The Gasoline Engine with Direct Injection and Direct Start – Potentialities and Limitations

Authors

Dipl.-Ing. J. Gerhardt, Dr.-Ing. W. Kassner, Dipl.-Ing. A. C. Kulzer, Dr.-Ing. U. Sieber, Robert Bosch GmbH, Stuttgart

Year

2003

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 539

Summary

The Otto engine with electronically controlled direct injection (DI) has been in production since the middle of the nineteen nineties. However, the improvement of fuel economy has been less than was predicted in the first estimations of DI engine development. This lies not only in that the potential of DI engines is not yet completely exhausted, but also that PFI engines have been improving simultaneously. Additional measures for improved fuel economy have to be explored in order to fulfil the ACEA goals for 2008. The current DI development is focusing on further improvement of combustion processes (e.g. spray-guided combustion) and the combination of several external measures to extend fuel economy, for example engine downsizing and unthrottled engine operation. This paper presents an unconventional approach for further improving the fuel economy of DI engines: namely engine starting using only fuel injection and ignition, without use of external energy, called “DI direct-start”. The present development goal for DI direct-start is a comfortable start-stop vehicle operation. The combustion-independent DI direct-start function is described in detail and the results from a 2-year study at Bosch are presented. The potential of DI direct-start for improving fuel economy and emissions is explored. Possible operating scenarios, such as start-stop operation, are then described.

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