By September 25, 2013 Read More →

BMW M revealed technical detail of the new BMW M3 and BMW M4

BMW M3 and M3 on trackBMW M GmbH revealed some technical details of the new M3 Sedan and BMW M4 Coupe models. The new BMW M3 will be powered by a six-cylinder turbocharged engine. (more details about the engine can be found from here). The engine’s impressive torque is sent on its way by a forged crankshaft with high torsional rigidity, whose low weight also allows a significant reduction in rotating mass. The crankshaft therefore helps to optimise the engine’s responsiveness and acceleration and makes an important contribution to its high-revving character.

The engine sends its power to the wheels through a six-speed manual gearbox as standard. This gearbox is significantly more compact than its predecessor and 12 kilograms lighter, allowing it to assist the car’s optimum (virtually 50:50) weight distribution. As a means of increasing shift comfort, the manual gearbox uses innovative new carbon friction linings in its synchroniser rings. Dry sump lubrication provides an efficient supply of oil to all parts of the gearbox. The new gearbox also works a lot more quietly than before and blips the throttle on downshifts – previously a feature reserved for the M Double Clutch Transmission. This engagement speed control function helps to enhance stability and was originally developed by motor sport engineers.

The optional seven-speed M Double Clutch Transmission with DriveLogic takes a very special route to combining the apparently conflicting values of absolute sports performance and comfort. As well as changing gear automatically, in manual mode the transmission enables ultra-fast gear changes with no interruption in the flow of power. The integrated Launch Control function ensures optimum sprinting performance off the line, producing acceleration figures that would be out of range with the manual gearbox. The M Double Clutch Transmission also offers drivers extra functions, such as selectable modes which make the BMW M3 and BMW M4 more comfortable, easier on fuel or even sportier. The extra gear over the manual gearbox allows more tightly spaced ratios – and delivers the positive effects on performance and efficiency you would expect as a result.

The material properties of carbon have allowed the engineers to follow a fundamentally new approach in the manufacture of the drive shaft. This component feeds the engine’s torque from the gearbox to the rear differential and works under extremely heavy loads – especially in high-performance vehicles. The impressive stiffness and low weight of CFRP as a material allow the drive shaft to be constructed as a single-piece unit with no centre bearing. As well as a weight saving of 40 per cent over its predecessor, this leads to a reduction in rotating masses and, in turn, to sharper responses to movements of the accelerator, combined with enhanced dynamics.

Another feature that adds fresh polish to the dynamic repertoire of the BMW M3 Sedan and BMW M4 Coupe is the Active M Differential. Unlike the manual system used by the outgoing BMW M3, here an electric actuator constantly varies the locking effect, as required. That enables better traction, the adjustability of the car is improved, and understeer coming out of corners is dialled out to impressive effect. M Dynamic Mode – a subfunction of the Dynamic Stability Control (DSC) system – quenches the thirst of enthusiastic drivers for keen dynamics. While DSC intervenes as required to counteract understeer and oversteer, M Dynamic Mode allows greater wheel slip and therefore easy drifting.

Low weight and a high level of structural rigidity are essential ingredients in ensuring the cars provide an ultra-dynamic driving experience. In the double-joint spring strut front axle alone, the use of a lightweight aluminium construction for components such as control arms, wheel carriers and axle subframes saves five kilograms over a conventional steel design. Play-free ball joints and elastomer bearings developed specially for the BMW M3 Sedan and BMW M4 Coupe ensure an optimum and direct transfer of forces both laterally and longitudinally. An aluminium stiffening plate, CFRP front strut brace and additional bolted joints between the axle subframe and the body sills all help to increase the rigidity of the front structure.

Also lighter than the construction in the outgoing BMW M3 is the new fivelink rear axle. All the control arms and wheel carriers are manufactured using forged aluminium, which reduces the unsprung masses of the wheel-locating components by around three kilograms compared with the previous model generation. The rigid connection between the rear axle subframe and the body – without the use of elastic rubber elements – is borrowed from motor sport and serves to further improve wheel location and therefore directional stability.

The development of the tyres for the cars was incorporated from the outset into the construction process for the axles. For high-performance sports cars like the BMW M3 Sedan and BMW M4 Coupe, in particular, steering feel and precision are the foremost considerations in the development of tyres for the front axle, alongside lateral stability and braking forces. At the rear axle, meanwhile, traction, lateral stability and directional stability take centre stage. For this reason, both cars will leave the factory on low-weight forged wheels with mixed-size tyres. The specially developed forged wheels make a significant contribution to the reduction in the cars’ unsprung masses and, in turn, to the optimisation of dynamic qualities and efficiency.

The electromechanical steering system used in the BMW M3 Sedan and BMW M4 Coupe is a new development from BMW M GmbH. It has been tuned specially to assist the cause of dynamic driving and offers the gifts of direct steering feeling and precise feedback. The integrated Servotronic function electronically adjusts the level of steering assistance according to the car’s speed, providing optimum steering characteristics at all speeds. The steering for the BMW M3 Sedan and BMW M4 Coupe also offers the driver three steering characteristics as standard, which can be selected at the touch of a button. COMFORT, SPORT and SPORT+ modes allow the level of steering assistance to be adapted to suit the situation at hand and the driver’s personal tastes.

The optional Adaptive M suspension likewise comes with COMFORT, SPORT and SPORT+ modes, enabling the driver to choose between a more comfortable damper setting for motorway driving, for example, a stiffer set-up for dynamic driving on country roads, and a third option that minimises wheel movements and maximises dynamic performance for use on the track.

The BMW M3 Sedan and BMW M4 Coupe come as standard with BMW M compound brakes boasting impressive feel, outstanding stopping power and high resistance to fade. Far lighter than conventional equivalents, these brakes contribute to a substantial reduction in unsprung masses and therefore help to enhance dynamic performance. Even lighter BMW M carbon ceramic brakes can also be specified as an option, their further optimised performance attributes equipping them even more effectively for track use.

 

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