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