X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4488375 for flyrotary@lancaironline.net; Thu, 30 Sep 2010 19:20:13 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=alventures@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao106.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100930231937.RJKD3042.fed1rmmtao106.cox.net@fed1rmimpo03.cox.net> for ; Thu, 30 Sep 2010 19:19:37 -0400 Received: from BigAl ([72.199.216.236]) by fed1rmimpo03.cox.net with bizsmtp id DBKc1f00K56cS2o04BKc3h; Thu, 30 Sep 2010 19:19:37 -0400 X-VR-Score: 0.00 X-Authority-Analysis: v=1.1 cv=bpc8uEicDnqxZSslY2USwZnb9rPJRdwMtO2+C0QOm0U= c=1 sm=1 a=5W9vv1tIMrIA:10 a=lN8H/RjlhkCyIsyuOn2r7w==:17 a=Ia-xEzejAAAA:8 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=pedpZTtsAAAA:8 a=lLD5zvyUEOWmkPYJtJkA:9 a=oA6oMoO66KC4JlqxrmIA:7 a=H1tbKAElbgsmpolwWa_K4B1Fk4cA:4 a=CjuIK1q_8ugA:10 a=EzXvWhQp4_cA:10 a=eJojReuL3h0A:10 a=pmWzzpIBPaip6OnG:21 a=-wmpjl3G-d-tEpI3:21 a=O16sh1F8op18iMZN5LsA:9 a=AYgtXj_GckEeaSaP4DwA:7 a=J6CA5jTZSRTr4nCGadf5bB0LJpEA:4 a=or9_CTjbPwJjGWF-:21 a=mMAixb_xj7D2E5-G:21 a=lN8H/RjlhkCyIsyuOn2r7w==:117 X-CM-Score: 0.00 Authentication-Results: cox.net; none From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: New SAG Theory Date: Thu, 30 Sep 2010 16:20:12 -0800 Message-ID: <0CC541DAFEA14198B9017C2C3E04103E@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0028_01CB60BB.5BAFCD70" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6863 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 Thread-Index: Actgskd8eJDatNz6TCK8BceI9yc7rQAR1+4g Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0028_01CB60BB.5BAFCD70 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I'll preface this with the fact that I have never experienced SAG; but = it is an interesting subject. I don't run much 100LL, and I change the plugs = at about 40 hours. A couple questions come to mind: =20 Is all of the discussion of the copper core, etc; relevant to a specific brand/part# plug? What heat range? I use B9EGV racing plugs - do they have a copper core? It's a fine wire electrode; fairly high heat range number ('colder' plug). =20 If the issue is preignition - is that consistent with the large drop in = EGT? =20 Al =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese Sent: Thursday, September 30, 2010 7:14 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: New SAG Theory Discussions of SAG =20 Ed, =20 You take good notes. =20 Just a couple of clarifications: The decrease in the thermal = conductivity of the copper core may be the result of thermal cycling causing = development of porosity within the copper. This is independent of the corrosion = going on between the Mn alloy electrode sheath and the insulator. So there = are two essentially independent mechanisms contributing to the heat range = change of the spark plug with age. =20 =20 The development of the porosity within the copper is not particularly affected by the type of fuel whereas the corrosion between the Mn alloy sheath and the insulator is accelerated by the use of 100LL. =20 The cure is still to install new spark plugs. =20 =20 I have colder spark plugs from Racing Beat that are recommended for prolonged use in high RPM high power applications. At best, the colder plugs will merely delay the onset of SAG but won't prevent it from = happening eventually. It will be some time before the results of using those = plugs will be known. =20 Steve Boese =20 =20 =20 _____ =20 From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf = Of Ed Anderson [eanderson@carolina.rr.com] Sent: Thursday, September 30, 2010 8:46 AM To: Rotary motors in aircraft Subject: [FlyRotary] New SAG Theory Discussions of SAG In a nut shell, Steve's excellent data gathering (how many of use have access to a scanning electron microscope or spectrum analyzer {:>)) and analysis indicates a possible alternative reason for SAG other than = fouling. =20 It basically boils down to a theory of pre-ignition based on the deteorating heat removal capacity of the plug. =20 =20 There is a copper core (the photos showing the two cores) in the center = of the ceramic cone which is responsible for conducting 90% of the heat = away from the center electrode. Based on Steve's' electron microscope = viewing of two cores (one new and one having been used in a 100LL environment), it appears that the plug using leaded gasoline has corrosion occurring on = the boundary between this copper core and the surrounding (hot) elements. = This layer of corrosion hinders heat removal from the plug leading to parts = of the plug becoming hot enough to trigger pre-ignition. =20 This SAG tends to happened at high power settings and reducing power = tends to make it go away (for a while). Steve's theory is that the plug encounters max heat and temperature at high power settings and that = reducing the power permits the plug to cool off enough for the pre-ignition to go away (for a while). =20 So we now have two theories - one is the fouled plug and one of the overheated plug causing SAG. Preignition generally leads to detonation which does not appear to be happening (at least no one is finding the typical detonation damage to the rotary engine). A possible reason is = the quenching effect of the less than optimum shape of the rotary combustion space may tend to delay or prevent the onset of detonation damage that = one would expect from continuous preignition caused by a too hot plug. =20 I believe Steve intends to see if he can find some colder plugs (the = ones that conduct heat better) and see if that extends the time between SAG. Currently I find that roughly 25-30 hours is about the max I can get = using 100LL before SAG sets in, whereas Tracy and others have well over 150 = hours using unleaded Mogas. So if the colder plugs extend the time before = SAG, I would say that pretty much would suggest Steve's theory is correct - if = Not, then perhaps the fouled Plug theory still has merit or it could be some other phenomena happening. =20 Steve, my apologies if I did not present your case as well as you could =20 Ed =20 Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com =20 . =20 =20 =20 From: Bill Bradburry=20 Sent: Thursday, September 30, 2010 9:59 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Discussions of SAG =20 I understand that there was a presentation on SAG at the meeting. Can someone go over the alternative theory with the ones of us that were not = in attendance? It looked like someone had a scanning electron microscope = photo that they were showing! Wow! Are we getting sophisticated or what!! = Was this an explanation of the cause, or ideas for prevention, both?? =20 Bill B =20 ------=_NextPart_000_0028_01CB60BB.5BAFCD70 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I’ll preface this with the = fact that I have never experienced SAG; but it is an interesting subject. I = don’t run much 100LL, and I change the plugs at about 40 hours. A couple = questions come to mind:

 

Is all of the discussion of the = copper core, etc; relevant to a specific brand/part# plug? What heat = range?

I use B9EGV racing plugs – = do they have a copper core? It’s a fine wire electrode; fairly high heat = range number (‘colder’ plug).

 

If the issue is preignition = – is that consistent with the large drop in EGT?

 

Al

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese
Sent: Thursday, September = 30, 2010 7:14 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = New SAG Theory Discussions of SAG

 

Ed,

 

You take good notes.

 

Just a couple of clarifications:  The decrease in the thermal = conductivity of the copper core may be the result of thermal cycling causing = development of porosity within the copper.  This is independent of the = corrosion going on between the Mn alloy electrode sheath and the insulator.  = So there are two essentially independent mechanisms contributing to the = heat range change of the spark plug with age. 

 

The development of the porosity within the copper is not particularly = affected by the type of fuel whereas the corrosion between the Mn alloy sheath and = the insulator is accelerated by the use of 100LL.

 

The cure is still to install new spark plugs. 

 

I have colder spark plugs from Racing Beat that are recommended for = prolonged use in high RPM high power applications.  At best, the colder = plugs will merely delay the onset of SAG but won't prevent it from = happening eventually.  It will be some time before the results of using those = plugs will be known.

 

Steve Boese

 

  

 

From:<= font size=3D2 color=3Dblack face=3DTahoma> Rotary motors in aircraft [flyrotary@lancaironline.net] On = Behalf Of Ed Anderson [eanderson@carolina.rr.com]
Sent: Thursday, September = 30, 2010 8:46 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] New = SAG Theory Discussions of SAG

In a nut shell, Steve's excellent data gathering (how many of use have access to = a scanning electron microscope or spectrum analyzer {:>)) and analysis indicates a possible alternative reason for SAG other than = fouling. 

 

 It basically boils down to a theory of pre-ignition based on the = deteorating heat removal capacity of the plug. 

 

There is a copper core (the photos showing the two cores) in the center of the = ceramic cone which is responsible for conducting 90% of the heat away from the = center electrode.  Based on Steve's' electron microscope viewing of two = cores (one new and one having been used in a 100LL environment), it appears = that the plug using leaded gasoline has corrosion occurring on the boundary = between this copper core and the surrounding (hot) elements.  This layer of = corrosion hinders heat removal from the plug leading to parts of the plug becoming = hot enough to trigger pre-ignition.

 

This SAG tends to happened at high power settings and reducing power tends to = make it go away (for a while).  Steve's theory is that the plug encounters max = heat and temperature at high power settings and that reducing the power = permits the plug to cool off enough for the pre-ignition to go away (for a = while).

 

So we now have two theories - one is the fouled plug and one of the overheated = plug causing SAG.  Preignition generally leads to detonation which does = not appear to be happening (at least no one is finding the typical = detonation damage to the rotary engine).  A possible reason is the quenching = effect of the less than optimum shape of the rotary combustion space may tend to = delay or prevent the onset of detonation damage that one would expect from = continuous preignition caused by a too hot plug.

 

I believe Steve intends to see if he can find some colder plugs (the ones = that conduct heat better) and see if that extends the time between SAG.  Currently I find that roughly 25-30 hours is about the max I can get = using 100LL before SAG sets in, whereas Tracy and others have well over 150 = hours using unleaded Mogas.  So if the colder plugs extend the time = before SAG, I would say that pretty much would suggest Steve's theory is correct - = if Not, then perhaps the fouled Plug theory still has merit or it could be some = other phenomena happening.

 

Steve, my apologies if I did not present your case as well as you = could

 

Ed<= /p>

 

Edward L. Anderson
Anderson Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

 

.

 

 

 

Sent: Thursday, September 30, 2010 9:59 AM

Subject: [FlyRotary] Discussions of SAG

 

I understand = that there was a presentation on SAG at the meeting.  Can someone go over the alternative theory with the ones of us that were not in = attendance?  It looked like someone had a scanning electron microscope photo that they = were showing!  Wow!  Are we getting sophisticated or what!!  = Was this an explanation of the cause, or ideas for prevention, = both??

 

Bill = B

 

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