**4. Conclusion**

The automotive market, throughout the last few years, is subject to conspicuous changes in the scope of clients' preferences. The sales of diesel engine cars gradually grow. Compared to the engine with spark-ignition, the diesel engine has a higher efficiency, lower fuel consumption and longer operation life. A diesel engine is much more easily adaptable to supercharging, which enables obtaining significant power gain without changing the stroke, displacement volume or engine speed. In a diesel engine that works with higher air-to-fuel ratio, the combustion is more efficient with lower carbon and hydrocarbons content in the exhaust gases. From the end user's point of view, the most important effect is the operation cost economy as the diesel engines consume less fuel. To meet the present and future demands, the automotive manufacturers work over new designs and technologies in diesel engines and offer a wide range of car models fitted with such drive units. The development of high-speed diesel engines is explicitly guided by the direct injection strategy and growth of the fuel injection pressure, exceeding 200 MPa. Such tendency forced intensive research and development works over new generations of injection systems. They must provide such parameters of mixture and the rate of the combustion process that would be able to meet the future requirements related to pollutant emissions in the exhaust gases and reduction of CO2. These are the basic criteria determining the trends in the development and improvement of high-speed diesel engines and their injection systems but, in other hand, they signalize the scale of issues that the engineers and manufacturers of such devices must face. The classic injection systems cannot provide the proper rate of the injection process. Fulfilling the future requirements related to exhaust emissions and noise reduction combined with the fuel economy increase requires the absolute application of electronic control systems. This, in turn, is conditioned by the introduction of extended injection rate algorithms that may only be described by complicated 3D functional surfaces. The algorithms must also take into account the additional control parameters and functions and everything requires the strict application of adjusted values feedbacks.

Undoubtedly, the present state-of-the-art accumulation fuel systems provide great features and control precision of the injection process, but this advantage alone would not be able to meet further demands for green engines; it seems that development of direct injection strategy is closed to the systematic limitations. It is necessary to combine various progression trends, both in design and technology domains. As anticipated, the combustion engine shall be the basic drive source in the next 30-40 years, so the issue of development directions of the injection systems remains still an open question.
