Type Name
Identifying DENSO Spark Plug
Thread and Hexagon size
Heat Range
Thread Reach
Special Design
Internal Construction
Special GAP configuration
Gap
Thread and Hexagon size
Letter
Thread Size
Hex. size
Description
L
18mm
22.0mm
M
18mm
25.4mm
MA
18mm
20.8mm
Taper seat
*J
14mm
20.8mm
Extended electrodes
*P
14mm
20.8mm
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
*PK
14mm
16.0mm
Platinum-tipped electrodes
S
14mm
20.8mm
Special surface gap for Mazda RE/thread reach 21.5mm
SF
14mm
20.8mm
Surface gap
*SK
14mm
16.0mm
Iridium-tipped centre electrode
Platinum-tipped ground electrode
T
14mm
16.0mm
Taper seat
W
14mm
20.8mm
TR
14mm
20.6mm
Thread reach 12.7mm
X
12mm
18.0mm
XU
12mm
16.0mm
U
10mm
16.0mm
Y
8mm
13.0mm
*These letters indicate including thread reach 19.0mm.
Heat Range
Thread Reach
Letter
Reach
Description
E (Flat seat)
19.0mm (3/4") or
20.0mm
W16EXR-U
W25EBR
E (Taper seat)
.708"
T16EPR-U
F
12.7mm (1/2")
W20FP-U
FE
19.0mm (3/4")
Half thread
U24FER9
G
21.8mm
X27GPR-U
L
11.2mm (7/16")
W14L
None
18mm thread (Flat seat)
12.0mm
M24S, L14-U
14mm thread (Flat seat)
9.5mm (3/8")
W20S-U, W9PR-U
18mm thread (Taper seat)
.480"
MA16PR-U
14mm thread (Taper seat)
.460" or
.325"
T16PR-U
T20M-U/WA20M-U
Special Design
Letter
Description
Example
A
Dual ground electrodes for Mazda RE
W22EA
*A
Electrode projection (7.0mm)
QJ16AR-U
B
Triple ground electrodes
W20EPB
*B
Electrode projection (9.5mm)
J16BR-U
*C
Electrode projection (5.0mm)
QJ20CR11
D
4-ground electrodes for Mazda RE
W27EDR14
*H
Electrode projection (8.5mm)
QJ16HR-U
K
Special type for Honda CVCC
W16EKR-S11
LM
Special type for lawn mowers
W14LM-U
M
Compact type
W20M-U
N
Racing type (nickel ground electrode)
W27EN
PT
Racing type (platinum ground electrode)
W27EPT
P
Project insulator nose
W16EP-U
S
Regular type
W24ES-U
T
Dual ground electrodes for Toyota T.G.P.
W20ET-S
X
Extra projected insulator nose
W16EX-U
*When the first suffix is J or QJ/KJ.
Internal Construction
Letter
Description
None
Non resistor
R
Resistor
Special GAP configuration
Letter
Description
Example
GL
Platinum center electrode
X22EPR-GL
L
Special type for Honda and extra project type for moped
KJ20CR-L11
W14FP-Ul
S
Semi-Surface gap
W20EPR-S11
U
U-groove ground electrode
W16EX-U
US
Star centre electrode with U-groove
W14-US
V
Thin centre electrode
W24ES-V
Z
Thin platinum centre electrode with tapered ground electrode
W24ES-ZU
C
Cut-back ground electrode
W27EMR-C
P
Platinum-tipped plug for DIS
PQ20R-P8
Gap
Letter
Gap
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")
SPARK GAP
inch
.020
.024
.028
.032
.035
.040
.044
.048
.060
.080
mm
.05
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.5
2.0
