In this work, a fully instrumented four-cylinder spark ignition engine was converted into bi-fuel gaseous engine to run with LPG and hydrogen blends. Hydrogen, as supplementary fuel, was introduced into intake manifold using manifold port injection technique. Two configurations for hydrogen fueling system were taken into consideration. The first system is based on separated port inputs of fuels method. In fact, hydrogen is injected at the intake manifold plenum level. The second is based on the same port inputs of fuels method. LPG and hydrogen were streamed simultaneously through a two-input air/gas mixer. Computational fluid dynamic (CFD) simulations were performed in order to study the effect of hydrogen injection location on in-cylinder flow characteristics and mixture homogenization using the 3D CFD code SolidWorks Flow Simulation "SWFS". CFD investigation was aimed at analyzing the velocity, turbulence structures and hydrogen diffusion into the mixture at quasi-steady and unsteady engine conditions during the intake process using the two hydrogen fueling configurations. The outcomes from the simulations were used to justify the selection of separated LPG-H-2 inputs as the hydrogen fueling system. Experimental investigations are carried out to validate the adequate fueling system and identify the hydrogen enrichment effect on LPG gaseous engine performances and emissions. Experimental measurements were achieved by blending a percentage of hydrogen (0%, 5%, 10%, 15% and 20% in volume) with LPG and supplied to the engine. As results, the brake power was increased using 20% hydrogen addition ratio by 17.5% compared to standard pure LPG operation. Brake thermal efficiency was improved by 4.5% at maximum engine speed. A decrease of carbon dioxide emissions was attained by 15.1% at maximum engine torque (2500 rpm). There was considerable reduction in hydrocarbon levels. (C) 2018 Elsevier Ltd. All rights reserved.