Am starting to get parts together for my next service. Am wondering wether to go from a heat grade 7 plug to a heat grade 8 plug as when last mapped to current 400 bhp wth the ignition advanced slightly was getting Det. Wondering if this was more due to the plug not dissipating the heat quickly enough rather than ignition advanced a bit too far. I have looked at NGK's website about the heat ranges so I understand the self cleaning requirements.
Thanks Steve

 

Well, it cm only help in removing heat - but how much advance they'll still allow to run, who knows. Also, if they are too cold a plug you can have cold start issues and rough low speed running - or can this always be got around in the map?