DuPont™ Vespel® Polyimide Bushings Precisely Guide Connecting Rods in MAHLE’s Electrical Wastegate Actuators

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These new bushings operate virtually without wear and with minimal friction.

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The challenges placed on the guide bushing are extremely severe. In working together with DuPont, we found a special Vespel® TP grade which meets all these requirements.

MAHLE's electrical wastegate actuators control the volume of exhaust gas which is lead past the turbo charger for boost pressure control. In its current actuator series this tier-1 supplier uses bushings made from DuPont™ Vespel® TP injection moulding grade to constantly guide the associated connecting rod smoothly and precisely over the engine's service life. Unlubricated, exposed to high temperatures and aggressive substances present in engine exhaust gases, these bushings operate virtually without wear and with minimal friction.

MAHLE's electrical wastegate actuators enable an optimized interaction between engine and turbocharger, in downsized engines specifically. The connecting rod guide bushing made from Vespel® helps to achieve rapid actuating speeds and precise boost pressure control, enabling a very high responsiveness and low fuel consumption in stopped traffic. Positioned on the output side of the actuator, the bushing provides linear guidance for the lever which actuates the wastegate on the turbocharger, absorbing varying lateral forces arising from a toggle mechanism.

In the immediate vicinity of the engine, just a few centimetres away from a turbocharger which can be as hot as 1000 °C, this bushing must be able to withstand ambient temperatures of up to 140 °C. Being so close to the compressor, it is permanently exposed to vibration. It must not corrode when exposed to splashes and jets of water contaminated with dirt particules, oil, grease and salt. As Bernd van Eickels, Actuator Development Manager at MAHLE Filtersysteme GmbH explains: "The challenges placed on the guide bushing are extremely severe. In working together with DuPont, we found a special Vespel® TP grade which meets all these requirements. One particularly positive feature was that this grade, unlike other plastics we tested, has no tendency to incorporate dirt particles or chips. The bottom line is that the guide bushings ensure a virtually constant actuator force over the entire service life."

Peter Bergmann, European Transportation Market Segment Leader, DuPont™ Vespel® & DuPont™ Kalrez®, adds: "The specified Vespel® grade is part of the wide range of Vespel® TP thermoplastic injection moulding materials which are particularly suitable for mass producing components with a complex geometry. We recommended it to MAHLE because it was specifically designed for use at high temperatures and with exposure to aggressive chemicals. Optimised with various fillers, this polyimide combines good mechanical properties and excellent dimensional stability with very good friction and wear behaviour."

An electrical wastegate actuator …

… is an actuator for controlling boost pressure in modern spark-ignition engines which diverts some of the exhaust gas past the turbocharger via a bypass valve (wastegate) to ensure that the desired boost pressure is not exceeded and to limit maximum turbine speed. In the absence of this control of the exhaust gas stream, the turbocharger would spin ever faster as engine speeds rise and the throttle valve opens until an excessive boost pressure would result in knocking damage or the turbine shattering at above 230,000 to 300,000 min-1 (depending on turbocharger size) and at 1000 °C or more. Either can cause huge engine damage. With the aim of making actuation independent of intake manifold pressures (vacuum/overpressure), MAHLE was the first manufacturer to design such actuators for electrical operation, first bringing them into mass production in 2009. This design combines various advantages, such as faster pressure build-up in the event of abrupt load changes, quicker heating of the catalyst, gentler operation of the turbocharger in the cold start phase and reduced fuel consumption under partial load when no boost pressure is required.

MAHLE is a leading international development partner and supplier to the automotive industry. With its products for combustion engines and their peripherals as well as solutions for electric vehicles, the group addresses all the crucial issues related to the powertrain and air conditioning technology—from engine systems and components to filtration to thermal management. In 2015, the group generated sales of approximately EUR 11.5 billion with around 76,000 employees and is represented in 34 countries with over 170 production locations and 15 R&D-Centers.

DuPont Performance Materials (DPM) is a leading innovator of thermoplastics, elastomers, renewably-sourced polymers, high-performance parts and shapes, as well as resins that act as adhesives, sealants, and modifiers. DPM supports a globally linked network of regional application development experts who work with customers throughout the value chain to develop innovative solutions in automotive, packaging, construction, consumer goods, electrical/electronics and other industries. For additional information about DuPont Performance Materials, visit

DuPont (NYSE: DD) has been bringing world-class science and engineering to the global marketplace in the form of innovative products, materials, and services since 1802. The company believes that by collaborating with customers, governments, NGOs, and thought leaders we can help find solutions to such global challenges as providing enough healthy food for people everywhere, decreasing dependence on fossil fuels, and protecting life and the environment. For additional information about DuPont and its commitment to inclusive innovation, please visit

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Sandrine Gessier
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