rc51jim Posted June 15, 2016 Share Posted June 15, 2016 Has anyone done any testing with different heat range plugs? My gen5 says to use NGK CR9EH9, middle 9 being the heat range indicator. I bought the bike used, and it had CR8EH9, slightly hotter according to NGK. Original plugs looked fine (don't know how many miles they had on them) and I had replaced them when I bought it with the CR9EHIX9 (Iridium). When I checked the valves last winter the new plugs still looked fine also. Just wondering if anyone had tried different heat ranges, taken any photos, etc. Thanks, Jim Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted June 20, 2016 Member Contributer Share Posted June 20, 2016 Why? Have you modded the bike? Is there an engineering reason behind "trying" different heat range plugs? I imagine if you're bored and want to see how different heat ranges effect things like reduced plug life, poorer fuel economy and power, decreased range of proper spark initiation et al you CAN...experiments can be fun. But if you're looking to eek out something by operating the bike in its design parameters--the factory plugs are optimal for that regime and I'm not sure you'll get much out of it unless you like the educational benefits of doing experiments, taking and analyzing data and the like. Just thinking out loud. YMMV--literally. Matt Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted June 20, 2016 Member Contributer Share Posted June 20, 2016 Here is a decent place to read up on why you should consider a change in heat range for plugs...maybe if you add 75hp to 100hp... https://www.ngk.com/learning-center/article/207/i-have-slightly-modified-my-motor---do-i-need The spark plug design determines its ability to remove heat from the combustion chamber. The primary method used to do this is by altering the internal length of the core nose. In addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. *When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, keeping the firing tip cooler. *A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter. An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as adding a turbo or supercharger, increasing compression, timing changes, use of alternate fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature, necessitating a colder plug. A good rule of thumb is, one Heat Range colder for every 75–100hp added. In identical spark plug types, the difference from one fullHeat Range to the next is the ability to remove 70°C to 100°C from the combustion chamber. Link to comment Share on other sites More sharing options...
rc51jim Posted June 21, 2016 Author Share Posted June 21, 2016 Yes, I'm aware of the reason for different heat range plugs. Due to the fact my bike came with one heat range hotter plug than stock, wondered if anyone had experimented (I'm not willing to). I replaced the current set (which looked fine and were a #9 Iridiums, and didn't show any wear) with another set of 9 Iridiums. Previous owner (or dealer) probably either put in 8's by mistake, or couldn't get 9's. No matter, 9's work fine. Link to comment Share on other sites More sharing options...
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