[iqraceworks]

Originally Posted by johnscales

Old post but I have something interesting to add.
I've just changed out my one step colder plugs with another set and have been running NGK's for the past 5 years. Please bare with me while I explain stuff.
After many years of running @.022 and self tuning and averaging between 17 - 21 mpg mixed driving I happened upon a map over the past couple of months that has been giving me between 25 and 28 mpg whilst maintaining 560whp (virtual dyno, same stretch of road for the past 7 years).
Upon changing out my old NGK's a couple of days ago (about 5k on them) and gapping the new ones to the usual .022 my mpg has fallen back to 18 -19 mpg range.
Hmmm... the new map was good for 25-28mpg previously so what gives?
I've just checked the gapping on my older plugs and found that four of the six plugs are .023 or a very tight .023. The other 2 are a 'loose' .022 but not quite .023 (sort of .0225) .
I am about to pull and regap all of the new 6 plugs to .023.
Could .001 inch really make a difference of 7 to 10 mpg? I'm doubtful but am definitely up for the investigation. About to find out for real. No theoreticals. Will check and update in this post in the next couple of days as it will be amazing if this small change could have such a big difference in engine efficiency.
Btw the older SP's are all good/clean colourwise. Cylinder 6 was running hot but a guy across the road from me mentioned that 'cylinder 1 or 6 usually runs hotter than the rest' before I even pulled it.
He knows nothing about N54's and seemed to mention it as being 'a thing' with most engines so I'm ok with that.
For info my mods are FBO (5" intercooler) with RBTwos turbos + meth.

No....something else is going on. You would never notice .001" change in gap.......lots of other factors that would affect things long before that.