Discrete droplet model (DDM) is widely used to calculate diesel sprays. In DDM, the spray tip penetration is usually underpredicted. The predicted D_<32> value is sometimes too small. Therefore, it is required to examine modeling of droplet breakup, collision and drag force. In this study, 'breakup time' was introduced into TAB model as a breakup onset condition. The effects of coefficient, K, and breakup time on the spray tip penetration, D_<32>, and spray shape are discussed. As a result, it was found that good agreement between the calculation and measurement could be attained by using different combined values of K and breakup time.