Just in case that someone is out there looking for plugs replacements, I read and compared the whole NGK catalog and got this, I hope it helps some of you. Either way I stick to the PFR6E-10, but as per the catalog, the difference is the design of the tip to improve where the spark starts.
OPTIMUM SPEC FOR F4R730: PFR6E-10
SPEC REPLACEMENT (as per the catalog): BKR6E-11 (LOWER LIFE, TO BE REPLACED EVERY 15,000Km)
Nomenclature stands for:
P-PLatinum
F-Thread size and shell
R-Resistor type plug
6-Temperature
E-(please see below)
10-size of the gap in mm x 10 (1mm gap = 10 designation)
A-SPECIAL DESIGN NOT SPECIFIED
B-SPECIAL DESIGN NOT SPECIFIED
E-V GROOVED CENTER ELECTRODE
G-FINE WIRE NICKEL ALLOY CENTER ELECTRODE
J-WITHOUT INFO
N-SPECIAL SIDE ELECTRODE
M-2 GROUND ELECTRODES (FOR ROTARY ENGINE!!)
Q-4 GROUND ELECTRODE
T-3 GROUND ELECTRODE
X-BOOSTER GAPA-SPECIAL DESIGN NOT SPECIFIED
B-SPECIAL DESIGN NOT SPECIFIED
E-V GROOVED CENTER ELECTRODE
G-FINE WIRE NICKEL ALLOY CENTER ELECTRODE
J-WITHOUT INFO
N-SPECIAL SIDE ELECTRODE
POSIBLE REPLACEMENTS (IN PLATINUM) I CAN THINK OF (FROM NGK AND CROSS-REFERENCES)
*Adjustment to 1mm gap is needed for plugs other than the PFR6E-10.
Without number seems to be 0.8mm gap.
AUTOLITE NGK
AP63 PFR6B
BOSH NGK
FR6DPP33X PFR6A-11
FR6DPP332 PFR6B
FR5DPP222 PFR6B
FR7DP1X PFR6B-11
FR6DPP33X PFR6G-11
FR5DPP222 PFR6J-11
FR7DPP22U PFR6N-11
FR7DPP33 PFR6Q
FR6DPP22U PFR6T-10G
F7KPP332U PFR6X-11
CHAMPION NGK
RC8PYCB PFR6G-11
RC8PYPB4 PFR6G-11
RC8PYP PFR6J-11
RC11PYPB4 PFR6N-11
DENSO NGK
K20PR11 PFR6B-11
PK20PR-L11 PFR6G-11
PK20PR-L11 PFR6G-11
PK20PR-L13 PFR6G-13
PK20PR-P PFR6J
PK20PR-P11 PFR6J-11
PK20PR-P8 PFR6J
PK20PR-TP PFR6M
SINCE PFR6E-10 IS ONLY PRODUCED BY NGK IT APPEARS THAT THE V-GROOVE IS NGK EXCLUSIVE
Sources:
www.ngksparkplugs.com/techinfo/spark.../partnumberkey.pdf
http://www.google.com/url?sa=t&rct=...Nvyb7Ikal67BOV2HQ&sig2=dYs-LRXcVMPNQWSt-UKsqw
+2 hours of reading both files...