In this study, spark ignition of hydrogen enriched natural gas (HCNG), a fast emerging alternative gaseous fuel, was experimentally investigated in a suitably modified single cylinder spark ignition (SI) engine. Port fuel injection of the HCNG engine using a high volume flow rate solenoid injector, controlled by a customized injector control unit and electronic control unit (ECU) was done and the fuel injection timings and duration were controlled for each load. Fuels with different H/C ratios in the final HCNG mixture were investigated for their engine performance, emissions and combustion characteristics. Engine investigations were carried out at constant engine speed of 1500 rpm for different H/C ratios (4, 4.22, 4.5, 4.85, 5.33 and infinity). Spark timing was kept constant (32 degrees bTDC) for all test blends. Relative air-fuel ratio (RAFR) was kept constant for all loads during the experiments in order to avoid misfire at lower engine load. Hydrogen exhibited higher pressure peak (P-max) but lower maximum brake torque (MBT) compared to other test fuels due to lower knocking limit. Brake thermal efficiency (BTE) was superior for test fuel with H/C: 4.5. NOx emissions were higher for test fuel with H/C: 4.22 and relatively lower for hydrogen compared to baseline natural gas. (C) 2016 Elsevier Ltd. All rights reserved.