Mazda recommends using NGK spark plugs for the FC3S.  Leading plugs are BUR7EQ, while trailings are BUR9EQ.  The plugs do come in non-platinum (resistor) and platinum versions.  Platinum spark plugs last a little bit longer (than non-platinums), but they cost about twice as much.  There is no performance gain from running platinum spark plugs other than the longer life.

NGK, stock
NGK Model Part Number Thread Size Reach Hex Size Heat Range Plug Type
BUR7EQ 3559 14mm 19.5mm 13/16" 7 Resistor
BUR7EQP 4764 14mm 19.5mm 13/16" 7 Platinum
BUR9EQ 5483 14mm 19.5mm 13/16" 9 Resistor
BUR9EQP 5255 14mm 19.5mm 13/16" 9 Platinum
NGK heat range = 7, 9

A popular upgrade is to run BUR9EQ spark plugs in the leadings also, requiring you to just buy one type of spark plug when you need to replace all four of them.

An upgrade to running 7's or 9's is to run even colder spark plugs.  NGK makes several colder heat range spark plugs.  Be prepared for the over US$30 per spark plug.

NGK, race
Part Number Thread Size Reach Hex Size Heat Range Plug Type
R6725105 14mm 21.5mm 13/16" 10.5 Platinum
R672511 14mm 21.5mm 13/16" 11 Platinum
R6725115 14mm 21.5mm 13/16" 11.5 Platinum
T-813J-N13 14mm 21.5mm 13/16" 13 Platinum
NGK heat range = 10.5, 11, 11.5 NGK heat range = 13





Dendo Iridium Power Racing
Model Stock No. Thread Size Reach Hex Size Gap Heat Range Plug Type
1RE01-27#4 5719 14mm 21.5mm 20.6mm 0.7mm 27 Iridium
1RE01-31#4 5720 14mm 21.5mm 20.6mm 0.7mm 31 Iridium
1RE01-32#4 5721 14mm 21.5mm 20.6mm 0.7mm 32 Iridium
1RE01-34#4 5722 14mm 21.5mm 20.6mm 0.7mm 34 Iridium





Heat Range Chart
Denso NGK Champion Bosch
9 2 18, 19 10, 11
14 4 16, 14 9
16 5 12, 11 8
20 6 10, 9 7, 6
22 7 8, 7 5
24 8 63, 61 4
27 9 59 3
29 9.5 57  
31 10 55 2
32 10.5 53  
34 11    
35 11.5    




Questions?  Comments?  Send mail to:  reted@fc3spro.com

02/27/2004