The theoretical analysis of the charge exchange process in a spark ignition engine has been presented. This process has significant impact on the effectiveness of engine operation because it is related to the necessity of overcoming the flow resistance, followed by the necessity of doing a work, so-called the charge exchange work. The flow resistance caused by the throttling valve is especially high during the part load operation. The open Atkinson-Miller cycle has been assumed as a model of processes taking place in the engine. Using fully variable inlet valve timing the A-M cycle can be realized according to two systems: system with late inlet valve closing and system with early inlet valve closing. The systems have been analysed individually and comparatively with the open Seiliger-Sabathe cycle which is a theoretical cycle for the classical throttle governing of the engine load. Benefits resulting from application of the systems with independent inlet valve control have been assessed on the basis of the selected parameters: fuel dose, cycle work, charge exchange work and a cycle efficiency. The use of the analysed systems to governing of the SI engine load will enable to eliminate a throttling valve from the system inlet and reduce the charge exchange work, especially within the range of part load operation.
 Bernard L., Ferrari A., Rinolfi R., Vafidis C.: Fuel economy improvement potential of UniAir throttle-less technology. In: Proc. ATA Int. Symp. “SIE: the CO2 challenge”, 02A5012, Venice 2002.
 Mianzo L., Newton S., Popovic Z.: Integrated control and power electronics for an electro-mechanical valve actuation system. Proc. IEEE/ASME, 2005.
 Picron V., Postel Y., Nicot E., Durrieu D.: Electro-magnetic valve actuation system: first steps toward mass production. SAE Tech. Pap. 2008-01-1360, 2008.
 Sugimoto C., Sakai H., Umemoto A., Shimizu Y.: Study on variable valve tim- ing system using electromagnetic mechanism. SAE Tech. Pap. 2004-01-1869, 2004.
 Farzaneh-Gord M., Reza Behi M., Yahyaie A., Mirmohammadi S.: Esti- mating recoverable work of an engine by utilizing the CO2 Brayton power cycle and capturing heat lost. Arch. Thermodyn. 30(2009), 3, 89-110.
 Farzaneh-Gord M., Hajializadeh H., Khoshnevis A.B.: The first and second law analysis of a spark ignited engine fuelled with alternative fuels. Arch. Thermodyn. 30(2009), 1, 73-98.