Another generation of the 3-Series, BMW’s successful sports sedan, will soon have its world premiere but before that event, it has already been subjected to a ‘lifetime of hard work’. This is part of the final phase of an extensive programme of testing that every new BMW model must go through as part of its pre-production development. Here, the full range of stresses and strains a car will encounter over many years of everyday driving are reproduced in concentrated form. From extended periods driving flat out to endless stop-start traffic, sub-zero temperatures to searing heat, twisty country roads and high-speed autobahns to pothole-infested tracks, ice and snow to gravel and desert sand – the prototypes sent through the test programme

The tests the engineers have created cover just about everything their production equivalents will come across in everyday life. Only they have been done at a much higher level of intensity and engineers on board to record in detail every response to the various weather and road conditions and countless other influencing factors. In short, the testers ensure there are no circumstances – however unusual – which might compromise driving pleasure in the car that customers will buy in future.

One test site is Death Valley in the US state of Nevada. Here, it is not only the automatic climate control system of the new BMW that can expect a taxing work-out. The multi-day heat tests see the cars fried repeatedly in the sun for several hours, then cooled and thoroughly checked over. Everything has to work; there can be no squeaks or creaks – even when the temperature tops 50 degrees C. in the shade outside the car and 60 degrees inside, and the interior is then cooled again as quickly as possible. 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.

The heat certainly gives the electronics a hard time but that’s not all. 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 tyre pressure indicator – are tested extensively in the shadows of the huge forest of electricity pylons.

At the same time, another development team is putting engines, transmissions and brakes through their paces. They are even given police protection for their runs up and down the 4,000-metre-high Mount Whitney. While law enforcement secures the test route at the top and bottom of the climb, the testers race the prototypes up the snaking roads and back down – accelerating hard and braking suddenly to a standstill with crushing frequency.

At the other extreme is the BMW Group’s winter testing centre in Sweden not far from the Arctic Circle. This location offers the perfect conditions for a testing programme that eclipses anything day-to-day driving in central Europe, North America or Asia. Besides testing imperviousness to extreme cold, it also provides the stage for the new model’s chassis controls systems to show off their full range of abilities.

The expanses of ice on a frozen lake are where the engineers fine-tune the DSC stability system and its many functions. Indeed, on this glassy surface, you don’t need to drive quickly to provoke the control systems into action and therefore analyse their responses. Here again, cutting-edge technology helps to identify and consistently eliminate weak points. If an inconsistency crops up during testing, the engineer presses a button on the small testing screen next to the transmission’s selector lever to log it for subsequent analysis. For the problem to be solved, the relevant situation has to be reproduced exactly. The vehicle data is stored on a large hard drive in the car’s boot, pored over every day and reworked.

When prototypes start to be driven in the world outside the BMW’s tightly protected facilities, great effort has to be made to prevent curious onlookers from recording too many details of the new model. So for now, every prototype of the new 3-Series is clad in camouflage that consists of black-and-white wrap as well as plastic cladding (which distorts the lines and surfaces of the car). The lighting units, sections of the window surfaces and, of course, the brand badges also get a layer of camouflage.

A camouflaged prototype of the next 3-Series being driven in real-world conditions in Las Vegas.

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. Experience over many years of testing has shown that lack of discipline in this area can result in pictures of the displays and controls appearing in magazines and websites.

Optimisation of aerodynamics and passive safety also takes place largely behind closed doors. At the BMW Group’s Aerodynamic Test Centre, full-size vehicle models, prototypes and production vehicles are tested using precise reproduction of real-life airflow conditions on the road. At the centre’s wind tunnel, the new BMW 3 Series Sedan has been given the detailed touches required to bring its drag coefficient down to 0.23. Every variant is checked to establish how the wheel design and tyre size, for instance, impact on the aerodynamic characteristics of the new model and therefore its fuel consumption and emissions.

Differences in the stipulations for occupant protection applicable in different continents mean that several pre-production examples of a new model have to be deformed in a controlled process as part of crash testing at BMW’s Safety Centre. This will ensure that the new 3-Series meets the full set of safety requirements to score top marks in all the relevant crash tests worldwide.

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[Chips Yap]

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