In order to determine the effectiveness of the catalytic coating applied to the engine valve, a study model. For this purpose built test stand made of elements of the real engine. The catalyst temperature was controlled by electric heating. The position of the working gas fumes were collected with a spark-ignition engine, idling. Performed a simultaneous measurement of gas composition at the inlet to the model and the output from the system. The study was conducted at a constant flow rate and variable temperature exhaust gas catalyst sys- tem. The results of the study are presented in the form of comparative charts. It has been found highly effective activity of the catalyst for carbon monoxide and relatively high efficiency for hydrocarbons. Measurements of nitric oxide levels showed no significant changes in concentration in a range of temperatures.