X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 29 Nov 2011 12:22:40 -0500 Message-ID: X-Original-Return-Path: Received: from nm22-vm0.bullet.mail.ne1.yahoo.com ([98.138.91.60] verified) by logan.com (CommuniGate Pro SMTP 5.4.2) with SMTP id 5263203 for lml@lancaironline.net; Tue, 29 Nov 2011 07:53:35 -0500 Received-SPF: none receiver=logan.com; client-ip=98.138.91.60; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.50] by nm22.bullet.mail.ne1.yahoo.com with NNFMP; 29 Nov 2011 12:53:02 -0000 Received: from [98.138.89.162] by tm3.bullet.mail.ne1.yahoo.com with NNFMP; 29 Nov 2011 12:53:01 -0000 Received: from [127.0.0.1] by omp1018.mail.ne1.yahoo.com with NNFMP; 29 Nov 2011 12:53:01 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 966934.42439.bm@omp1018.mail.ne1.yahoo.com Received: (qmail 66251 invoked by uid 60001); 29 Nov 2011 12:53:01 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=HE/6Wdja+ECnbSqo36rbIsE8ZQrpZkMjpY8/glvABu/0aoyhyqrilyu2Y69YPYA1GTxIxGjI3IHVsozbZnRe2K2MYeRoqYxU6yeVLgWawNHpsMjdMf1m1DjspXVgrHmWwTbxTTR+aq4VYoQtxK8EnkKIGzCFP9mrwoOISGC3BPo=; X-YMail-OSG: BTAANd8VM1kEoN0cEmp.oNJeXuRsmjtxN9gSaYNlkpvpHab ia9ZzMJNaGMLFlD63kHx9GIwODtqsXshLPoUwBJVLqW0L.z9GQ5NOP.WoheG GKUBOnyhZIruQhKhZw0SrkS3VzthKK9vXQf4IkB7I1E9bUJ.O_hp9zmQQkQ1 Oc1NMDLfH54AYke_iRvraYWEBwmp5ndR_OBjKsJTV0w1iwbRTmEAJJWcp1ts GoTDIUMrFc_j4u.jJajWIg0QjnTSfsNIu9oBV1RsjOjbe09k47.LlfIdssxo Cg7cCfYlxM43RiTzHEBTjluGhHlvxAOviV9YSc9ANyyng3d0W9shGoWxTXx8 gN63GZASR2Y1LH_.ALyTK9fAIzY3Ymfvq1k1iNJnyGriJ8IQnI5W7R_Y1.4a io_ldXDu4jJ0FUx6dH0EQlAqWdqSbTZAPmocGjsU7 Received: from [97.122.154.219] by web125615.mail.ne1.yahoo.com via HTTP; Tue, 29 Nov 2011 04:53:01 PST X-Mailer: YahooMailWebService/0.8.115.325013 References: X-Original-Message-ID: <1322571181.57303.YahooMailNeo@web125615.mail.ne1.yahoo.com> X-Original-Date: Tue, 29 Nov 2011 04:53:01 -0800 (PST) From: Gary Casey Reply-To: Gary Casey Subject: Re: E-Mag/P-Mag X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="478688329-1724821164-1322571181=:57303" --478688329-1724821164-1322571181=:57303 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable I agree with Scott. =A0I'm certainly not an expert on the certification req= uirements, but as I recall after an electrical failure (like a failure of o= ne mag) the engine has to produce at least 90% power and be free from deton= ation, overheating and other bad stuff. =A0Just imagine a circle with two i= gnition points spaced from the center. =A0With both igniting fuel at the sa= me time, two ever-expanding circles of flame will gradually burn all the fu= el. =A0With only one lighting the fuel, it's "circle of fire" will have to = expand clear to the opposite side of the chamber, which will take longer. = =A0One problem with that is that the air/fuel mixture at the far end of the= chamber will have longer to get hot from the high pressure in the chamber = and heat radiated from the flame front. =A0Consequently, I'm sure that the = detonation margin will be less when running on one plug. =A0When running on= e EI, one plug will likely fire before the other. =A0Not as bad as the seco= nd not firing at all, but complete combustion is still delayed a little. =A0D= oes the mag still contribute? =A0I'm sure it does, as the flame certainly h= asn't progressed to the location of the mag-fired plug. =A0I'm also sure th= e mag actually fires, even though the pressure in the chamber is somewhat h= igher than it would be if the EI hadn't fired its plug first. =A0But does t= he EI produce a "more reliable" spark? =A0No, I don't think so - the mag li= ghts the fire every time, just as the EI. =A0Is the EI-produces spark "bett= er"? =A0In some ways. =A0The CD system used by Lightspeed will certainly fi= re a fouled plug better. =A0When my engine was new it would foul plugs real= ly bad during ground running, and the mag couldn't fire its plugs at all, w= hile the Lightspeed would keep the engine running just fine, thank you. =A0= The E/P-mag uses an inductive system and it won't be quite as good with fou= led plugs, but it will be better at running far lean of peak. =A0In normal operation with reasonably good plugs the mag will do just fine. =A0So you = pays your money and takes your choice :-).=0A=0AIf you have increased the c= ompression ratio beyond what Lycoming or Continental had designed into the = engine, don't be misled into thinking that they would just too dumb to do i= t themselves. =A0They had to guarantee freedom from detonation under the wo= rst condition, which is most likely 115F ambient, dry air, redline cylinder= head temperatures while running on one mag. =A0When we raise the compressi= on ratio like I have we have to recognize that we have probably reduced or = destroyed that margin. =A0If one ignition fails, reduce manifold pressure a= s much as possible, run rich and land (running LOP pretty much requires tha= t 2 plugs be firing because of the slow flame travel).=0AJust my opinion,= =0AGary=0A=0AFrom Scott:=0AChris,=0A=A0=0ABesides the two plugs being backu= p, the flame front is more effective with 2 ignition sources.=A0 Some dual= =A0EI's that communicate with each other change the timing slightly if one = of them=A0has ceased operating.=A0 As can be seen from my experience, =A025= DBTDC (both mag and single EI)=A0 cover a broad range of cruise flight con= ditions and the EI is producing a better and=A0more reliable spark.=A0This = is probably why there is a more modest cruise performance improvement=A0fro= m only one EI.=A0 At high altitudes or low power,=A0the mag is lagging the = advanced EI spark and the flame fronts are started differently or the mag i= s already firing into an already started combustion event.=A0 This still im= proves the power delivered from a better timed fire.=0A=A0=0ATo experience = your question, turn off one of your mags in cruise.=A0 You know=A0what happ= ens at the=A0pre flight mag check - RPM drops and RPM is a component of pow= er.=A0 The loss of power is related to the entire combustion event timing n= ot matching the twin flame front condition.=0A=A0=0AScott=0A=A0=0AIn a mess= age dated 11/28/2011 9:53:59 A.M. Central Standard Time, chris_zavatson@yah= oo.com writes:=0AGary, Scott,=0A>A little off-thread, but...=A0=0A>Do our= =A0Lycoming=A0cylinders require=A0that each spark=A0plug fires to properly= =A0propagate=A0the combustion event throughout the entire cylinder?=A0 On t= hose planes that have one mag and one=A0EI=A0(and while the=A0EI=A0has adva= nced=A0its spark), does the mag contribute or can it even still fire?=0A>= =A0=0A>Chris Zavatson --478688329-1724821164-1322571181=:57303 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
I agree with S= cott.  I'm certainly not an expert on the certification requirements, = but as I recall after an electrical failure (like a failure of one mag) the= engine has to produce at least 90% power and be free from detonation, over= heating and other bad stuff.  Just imagine a circle with two ignition = points spaced from the center.  With both igniting fuel at the same ti= me, two ever-expanding circles of flame will gradually burn all the fuel. &= nbsp;With only one lighting the fuel, it's "circle of fire" will have to ex= pand clear to the opposite side of the chamber, which will take longer. &nb= sp;One problem with that is that the air/fuel mixture at the far end of the= chamber will have longer to get hot from the high pressure in the chamber = and heat radiated from the flame front.  Consequently, I'm sure that the detonation margin will be less when running on one plug.  Wh= en running one EI, one plug will likely fire before the other.  Not as= bad as the second not firing at all, but complete combustion is still dela= yed a little.  Does the mag still contribute?  I'm sure it does, = as the flame certainly hasn't progressed to the location of the mag-fired p= lug.  I'm also sure the mag actually fires, even though the pressure i= n the chamber is somewhat higher than it would be if the EI hadn't fired it= s plug first.  But does the EI produce a "more reliable" spark?  = No, I don't think so - the mag lights the fire every time, just as the EI. =  Is the EI-produces spark "better"?  In some ways.  The CD s= ystem used by Lightspeed will certainly fire a fouled plug better.  Wh= en my engine was new it would foul plugs really bad during ground running, = and the mag couldn't fire its plugs at all, while the Lightspeed would keep the engine running just fine, thank you.  The E/P-mag uses= an inductive system and it won't be quite as good with fouled plugs, but i= t will be better at running far lean of peak.  In normal operation wit= h reasonably good plugs the mag will do just fine.  So you pays your m= oney and takes your choice :-).

If you have increa= sed the compression ratio beyond what Lycoming or Continental had designed = into the engine, don't be misled into thinking that they would just too dum= b to do it themselves.  They had to guarantee freedom from detonation = under the worst condition, which is most likely 115F ambient, dry air, redl= ine cylinder head temperatures while running on one mag.  When we rais= e the compression ratio like I have we have to recognize that we have proba= bly reduced or destroyed that margin.  If one ignition fails, reduce m= anifold pressure as much as possible, run rich and land (running LOP pretty much requires that 2 plugs be firing because of the slow flame trav= el).
Just my opinion,
Gary

Fro= m Scott:
Chris,
 
Besides th= e two plugs being backup, the flame front is more effective with 2 ignition= sources.  Some dual EI's that communicate with each other change= the timing slightly if one of them has ceased operating.  As can= be seen from my experience,  25 DBTDC (both mag and single EI)  = cover a broad range of cruise flight conditions and the EI is producing a b= etter and more reliable spark. This is probably why there is a mo= re modest cruise performance improvement from only one EI.  At hi= gh altitudes or low power, the mag is lagging the advanced EI spark an= d the flame fronts are started differently or the mag is already firing into an already started combustion event.  This still improves the po= wer delivered from a better timed fire.
 
To exper= ience your question, turn off one of your mags in cruise.  You know&nb= sp;what happens at the pre flight mag check - RPM drops and RPM is a c= omponent of power.  The loss of power is related to the entire combust= ion event timing not matching the twin flame front condition.
&nb= sp;
Scott
 
In a message dated 11/2= 8/2011 9:53:59 A.M. Central Standard Time, chris_zavatson@yahoo.com writes:=
Gary, Scott,
A little off-thread, but... 
Do our Lycoming cylinders require that ea= ch spark plug fires to properly propagate the combustion event throughout the entire cylinder?  On those = planes that have one mag and one EI (and while the EI has advance= d its spark), does the mag contribute or can it even still fire?
=
 
Chris Zavatson
<= /span>
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