Spark plug "heat" questions....

Rapidrob

Rapidrob

#1
#1
I've been running a NGK BP6ES spark plug in my Predator 6.5 engine at my altitudes of 6,000-10,000 feet. The engine runs very strong and I have not changed out the jet for high altitude. The plugs insulator looks a little dark but not fouled.
Would there be any advantage going to a hotter plug such as BP5ES? I am not sure changing the jet out would help, and I would be more concerned running the engine too lean and possibly doing damage to the upper end?
 
MB165

MB165

Active Member
#2
#2
Hey rob, switching wont make any difference in performance. The bpr5es one notch "hotter" so it may help burn off extra carbon. keep in mind how much the engine gets loaded down and brought up to full power and temp. if your just putting around with a lot of idling the bpr5 may run cleaner (even a bpr4es). At your altitude a jet change may help clean things up, depending on whats available, go in small increments. I wouldn't be too worried about top end damage, going too lean youll notice it wont run correctly and using the spark plug as a guide, the center electrode will look like a unused plug, maybe even have little pockmarks melted into it.......that's a stretch on a unmodified engine, but if it actually does run well, that's a situation where you could switch to a colder heat range......
 
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