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It has become more urgent to use alternative fuels in diesels with growth of the world prices on petroleum and reduction of petroleum stocks. It is also important the reduction of emissions of carbonic gas concerning to group of “greenhouse gases”. Therefore, the vegetable raw material fuels represent the interest to use in a diesel. One of the most perspective alternative bio-fuels is the colza-oil. A number of problems are arising at work of diesel on the colza oil. The problems are eliminated by using mixes of colza-oil with diesel fuel. However, these mixes have increased density, viscosity, and superficial tension in comparison with standard diesel fuel. It results in deterioration of the fuel spray and mix-creation. It is offered the design of an injector, ensuring improvement of fuel spray and mix-creation in a highspeed diesel engine working on mixes of diesel fuel with colza oil. The researches of the offered injectors are carried out at a four cylinder diesel engine.

The reliability, efficiency and ecological parameters of diesels are mainly determined by their operational perfomance in unstable conditions when the air supply to cylinders lags as compared to the fuel supply. Hereat, the excess air coefficient decreases, which results in decreasing the fuel consumption efficiency as well as the exhaust gas smoke. The aforesaidnecessitates the adjustment of the fuel feed depending upon the amount of the air supplied into cylinders. The modelling of the diesel controller system for the rotation frequency regarding the adjustment of the fuel feed depending upon the supercharging pressure is considered. The mathematical model of the diesel is based on calculating the gas - dynamic processes in each cycle of the cylinder operation, which makes it possibleto take into account the nonlinear characteristics of the diesel in different operational conditions as well as the discreteness of the fuel injection.