Peter Schmieg
Application Development
Engineer
DSM Engineering Plastics
Evansville, Ind.

Edited by Jean M. Hoffman

Turbocharger inlet elbows made from polyamide 46 can be molded in a single shell or as a two-piece welded design. They bolt directly to the turbocharger side thanks to the resin's resistance to high temperatures.

Turbocharging makes it possible to use smaller engines to get a given amount of power output. This makes fuel combustion more efficient and puts less unburned fuel in the exhaust system. Turbocharged diesels in passenger vehicles have gained ground in European markets and are expanding into other regions of the world.

However, the high temperatures inherent in turbocharging and the ever-smaller engine compartments bring new challenges for materials used in these systems. At the same time, turbocharger technology is evolving. Ongoing efforts aim to squeeze more performance and bigger environmental benefits out of turbocharged engines.

For a fatigue life of 1 million cycles, Stanyl PA46 can withstand 50 to 100% more stress.

The introduction of variable-turbine geometry (VTG) technology is one example. Here, guide vanes in front of the turbine wheel regulate turbine output by changing the inflow angle and speed at the turbine wheel inlet. This helps maintain a high level of efficiency over a broad engine operating range, from acceleration to high-speed cruising. The vanes are activated through a simple on/off actuator or alternatively by a completely variable system with actuation through a combination of gears, a dc motor, engine control unit (ECU), and sensors.

Turbosystems with VTG technology are candidates for high-performance engineering plastics such as polyamide 46 (PA46). Polyamides have excellent high-temperature resistance. They retain mechanical properties (stiffness, fatigue resistance, and wear and friction properties) while operating at excess of 200°C (390°F). This makes them useful for turbosystem air-inlet elbows, VTG gears, hot charge air ducts, and charge air cooler end caps. Further, they offer processing advantages because of superior flow and moldability.

PA46 TAKES ON ALUMINUM

Polyamide 46 has been widely used for charged air cooler end tanks and can cost 30% less than conventional end tanks made from aluminum.

Stanyl PA46, for example, has been widely used for charged air cooler end tanks. Cost savings as high as 30% are possible over conventional end tanks made from aluminum. Additionally, the PA46 drops end-tank weight by 20 to 30% and has a higher strength-to-weight performance than aluminum and other competing thermoplastics.

The polyamide end caps can be crimped on to the end tank. This saves production time and costs associated with welding on aluminum end caps. Additionally, the inherently easy flowing Stanyl PA46 also lets molders use less injection pressure and a single gate when molding large lengths. This helps make the end tanks flatter and less prone to warp. And it reduces the risk the tanks will leak during service. Injection molding also lets designers easily add brackets for attaching the end caps to the vehicle body.

AIR DUCTS AND ELBOWS

The air duct from the turbo compressor side to the inlet side of the charged air coolers delivers compressed air to the inlet side of the intercoolers at a temperature as high as 200°C with a pressure of up to 3 bars. Conventional turbo systems use aluminum air ducts that are either cast or hydro-formed. Silicone rubber with textile inlays is another option. But air ducts made from these materials are expensive and don't easily integrate brackets or sensors.