MAHLE is a pioneer in creating realistic testing and measurement conditions for vehicle air conditioning and engine cooling beyond road trials.
The current climate wind tunnels in Stuttgart and Troy, Michigan can be cooled down to -30 degrees and heated up to +50 degrees.
And the engineers there can whip up hurricanes with wind speeds of around 130 kilometers per hour.
In 1937, the first wind tunnel of the German automotive industry was built in Stuttgart-Feuerbach. The builder was Behr, a radiator specialist who has belonged to MAHLE for many years. Even back then, it was a brilliant idea to bring the road into the lab to test components under repeatable conditions.
The news spread quickly and Mercedes – practically a neighbor – became one of the first customers. And what better first test object than the legendary Silver Arrow? Its radiator grille was made more aerodynamic by the development teams in the wind tunnel. Today's test setup makes us smile, but at the time it was state-of-the-art: a huge wind machine – similar to a turbine – was bolted onto metal rails. The Silver Arrows, with their V12 four-stroke Otto engines, were placed on a wooden construction that resembled a lift.
The optimizations in the wind tunnel seem to have paid off: The Silver Arrow W154 was the most successful model to date, winning three out of five Grand Prix races and frequently leaving the competition behind in subsequent years.
As a pioneer, MAHLE has continuously developed the climate wind tunnel over the following years and decades. In 2000, it was completely modernized as part of a new construction and is now a high-tech facility that sets standards for technological progress. As an internationally leading original equipment manufacturer for vehicle air conditioning and engine cooling, MAHLE not only invests heavily in the research and development of its own products but also offers customers comprehensive development services under realistic road conditions.
Testing components on the road is a complex task. Because anyone who produces for the global market today must test their products under all climatic conditions – extreme heat and cold, high and low humidity, solar radiation, wind. The climate wind tunnel covers all this: temperatures from -30 to +50 degrees, humidity up to 95 percent, sun position-simulating lamps with enormous heat output, and a 315-kilowatt fan that generates winds of up to 130 kilometers per hour. In short: Global weather events can be reproduced in one place, without driving a kilometer on the road. That's why there's also a dynamometer for passenger cars, vans, or trucks, which can simulate almost realistic road drives of all types of drive systems.
The technological shift towards alternative drives is also noticeable in the climate wind tunnels. Because today, every second test vehicle has a high-voltage component. This shows that the tuning, optimization, and efficiency enhancement of all circuits of electric vehicles are gaining in importance.
This applies especially, or even primarily, to the charging of electric cars. Fast charging with up to 350 kilowatts puts stress on the Li-ion battery and heats it up considerably, particularly when the electric vehicle is sitting in intense heat under the sun. To maintain the longest possible lifespan, the battery must always be kept within the optimal temperature window of between 15 and a maximum of 40 degrees Celsius. The vehicle's thermal management system, which is a complex interplay of cooling and air conditioning systems, ensures that the sensitive battery does not overheat and risk damage. At the same time, the temperature in the driver's cabin must not become too high.
To realistically test these conditions and calibrate the thermal management to handle them, MAHLE has now equipped its climate wind tunnel in Stuttgart with a direct current fast-charging system. The testing engineers can charge electric vehicles there with up to 350 kilowatts in under five minutes for a 100 kilometer range - under all climate conditions, including extreme heat. The measurement data provide insights into the effects on the Li-ion battery and interior comfort, thus providing important findings for vehicle development.
The first fully air-conditioned wind tunnel in Europe for the development of vehicle heating and cooling systems, ranging from passenger cars to touring buses, was established. It remained in regular operation for more than 40 years until it was replaced by the KWK 2000.
The blower tunnel from 1937 was replaced by a new facility, now allowing continuous speeds of up to 220 km/h. In parallel, a third wind tunnel was put into operation, which could reach temperatures up to +50°C, regulate air humidity, and simulate solar radiation.
Construction of the new large climate wind tunnel was commissioned, set to establish a new standard in the industry. For the first time, the KWK offered the ability to simulate any solar radiation from all directions, including the investigation of transient effects in the event of sudden shading by a cloud or while driving through a tunnel.
In the spring, the earthworks for the KWK 2000 began.
The KWK 2000 was completed on schedule and put into operation. The noise level in the measurement chamber was 20 dB below that of Wind Tunnel 1, and thus actually below the specified 70 dB(A) at 50 km/h. This opened up the possibility of conducting acoustic evaluations in the vehicle interior within a climate wind tunnel.
In Troy, New York, a sister wind tunnel was ceremoniously opened after 21 months of construction. The KWK in the USA largely mirrors the technical capabilities of the KWK in Stuttgart; it is just larger and can also handle higher braking loads.