I just wanted to add to this older thread information from sparkplugs.com that explains the hotter-colder plug designation, which is hinted at above but not really explained. (After searching the forum I still couldnt find this info in any thread, so here it is)
For example, Flash's Supercharger installation instructions mention using a spark plug that is one step colder than stock. The sparkplugs.com website identifies NGK plug BPR6EIX as the correct model for "stock" as others have mentioned above (This plug is also identified as part number 6637)
So, according to the information below, one step "colder" for NGK should be BPR7EIX.
That plug is SKU: <a class="" href="http://www.sparkplugs.com/Quickwatch.aspx?zpid=9492">#BPR7EIX</a>
ITEM: <a class="" href="http://www.sparkplugs.com/Quickwatch.aspx?zpid=9492">#NGK4055</a>
CAUTION: different manufacturers use the heat codes differently, read up to be sure what you are getting.
This link
http://www.sparkplugs.com/learning-cente...otter-plug
has this to say:
NGK:
NGK indicates the heat range in the middle of the plug number. For example, BCPR6ES-11 has a heat range of 6. (The number after the “-“ is the Gap.) NGK plugs are colder the higher the number, hotter the lower the number.
Starting with part # BKR6E-11 (Heat Range 6), a colder plug would # BKR7E-11 (Heat Range 7), a hotter plug would be # BKR5E-11 (Heat Range 5).
Now I'm really itching to get that Stage 3 supercharger installed!
--michael
