This work conducts an analysis of the advantages coming from application of the constant depression carburettor with a fuel feeder.The fuel feeder enables an automatic change of the dynamic characteristic to the economic characteristic of the carburettor. The computer analysis of the characteristic of the constant depression carburettor was conducted based on a mathematical model. The comparison was made between the prototype of the constant depression carburettor and a standard one. The greatest advantages are for the partial loads of an engine. The fuel consumption was decreased by about 18% comparing to the standard carburettor. The additional advantage of a constant depression carburettor is the automatic change of its economic characteristic to dynamic one during the work of an engine.