Ultimate/Racing Class Iridium SP
 

Has anyone used these on an 8. I want to update and change the stock spark plugs.

http://www.sparkplugs.com/results_app.asp

I saw that.... although the link does not work :o

Ultra/Racing spark
colder Denso 34 trail and 31 leading
racing Denso 31 trail and 27 leading

That is 10 Trailing and 9 leading in the NGK range for 31/27 plugs. I only see one FEED RX-8 in Japan use 11 and 10 plugs in their show/racing car. But they sells 10/9 to me as their racing plugs :confused:

conversion table
https://www.rx8club.com/attachment.p...chmentid=43435

Stock is at the bottom of your link

9 Trailing and 7 leading.

To understand the heat range. Richard Paul and Rotary God has a very good thread about it.
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/understanding-spark-plug-heat-range-53327/

I am about to put the 10/9 combo in my car because I track my car and only use my car in the weekends.

In terms of brand name, I think Denso and NGK are both very good and hard to compare one with another. Australian NGK is the only one I don't trust, so I use Made in Japan NGKs.... :)

Hope this helps.

Loved your video's takahashi. You rock. what kinds of mods do you have on that 8 of yours anyway?

You mean my track day video at Sandown, or the video at the night with Paris Hilton... ;)?

Well the mod with Paris Hilton is Tiger Penis Soup :D.

and the mod for my car at that time on the wet track is mainly strut, sway and brakes... I should have something better next time on the dry :D. I did take something else after that but the quality is not that good (I set the video too high and the mirror blocking the view in front :()