REFLECTOR: Denso X27GPR-U spark plug problem

[Alex Balic]

Yea, the (almost) direct contact with the metal residue would definitely
wear the electrode away. That is how EDM machining works.

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Sunday, October 31, 2010 7:39 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Denso X27GPR-U spark plug problem

 

metal filings on the electrodes would do that.  They would get really hot.

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Denso X27GPR-U spark plug problem
From: Matt Bucko  <mailto:mbuc310 at cox.net> <mbuc310 at cox.net>
To: Velocity Aircraft Owners and Builders list  <mailto:reflector at tvbf.org>
<reflector at tvbf.org>
Date: 10/31/2010 06:15 PM



That looks like an over heated plug, If I ever saw one.

On 10/31/2010 10:09 AM, 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 
h
ave 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 fo
 
uling.  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
  
 
_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
 
Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
 
 
_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
 
Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html





-- 
There is no fear in love; but perfect love casteth out fear.
Bible, 1 John iv. 18.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20101101/65fa74c7/attachment.htm>