Exhaust gas turbochargers from Bosch Mahle Turbo Systems

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Dual-stage turbocharging of the downsizing technology demonstrator to illustrate an excellent transient behavior and outstanding specific engine output at the same time.

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Turbocharger for downsizing gasoline engines to reduce fuel consumption.

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The electrical wastegate actuator improves engagement by avoiding the so-called turbo lag. In addition the fuel consumption is reduced because the exhaust gas counter pressure is kept as low as possible.

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For gasoline engines, a turbocharger with fixed turbine geometry and wastegate has been developed for a power range of 65 to 100 kW.

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Stuttgart/Germany, September 2009—Exhaust gas turbochargers are a key technology in automakers’ efforts to reduce the fuel consumption of internal-combustion engines and to meet emission standards. Only a year after the company’s founding, Bosch Mahle Turbo Systems now offers two validated turbocharger models for diesel and gasoline engines, both of which have successfully completed initial customer tests. Start of series production is planned for 2011.

For gasoline engines, a turbocharger with fixed turbine geometry and wastegate has been developed for a power range of 65 to 100 kW, whereas for diesel applications a turbocharger with variable turbine geometry has been developed for a power range of 90 to 120 kW. These products feature technologically advanced components in order to satisfy future demands on the engine as regards precision of control, emissions behavior, and quality. Such components include an electric wastegate actuator, highly durable, precision-milled (not cast) compressor wheels, and especially robust and stable rotor bearings suitable for start-stop operation and fuel-efficient motor oils. What is more, by using special coatings, the compressor can be prepared for the higher wear incurred in low-pressure exhaust-gas recirculation. Bosch Mahle Turbo Systems has already laid the groundwork in its current development activities for a rapid extension of its product portfolio.

With the very first of these products, the company has set its sights on two immensely important and high-volume market segments. The first of these segments is gasoline engines, for which the strong current trend to downsizing opens up clear growth potential for turbocharging in the power range mentioned above. Through downsizing, market-standard gasoline engines with port-fuel injection ranging in displacement from 1.5 to 2.5 liters are replaced by highly fuel-efficient engines featuring the same performance but limiting themselves to a displacement of less than 1.5 liters. Lower fuel consumption of downsized engines is mainly achieved by a general load shift to higher load factors resulting in engine operating modes with higher efficiency. But only turbocharging – in combination with gasoline direct injection – makes downsizing really acceptable to customers since only turbocharging can allow the engine to achieve the original performance of the larger naturally aspirated engine with port-fuel injection.

The second important, high-volume market segment is the diesel engine, which we can hardly imagine today without turbocharging. Turbocharging is not only responsible for the diesel’s increase in torque and overall performance, but is also indispensable for its ability to meet emission standards. Furthermore, downsizing concepts are also and increasingly being developed for diesel engines.

In these targeted market segments, Bosch Mahle Turbo Systems puts its faith in outstanding product qualities: spontaneous build-up of boost pressure in acceleration phases typical for today’s driving, resulting from the rotor’s low moment of mass inertia and from the low friction of its bearings. Excellent transient performance has been achieved together with a robust design. Thus, high-efficiency turbine and compressor wheels with closed and contoured back plates as well as twin shaft sealing rings for reduced blow-by enable the new turbochargers to withstand the severe demands of high-load engine performance and ensure a long service life. Completely precision-milled compressor wheels, whose symmetrical, evenly balanced geometry effectively diminishes vibration and related noise of the compressor are key for quiet turbocharger operation. The high temperatures generated by turbocharged engines generally, but especially by the super-turbocharged engines of the future, also put a strain on the turbocharger itself. However, the products of Bosch Mahle Turbo Systems have been optimized in this regard as well.

Start of production from 2011
Over the past few months, considerable investments exceeding ten million euros have been made. This investment was necessary for the build-up of Bosch Mahle’s engineering site in Stuttgart and its planned manufacturing sites in Blaichach/Immenstadt (Germany) and in St.Michael (Austria). Following a groundbreaking ceremony in September 2008, the St. Michael site already boasts a completely new production facility with roughly 100,000 square feet of usable floor space. Essential plant equipment is already being installed to allow pre-series production of turbochargers to begin as early as the beginning of 2010. These products will be manufactured by series production equipment. Series production is slated to be ramped up from 2011, with an initial annual capacity set at up to 1.5 million turbochargers.

Bosch Mahle Turbo Systems is a joint venture of MAHLE and Robert Bosch GmbH, with both companies holding 50 percent of the share capital. The company was set up on June 2, 2008, and currently employs some 130 associates.