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For the Academic Engagement factor, we removed items KLST 13 (p = .235), 23 (p = .304), and 24 (p = .490).
In the Academic Engagement factor, Item 10 (p = .246) from the KLST was found to be nonsignificant.
Factor loadings for items from the Precision Accuracy subscale were positive and ranged from 0.150 (KCS 52) to 0.391 (KCS 45), whereas factor loading estimates stemming from the Self-Monitoring and Persistence subscales were negative, ranging from -0.177 (KLST 26) to -0.065 (KLST 22).
The results show that increasing the water content in air results in a substantial increase in the knock resistance of the fuel/air mixture: at 4.3 g [H.sub.2]O/kg dry air the KLST is 19[degrees]CA BTDC while at 11 g [H.sub.2]O/kg dry air the KLST is 21[degrees]CA BTDC for the same fuel.
Comparison between the calculated knock resistance (PKI) and the measured knock resistance (KLST) shows excellent agreement for the experimental variations in water content in air studied; moreover, the effect of varying water content in air on the pressure profile is very well captured by the updated knock model.
kPa 3.72 2.70 [P.sub.H2O], kPa 0.69 1.08 Humidity, % 18.4 40.1 g [H.sub.2]O/kg dry air 4.30 6.80 Air factor, [lambda] 1.54 1.54 [P.sub.intake], bar 2.10 2.12 [T.sub.intake], K 337.3 337.9 KLST, [degrees]CA BTDC 19.0 20.0 condition 3 condition 4 Methane 0.9542 0.9545 Ethane 0.0002 0.0000 Propane 0.0449 0.0447 n-Butane 0.0002 0.0002 i-Butane 0.0006 0.0005 [P.sub.H2O], Sat.
Figure 12 shows the same excellent correlation between the PKI methane number and the measured KLST as the PKI itself in Figure 11.
In Figures 13 and 14 we compare the KLST for the gases shown in Figure 11 with the methane number (MN) computed using the AVL method [2] (version 3.2) and the MWM method [37], respectively.
For engine operators, the observed large spread (roughly [+ or -] 2[degrees]CA) means that AVL barely allows distinction between a KLST of, for example, 20[degrees]CA BTDC and 16[degrees]CA BTDC for this engine, while using the method derived in this study allows a distinction of [+ or -] 0.75[degrees]CA, at the current level of verification, for example between 20 and 18.5[degrees]CA BTDC.