The estimation of knock-points of fuels by a weighted mean square error criterion

For fuels tested at critical compression ratio, the in-cylinder pressure development exhibits a distinct change in the pressure rise rate, argued to be the onset of knock. The estimation of the position of knock is important for the evaluation of the burn duration of the fuel and its development features leading up to the autoignition of the end-gas. This paper presents a weighted mean square error criterion for the estimation of the knock-point of fuels tested in a spark-ignition engine. The bootstrap method was applied for estimating the mean square error. It is shown that the criterion can be applied for estimating the knock-point of different fuels tested under varying critical compression ratios. In addition, following the accurate estimation of the knock-point, the estimation of important fuel properties is presented.