· High torque available already at low speed

· Basis for fuel-saving downsizing concepts

Modern diesel engines with their high torque provide great driving pleasure, however, sometimes they are characteristically weak when starting the car due to the so-called "turbo lag". With the usual turbo chargers, the engine at low speed does not supply sufficient combustion air. The controlled two-stage turbo charging of diesel engines, developed by Erphi Electronic GmbH, part of Bosch Engineering GmbH, is doing away with that.

The charging system consists of two connected turbo chargers which differ in size. The smaller high-pressure charger responds already at low engine speeds and is supplemented at medium speed by the larger low-pressure charger. Once the sophisticated control software switches the smaller charger off at higher speed, the larger charger completely takes over the air compression. This strategy achieves a regular high torque curve. There is no more turbo lag, the diesel engine becomes even more powerful and economic, especially in downsizing concepts. In this type of downsizing, smaller but equally powerful engines with two-stage charging are used instead of conventional turbo-charged engines. A pilot vehicle built by Erphi has confirmed the potential of the innovative charging system. Its specific values – 82 KW output and 210 Newton meters torque per liter of piston swept volume – would have been unthinkable just a year ago.

The Bosch subsidiary Bosch Engineering GmbH specializes in the development of sophisticated systems and extraordinary niche projects. The service provider benefits from the decades of competence accumulated by the parent company in this respect. Some 600 employees design and apply individual software for engine, transmission and restraint control systems in close cooperation with the customer as well as brake control systems for low-volume models, sports cars and motor racing. The company moreover develops and applies modular functions and concepts for the drive train and systems for chassis and vehicle handling and bus systems.

Erphi Electronic GmbH as part of Bosch Engineering GmbH is an acknowledged development partner of the automotive industry in the fields drive train with focus on diesel injection systems and super-charging. The staff of the company is, on the one hand, highly specialized in their knowledge and, on the other hand, are providing over a broad general experience as is required, for example, for the development of a charging system. This demands an expert knowledge of the thermo dynamics of an engine as well as know-how in simulation and systems integration.

Bosch Engineering, in conjunction with cooperation partners, realizes projects from the planning stage through mechanical adaptation and testing up to the point of certification. The company, furthermore, offers consulting services for project management, development and test processes.

PI4752 - March 2005