The aim of this research is to contribute into the diffusion of biomass power systems by analyzing and testing the throat sizing influence on the operation of a gasification plant coupled with an internal combustion engine. In order to do this, the assessment of the proper operation range for some of the driving process parameters has been carried out. The analysis has been focused on such parameters as pressure drop of the fixed bed reactor, the inlet air flow, the syngas production, electrical power production and efficiency, looking for improving the performance and guaranteeing the proper system operation. Two different campaigns of tests have been carried out for figuring out the best design on the reactor. Based on this analysis, the most convenient throat diameter has been determined (in this case, around 10 cm), producing an increment in the production of syngas of about 31%. This modification has demonstrated also an increment of the electrical power produced by the gasification plant of about 40%, which means an increment in the motor generator efficiency of 35%. (c) 2015 Elsevier Ltd. All rights reserved.