Abstract: The article describes the test results of the uniqueness of the work cycle of two-cylinder internal combustion piston FIAT 0.9 TwinAir engine, while being powered by 95 octane petrol fuel and LPG gas. The engine was working according to load characteristics. The engine mounted on the test bench was equipped with a sequential LPG gas fuel supply system. The gas fuels differ significantly from the petrol fuels in their physiochemical properties. In order to rationally utilize gas fuels to power internal combustion engines, the knowledge about basic fuel burning process of these fuels is required. The article shows the analysis of individual engine work cycles of the technologically advanced engine in order to evaluate the influence of powering by LPG gas fuel on the rate of uniqueness of its work cycles. The measure of uniqueness of the inter-cylinder processes are the work cycle uniqueness indicators, which are as follows: the maximum work cycle pressure uniqueness indicator, the average measured work cycle pressure uniqueness indicator, the measured pressure work cycle graph uniqueness indicator and the measured pressure work cycle partial graph uniqueness. The carried out research and its analysis has shown that powering the engine with LPG gas has an influence on the engine work cycles and its uniqueness. The burning process of the mixture consisting of air and LPG gas is quicker, which has an effect on the higher speed of pressure increase rate in comparison with the engine being powered by petrol fuel. Achieved maximum in-cylinder pressure values while the engine was powered by LPG gas were higher in comparison with it being fuelled with conventional fuel. This causes an increase of the gas lads on crank-piston system, which are influencing directly the piston with higher heat load, and the thermal load of the engine.
B I B L I O G R A F I A[1] Ambrozik, A., Ambrozik, T., Kurczyński, D., Łagowski, P., Conversion of Fiat 0.9 multiair engine to multi-fuelling, Journal of KONES, Vol. 20, No. 4, pp. 9-15, 2013.
[2] Ambrozik, A., Kurczyński, D., Łagowski, P, Warianek, M., External speed-torque characteristics of Fiat 0.9 TwinAir petrol and CNG-fuelled engine, Combustion Engines, Vol. 171 (4), pp. 222-226, 2017.
[3] Baczewski, K., Kałdoński, T., Paliwa do silników o zapłonie iskrowym, Wydawnictwo Komunikacji i Łączności, Warszawa 2005.
[4] Helmers, E., Bitte wenden Sie jetzt – Das Auto der Zukunft. Wiley-VCH, Weinheim 2009.
[5] Kurczyński, D., Łagowski, P., Warianek, M., Ecological indicators of the PERKINS 1104d-E44TA engine after its adaptation for being powered with natural gas and diesel fuel, Journal of KONES Powertrain and Transport, Vol. 24, No. 3, 2017.
[6] Kurczyński, D., Łagowski, P, Warianek, M., Parameters of the combustion process in the fiat 0.9 TwinAir engine, working under selected load characteristics and powered with LPG and CNG gas fuels, Proceedings of the Institute of Vehicles, 1 (115), pp. 81-90, 2018.
[7] Lotko, W., Laboratorium diagnostyki pojazdów, Wydawnictwo Politechniki Radomskiej, 2005.
[8] Racewicz, S, Olejnik, A., Control of Fiat MultiAir valve-lift system using atmega microcontroller, Journal of KONES Powertrain and Transport, Vol. 4, No. 3, 2017.
[9] Merkisz, J., Kozak, M., Wymagania jakościowe stawiane benzynie przez nowe generacje silników o zapłonie iskrowym (cz.1, cz. 2), Paliwa, oleje i smary w eksploatacji, Nr 104, pp. 5-8, Nr 105, pp. 23-26, 2002.
[10] Repka, J., Labuda, R., Kovalčík, A., Bárta, D., Skrúcaný, T., Indicated pressure of internal combustion engine, Scientific proceedings XXII International Scientific-Technical Conference “trans & MOTAUTO ’14”, Vol. 1, pp. 58-61, 2014.
[11] Rychter, T. J., Spalanie ubogich ładunków w użytkowym silniku ZI, Biuletyn informacyjny Instytutu Techniki Cieplnej Politechniki Warszawskiej, Nr 66, Warszawa 1985.
[12] Wedler, M., Alternative Kraftstoffe und Antriebssysteme fuer PKW-Fahrzeuge, GRIN Verlag, Norderstedt 2008. 
DOI 
YADDA/CEON