Abstract
The purpose of this research is to develope a method of back flow compensation using frequency characteristics of the signal from an air flow sensor (AFS). Parameters of the AFS signal which has strong correlation with back flow ratio were searched. The parameters were searched on terms of simulation, mathematical analysis and experiments.
The simulation results showed that normalized powers f2/f1 and f3/f1 have strong correlations with back flow ratio, where f1 is the intensity of the frequency of the pulsation, f2 is the intensity of twice of the frequency of the pulsation, and f3 is the intensity of three times of the frequency of the pulsation. These two correlations were robust to the design of the induction system, engine revolution speed and load. The back flow ratio can be estimated using normalized power f2/f1 and f3/f1 within the accuracy of 5%. The correlations between the normalized powers f2/f1, f3/f1 and the back flow ratio were validated by mathematical analysis. The correlations were also evaluated by experiments using four cycle engine. The experimental results showed that the back flow ratio was estimated using the normalized powers f2/f1, f3/f1 within the accuracy of 5%.
