Al-Si based alloys are used to automobile parts for weight reduction. The engine block and chain cover were fabricated using the ADC12 and newly developed ADC12-M1 alloys through the high pressure die-casting. The ADC12-M1 alloy was fabricated by the addition of titanium and boron into the ADC12 alloy. Computational science such as JMatPro and Thermo-Calc was utilized in order to estimate the solidification behavior since the mechanical property of as-cast material is affected by the solidification behavior. The ADC12 and newly developed ADC12-M1 alloys belong to eutectic and hypo-eutectic alloys calculated by Thermo-Calc software, respectively. The cooling curves with the different cooling rates, fraction liquid and latent heat generation are estimated using JMatPro based on the Al-Si binary alloys in order to understand the solidification behavior between the eutectic and hypo-eutectic chemical composition. The cooling curves, fraction liquid and latent heat generation are more sensitive in the hypo-eutectic chemical composition than that in the eutectic one. The eutectic chemical composition is shifted into the higher concentration of silicon by the titanium and boron additions, resulting in that the higher difference of the yield strength is obtained in the hypo-eutectic ADC12-M1 alloy than that in the eutectic ADC12 alloy.