The piston combustion engine, which is working on the HCCI technology principle, is very sensitive to changes of the external atmospheric conditions. These changes are immediately influencing the engine power characteristics. At best only they effect decreasing of the maximum engine power. However, in a more difficult situation, there is the possibility of excessive detonation combustion process during certain changes in atmospheric conditions. The exhaust system temperature significantly affects the maximum output power and the combustion engine characteristics. With increasing temperature of combustion products in the exhaust system there is an overall reduction in maximum power and its transfer to a higher engine speed because of the length of an exhaust manifold is theoretically shorten. Therefore, to achieve the maximum values of output parameters, it is necessary to ensure an optimal temperature value of the combustion products in the exhaust system. This article also provides optimal temperature range of working temperature as well as it presents a theoretical analysis of the impact for atmospheric conditions in this interval. Based on theoretical results there has been developed a measuring method, which allows to regulate the input amount of the fuel mixture supplied to a cylinder during change in atmospheric conditions and its functionality was experimentally verified.