You are here

Charge air duct made from high-temperature polyamide for BMW turbo engine

News International-French

14 Oct 2016

MANN+HUMMEL has manufactured pipes between the turbocharger and the charge air cooler for the 2.0-liter four-cylinder turbo engine of the BMW Group by blow molding with the BASF high-temperature polyamide Ultramid Endure D5G3 BM.

Charge air duct made from high-temperature polyamide for BMW turbo engine

The turbocharger with integrated charge air cooler is used in numerous vehicles, e.g. in the BMW 4, 5 and 7 series as well as in the X3, X4 and X5 models of the BMW Group.

With Ultramid Endure D5G3 BM (BM = blow molding), charge air ducts can be efficiently manufactured by blow molding. The BASF polyamide 66 with 15% glass fibers has a high heat-aging resistance, can be processed easily and shows extraordinary acoustic properties. It is temperature resistant up to 220°C at continuous use, with possible peak temperature loads of up to 240°C. The blow molding type supplements the Ultramid Endure portfolio for injection molding, which has been successfully established on the market since 2010. Like the injection molding grades, Ultramid Endure BM obtains its extraordinary heat stabilization through a well-established technology, which suppresses the oxidative attack by atmospheric oxygen. The protection is not limited to the surface, but pervades the material as a whole.

The tailor-made properties of Ultramid Endure BM yield numerous benefits for molders and car manufacturers: favorable system costs due to lower processing temperatures, shorter cycle times and reduced energy consumption are combined with a high technical performance, which leads to durable and powerful engines. Thus Ultramid Endure BM shows a better cost-performance ratio than, for example, polyphenylene sulfide (PPS) or aluminum, from which conventional charge air ducts are manufactured. Within the charge air duct, the charge air pipe guides compressed hot air from the turbocharger into the integrated charge air cooler. Here, pressures higher than 2.5 bar can occur.

With Ultramid Endure BM, processors save assembly costs and car manufacturers component weight. The high-temperature polyamide can replace pipes made from rolled aluminum sheets. As the tubular sections can no longer be round in the small installation spaces, metal pipes must be manufactured in expensive hydroforming. Pipes made from the BASF material can also be blow-molded into different pipe forms. The interior surface remains smooth here, which leads to reduced air resistance compared to other plastics.

High melt stability, good swelling, simple weldingFor blow molding, the plastic is also required to have a special melt strength and favorable swelling properties. A high melt stability counteracts the length variation of the pipe. The smaller the variation in length, the better suited the product is for suction blow molding. The same applies to pipe swelling: a certain amount of swelling is required, yet too much swelling causes problems when inserting the pipe into the mold. What is more, materials that swell severely tend to expand, which leads to a frusto-conical shape of the pipe. Ultramid Endure BM, however, remains largely cylindrical. As it also responds well to changes in the processing parameters, corrections can be made easily during the production process.

Ultramid Endure BM can be welded particularly well with PA66 components using e.g. infrared welding. Components under the hood are often connected with one another by welding. Due to the reduced glass fiber content, the weld line can represent a weak spot, particularly after aging. The innovative stabilization mechanism in Ultramid Endure BM not only protects the polymer itself, but also strengthens this potential weak spot. The weld lines also withstand continuous operation at high temperatures very well. Even after 1,000 hours at 220°C, there is no sign of any cracking at the joint. The weld line strength remains just as high.

Good acoustic propertiesAcoustics have become a relevant brand factor and are extremely important in the automotive industry. New engine concepts and increasing demands from customers and legislative authorities call for materials that are acoustically advantageous. Ultramid Endure BM shows excellent damping behavior and is therefore suitable for demanding acoustic requirements. For example, Ultramid Endure can be used to reduce the production of disturbing airborne noise emitted from the vibrating component surface directly at the source. Depending on the temperature and the level of humidity, the material has damping values which are up to ten times better compared with polyphenylene sulfide.