Table 3.

Summary of regression results for all selected combustion parameters of introduced approach and comparison method.

	DWT + XGBoost
	Engine 1						Engine 2
	Validation			Test			Validation			Test
Target	RMSE	MAE	R 2	RMSE	MAE	R 2	RMSE	MAE	R 2	RMSE	MAE	R 2
PFP	$3.98$	$3.00$	$0.98$	$5.69$	$4.35$	$0.96$	$3.87$	$2.97$	$0.87$	$3.7$	$2.89$	$0.82$
MFB10	$1.38$	$1.09$	$0.83$	$1.43$	$1.14$	$0.77$	$0.84$	$0.66$	$0.53$	$0.82$	$0.65$	$0.48$
MFB50	$0.79$	$0.55$	$0.97$	$0.89$	$0.63$	$0.95$	$0.71$	$0.54$	$0.80$	$0.66$	$0.52$	$0.74$
MFB90	$1.42$	$1.05$	$0.96$	$1.43$	$1.09$	$0.79$	$1.63$	$1.20$	$0.91$	$1.42$	$1.10$	$0.74$
	Time/Frequency + XGBoost
	Engine 1						Engine 2
	Validation			Test			Validation			Test
Target	RMSE	MAE	R 2	RMSE	MAE	R 2	RMSE	MAE	R 2	RMSE	MAE	R 2
PFP	$6.25$	$4.77$	$0.96$	$7.73$	$6.06$	$0.92$	$5.24$	$4.12$	$0.76$	$4.99$	$3.95$	$0.67$
MFB10	$1.70$	$1.34$	$0.73$	$1.90$	$1.50$	$0.59$	$0.97$	$0.76$	$0.39$	$0.96$	$0.76$	$0.30$
MFB50	$1.78$	$1.24$	$0.86$	$2.03$	$1.44$	$0.71$	$1.01$	$0.77$	$0.60$	$0.90$	$0.71$	$0.51$
MFB90	$2.60$	$1.88$	$0.86$	$3.01$	$2.17$	$0.69$	$1.91$	$1.47$	$0.63$	$1.82$	$1.40$	$0.56$