The new generation BMW 3 Series is entering the final phase of an extensive program of testing. The vehicle has been exposed to a wide range of conditions, including extended periods driving flat out, endless stop-start traffic, sub-zero temperatures and searing heat, twisty country roads and driving on high-speed autobahns, as well as on tracks covered in potholes, ice, snow, gravel and sand.
At Death Valley in Las Vegas, Nevada, the sedan’s climate control system underwent extensive evaluation. Meanwhile the multi-day heat tests saw the car fried in the sun for several hours, then cooled and thoroughly checked over.
The electromagnetic rays emitted by the hydroelectric plant at the Hoover Dam represent the ultimate test of strength for the functional reliability of the electronic systems on board the new 3 Series. This is why all the car’s functions – from the digital instrument cluster to the tire pressure indicator – were tested in the shadows of the huge forest of electricity pylons on the banks of Lake Mead.
At the same time, another development team put the engines, transmissions and brakes through their paces up and down the 4,000m-high Mount Whitney. With police protection, the test route was secured at the top and bottom of the climb.
Test drivers hustled the prototypes time and again up the snaking roads and back down – accelerating hard and braking suddenly to a standstill. The bone-dry desert roads of Death Valley and beyond also provide an ideal place to find out how effective the cars’ flaps, doors, bonnets and lids are at keeping out dust.
Arjeplog in Sweden provides the perfect conditions for a testing program, which exceed any found in day-to-day driving in Central Europe, North America or Asia. The closed-off expanses of ice at Lake Kakel and the ‘Mellanström-Runde’ – one of the most popular test routes around Arjeplog – are ideally suited for fine-tuning the DSC stability system and its myriad functions. Here the link between DSC and the xDrive all-wheel-drive system and the interplay with the 3 Series’s M Sport differential were refined down to the last detail.
Dynamics were also tested at the company’s proving ground in Aschheim, a few miles northeast of BMW’s development center in Munich, as well as at BMW Group’s test facility in Miramas, Southern France. The 30-year old facility houses a long asphalt oval, freeway ‘ring’ for high-speed testing, slalom, and twisty and spherical tracks, plus several handling courses and circuits with surfaces of every kind. A detailed analysis and optimization of the 3 Series’s acceleration, steering and braking responses was also carried out here.
Precise tuning of all powertrain and chassis systems was carried out at the Nürburgring.
If any inconsistencies are found during testing, the engineer can simply press a button on the test screen next to the transmission’s selector lever to log it for subsequent analysis. Vehicle data is stored on a large hard drive in the car’s boot.
In the basement of BMW’s Research and Innovation Centre (FIZ) in Munich, pre-production vehicles are kitted out with a made-to-measure, patterned camouflage. Applying the black-and-white wrap requires an expert hand and takes a whole working day to complete. Then comes the plastic cladding, which distorts the lines and surfaces of the car. The light units, sections of the window surfaces and, of course, the brand badges also get a layer of sticky camouflage. The interior needs to be hidden from sight as well. To this end, the cockpit is ‘curtained off’ with black matting, which the test engineers partially remove at the start of testing and then painstakingly replace at every pause in proceedings – so that no prying eyes can spot or even get a photograph of the displays and controls.
Simulation was also a key development tool. At the initial, purely digital stage of development, more than 12,000 maneuvers were replicated in order to fine tune the car’s dynamics. Then development mules were constructed consisting of just a body and chassis and evaluated on a kinematics and compliance rig. A variety of road surfaces and types can be reproduced on this test rig, from cobblestones to the Nürburgring, enabling assessment of the rigidity of the body structure or the susceptibility to vibrations of axle constructions.
Optimization of the 3 Series’s aerodynamics and passive safety also took place largely behind closed doors at BMW Group’s Aerodynamic Test Centre in Munich. The car was fine tuned inside the wind tunnel to achieve a drag coefficient of just 0.23. The introduction of the WLTP test procedure has meant all available wheel variants must also be put through an aerodynamics test. Every variant is checked to establish how the wheel design and tire size impact on the aerodynamic characteristics of the car.
Due to the differences in vehicle safety regulations worldwide, several mules had to be crash tested.