KOKISF

Like I state up there whats the one step colder plug for the isf, ive heard denso irridium ikh 22 and the two step colder is the ikh 24 can anyone confirm?

abohler

I am in the process of doing this right now. The ISF plug is -5. Going one colder would be -6, if you are running a lot of nitrous or something I may even suggest -7, but the idle will be a little more rough.

shyguyF

The oem ISF spark plugs are 20 in heat range so one step colder is 22, two steps are 24.
Denso they use scale 14 16 ........20 22 24... in heat range for their spark plugs.
NGK they use scale 4 5 6.....7 8 9....in heat range for their spark plugs.
I'm running IKH20 plugs for my F but not recommended for our engine. but not problem to mine so far.

tgui

Are you doing something that makes combustion that much hotter on average? On turbo cars with big turbos colder plugs can help fight predetonation, but thats because you're heating up the cyl that much more. Colder plugs on a stock-ish engine I'm guessing might do nothing... to hurting performance, but thats just a guess.

KOKISF

So denso is not recomended for the F ? Im spraying bro!

KOKISF

Still no one has the correct spark plug number for a one step colder plug for the oen ngk plug?

shyguyF

I do not say Denso not recommended for the F b/c OEM spark plugs for ISF is Denso FK20HBR11. If you really want one step colder spark plugs you can pick Denso IKH22 ( iridium power ).