REFLECTOR: Denso X27GPR-U spark plug problem

[Michael Watson]

John,

I agree with scott,  that looks like an overheated oil soaked plug. Was that
plug remover from the TOP or BOTTOM of cylinder 4?

The Franklin manual states that you should lean the mixture over 5K, I start
leaning at 3500 ft, 200 ROP then at 5000 ft I lean to 100 ROP.
I have never ran my engine LOP, gas is cheaper than an engine overall.  At
those settings, I'm burning 12.6 and 11.4 GPH. I also burn
1 qrt of oil every three hours, but that's the nature of the Franklin
engine. I used to get slight oil fouling on my bottom plugs so I changed
them to Autolite * UREB36S iridium plugs*,($300.00+) the engine rums much
smoother, mag drops are smooth and even. problem solved.


On Sun, Oct 31, 2010 at 1:09 PM, <aminetech at bluefrog.com> wrote:

> 100 hours ago I replaced standard aircraft plugs with Denso X27GPR-U spark
> plugs.  They worked great until recently when on 2 occasions I noticed a
> faint missing sound right after takeoff.  It went away after a few seconds.
>  When I inspected the plugs, 5 were in perfect condition.  The gap on the #4
> cylinder was completely filled in with a black, layered, flakey material
> that resembled rust on severely corroded steel.  Unfortunately I didn’t take
> a picture of that.  The attached pic is what it looked like after brushing
> the plug clean.  As the pic shows, the outer electrode is severely eaten
> away.  (I sent this pic to Klaus 10 days ago, but no response) I replaced
> with a new plug and the engine ran fine.  After 10 hours the EI ran poorly
> during a mag check, so I pulled the #4 plug and found a “string” of material
> spanning the electrodes.  (see pic in next email)  I’m sending the pic in
> another email as both may be to big to send together.  Two people have told
> me it looks like oil fouling, however my oil consumption is normal at 1 qt/4
> hrs.  Also, several years ago when I did have high oil consumption (1 qt/hr)
> due to 2 broken rings, the plugs did not foul.  Still, with 2 people
> suggesting oil, it behooved me to look into it, so I collected the deposits
> for testing.  They are magnetic.  I did an ash test which vaporizes all
> non-metal materials.  No smoke occurred during the test which indicated
> nothing was vaporized.  There was no weight loss which confirms that the
> deposit is all metal(s).  During the ash test the material had a dark red
> glow which is consistent with iron.  No other colors which would indicate
> certain other metals, were present.  So, I’m certain that oil is not a
> factor here.  Several years ago I had the same thing happen with a standard
> aircraft plug/EI ignition on the #1 cylinder.  One common element between
> then and now is that I flew several hours at 2-3000 msl at reduced  power
> just prior to the fouling.  This altitude is unusual for me.  I normally fly
> 7-12k.  At low altitude and full rich the fuel burn is 13-15 gph (depending
> on throttle setting).  That seems a lot so I lean it a bit to get 10-12 gph.
>  Maybe that’s a problem, but CHTs aren’t affected.  I think I’ll try full
> rich and see it that helps.  Does anyone else lean at low altitude?  Any
> ideas or operating data with Franklin engines will be appreciated.
>
> John
>
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-- 
Mike W.
1997 Velocity Elite RG
Franklin /IVO Electric CS
Dual GRT EFIS HX Synthetic Vision
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