The paper quantifies the forces applied to the main bearings of three six-cylinder turbocharged diesel engines and reviews their exciting properties in both time and frequency domains. The engine structure response at the bearing supports and the outer engine surfaces are correlated. It is shown that the engine structure response is a transient phenomenon and is a maximum in the vicinity of the applied force. By representing the engine response in terms of displacement it is possible to recognise the applied force time history and thus the identification of the specific parts of the engine structure primarily excited by moments and by direct force. The displacement technique for quantifying engine response provides detailed information of the distortion of the running engine enabling the prediction of mechanical inputs which can control the turbocharged engine noise. This is essential for quantifying input data for theoretical models and establishing structure changes to control engine radiated noise.