Due to the lower volumetric energy density and the lower heating value of an ammonia-air mixture, ammonia-fueled engine to suffer from a power deficit in comparison with gasoline engines. Therefore, this study was carried out of the use of a Combination Power System (CPS) to increase the power output of Spark Ignition (SI) engines using ammonia. In this case, it is necessary to select a rational combination of the required power of the SI engine and the electrical machines. Two-cylinders 2CH 7.6/7 and four-cylinders 4CH 7.6/7 engines were tested with ammonia and gasoline fuels. During the test the mixtures of ammonia-air and gasoline-air stoichiometric (λ = 1), the compression ratio (CR = 9.9) is kept unchanged. The results show that, the use of a CPS makes it to reduce the swept volume and the fuel consumption of the SI engine in a cycle drive during medium and high load operating conditions, while the average effective engine efficiency increases. Although the fuel consumption of the SI engine in a cycle drive is reduced by 18%, and the average effective efficiency is increased by 29%, the CPS provides required power.