Thought I'd post some pics of the plugs I just pulled this evening.
Setup Notes: Most recent tune I developed with the EFI standalone ECU, several hundred miles on these plugs, including 2 track sessions, 3.2" pulley, BOE air intake
(there's not much to it really, tube and KN filter
), Weapon R headers, Vonhep muffler, about 245whp and a very flat torque curve (the dyno is from earlier this summer), 91 octane gas, track safe tune with 24.5degrees total timing at 8.5psi boost...
I'm happy to share the map with anyone that wants it... There's surely some more left in this tune, but it will get somebody to a close starting point...
Things to notice:
-The set of 4 is burning near identical, as they should with this type of manifold. There is some valve shrouding which browns the plugs a bit, but that's not relevant...
-The 2nd plug is positioned in a way that you can see the advance mark in the electrode. It's the distinct color change on the plug. That is an approximate indicator that the timing is about right on this engine. Not a whole lot of room to advance the timing further without making a change to the VE (volumetric efficiency)....
-On the cut away plug you can see the mixture ring. This is a slightly fat tune- which is great for a track car. I would consider this plug perfect...We want 1-2mm of black at the base of the insulator and then taper off to white or very light brown throughout the middle to the tip of the insulator. This indicates a little safety up top but a lean enough cruise that we're still getting a good *efficient* cruise. In other words, the further down the insulator we observe, the more RPM and load is on the motor. The tip of the insulator indicates the cruise and part throttle mixtures, while the base indicates top end mixtures...
These plugs are just a bit hot, as indicated by the several burnt threads. We should really only have 3-4 burnt threads. That said, they're not grossly hot, as they read very well. This was a NGK 6 series heat range. I'll be replacing with a 7 and going back to iridium tipped plugs. I use the cheapy v-power plugs as you see here while developing the tune since I go through them quickly...
Thought some might find this interesting...
Best,
Phil