what heat range plug is good for a forced induction miata?

also, what heat range is the stock miata plug and should i go 1 or 2 colder?

 

I think everyone and their mother, almost, uses a ngk bkr7e (I think thats the model #, if not its close).

 

Go to your favorite parts store and get the standard copper $1/ea NGK plug for the miata. No need to go cooler on a street car.

 

I run bkr7e NGK

 

thx

 

ngk is showing that it is a v power plug. with the v cut electrode. is that good to use? or do they not accually have that groove?

 

I use BKR7E-11 (11 just means its pre-gapped, 1.1mm i think) and I believe it is also a v-power.

 

they do have a groove

 

You dont want to use the 11, its gapped too big. The regular bkr7e is pregapped to .35

 

I just walked out to the garage to look. Get a package of 4 x NGK BKR6ES-11 stock no 5553. Comes in a silver box, no groove, and is around $4.50.

Get a gap feeler and close them down to .35 or so if you have a miss that only occurs under boost.

 

Maybe I remembered the number wrong then. They've been in for a year with no issues.

 

I'm not going to say there's anything wrong with going with heat range 7 and a small gap for safety BUT you really want to run a hotter plug and larger gap unless you have a problem doing so. A colder plug is less efficient than a hotter plug. BUT too hot of a plug in the wrong/ignorant hands can lead to big $$ damage.

 

thats the exact plug and gap i used on the turbo civic. worked great.

 

That temp range also comes in the NGK Iridium range.

 

-11 mean they are pregapped at .044"

BKR7Es are pregapped at .035" (Stock Number 6097)


The stock 1.6 used BKR6E-11 plugs. The 1.8 uses BKR5E-11 plugs. You want to go 1 heat range colder for every 75-100 hp added. So if you have a 1.6 you'll want a heat range 7 with ngk plugs and if you have a 1.8 you can just buy 1.6 plugs.

 

Why? Colder plugs just waste power. Unless you have a detonation problem , stick with stock heat range for your street car. Race car, I'd probably go a step down for safety.

 

so they don't burn off the carbon deposits and foul.

 

no a colder plug is more likely to foul

 

exactly, that's why im running colder. I'm really doing it for the extra detonation protection as they keep the intake temps every so slightly colder.

 

Hmm I'm not sure you're with me on this homie.

The hotter plug
hotter cylinder temps
higher cylinder pressure
burn off deposits
more efficient

The colder plug
more likely to foul the plug
more likely to leave deposits on the cyl walls
lower cyl pressure
takes heat from combustion and *delivers it to the cooling system*
less efficient