A frequency-domain, system-identification method using a binary multifrequency signal was developed to find the transfer function between smoke intensity and throttle position in a diesel engine. This paper describes the simulation study performed to test the identification method developed. With an assumption of a diesel operation in a limited region about the normal operating state, the linear theory was adopted. Because that air fuel ratio is one of the most important operating variables causing smoke production in diesel combustion, single-input and single-output model was adopted.