So is this a problem, or not ?

[richardcox_lotus]

As some of you may recall, I've just changed from NGK BPR7ES to BP6ES as the former were fouling very easily. This is a photo of the new plug in #3 Cylinder after about 80 miles, the majority of which were either in a traffic jam or going about 60-70 mph in very hot conditions. Engine idles faster than I would like (see other post), but generally runs OK

Is this an overheated plug ? I fear I may be falling between 2 stools - 6's too hot & 7's too cold.

Regards

Richard

[stuartgb100]

Richard,

Here's a link to one of several 'reference' sites which will give a representative cross-section of whys and wherefores as to spark plug woes:

http://www.dansmc.com/Spark_Plugs/Spark ... talog.html

BTW, with a fairly common topic, it's often useful to Search the Forum first. That way there's a good chance to narrow down the problem, and make the actual question much more focused.

HTH,
Regards,
Stuart.

[M100]

You might be running slightly lean but there is nothing fundamentally wrong with that plug colour, the reference colours you see in things like Haynes manuals and possibly on the NGK website are from engines fuelled with leaded fuel. Run unleaded, or even with a lead additive and the plugs always look much lighter indicating lean running or overheating.

You should see what plugs look like in an Elise or more particularly 90's Elans, even with the right grade they run almost white.

[richardcox_lotus]

Thanks for the replies guys. I had seen that NKG chart before, my concern is what looks to me to be a scorch mark in the insulator core. I'm not worried by the overall colour. Pls note I'm running with Tetraboost leaded additive, so the RON is quite high (I'd say 99ish)

[thor]

By the way, I'm about to change mine, what should the gap be....?
+2S130/5 with lumenition..