I'm ditching the stock eta WR9LS plugs for some cooler NGK's. The problem is that I can't figure out the heat range on them. I see guys using the BPR8ES, but I don't know if thats cooler or hotter than a BPR7ES. I was under the impression that a higher heat range meant a cooler plug, but I've found contradictory info on this.
EDIT:
I figured it out. The next question would be if BPR9ES is too cold for around town driving?
I've used NGK's in my motocross bikes for years. BMW also uses them in newer designs. The problem I have with the Bosch plugs I have is that they are relatively hot, which can lead to the plug becoming a point of preignition. At 12 psi, I think thats whats keeping me from going further. Less timing doesn't make any difference, and I don't think its leaning out. I'll see when the new, terminal stud BPR8ES's get here. The last box of BPR9ES's I got had non removable terminal caps. Thats okay though, as I'm thinking maybe a 9 would be colder than I need to go anyway. I'd hate to have them foul out while I'm driving around town.
I had always thought that Bosch plugs were the way to go, but now I only use NGK plugs and highly recommend them. they made a world of difference on my bimmers.
I use NGK in everything. Granted, I have to spend $45/ea for the plug and another $45 for the custom cap to go with them for the racebikes, but they've always been bulletproof.
Working well in the bug-piston motor now. Don't remember off the top of my head what range I used in there, though. Likely an 8, though.
I've always used NGK in everything. I like Iridiums when they're available for a certain application. They're expensive but last a long time and work awesome.
Would have used them in the 535 but they're not available, so I went with copper cores.
