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The paper presents some results concerning the use of a Biodiesel type fuel in a direct injection (D.I) Diesel engine. The fuel was produced from waste vegetable oil, collected from the local McDonalds' branch. The engine was fueled with a blend containing 50% Biodiesel and 50% Diesel fuel (B50, Biodiesel blend). The tests were developed on a D-110 Diesel engine (S/D= 130/108 mm, ε = 17, three in line cylinders); the output power, torque, BSFC, combustion pressure, pressure rate and autoignition delay were measured and the heat release rate was calculated. We noticed a slight decrease of the power indices when the Biodiesel type fuel was used (output power and torque) and also of the peak combustion rate. The peak heat release rate decreased, while the autoignition delay has decreased by 2…4° CA.

The paper attempts to determine which traction model best fits with experimental data for a romanian lugged tractor tire. Different models for predicting net traction and traction efficiency for off-road conditions were considered. These models assume different tire-ground pressure distributions (constant, parabolic) over the undertread area and different contact patch length calculations. Experiments were conducted and the results were compared to the theoretical data. Two of the models are the best fit with the experimental data; both models assumed a parabolic pressure distribution over the undertread.

The paper presents an analysis of the influence of the most important factors that affect the working process of a direct injection spark ignition engine, especially the injection timing. In the first part of the paper we study the engine's constructive solution and the changes in the engine's performances induced by the alteration of the compression ratio. This phase allowed us to choose the most appropriate variant. In the second part we study the influence of the injection timing over the engine's performances, for two different compression ratios and two injection rates. The most significant results are emphasized using the engine's speed characteristics, determined on the test bed.

The paper presents some aspects concerning the working process of an original cyclic dose governor, used for the in-line fuel injection pumps of the direct injection spark ignition engines. Regarding this mechanism as an automatic regulation system, depending of the crank speed and using the transfer functions which are specific to each element, we have obtained the equations that describe the working process of the governor. In order to integrate the system's characteristic differential equations numerical methods were applied, using the LTITR function (Linear Time Invariant Time Response Kernel), adapted from MathLab's 4.2 library. Thus we have obtained graphical representations of the function that describes the governor's response to the engine's speed variation, for the whole speed range of a spark ignition engine and for the 12 dimensional variants of the governor's constituent parts.

Vegetable oils are an interesting alternative to diesel fuel, as they are a renewable source of energy, have a low sulfur content, are safe to store, do not cause skin ailment. However, using vegetable oils in order to fuel direct injection diesel engines creates problems due to their low heat energy and high viscosity. The purpose of the experiments we made was to determine how the injection equipment behaves when sunflower oils are used and how these oils alter the power indexes of the engine. During the test we used three types of sunflower oil and vegetable oil-diesel oil mixtures; both the injection equipment tests and the engine tests were conducted at 20% load, 40% load and full load. We noticed changes in the injection equipment working parameters (injection pressure, cyclic dose etc.) and in the engine's power indexes (output power and torque, fuel consumption etc.).