I experience the same popping in my TSIO550 powered ES-P.  A test 
pilot for Columbia told me that it is very common when running LOP 
and is aggravated by the low inertia composite prop.  The engine has 
slight variations of fuel mixture and occasionally the fire in a 
cylinder goes out - leading to the sound.  He said if running high 
power LOP to expect it and get used to it - and it does no harm to 
the engine.


I am unfamiliar with any science that supports that set of notions.  
I've got to ponder that.  'Tis a puzzlement.

Lancair , Walter, et al,

 

Hmmmm, Lean misfire is certainly a possibility.  Arcing mags is another.  Hey, I have an idea, how about an electronic ignition?  At least the spark is there all the time.

 

  Check the CAFE tests of electronic ignitions concerning lean misfire (of course one has to be a member of EAA and then poke around).

 

Grayhawk