[crewdog434]

Good morning fellow flyers, just thought I would share some findings regarding a recent spark plug change. During the first couple of years of operating my LightSpeed II, using the the standard Denso spark plugs, I changed to NGK BR8ES plugs. I noticed that during full-power climb-out, my CHT's would slowly climb to the 425 deg F range at an IAS of 100kts. Two weeks ago, during my annual condition inspection, I switched to a colder spark plug, NGK BR9ES. Now, during the same power setting/airspeed, up to 6500' MSL, the CHT's barely tick past 400 deg F. A significant difference! I realize that ambient air temps/loaded weight/etc, will affect the CHT's, but switching to a slightly colder plug made me happy. I also realize that a colder spark plug runs the risk of fouling much easier, but I replace the plugs annual, anyhow. Not too concerned.

 

[Walt]

The 9 should work fine, but I seriously doubt the cooler range of the plug had anything to do with lower EGT. Perhaps the old plugs just needed to be changed.