“…The effects of the equivalence ratio, engine load, engine coolant temperature, and engine speed on the ionization current signal were investigated by Huang et al It was shown that the ionization current signal could be used with ANNs for the prediction of the equivalence ratio [5]. The estimation of the peak pressure position and AFR using the ionization current and ANNs was investigated by Wickstr€ om et al According to the results of this study, the estimation performance of the peak pressure position with ANN was two times better than a linear model and the estimation performance of the AFR with the ANN was 10 times better than the linear model [6]. The estimation of the AFR using the ionization current and neural networks was studied by Hellring et al For estimation with an un-normalized ionization current, a network with two hidden layer consisting of 20 neurons was selected and for a normalized ionization current, a network with two hidden layers with 10 neurons was selected.…”