http://www.greddy.com/prod_spark_plugs.htm

does anyone know what the heat numbers (9-10-11) mean ?

 

How cold are the plugs, usually japan plugs are opposite from euro plugs, thus the 10s are colder than the 9s.
RX8 has NGK iridium plugs 9 for leading (if i'm not wrong) and 10s for trailing.

Usually one goes for 10s all around.

 

Anyone has these installed?

 

i called greddy over a year ago and they said that they will not work. i wanted t install them when i got the turbo put in

 

so it only works on the rx-7?

 

correct they only work with the 7. and greddy said they dont know when they will be making them for the 8

 

hmmmmm

 

I have those plugs in my car. They run fine but they are for rx7s. No problem installing them and running them, 6000 km now.

 

these are just rebranded plugs. i forget which brand was the original maker, but if you ask Gotham Racing in the vendor forums... they can tell you.

 

https://www.rx8club.com/series-i-major-horsepower-upgrades-93/understanding-spark-plug-heat-range-53327/
http://www.silverbulletrx7.com/plugs/