Identifying Spark Plugs

• Identifying DENSO Spark Plugs
• Identifying NGK Spark Plugs
• Identifying BOSCH Spark Plugs

Identifying DENSO Spark Plugs

Thread and Hexagon size:  W 16EXRU11

	Letter	Thread Size	Hex. Size	Description
	I	8mm	13.0mm	0.4mm Iridium centre electrode
	L	18mm	22.0mm
	M	18mm	25.4mm
	MA	18mm	20.6mm	Taper seat
#	J	14mm	20.6mm	Extended electrode
#	P	14mm	20.6mm	Platinum-tipped electrodes
#	PQ	14mm	16.0mm	Platinum-tipped electrodes
#	Q	14mm	16.0mm
#	QJ	14mm	16.0mm	Extended electrode
#	K	14mm	16.0mm	ISO
#	KJ	14mm	16.0mm	ISO Extended electrode
#	PK	14mm	16.0mm	Platinum-tipped electrodes
#	PT	14mm	16.0mm	Platinum-tipped electrodes
	S	14mm	20.6mm	Special surface gap for Mazda. Thread reach 21.5mm
	SF	14mm	20.6mm	Surface gap
	SK/SVK	14mm	16.0mm	Iridium-tipped centre electrode & Platinum-tipped ground electrode
	T	14mm	16.0mm	Taper seat
	W	14mm	20.6mm
	TR	14mm	20.6mm	Thread reach 12.7mm
	X	12mm	18.0mm
	XU	12mm	16.0mm
	U	10mm	16.0mm
	Y	8mm	13.0mm
# = 19.0mm thread reach

Heat Range:  W 16 EXRU11

Hot					Cold
9	14	16	20	22	24	27	31	34	37

Thread Reach:  W16 E XRU11

Letter	Reach	Example
D	19.0mm + 1.5	KJ20DRM11
E (Flat seat)	19.0mm (3/4") or 20.0mm	W16EXRU / W25EBR
E (Taper seat)	.708"	T16EPRU
F	12.7mm (1/2")	W20FPU
FE / UH	19.0mm (3/4") Half thread	U24FER9
G	21.8mm	X27GPRU
H	26.5mm	K16HPRU11
L	11.2mm (7/16")	W14L
N	17.5mm Half thread	T16NRU11
V (Taper seat)	25.0mm	PT16VR13
No Letter:-
18mm thread (Flat seat)	12.0mm	M24S, L14U
14mm thread (Flat seat)	9.5mm (3/8")	W20SU, W9PRU
18mm thread (Taper seat)	.480"	MA16PRU
14mm thread (Taper seat)	.460" or .325"	T16PRU, T20MU

Electrode Design:  W16E X RU11

	Letter	Description	Example
	A	Dual ground electrodes for Mazda RE	W22EA
#	A	Electrode projection (7.0mm)	QJ16ARU
	B	Triple ground electrodes	W20EPB
#	B	Electrode projection (9.5mm)	J16BRU
#	C	Electrode projection (5.0mm)	QJ20CR11
	D	4-ground electrodes for Mazda RE	W27EDR14
#	H	Electrode projection (8.5mm)	QJ16HRU
	K	Special type for Honda CVCC	W16EKRS11
	LM	Special type for lawn mowers	W14LMU
	M	Compact type	W20MU
	MP	Compact Type and projected insulator nose	W22MPRU
	PT	Racing type (platinum ground electrode)	W27EPT
	P	Projected insulator nose	W16EPU
	S	Regular type	W24ESU
	T	Dual ground electrodes for Toyota T.G.P	W20ETS
	V	Semi-surface	W20EVRZU
	X	Extra projected insulator nose	W16EXU
	AZ	Thin platinum centre electrode and  ground electrode	K27AZ
# = When suffix is J, KJ or QJ

Internal Construction:  W16EX R U11

Letter	Description
No Letter	Non resistor
R	Resistor

Gap Configuration:  W16EXR U 11

Letter	Description	Example
C	Cut-back ground electrode	W27EMRC
L	Special type for Honda and extra project type for moped	KJ20CRL11, W14FPUL
M	Special ground electrode	KJ20DRM11
N	Special internal construction	U27ESRN
P	Platinum-tipped plug for DIS Double Layer	PQ20RP8
S	Semi-surface gap	W20EPRS11
U	U-groove ground electrode	W16EXU
US	Star centre electrode with U-groove	W14US
V	Thin centre electrode	W24ESV
Z	Tapered ground electrode	VK20PRZ11
ZU	Thin platinum centre electrode with tappered ground electrode	W24ESZU

Spark Gap:  W16EXRU 11

Number	Gap (mm)	Gap (inch)
9	0.9mm	.035"
10	1.0mm	.040"
11	1.1mm	.044"
13	1.3mm	.050"
14	1.4mm	.055"
15	1.5mm	.060"
20	2.0mm	.080"

Identifying NGK Spark Plugs

Thread, Hexagon and Pitch size:  BC  PR6ES11

Letter	Thread	Pitch	Hex
A	18mm	1.50mm	25.4mm
B	14mm	1.25mm	20.8mm
C	10mm	1.00mm	16.0mm
D	12mm	1.25mm	18.0mm
E	8mm	1.00mm	13.0mm
G	PF 1/2" pipe		23.8mm
AB	18mm	1.50mm	20.8mm
BC	14mm	1.25mm	16.0mm
BK	14mm	1.25mm	16.0mm
DC	12mm	1.25mm	16.0mm
Part numbers:- BM_A and BPM_A
	14mm	1.25mm	19.0mm
Part number:- CM-6:
	10mm	1.00mm	14.0mm
Taper Seat Types
			Hex
A_F type			20.8mm
B_F type			16.0mm

Construction Shape and Features:  BC PR 6ES11

Letter	Construction shape/feature
M	Compact (Bantam)
L	Short type
P	Projected centre electrode insulator
R	Resisitor type
U	Surface or semi surface discharge
Z	Inductive suppressor
Letters may be combined

Spark Plug Heat Rating:  BCPR 6 ES11

Number	Heat Rating (Hot -> Cold)
2	Hotter Plug Temp.
4
5
6
7
8
85	(8.5)
9
95	(9.5)
10
105	(10.5)
11
12	Colder Plug Temp.

Thread Reach:  BCPR6 E S11

Letter	Detail	Size(mm)
E		19.0mm
H		12.7mm
L		11.2mm
EH	Total reach	19.0mm
EH	Thread	12.7mm
BM_A, B_LM types		9.5mm
CMR_A types		9.5mm
No Letter:
A_ type		12.0mm
B_BM_ type		9.5mm
CM_ type		8.5mm
G_ type		22.5mm
Taper seat types:
F	A_F type	10.9mm
	B_EF type	17.5mm
	B_F type	11.2mm
	BM_F type	7.8mm
	BPM_F type	7.8mm

Firing End Construction:  BCPR6E S 11

	Description
CS	Short, angled ground electrode
CM	Short, angled ground electrode, compact type
F	Taper seat (no gasket), 'V' - Grooved centre electrode
FS	Taper seat (no gasket)
G	Fine wire nickel centre electrode
K	2-ground electrodes, intermittent gap
KC	2-ground electrodes
KUB	2-ground electrodes semi-surface discharge
T	3-ground electrodes
Q	4-ground electrodes
P	Platinum tip
S	Standard super copper core centre electrode
U	Semi-surface discharge
V	Fine wire Gold Palladium centre electrode. 0.8mm dia.
-VG	'V'-Grooved centre electrode
VX	Fine wire Platinum centre electrode. 0.8mm dia.
I	Iridium tip
IX	Fine wire Iridium centre electrode. 0.6mm dia.
W	Tungsten electrode
X	Booster gap (not applicable to 'VX' or 'IX' types)
Y	'V'-Grooved centre electrode with extra protection
Z	2.9mm dia. centre electrode (not applicable to DPR_Z or G_2Z
-L	Half heat range
-LM	Compact design.  Insulator top: 14.5mm high
-N	Strong ground electrode design
No Letter: 'V'-Grooved centre electrode (14mm thread dia. 19mm reach plugs only, eg: BKR6E
Others: A,B,D etc, - special design

Spark Plug Gap:  BCPR6ES 11

	Spark Gap(mm)
8	0.8mm
9	0.9mm
10	1.0mm
11	1.1mm
13	1.3mm
14	1.4mm
15	1.5mm
No Number = standard gap

Identifying BOSCH Spark Plugs

Hex and Thread Size:  W R6DC+

Letter	Hex Size	Thread Size
D	20.8mm	18mm x 1.5mm
F	16mm	14mm x 1.25mm
H	16mm	14mm x 1.25mm
K	14mm	14mm x 1.25mm
M	26mm	18mm x 1.5mm
T	16mm	10mm x 1mm
U	16mm	10mm x 1mm
V	14mm	14mm x 1.25mm
W	20.8mm	14mm x 1.25mm
X	17.5mm	12mm x 1.25mm
Y	16mm	12mm x 1.25mm
Z	14mm	12mm x 1.25mm

Design Type:  W R 6DC+

Letter	Description
B	Water-tight, for shielded ignition cable 7mm dia.
C	Water-tight, for shielded ignition cable 5mm dia.
E	Surface gap spark plug without ground electrode
G	Surface gap spark plug with ground electrode
H	Half thread
L	Surface air gap spark plug
M	For motor sport
Q	Quickheat
R	With interference suppression resistor

Heat Range:  WR 6 DC+

Number	Heat Range (Hot -> Cold)
12	Hottest
11
10
9
8
7
6
5
4
3
2
09
08
07	Coldest

Thread Length:  WR6 D C+

Letter	Total Thread Length	Thread Length	Insulator and Tip Projection
A	12.7mm	11.2mm	1mm
B	12.7mm	11.2mm	3mm
C	19mm	17.5mm	1mm
D	19mm	17.5mm	3mm
E	9.5mm		1mm
F	9.5mm		3mm
G	12.7mm		4mm
H	19mm	17.5mm	7mm
K	19mm	17.5mm	4mm
L	19mm	17.5mm
M	26.5mm	25mm	3mm
N	26.5mm		4mm
S	26.5mm		5mm
T	26.5mm		7mm

Electrode Material:  WR6D C +

Letter	Description
C	Copper
E	Nickel-Yttrium
P	Platinum
S	Silver
I	Platinum-Iridium

Version:  WR6DC +

Letter	Type
R	Burn-off resistor
S	0.7mm gap
T	0.8mm gap
U	1.0mm gap
V	1.3mm gap
W	0.9mm gap
X	1.1mm gap
Y	1.5mm gap
Z	2.0mm gap
+	Super Plus Technology
Extra Prefix Letters:
D	2-Ground electrodes
T	3-Ground electrodes
Q	4-Ground electrodes

Information quoted and displayed on the this page is strictly copyright Nippon Denso(UK) Ltd, NGKNTL (UK) Ltd, Robert Bosch(UK) Ltd and Champion Automotive(UK) Ltd. All rights reserved. Layout and design copyright RoadRunner Autoparts Ltd.