In this study, a series of tests have been carried out to evaluate the effects of the injection rate and timing on bsfc, NOx, and PM emissions in a heavy-duty diesel engine with TICS FIE system. Injection line pressure, cylinder pressure, NOx and smoke were measured with various injection times and injection rates. The injection rate was altered at a fixed injection timing, which could be realized either by changing the TICS setting time or by using different cam profiles. The injection time was varied by using TICS timing control function at a given setting time. A parametric study of the injection rate in in-line pump system was tried to correlate injection rate variations with combustion characteristics and emission. Two parameters, the injection pressure rising rate and the initially injected fuel quantity were introduced to characterize fuel injection. A simply formulated wave propagation model was applied to estimate the initially injected fuel quantity from the injection line pressure. Also, an apparent heat release calculation from measured cylinder pressure data was used as an effort to understand combustion characteristics.From this work, it was found that two introduced parameters well described the relationships between injection rate and emission. It is anticipated that a revised injection rate can be proposed for improving NOx-PM trade-off in a heavy-duty diesel engine by using introduced parameters.