Diagnostic Method

When a misfire occurs, the engine speed will decrease and the crankshaft position speed will change. Calculate the interval difference value (diagnostic value) from crankshaft position speed by the following formula, and judge whether a misfire is occurring or not comparing the calculated result with judgment value. Count the number of misfires, if the misfire ratio is higher during 1000 revs. or 200 revs., judge corresponding cylinders as NG.

Diagnostic value calculation (Calculate from angle speed) →	Misfire detection every single ignition (Compare diagnostic value with judgment value) →	NG judgment (Misfire occurrence judgment required by the law) (Compare number of misfire with judgment value)
	180° Interval Difference Method 360° Interval Difference Method 720° Interval Difference Method	FTP 1.5 times misfire NG judgment Catalyst damage misfire NG judgment

As shown in the following figure, pick a cylinder as the standard and name it omg 0. And the former crankshaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third is named omg 3, etc.

Fig 1: Crankshaft Position Speed And Ignition Order Chart

Courtesy of SUBARU OF AMERICA, INC.

180° Interval Difference Method

Diagnostic value	domg 180 = (omg 0 - omg 1) - (omg 1 - omg 2)
Judge as a misfire in the following cases. domg 180 ≥ judgment value of positive side domg 180 ≤ judgment value of negative side (Diagnostic value before 180° CA)

Fig 2: Crankshaft Position Speed Graph - 180° Interval Difference Method

Courtesy of SUBARU OF AMERICA, INC.

360° Interval Difference Method

Diagnostic value	domg 360 = (omg 1 - omg 0) - (omg 3 - omg 2)
Misfire judgment	domg 360 > Judgment value → Judge as misfire

Fig 3: Crankshaft Position Speed Graph - 360° Interval Difference Method

Courtesy of SUBARU OF AMERICA, INC.

720° Interval Difference Method

Diagnostic value	domg 720 = (omg 0 - omg 1) - (omg 4 - omg 5)
Judge as a misfire in the following cases. domg 720 ≥ judgment value of positive side domg 720 ≤ judgment value of negative side (Diagnostic value before 180° CA)

Fig 4: Crankshaft Position Speed Graph - 720° Interval Difference Method

Courtesy of SUBARU OF AMERICA, INC.

FTP 1.5 times misfire (Misfire occurrence level which influences exhaust gas)

Judgment Value (Judge that malfunction occurs when the misfire ratio is high in 1000 engine revs.)

Malfunction Criteria	Threshold Value
FTP emission diagnostic value	≥ 37 x 100/2000% in 1000 revs.

Time Needed for Diagnosis: 1000 engine revs.

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

Catalyst damage misfire (Misfire occurrence level damaging catalyst)

Judgment Value

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria	Threshold Value
Catalyst damage misfire diagnostic value	≥ Value from Map

Map

CHARGING EFFICIENCY SPECIFICATION - MAP

		Charging efficiency (%)
		15	30	45	60	75	90	105	120	135	150	165	180
Engine speed (rpm)	700	25	25	-	-	-	-	-	-	-	-	-	-
	1000	25	25	25	25	25	25	-	-	-	-	-	-
	1500	25	25	25	25	16.75	16.75	16.75	-	-	-	-	-
	2000	25	25	25	25	16.75	14.25	12.5	-	-	-	-	-
	2500	25	25	19.75	17	14.25	12.5	11	11	-	-	-	-
	3000	25	25	19.75	17	14.25	12	10.5	10	7.75	6	-	-
	3500	25	25	19.75	17	14.25	11	9	7.75	6	5	5	5
	4000	-	25	19.75	17	14.25	11	8.25	6.25	5	5	5	5
	4500	-	25	17.5	14.25	12.5	9	6.75	5	5	5	5	5
	5000	-	25	16.75	12.5	11	8.25	6	5	5	5	5	5
	5500	-	25	16	12	11	7.25	5	5	5	5	5	5
	6000	-	25	15	11	11	6	5	5	5	5	5	5

Time Needed for Diagnosis: 200 engine revs.

Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.