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Steve, those plugs look quite a bit more worn and eroded than what I see at
the end of 25-30 hours. In mine the center electrode has just barely lost
the sharp corners around the end of the center electrode. There is
considerable coating of the center electrode with (what I believe) are lead
crystals - the white ceramic is almost starting to look black. But, yours
look to have taken more stress - particularly the second photo where the
center electrode looks almost rounded at the point.
But, while always difficult to tell from just a photo, your plugs look
somewhat similar (but not nearly as bad) when I unintentionally set my
static timing about 15 deg beyond the 30 deg Tracy recommended for a total
of around 45 deg before TDC. When I flew I notice that if I opened the
throttle for full power the exhaust changed to a staccato popping sound,
pulling back on the throttle stopped the popping characteristic of the
exhaust.
When I got back on the ground I pulled the plugs. All four plugs had the
ceramic cone either shattered or cracked. The two leading plugs had half of
the cone missing - apparent either disintegrated or fail into the engine and
go blown out the exhaust without doing damage - and were the most seriously
damaged. The center electrode had eroded at least 1/8" almost down to the
cone. The grounding electrodes were severely eroded as well. I mean there
was absolutely no question that these plugs had been hammered hard. I
believe due to the overly advanced ignition that I was encountering
detonation or severe preignition. Not saying your ignition is not set
properly, but then I thought mine was too {:>).
Many of us do run our engines on the severely lean side of the curve which
according to the spark plug manufactures can apparently contribute to SAG
and perhaps even the conditions of your spark plugs.
ED
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of sboese
Sent: Tuesday, July 07, 2009 5:05 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Emailing: rotor 2 leading, rotor 2 leading b
Ed,
Here are two pictures of a plug removed after 15 hours of use, half with
100LL. All the plugs look very similar. Does this plug look typical to you
and satisfy your definition of "no discernable wear"? I'm just trying to
satisfy myself that I'm not seeing something anomolous.
Steve Boese
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