Identifying Spark Plugs

Identifying DENSO Spark Plugs

Denso Spark Plug Breakdown Chart

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

Denso Spark Plug Breakdown Chart

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
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.
85 (8.5)
95 (9.5)
105 (10.5)
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

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

Bosch Spark Plug Breakdown Chart

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
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.