From a US chart, W6DC = BP6ES. However I think W6DC run colder, and W7DC are closer in performance to a BP6ES.
Here's the link-
http://www.clubplug.net/bosch_ngk.html
Note I'm comparing
resistor plugs here ^^ WR6DC & BPR6ES (the above are not now listed in US) but the heat range numbers are same.
Note Bosch numbers increase with hotness, and NGK decrease.
I have used Bosch plugs before, IMO they are only better than NGK by having a thicker ground electrode.
Note I'm currently running BPR6ES in the 1360 and BPR5EY in the 1412 stroker. Used with Bosch inductive core leads, I've had no problems.
_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
