> > > >   I broke the  ceramic

cone (around the center electrode) on two spark plugs when I had the

old

engine ignition timing overly advanced.  It just chewed the plugs to
pieces and cause their failure in as little as 10 hours.

Glad your trip was safe and fun - way it should be.

Ed

 Ian & Irene Beadle wrote:

Ed. How much is 'over advanced'?
Ian RV6A

Ed Anderson wrote:

 Ian, I don't know for certain.  But, I erroneously set my ignition timing
to 30-33 deg BTDC while tuning the engine at 5000 rpm on the ground.  It
should have been set around 24 deg BTDC to comply with the Ignition computer
instructions from Tracy Crook.  So I estimate it was at least 6-9 deg more
advance than called for.

I noticed when flying, after setting the timing so, that when ever I leaned
the fuel mixture the exhaust note would change from a steady drone to a more
of a   staccato  sound - more of a popping sound.  It did not make this
sound when the mixture was rich.  Well, it was a different sound from what
the engine normally produced, so I pulled to spark plugs after approx 8
hours (around 3 flights) and found the ceramic cone on both leading plugs
cracked and half gone.  The center electrode was eroded so much that the gap
was almost 3/8" and the three side electrodes were also heavily eroded.
Looked like they had been ridden hard and put away wet. It was not too long
after that I discovered that I had a coolant leak into the combustion
chamber on the rear rotor.  Don't know if there were any connection between
what may have been detonation from the advanced timing or not.  One other
thing of note, at that time I was flying on 87 octane motor gas whereas I am
now flying on 100LL.

Ed Anderson

 
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