- Published in Features.
Test engineers have the job of taking the latest vehicles to all corners of the world to see how they cope in environmental and climatic extremes, be that the intense heat of Death Valley in the US or the icy cold of northern Sweden. But logistics make such trips difficult and climate variations mean repeatability is difficult to achieve.
OEMs could never do away with real-world testing altogether, but conducting more work in the laboratory speeds up vehicle development – which is why BMW has invested more than €130 million in its new test facilities in Munich. The 14,480m2 energy and environmental test centre allows engineers to assess vehicles in all manner of temperatures and conditions, including wind, rain, snow and ice.
“It’s much quicker and more accurate than testing on the road,” says Sven Klussmann, manager of the test centre. “We can simulate 50 different drive cycles and conduct up to 20 tests a day, much more than is possible out on the road.”
The facilities include five test cells: thermal wind tunnel, climatic wind tunnel, environmental wind tunnel, altitude test chamber and cold test chamber.
“The different areas allow us to test vehicles in environments that range in temperature from -30°C to 55°C, humidity from 5%-95%, and altitudes from 200m below sea level to more than 4,200m above,” says Klussmann.
Thus the centre can simulate locations such as Colorado’s Rocky Mountains and the low-lying Miramas area of southern France to assess the relationship between powertrain efficiency, emissions levels and altitude. An altitude of 4,200m above sea level equates to 620mbar of air pressure, for example, which has a direct, negative impact on CO2 emissions behaviour.
The centre allows BMW’s test engineers to work on specific drive profiles and repeat them without fear of the conditions changing. “On the road, the conditions can change depending on whether you’re testing in the morning or the evening, giving a big range of measurements that you have no control over,” says Klussmann.
One test in the thermal wind tunnel simulates a 100km drive through Miramas while towing a trailer. The profile dictates that motorway speeds should not exceed 90km/h, while on the cross-country section speeds should be 60-80km/h with some parts set at full throttle. The uphill section has a maximum speed of 60km/h, with 40km/h in corners, and includes areas of maximum acceleration.
“Thermally conditioned air is used to simulate airflow around and through the car in the wind tunnel,” says Klussmann.
It would not be possible to conduct this type of test on the road because there would be too many variants, such as changing weather conditions and other vehicles impeding the analysis. Within the confines of the test centre, however, the engineers can gain precise measurements as the test can be done repeatedly and under identical scenarios.
OEMs have used such test centres for a number of years but, as technologies have developed, the scope and accuracy of the assessments have improved. Analysing the de-icing of windscreens in the cold test chamber is one example of how the technology has evolved.