MATERIALS: A newly-developed two-component air duct, from MAHLE of Stuttgart, Germany, connects the intercooler and throttle body of the three liter, six cylinder twin-turbo engine from BMW. Blow-molded using stiff yet elastic DuPont™Hytrel® HTR4275, the air duct fulfills its task in a particularly efficient manner due to the very low material usage of the design and despite the high pressures and flow velocity encountered in such a high-performance petrol engine. By reducing the part to just two basic components, the time required for production and assembly is significantly reduced compared to the previous version, which was used up until mid-2009, and consisted of a series of pipes and clamps. Moreover, blow-molding technology enables greater flexibility in the integration of application-specific connections, such as those required for resonators, sensors or the discharge of gases. Together, the combination of lower weight, more efficient production and assembly, and the integration of variable functionality, provides for a significant cost advantage over the earlier model, which was produced using glass-fiber reinforced nylon and elastomers.
Used on the ‘cold’ side of the engine, the innovative air duct, consisting of two Hytrel® sections measuring 300 mm and 400 mm respectively, is one of the first mono-material solutions of its kind in Germany.
Hytrel® thermoplastic polyester elastomers from DuPont provide the flexibility of rubbers, the strength of plastics, and the processibility of thermoplastics. Hytrel® HTR4275 is a specially-modified grade for use in blow-molding, with an increased melt viscosity, a hardness of 55 Shore D and a relatively high stiffness of 170MPa at 23C and 60MPa at 100C. Thus it combines good mechanical properties at high temperatures—a prerequisite for air ducts which are located under the hood and consistently exposed to internal pressure —with high elasticity across a broad temperature range. As with all Hytrel® grades, this blow-molding grade offers long-term resistance to hydrocarbons and other media typical for the automotive sector.
-Edited by Kelsey Anderson