The aim of the paper is to analyze and evaluate the basic parameters of the combustion process in a modern Fiat 1.3 Multijet diesel engine, fuelled esters (FAME) and diesel oil. During the tests on an engine test bed, the pressure waveforms in the cylinder were measured, on the basis of which the averaged actual indicator graphs were established in the determined engine operating conditions. On their basis, the pressure increase rates were determined and heat release characteristics were prepared based on the equation of the first principle of thermodynamics. The characteristics of the relative amount of heat released and the characteristics of the relative heat release rate were determined. The use of rapeseed methyl esters to supply the engine had an impact on the parameters of the combustion process as compared to its supply with diesel oil. Differences in the waveforms of heat release characteristics of the engine powered by the tested fuels are significantly greater at low loads. At the lowest engine loads, esters burn much faster than diesel oil. With the increase in engine load, the differences in the waveform of heat release characteristics during combustion of these fuels were significantly smaller.

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The article presents the results of measurements of concentrations of selected exhaust components of the Fiat 0.9 TwinAir spark-ignition engine operating according to load characteristics. The tested engine has an indirect, multi-point petrol supply system and has been retrofitted with an indirect CNG injection system. The results of the tests are a comparison of selected economic, ecological and energetic indicators of engine operation obtained when fuelled with CNG and 95 octane petrol. The operation of the engine fuelled with gaseous fuel was preceded by autocalibration of the controller of the fuelling system. The article presents the results of tests of concentrations of harmful components of exhaust gases: carbon dioxide CO2, carbon monoxide CO, nitrogen oxides NOx and HC hydrocarbons. Moreover, the values of lambda λ air excess coefficient are presented and fuel consumption is compared. The obtained results of the tests of the engine fuelled with CNG gas show a significant decrease in the value of the obtained torque in comparison to the engine torque when fuelled with petrol. The engine fuelled with compressed natural gas contributed to the improvement of its ecological properties and a reduction of fuel consumption, which are important factors of ecological and energy safety. Exhaust gas analysis showed a reduction in the concentration of harmful components of exhaust gases, mainly hydrocarbons and nitrogen oxides. A positive effect of the operation of the engine powered by CNG was also a significant reduction of carbon dioxide in the exhaust gases compared to the engine powered with gasoline.

The paper presents the results of the experimental study of the turbocharged spark ignition Fiat 0.9 TwinAir engine, with indirect, multipoint petrol injection system, powered by petrol and equipped with the injection system of the compressed natural gas (CNG) supplying gas into the intake manifold. The test results provide the comparison of the selected fuel-efficiency, energetic and ecologic indicators of engine work, obtained when it is powered by Pb95 petrol and the CNG gas. The paper compares the external torque-speed characteristics with factory-set engine controllers. Also presented are the concentration levels of harmful gases in the exhaust fumes: carbon monoxide (CO), nitric oxides (NOx), hydrocarbons (HC) and carbon dioxide (CO2). Results obtained on the engine powered by CNG are indicating lower power and torque, lower concentration of hazardous gases, in particular carbon monoxide and hydrocarbons as well as significantly lower consumption of the gas when compared to petrol.