hey when i swapping in my tr6's today and i noticed the electrode and the ceramic were farter out on the tr6's compared to the bosch supers that i pulled out. i thought the colder the plug , the farther in the electrode moves into the plug. is this not right?

 

Not right. The electrode usually stays in the same position but they make the ceramic fatter (conducts more heat, so the tip stays colder). On hotter plugs they make the ceramic slimmer to slow down the heat conduction.

The Bosch ones may have been extended tip or something like it.

Jim

 

I think at some point the heat range will have a diff length tip. The TR6 and TR7 are different lengths for example.

 

The heat range of the plug is EXTERNAL to the engine, not internal. The projected length of the tip can be the same across multiple heat ranges. Combine this with different materials, and who knows what a good plug will look like?