The paper presents a systematic approach towards the problems of dynamics of combustion engines. The notions of work processes of combustion engines and operating conditions as well as engine states of operation have been formally introduced. An axiomatic qualification of the engine operating process as static and dynamic has been proposed. The systematics of the engine operating states has been described. As an example of application of the proposed formalism the results of exhaust emission tests from the Detroit Diesel engine Series 50 have been shown (operating in the conditions of a HDDTT homologation test). The exhaust emissions were tested in the states: the whole test – increasing engine speed, decreasing engine speed and engine speed above idle. A high sensitivity of the average emission rate to types of discussed dynamic states has been observed.