Direct Injection for Future SI-Engines - Stand Alone Combustion Layout or Integrated Part of Multi-Function Fuel/Air Management Approach?

In the future generation of low consumption SI-engine layouts, it has become necessary to reduce costs as well as the complexity level and, increase the system reliability by the latter. To avoid driving the GDI-system in the critical, very lean stratified operation mode without losing the fuel consumption benefit, a solution is suggested, which combines a fully variable valve control system with a low level, robust GDI combustion layout.

The first part of the present paper presents the latest development in the field of high precision multi-hole GDI injector spray nozzles. The basic aspects of mixture preparation with multi-hole gasoline atomizers are highlighted and their spray behavior compared to that of the current swirl atomizer nozzle.

The second part of the paper presents primary optimization of a largely homogeneous GDI combustion layout combined with a fully variable valve timing control system including complete cylinder de-activation. Particular attention is paid to the new enhancement offered by the GDI mixture preparation in the field of flexibility of transient control of rotating cylinder de/re-activation. Experimental results are obtained on a single cylinder test engine.