Accurately estimating or measuring intake manifold absolute pressure plays an important role in automobile engine control. In order to achieve the real-time estimation of the absolute pressure, the high accuracy and high speed processing ability is commonly required for the automobile engine control system. However, the conventional numerical methods cannot satisfy the requirement of the strict time needed by high speed automobile engine. Therefore, in this paper, an analog LSI method is proposed to estimate this pressure in real time. Furthermore, a novel behavioral macromodel is given for further analog LSI design. Compared with conventional numerical method, the proposed method is highly advantageous in speed to simulate the automobile engine intake system.