So when i got my car years ago i had 8 spark plugs coming out which all looked the same, nice brown color. They were projected nose plugs Champion RV12YC. I replaced them by an NGK R plug OEM design which gets a bit dirty on cylinder 5 over time. Is it okay to use one projected nose plug as a test in that cylinder to see if that one stays clean? I mean would it harm anything cause of a deeper setting in the combustion chamber compared to 7 other plugs? Thanks. Robbie
I would make them all the same could always use 1 step colder for the extended plug if worried about detonation.
I will in the end run 8 the same plugs. I would like to know if i can run my test for a while? Thanks.
I made a mistake. They're both projected nose design. The Champions tip look brown and the NGK looks light gray. Also one of the old Champions showed a bit more fouling. Champions all seem more brown with some black on top of thread.
So in 1969 my car came with AC Delco R44TS which isn't a projected nose plug. Many cross references are projected nose plugs like Champion and NGK. My experience is the projected nose plug runs a bit better, more responsive. Why did the engineers chose to go with the R44TS design?
I wouldn’t run a different plug than all the rest…brand wise or any other. I do know for FACT by SkiDoo engineers that different lengths spark plugs, I.e. the tip length physically changes the ignition timing that won’t or can’t show up on a timing light. Extended tip moves the spark closer/deeper into the combustion chamber creating the spark placed in a different area. Physically making the spark sooner. Acts like advancing the timing. Think about it. Makes sense! Also it slightly changes the compression by “filling” the combustion chamber more… or less.
I always used an NGK UR-5 in an iron head. The UR-4 is closer to the heat range of an AC 44 or 45. My current engine has used the FR-5 since I have owned it. Same plug as the UR-5 except it is flat seat with a gasket. I believe Jim Weise uses the FR-5 plug in the majority of his aluminum head street engine builds. The 5 heat range is closer to an AC 43 plug. The projected nose plugs have a wider heat range. They run hotter at low RPM, and cooler at higher RPM.
So the 5 heat range of my plug is different than the 5 of the FR-5 plug? I see, it is the design that makes the difference right? The projected nose plug that is.
I personally think it’s better to use an extended tip plug thinking it uncovers the spark more. what ever the reason, it showed up on our dyno slightly with our snowmobile race engines, both our stockers and mod engines.
Yes, the 5 heat range is the same, but, the UR-5 has more of a projected nose. The theory is that due to the projected nose placing the gap further into the chamber, the plug runs hotter at lower RPM, but at higher RPM, the incoming charge cools the plug more giving it a wider heat range. UR-5 on left, BPR5FS on right, In addition, the UR-5 is NGK's V-Power plug. It has a V cut into the center electrode. It gives it more sharp edges. Sparks like sharp edges. The ground electrode also has a V cut into it.
