Auto Channel

Page 1: Introduction
Page 2: Concept
Page 3: Design
Page 4: Power Units
Page 5: Automatic Trans.
Page 6: Suspension
Page 7: All Wheel Drive
Page 8: Body & Safety
Page 9: Light Concept
Page 10: Features/Equipment
Page 11: Production
Page 12: History

Bodyshell and Safety

Stable but Light

• Superior balance of axle loads

• Optimised weight through an intelligent mix of materials

• All-round occupant safety with electronic management

Both the dynamic performance and the driving safety of a new car depend to a great extent on the design and construction of its body. And in developing the BMW 3 Series Coupé, BMW’s body specialists have succeeded in optimising both performance and safety through their work. The result is a virtually perfect combination of supreme agility and maximum solidity, innovative materials and the most advanced production technology serving to optimise the stability of the body without putting on any extra weight.

Safety and restraint systems activated electronically according to the specific requirements in each case ensure complete occupant protection all round. A further significant point is that the new BMW 3 Series Coupé offers even more generous space inside the passenger compartment. And luggage compartment capacity of 440 litres/15.4 cubic feet (430 litres/15.1 cu ft in the BMW 335i Coupé) again makes BMW’s new two-door model the absolute leader in its segment also in terms of grand touring qualities.

Sleek and dynamic, resting powerfully on the road – this is the convincing look of the new BMW 3 Series Coupé at very first sight. And indeed, the dimensions of the car confirm this significant impression, the 3 Series Coupé measuring 4.59 metres or 180.7´´ in length, 1.78 metres or 70.1´´ in width and 1.38 metres or 54.3´´ in height, making it, in particular, longer and lower than the BMW 3 Series Saloon.

A further significant improvement is the reduction in overall weight by 10 kilos or 22 lb ensured, inter alia, by the front side panels made of an innovative thermoplastic material 50 per cent lighter than side panels made of steel.

This reduction in weight at the front has a particularly positive effect on the car’s driving qualities. The axle load distribution of the new Coupé, in turn, is virtually ideal at almost 50 : 50, again offering all the qualities required for maximum agility.

Plastic side panels: light and robust.

The new thermoplastic material also offers enhanced options and flexibility in terms of design. The first point is that this material is easier to mould and finish in new forms than steel – an advantage offering the designer new freedom in creating the looks of a car or component. The second factor is a benefit which has already given the customer major advantages in developing reversible bumpers, that is the fact that plastic side panels are largely resistant to minor bumps, with the component involved returning to its original shape in the event of minor deformation. Collisions at low speeds, for example when manoeuvring in a car park, therefore remain almost totally harmless, leaving behind virtually no lasting traces.

In production the changeover from steel to a high-tech synthetic material has no effects, since the plastic side panels can now be integrated online in the painting process, that is directly without having to go through a special assembly phase. And given their significant resistance to thermal deformation as well as optimised elongation and moisture uptake, the plastic side panels, when painted, also look exactly the same as conventional steel components.

Innovative reinforcement of the B-pillar.

Like the low weight of the car, the high torsional stiffness of the bodyshell is an essential prerequisite guaranteeing the truly thrilling agility of the new BMW 3 Series Coupé. In the event of a collision, the use of high-strength steel on the large carriers and support bars, together with the exactly defined arrangement of crumple zones, ensures appropriate transmission and, respectively, highly efficient uptake of impact forces.

A particularly impressive example of the outstanding achievements in the process of development and construction is the reinforcement of the B-pillar for the first time featuring one complete tubular structure in the new BMW 3 Series Coupé. This reinforcement tube is manufactured out of ultra-high-strength steel in the thermal formation process, and is heat-treated before leaving the mould. Reflecting specific loads and forces at various points, the reinforcement tube is furthermore varied in design and thickness, thus guaranteeing maximum safety in conjunction with the crashbox tailored to impact loads.

Precise uptake of impact energy in the event of a collision.

The choice of materials and the arrangement of components also serve to ensure maximum crash safety on other parts of the body. This takes into account the different characteristics of various types of steel and other materials, the new BMW 3 Series Coupé naturally making optimum use of space available for deformation in order to avoid even the slightest impairment of the passenger cell.

In a head-on collision dynamic deformation zones in front of the body keep impact energy away from the bulkhead area and, accordingly, from the footwells. In the event of a collision from the side, in turn, the specially designed floor assembly transfers forces to the opposite side of the car in a carefully balanced, controlled process. The support beam for the bulkhead, finally, is made of innovative multi-phase steel offering extremely high strength and stability even with thin walls.

The overall combination of the car’s doors, reinforced B-pillars, seat structure and instrument panel beneath the A-pillars gives the entire side structure of the car maximum stability. The consequences of a collision from behind are minimised by longitudinal carrier bars, a wide range of reinforcement members, as well as the strong and highly resistant structure of the luggage compartment floor, rear panels, and side walls.

Stable pillars and crossbars protect the passenger compartment also in a rollover, the interaction of all deformation zones and carriers having been carefully analysed in the early stage of development of the new
BMW 3 Series Coupé both in virtual simulations and in actual crash tests. One point obviously considered with particular care in this context is the need to minimise repairs after a minor collision.

Precise management of safety elements.

The objective of BMW’s safety engineers was to maintain the passenger cell as a safe survival area even in a severe collision. Accordingly, various interacting, centrally controlled restraint and safety systems ensure individual occupant safety in the passenger cell, the frontal, hip, thorax, and curtain head airbags, belt latch tensioners and belt force limiters all being activated by sensor-controlled safety electronics as a function of the type and severity of a collision.

Sensors in the middle of the car, in the B-pillars and in the doors ensure safe detection of accident conditions at an early point in time. Using data then provided by such sensors, the car’s safety electronics check which components will offer the occupants optimum safety and protection, thus activating only those restraint and safety systems actually required.

The driver and front passenger are protected both by frontal airbags and by hip/thorax airbags housed in the seat backrests and activated in two stages, depending on requirements. The curtain head airbag opens up when required at the side out of the roof lining along the window areas between the A- and C-pillars. Providing ample coverage, it protects the car’s occupants at both the front and rear. And to reduce the risk of leg injury in a head-on collision, the footrest on the driver’s side deforms in a controlled, previously defined process.

Maximum safety on all seats.

The belt systems in the new BMW 3 Series Coupé combine superior comfort with ideal geometry. Perfect ergonomics, in turn, is guaranteed inter alia by the belt pivot point optimised for all seating positions and occupant sizes, avoiding the risk of false belt height adjustment.

The belt fastening point on the frame of the seat also helps to maximise belt restraint, with the belt resting perfectly around the occupant’s hips also when adjusting the seat for height. The belt latch tensioner makes sure that the belt rests firmly on the occupant’s body when an impact actually occurs, while the belt force limiter avoids the occurrence of peak loads and forces. Both of these safety features are naturally standard in the new BMW 3 Series Coupé also on the rear seats.

Safety electronics for efficient rescue activities after a collision.

The car’s safety electronics perform an important function also after a collision, not least by facilitating the immediate start of rescue activities: The safety electronics control unit automatically switches on the hazard warning flashers and interior illumination, opens the central locking and switches off the alternator – and to avoid a short circuit, the electronic control even separates the safety battery terminal, in which case the hazard warning flashers and interior lights as well as the emergency telephone function are supplied with power by a separate on-board power connection. A further important step is to deactivate the fuel pump preventing fuel from escaping out of the tank.

A wide range of tests has been carried out to verify both the behaviour of the car’s body in a collision and the function of all safety elements. From computer simulations all the way to various kinds of crash tests, BMW’s engineers have used all options to determine the optimum configuration and range of safety features. Ultimately, therefore, through its robust bodyshell and wide range of active and passive safety elements, the new BMW 3 Series Coupé has everything required for achieving best marks in all crash tests relevant the world over.