL often required to drive on wet roads may also opt for the forged 19-inch wheels featured on the standard M3. The ultimate in M Power ensured by high engine speeds The straight-six power unit already featured in the “standard� M3 owes its exceptional performance to BMW’s high-speed engine concept. This concept allows a particularly short transmission ratio giving the car superior power and performance throughout the entire speed range, six individual throttle butterflies ensuring that the engine responds perfectly to the gas pedal whenever required. Also revving up easily and smoothly all the way to 8,000 rpm, the power unit of the M3 CSL offers an even higher standard of all-round performance. An all-new air intake system with an extra-large air collector made of carbon-fibre–reinforced plastic ensures an ample flow of air to the 3.2-litre power unit, the intake manifolds with a much large diameter taking in fresh air through the large air scoop on the left-hand side of the front air dam enabling the engine to breathe even more freely, without the slightest throttle effect. The usual air mass metre has been dropped on the M3 CSL for precisely this reason, the mass of air drawn in by the system being calculated by the engine’s “brain� like in Formula 1. Indeed, this is one of the reasons why the DME memory is twice as big as before, with an increase in computer speed by 25 percent. The camshafts with their longer valve opening times also help to boost the power of the engine to an even higher level than before. To reduce the forces required for removing burnt combustion gas from the combustion chamber and thus increase the useful engine load accordingly, the exhaust valves have been modified once again in their geometry, the flow of gas also benefitting from the funnel-shaped pipe intakes leading into the rear silencer. And again reflecting the lightweight philosophy of the CSL, the entire exhaust system is made of pipes with even thinner walls at the side. The result of this successful fine-tuning is maximum output of 360 bhp (265 kW) at 7,900 rpm, with maximum torque of 370 Nm (273 lb-ft) at 4,900 rpm. This equals output per litre of no less than 111 bhp, an extremely high figure for a normal-aspiration power unit and, incidentally, the highest output per litre of any production six -cylinder in the world. The sports button in the centre console of the M3 CSL serves to significantly modify throttle butterfly control and management: In the sports mode the engine responds even more spontaneously to the accelerator pedal and the M3 CSL offers an even higher standard of performance throughout the entire engine speed range. Talking about performance, the refinements describe enable the M3 CSL to accelerate from 0–100 km/h in a mere 4.9 seconds, then continuing to 200 km/h in 16.8 seconds. Top speed is limited electronically to 250 km/h (155 mph).