Lightweight commercial vehicle cooling systems for EURO VI applications

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Stuttgart, September 2014 – The output requirements on commercial vehicle cooling systems have once again increased with the demanding limits imposed by the EURO VI exhaust emission standard. Thanks to lightweight design and cooling components with increased specific output, MAHLE has successfully adapted the cooling system to these stricter requirements without additional weight or fuel consumption. In the background, thermostats intelligently regulate the thermal cycle of the engine.

In the cost-sensitive commercial vehicle segment, transport efficiency is a significant factor in the purchasing decision. The pressure to develop efficient powertrains at reasonable cost, wherever possible without increasing weight is thus correspondingly high. The introduction of the EURO VI exhaust emission standard led, on the one hand, to more complex powertrain peripherals, and, in theory, toward increased fuel consumption. Nonetheless, fuel consumption in new EURO VI vehicles is similar or even lower than that of the EURO V variants thanks to extensive advances in drive train technology. With the cooling system for EURO VI vehicles, MAHLE has impressively demonstrated that a simultaneous increase in weight is not a must.

As one of the engine measures taken to meet the EURO VI limits, cooled exhaust gas recirculation (EGR) has become virtually universal. Its key advantage is lower specific fuel consumption combined with reduced NOX emissions. However this results in greater cooling capacity requirements, which must be compensated for without negatively affecting consumption. This is possible with a cooling system that is up to 25 percent larger than in a EURO V system, with aerodynamic optimisation. Extensive measures are required, however, to achieve this system without increasing weight. These include, on the one hand, lightweight design and, on the other hand, increased specific output of the components.

The core component of engine cooling is the radiator, which releases engine waste heat into the ambient air. In addition to the increased output, a significantly improved operational strength was also necessary. The pressure and temperature change loads rise both in intensity—for example through system pressures and pump output—and in frequency—for example through control intervention. At the same time, the target service life of the products has been raised to 1.6 million kilometres. With a significant increase in power density and lightweight design measures, greater weight associated with larger cooler surface areas was not only avoided but even overcompensated, despite stricter requirements. The cooling air ribs and coolant tubes had to be optimised for the increased output. Thin-walled, pressure-resistant, multichamber tubes were developed in order to reduce weight while increasing strength. Innovative tube penetration geometries relieve the tube-to-floor connection that defines the strength of the system.

The intercooler required only a slight increase in size due to the introduction of EURO VI, because while the use of EGR does raise boost pressure and turbocharger exit temperatures, the air ratio is reduced. The higher temperatures and pressures, combined with VTG turbochargers, also lead to significantly greater loads. Similar to the radiator, here again the power density was increased and wall thickness reduced by optimising each of the components.

Larger cooling modules also require larger fans. Greater performance requirements can be applied while reducing weight by increasing CFD-based power density and introducing FEM-based (finite element method) structural optimisation.

Finally, the EGR cooler frequently represents an additional new component that inevitably results in more weight. It was also possible to develop MAHLE’s proven, robust winglet tube technology further in this area. The pressure loss under contaminated conditions is an important parameter for the dimensioning of the radiator so that the required EGR rates for the reduction of emissions can be maintained. A further development in the winglet geometry allowed this pressure loss to be reduced by 25 per cent, making it possible to decrease the number of tubes by up to 15 per cent.

Overall, lightweight design and greater power density of all cooling components fully compensate for the anticipated weight increase of the output-enhanced cooling system. The optimised MAHLE cooling components also prevent a theoretical increase in consumption of up to two per cent in comparison with EURO V cooling systems.

For the aftermarket, MAHLE provides a broad portfolio of thermostats for commercial vehicle cooling systems. Together with the coolant temperature, they regulate the thermal cycle of the engine. Another example is the expansion elements that move a piston when the expansion material (wax) is heated. Expansion elements from MAHLE are maintenance free, durable, and available for a variety of control ranges within the temperature span of –20°C to +130°C. Depending on the degree of integration required by the vehicle manufacturer, expansion elements can already be installed in thermostat inserts, integral thermostats, as well as housing thermostats. The most effective managers in the thermal system are map-controlled thermostats: they already have an electrical heating resistor integrated in the expansion material. Consequently, they can be electrically activated and have a considerably faster effect on the engine temperature.

Both printed and digital product catalogues offer a quick overview of the Aftermarket product range in original equipment quality. To make sure that the right product is correctly installed, the repair shop can rely on a comprehensive MAHLE service portfolio. Web-based technical information and a telephone hotline leave no question unanswered. Product-specific fitting instructions, technical training, and the appropriate repair shop equipment from MAHLE all ensure a correct and professional repair. This is how—together with a dense network of service and sales partners—we are able to provide a continuous product and problem-solving chain. MAHLE—the expert solutions provider for the aftermarket.


MAHLE is the globally leading manufacturer of components and systems for the internal combustion engine and its peripherals as well as vehicle air conditioning and engine cooling. In 2014, some 64,000 employees at 140 production locations and ten major research and development centres are expected to generate sales of around EUR 10 billion.

About MAHLE Aftermarket

MAHLE Aftermarket, the business unit specialising in spare parts and service, uses the expertise from the series production of original equipment in its automotive aftermarket product range, and supplies trade, repair shop, and engine repair partners. MAHLE Aftermarket is represented at 23 locations and other sales offices worldwide, with 1,670 employees. In 2013, the business unit achieved a global sales volume of EUR 805 million.

Find out more about MAHLE Aftermarket GmbH at