A new collision model with improved physical accuracy and reduced numerical dependency has been developed and is used for engine spray calculations. A radius-of-influence of collisional interaction approach was employed along with dynamic discrete particle resolution improvement to reduce numerical dependency. The collision outcomes considered include bounce, coalescence, and fragmenting and nonfragmenting separation processes. The improved collision probability and outcome predictions were coupled to form a comprehensive model that was used to simulate nonvaporizing diesel sprays produced under conditions relevant to common-rail diesel injection systems. Spray penetration results from visualization studies, and drop-size and velocity data from phase Doppler particle analyzer measurements were used to assess the capability of the model for different injection pressures and various chamber densities. The predictions were reasonably good, indicating that the present improvements to collision modeling have increased the fidelity of spray modeling predictions, and are consequently expected to help improve the accuracy of multiphase flow simulations.