You need a spark plug designed to take the heat of Lean burn, that is what the 4 is in reference to in the zfr4f-11 Here's a break down:
Z= Extended Gap type plug
F= 19mm (3/4") reach, 16mm (5/8") Hex Metal shell size
4= Hot plug the range is 2-11 2 being hottest, 11 coldest (we need to hotter plug to stand up to the Lean condition)
F= Firing end construction (special design)
11= 1.1mm (.044") wide gap (wide gap like this is good for lean burn)
Originally Posted by jadziasman
The VX and CX both use the same NGK spark plug. Don't know why the CX and VX would have this in common. Go to NGK's web site. Maybe an explanation lurks there.
The CX is a swirl type combustion setup with 8 valves (swirl style allows for leaner A/F ratios) and that is why the CX and VX use the same spark plugs.
Thanks SVO, but I am just a sponge that spends many hours researching things on the intarweb and double-checking to make sure it's correct, lol. I've filled two 40Gig hard drives with documents, pdfs, and bookmarks of info, then I filled a 20Gig hard drive with MP3s to listen to while I search, haha.