Improvement of Diesel Engine Performance by Variable Valve Train System

Authors

T. Tomoda, T. Ogawa, H. Ohki, T. Kogo, Dr. K. Nakatani, E. Hashimoto, Toyota Motor Corporation, Japan;

Year

2009

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 697

Summary

In this research, the effect of variable valve timing and lift was studied to improve thermal efficiency of a diesel engine, while maintaining low engine-out emissions. At high load conditions, early closing of one intake valve to the other or early intake valve opening realizes an enhancement of actual swirl motion without increased pumping losses, and retarded intake valve closing reduces the effective compression ratio, which both result in an increase of EGR ratio and an advanced fuel injection timing. Consequently low NOx formation and an improved thermal efficiency can be achieved simultaneously. At low load conditions, heat release is small and fuel is dispersed with swirl because of the small fuel injection quantity, therefore increasing the effective compression ratio by early intake valve closing is effective to reduce HC.

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