i was just curious as to what the last letter before the pregap on NGK plugs stands for. for example, my stock z6 plugs are ZFR5J-11. i know the 5 is for the heat range and the 11 refers to the pregap. for many boosted sohcs i have seen people recommending ZFR6F-11 plugs for 1 step colder, which is what i'm currently running. what does the J and F stand for? are they significant, b/c i might be upping the boost and going to 2 step colder plugs, but i dont know if i should be looking for ZFR7J or ZFR7F. thanks

-alan

 

go here https://honda-tech.com/zerothread?id=379274 and read my third post

 

ok so if the last letter is the construction, then what kind is J?

 

my car came with ZFR5F11. When i modded out my car i used ZFR6F11. A few months ago i put nitrous on my car. I used the ZFR6F11's for the 35shot, but changed plugs when i jetted it up to 50. I'm using NGK BKR7E. They are great for forced induction, and my car runs fine all motor. They only cost $2 each. I got mine from http://www.sparkplugs.com
Numerous people recommended these plugs to me. They are gapped to .034" from the factory, which is prefect for my situation. Peace