Ok I'm going to start this out by asking a question then later I will explain. We all know that stock heat range plugs in B series motors, or most motors for that matter, is 6, correct? A popular plug for FI B series applications is the BKR7E which is supposedly 1 step colder, correct? Let me know if you agree/disagree with this and I'll go on.

 

hmm...i agree, i want to see where this is going

 

waiting...

 

still waiting

 

agree...
waiting....

 

Ok, so when I'm at the dyno the other day, we started having a miss problem which was related to running the wrong map on the AEM somehow. Anyways, we pull the plugs and they are pretty shot. I show them to my friend that works/owns the shop. This is a V8 oriented shop BTW. He looks at them and said they were the same plug that they use in their big block Ford mud racing truck. He had some extras laying around for it that he said I could use but he said they were BKR5E's not 7's. I said, why do you guys use hotter plugs in a truck you spray 200hp on? So he goes on to tell me that on NGK's and Autolite's they make the number smaller for colder and pretty much every other plug company goes the other way. I was/still am baffled at this. I have always heard that 7's were colder and some people even use 8's and 9's. But to clarify, heat range is determined by the amount of exposed porcelin (sp) in the center, the more exposed, the hotter the plug. So with this in mind we compared the two and the 5 had less exposed than the 7. So this would mean they were correct. 5's are colder. I was blown away, I have always heard 7's were colder. I still haven't researched this anymore so if anyone has the time please do so.

 

http://www.ngksparkplugs.com/techinf...overviewp2.asp

that should clarify things up a a bit.

 

Well, D-series motors use 5 heat range plugs, and so do the B18B's, and B-series vtec motors use 6's, so unless D-series and the lower compression B motor needs colder range plugs, I think your friend is mistaken.

 

Incorrect NGK is one of the only companies in the world for spark plugs taht are backwards, the Higher the number the colder the plug, most any other plug mfg will be smaller number is colder. I've pumped heads several times with the dumb local parts stores on this, even an Import Auto Parts store who said "I'vce been doing this for 25+ years blah blah blah" NGK is higher the number the colder the plug but Autolites and Champions lower the colder.

 

Ok, checked out a printout a DSM friend had and 7's are colder. It's the porcelin size in the plug that is different, not that is exposed like I thought. Like I said, I was scratching my head, these guys are pretty reputable too. Guess I'll have to break the news to them that me and my friend were right, hehe.