This study investigates how engine performance, cyclic variations and combustion parameters are affected by swirling flow in hydrogen spark ignition (SI) engine. Swirling flow was produced in the cylinder during the induction stroke by intake port having entry angles of 0 degrees, 10 degrees, 20 degrees and 30 degrees. In addition, tumble angle of 8 degrees was positioned for given entry angles. The engine was operated under lean mixture (phi = 0.6) conditions and engine speeds of 1400, 1600 and 1800 rpm. As a result, it was found that swirling flow enhances performance of hydrogen SI engine around 3% when operating engine with entry angle of 20 degrees. The combustion duration and the cyclic variation in hydrogen SI engine can be reduced with optimum swirling flow. The stability of combustion in hydrogen SI engine is mainly dependent on cyclic variations in the flame initiation period and the cyclic variations in this period can be reduced with controlled swirling flow. (C) 2014 Published by Elsevier Ltd on behalf of Energy Institute.