Hi, when i had my 03 sti serviced it was a standard 265 bhp, now fitted all prodrive parts and had a remap its now 345bhp should i now be using PFR7B plugs instead of the PFR6Bs that were fitted ?

 

yes mate i would use them 6s are good for standard cars but you would be better now with 7s

 

I'm pretty sure the number represents the heat grade for the plug. 6's are usually used for standard impreza's, 7's for modified impreza's and 8's for heavily modified impreza's. Hope this helps

 

on NGK plugs the higher the value the colder the plug. 7 is colder than 6 better for modified cars, and if you driver the car harder. 8's are good for heavily modified as mentioned, also good for track.

for Bosch plugs the numbers are opposite, the lower the value the colder the plug.


You can download the application guide from NGK

http://www.ngk.co.uk/

 

so could i cause any damage running with the PFR6B s at the moment ? dont do track days ,only give it stick over short distances, as i once had a burn up with an unmarked police car in a rover v8 vitesse in my youth which scarred me for life , blue lights at 130 will do that

 

As said, definitely use the 7's now. Also, regap them to 0.65 and they will be perfect.