BMW M3 Convertible (2001)

Ongoing development of the high-speed concept was however only one reason for developing this new engine, since the engineers at BMW M GmbH were required to fulfil a whole list of demands in creating the new engine: Lower weight, more torque and extra power as well as a wide range of useful engine speeds were just as important as an engine suitable for reliable use the world over. Particularly this final point was indeed a great challenge to BMW's engineers, since the engine was required from the start to comply with all legal requirements in terms of emission and noise control either currently in force or coming into force in the many countries in which the BMW M3 is sold.

With this high-performance engine boasting the most outstanding features and data, the development team was hardly able to use any of the regular series production parts as was still possible with the first generation of the BMW M3 back in 1985. So the only components they were able to carry over to the new M3 without modification were the oil sump gasket, the tightening cylinder for the ancillary unit belt drive, the rear crankshaft cover together with its seal, as well as the oil pressure and water temperature sensors. And the only features the new engine shares in common with the former power unit are its dimensions and the quasi-dry sump system.

Thanks to the skills of BMW's engineers, the new power unit meets all these - and other - requirements. Compared with the - already light - former engine, BMW's engine specialists have indeed succeeded in reducing the weight of the engine by another 6 per cent. And at the same time they have moved the engine's centre of gravity down even further in the interest of enhanced driving dynamics.

On account of the higher engine speed and more complex function data, the engineers at BMW M GmbH also had to develop a new engine control system: MSS 54. As on the previous engine, this multi-processor system masterminds two 32-bit micro-controllers and two timing co-processors, now however operating at an even higher cycle frequency.

In all, the computer power of the new control unit is now 25 million instructions per second (MIPS). And just how important and complex the functions of this new unit are for the entire operation of the engine as such is clearly borne out by the various processes covered by the multi-processor system, which supervises the angle spread on the intake and exhaust camshafts (double-VANOS) as well as the oil level, masterminds the electronic immobiliser, and controls the electronic throttle butterflies. Working individually for each cylinder, the control unit furthermore calculates the ignition timing, the volume of fuel injected and the injection time individually for each operating cycle as a function of engine load and speed. And last but not least, the control unit provides information for service and maintenance via an elaborate and sophisticated diagnostic system.

Perfect engine management based on an in-house development.

Cylinder-specific, adaptive knock control receives the knock signal via three body sound sensors, with each sensor monitoring two cylinders. The signal is adapted for each cylinder by a standardisation process geared to the respective operating point, allowing the system to program the best and most appropriate ignition timing throughout the entire ignition angle control map. Operating a switch on the dashboard, the driver of the BMW M3 is then able to activate a more sporting, that is a more progressive control line modifying accelerator travel and the throttle butterfly opening.

Electronic throttle butterfly control is now based on instant commands, with the driver's request for power being measured via the potentiometer on the gas pedal and converted into a desired signal and power level.

This wish for power is then corrected by the power manager taking the power requirements of the ancillary drive units into account as well as the maximum and minimum power required for Dynamic Stability Control (DSC) and Engine Drag Force Control (EDFC).

The target power level calculated in this way is then set within the system, taking the current ignition angle into account. In practice, what this means for the driver is that the engine virtually "reads" his style of motoring from the position of his foot on the accelerator, providing the power required quickly and efficiently.

Optimum gas charge cycle ensured by variable camshaft spread.

Variable camshaft spread on the intake and outlet camshafts (double-VANOS), which made its world premiere in its first version in the 1992 BMW M3, ensures an optimum gas charge cycle also in the engine of the BMW M3. On the road, this means more power, greater fuel economy, and low exhaust emissions.

Through its principle alone, VANOS technology allows appropriate management of the engine at all times. The sprocket wheel connected with the crankshaft by a duplex chain is linked to the camshaft by a spirally-toothed shaft adjustable along its axis. Such an axial shift on the shaft, on account of the spiral gearing, generates a radial, relative movement between the camshaft and the sprocket, with the spread angle on the intake camshaft being varied as a result by 60° and the angle on the outlet camshaft by 46°.

Axial adjustment of the toothed shaft is provided by an adjuster piston.

Engine oil is pre-compressed up to an operating pressure of 115 bar by a radial piston pump integrated in the VANOS housing. Map-controlled high-pressure adjustment, in turn, guarantees short adjustment times and therefore provides the optimum spread angle for each operating point depending on load and engine speed and synchronised to the ignition timing and injection volume.

One engine for all countries.

The newly developed straight-six displacing 3,246 cc is the first power unit suitable for all countries and national specifications. However, as opposed to the 252 kW/343 hp ECE version, the power unit is throttled on the US version of the BMW M3 to reduced output of 333 SAE-hp (249 kW/338 DIN-hp).

This means that with an increase in engine capacity by only 1.4 per cent over the former model, maximum output is up by 6.9 and maximum torque by 4.3 per cent.

This increase in power and torque is a direct result of the high-speed engine concept, consistent control of the charge cycle and minimisation of friction effects increasing the engine's specific output from 100 to almost 106 hp per litre.

Despite its high maximum running speeds, the engine offers a large useful speed range, developing 80 per cent of its maximum torque at just 2,000 rpm. No surprise, therefore, that this power unit thrilled specialists and car journalists right from the start, winning the coveted "Engine of the Year" trophy, a really outstanding award, six times in a row from 2001-2006.

Exceptional technology for an exceptional car.

On account of the high standard of performance the BMW M3 offers whenever required, numerous systems within the car had to be configured more elaborately and with greater attention to detail than in a "regular" road car. One of these special features is the supply of lubricant to the engine by quasi-dry sump lubrication: Due to the specific arrangement of the sump and the engine tilted to the right at an angle of 30°, the engine oil would be unable to flow back to a "normal" sump under high lateral acceleration in a left-hand bend and when applying the brakes all-out. Hence, the engineers working on the power unit connected the compressed oil pump with a reflow pump extracting oil on the right side from the small oil sump at the front and delivering the oil to the large oil sump at the rear. For all practical purposes, this completely closes the rear oil sump, with the reflow openings and compressed oil pump extraction point being precisely tailored to the acceleration forces prevailing in a car of this calibre.

Even faster than the engine: the chassis and suspension.

The engineers responsible for developing the BMW M3 gave particular attention from the start to the chassis and suspension. Following the philosophy that "the chassis must always be faster than the engine", they demanded the utmost of the chassis and suspension technology, a task obviously giving the suspension engineers a significant challenge considering the high-speed concept and outstanding performance of the M3 power unit.

However, they were able to set out from an excellent foundation right from the beginning, with the chassis and suspension of the third-generation BMW M3 being a consistent development of the former chassis. And the chassis on the second-generation is still acknowledged to this day as the benchmark in the sports car segment, being lauded by the experts of US magazine "Car and Driver", for example, as the "Best Handling Car".

The extra-stiff bodyshell of the BMW 3-Series Coupé, the large share of lightweight aluminium axle components, and well-balanced front-to-rear weight distribution of almost 50 : 50 were indeed ideal prerequisites for ensuring unfiltered driving pleasure with BMW standard drive feeding power to the rear wheels. And despite the somewhat larger dimensions of the new model, the chassis and suspension engineers succeeded in even outperforming the predecessor's handling qualities while at the same time maintaining a high standard of everyday practical use.

DSC and the M Differential Lock for extra traction.

Introducing the third generation of the BMW M3, BMW M GmbH also made DSC Dynamic Stability Control a standard feature of the car. Hence, wheels spinning on a wet road or in snow are now a thing of the past once and for all.

The engineers responsible for the new BMW M3 were however not able to simply take over the DSC system incorporated in the "regular" 3-Series, but rather had to modify the system on account of the enormous power and performance offered by the BMW M3. Particularly the immediate response of the BMW M3 power unit and the short final drive ratio call for numerous changes in the system.

From the beginning, differential locks on the rear wheels have been a standard feature on all BMW M Cars. And now, introducing the third generation of the M3, the engineers replaced the former torque-sensing self- locking differential with 25 per cent locking action by an all-new development providing a variable locking effect between 0 and 100 per cent.

Bearing the name Variable M Differential Lock, this new system is able to offer a decisive improvement of traction even in the most demanding situations, with the drive wheels running on a surface with different frictional coefficients. So in combination with DSC Dynamic Stability Control, the BMW M3 now offers driving qualities also in winter previously regarded as quite impossible on a sports car with rear-wheel drive.

High-performance brakes and M Power.

Wherever there is a lot of power from the engine, you also need a lot of brake power. Precisely with this in mind the BMW M3 was equipped from the start with an extra-large high-performance brake system featuring compound brakes in floating arrangement. In this case the inner-vented friction ring on the brake disc is connected in floating configuration with the aluminium brake cage by way of stainless-steel pins cast into the brake unit.

The result is a considerable reduction of thermal forces acting on the brake disc, with an appropriate increase in service life. Perforation of the friction ring serves to additionally reduce the weight of the brake discs by 0.7 kilos on each front wheel and 0.8 kilos on each rear wheel in comparison with conventional, single-piece brake discs.

Thanks to large, cross-drilled grey cast iron brake discs (diameter/thickness at the front: 325/28 millimetres (12.80/1.10"), at the rear: 326/20 millimetres (12.83/0.79"), stopping forces are really remarkable: Assisted by a 9-/10-inch tandem booster, the BMW M3 achieves deceleration of approximately 11 metres/sec2, with a stopping distance of just 35 metres or 115 feet from a speed of 100 km/h. So when it comes to brake performance, the BMW M3 once again compares very favourably with even the most thoroughbred sports cars.

More than "just" one BMW M3 in the range.

A year after introducing the BMW M3 Coupé, BMW M GmbH proudly presented the Convertible version of the M3 based on the E46 model series in 2001. While identical with the fixed-roof coupé all the way back to the A-pillar, the Convertible is nevertheless a very unique car, the striking waistline and the special character of an open-air sports car giving the Convertible an even wider and more powerful look. In all, therefore, the BMW M3 Convertible looks even more muscular and lower than its fixed-roof counterpart with which it naturally shares all technical highlights and refinements.

In autumn 2001 BMW nevertheless proved that even this exclusive standard can be enhanced to an even higher level: Presenting the BMW M3 GTR, the Company proudly launched an upgraded road-going version of the BMW M3 destined to proceed from one victory to the next in the American Le Mans Series (ALMS). So as of February 2002, the road-going version of this very special model, with engine power cut back from 330 kW/460 hp to 258 kW/350 hp, was available at a price of approximately Euro 250,000.

In technical terms the road model was related very closely to the racing version, a V8-high performance power unit with dry sump lubrication generating supreme power within the engine compartment featuring additional cooling slits. Other special features were the six-speed manual gearbox as well as a double-plate clutch again typical of a racing car.

The body was also similar to the racing version, with the roof, the rear wing as well as the front and rear air dams being made of carbonfibre-reinforced plastic in the interest of minimum weight.

Further improvement of the "basic" model.

Entering the year 2005, BMW introduced a very special feature for the M3: the Competition Package. At a price of Euro 5,300, the really discerning costumer ordering a new car was now able to choose this special feature giving the BMW M3 even more direct and sporting handling. The Package includes 19-inch wheels in the same styling as the rims on the BMW M3 CSL and fitted complete with Sports Cup tyres. In conjunction with the chassis and suspension optimised all round and the even more direct steering (with a transmission ratio of 14.5 : 1 instead of 15.4 : 1), this gives the car an even higher standard of all-round agility and performance on the road.

Benefiting from this special package, the driver of the "basic" BMW M3 was also able to enjoy the advantages of the M Track Mode carried over from the BMW M3 CSL. Brakes likewise coming from the BMW M3 CSL are naturally also included in the Package, to ensure appropriate stopping power with very short stopping distances at all times.

Given all these qualities, the third generation BMW M3 is just as popular among customers the world over as its predecessors. This explains why no less than 85,139 units were delivered to customers by summer 2006, among them no less than 29,633 Convertibles.