Sparkplugs options...

[dbMazda]

I have used many spark plugs in my 03 Mazda Protege DX.
I was wondering how they worked for you.
Out of all of the bunch I came up with the best as in.
NGK BKR6EK ( Needs better octane 89 - 91 )
NGK ZFR6F-11 ( Needs better octane 89 - 91 )

BOSCH F8DC4 ( NON-Resistor Needs better octane 91+ )
Air Bag light comes on & off. Nothing happens. Minor glitch!

NGK BKR6E-11 or
NGK BKR6E-11 MOD--- ( Needs better octane 89 - 91 )
http://performanceunlimited.com/documents/plugsidegapping.html

No spark hitting the piston. The spark hits the grounds before any where near the piston. Grounds better ground than the piston!
Only issue is octane. Advancing the combustion with sooner spark or faster combustion might make a pre-ignition.

( No cats? Need to burn more fuel to have less out of tail pipe to be read as too rich so ECU will turn down fuel less.
Also need 91 octane since less fuel is used. Less of 91 makes 87 in combustion. Better off not doing it! )

 

[dbMazda]

NGK BKR6EK are the same hight as NGK ZFR6F-11,
but the center electrode on the BKR6EK
is where the side electrode is at on the ZFR6F-11.
So the combustion is further in the cylinder than the ZFR6F-11.
Those plugs alone advance your timing being deeper in the cylinder.

BOSCH F8DC4 are non-Resistors, so the spark happens sooner & longer, burning more fuel.
The plugs do not hold back, building up a charge from the coil as well but still combustion
happens sooner. This is good because you burn more fuel.

NGK BKR6E-11 MOD they are good being a open gap, but they are an stock design plug.
They are not as advanced as ZFR6F-11, BKE6EK so this might be a good option if those plugs
make you engine knock.