X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 16 Nov 2010 19:11:08 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-junco.atl.sa.earthlink.net ([209.86.89.63] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4581033 for lml@lancaironline.net; Tue, 16 Nov 2010 10:14:30 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.63; envelope-from=douglasbrunner@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=mwNP+/0bIo6HaUi2zGsKc35yh/LLm+kSwlv7z8z6V86oqf6dO2UZUT4tG0wsFKEl; h=Received:From:To:References:In-Reply-To:Subject:Date:Message-ID:MIME-Version:Content-Type:X-Mailer:thread-index:Content-Language:X-ELNK-Trace:X-Originating-IP; Received: from [74.93.196.177] (helo=DougsLaptop) by elasmtp-junco.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1PINEH-0008O6-7t for lml@lancaironline.net; Tue, 16 Nov 2010 10:13:53 -0500 From: "Douglas Brunner" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Re: Electronic Ignition X-Original-Date: Tue, 16 Nov 2010 10:14:08 -0500 X-Original-Message-ID: <001b01cb85a0$ea668540$bf338fc0$@net> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001C_01CB8577.01907D40" X-Mailer: Microsoft Office Outlook 12.0 thread-index: AcuFmhTDdqxjAPPRS6KC9O7lGWr3DQABMiaA Content-Language: en-us X-ELNK-Trace: ad85a799c4f5de37c2eb1477c196d22294f5150ab1c16ac0f2b12df0f75675a42be1ab39569739c067495e84a46739f1350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 74.93.196.177 This is a multi-part message in MIME format. ------=_NextPart_000_001C_01CB8577.01907D40 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Scott, =20 I will concede your point about the hotter, longer and more consistent = spark, although in most flight regimes (no extreme of F/A mixture) it = probably doesn=E2=80=99t make much difference. =20 With respect to your comment: =20 =E2=80=9Cyour argument of moving timing by messing with the mixture is, = uh, not good operational practice=E2=80=9D =20 I think you misunderstood my point. I certainly do not advocate = =E2=80=9Cmessing with the mixture=E2=80=9D =E2=80=93 especially at power = levels above 70%. =20 =20 My point was that electronic ignition systems measure only 2 of the 3 = factors that influence timing. Mixture can have a significant effect on = when Peak Intracylinder Pressure (=3D effective timing) occurs. Hence = the effective timing at a best power mixture (50 to 100 deg ROP) would = be significantly advanced compared to the effective timing at best = economy mixture (approx 50 LOP). This is not accounted for by = electronic ignition systems and could lead to excessive spark advance. =20 D. Brunner =20 =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Sky2high@aol.com Sent: Tuesday, November 16, 2010 9:25 AM To: lml@lancaironline.net Subject: [LML] Re: Electronic Ignition =20 Doug, =20 I have a problem with your argument. It seems to be upside down. In = reference I refer you to my 11/2/2010 email entitled "NA Injected Engine = Performance LOP". In any event, for any given proper fuel/air ratio = (mixture), there is a narrow timing range that produces efficient = cylinder pressures at the correct crank angle range. The Lycoming = engine manual (for my 320) displays the acceptable range for the EGT for = best power as 100F to 180F ROP, and best economy as 0F to 80F LOP. = Running 50F ROP is very bad for cylinder pressures as stated by GAMI - = thus your argument of moving timing by messing with the mixture is, uh, = not good operational practice. =20 Secondly, you imply that the only function of an electronic ignition is = to advance the timing. Au contraire mon ami! An electronic ignition = provides for a hotter, longer, more consistent spark over a greater plug = gap that better insures the reliable and timely ignition of the = combustible mixture even though the F/A may be at some extreme. This = results in greater efficiency/HP depending on the way one looks at it. = See the pamphlet on the benefits of the LASAR electronic ignition that = shows speed increases for the same fuel burn or reduced fuel burn at the = same speed of a magneto driven engine. =20 The fixed timing of a magneto (i.e. 25 DBTDC) is a compromise. = Generally speaking, EIs advance the base spark timing minimally until = the power, as measured by RPM and MAP, is reduced below 75%. Bad = events, such as pre-ignition, detonation and incorrectly timed cyl = pressure, are less likely in this regime (that is why the GAMI lean test = is done at less than 75% power). Furthermore, EGTs (representing F/A = ratios) are still maintained in the engine manufacturer's recommended = ranges and the timing is a better match for the combustion event = pressures. =20 Note that during my best power cruises at middle altitudes (2500 RPM, = MAP > 22", EGT > 120F ROP), the EI timing is about 25 DBTDC plus or = minus a degree.=20 =20 Yes, more HP. Better speed for the same fuel burn holding other = conditions equal. Yes, in all the modes you mentioned. =20 I haven't reached TBO yet, I go too fast to accumulate that much time. =20 Scott Krueger IO 320 Dual Lightspeed Plasma III EI =20 In a message dated 11/15/2010 8:21:27 P.M. Central Standard Time, = douglasbrunner@earthlink.net writes: At the risk of starting a =E2=80=9Ctheological=E2=80=9D controversy, I = would like to raise some reservations about electronic ignition systems = (other than reliability and loss of electrical power) =20 Peak intracylinder pressure (the point in the combustion cycle at which = pressure in the cylinder is highest =3D effective timing) is related to = 3 things; spark timing, rpm and MIXTURE. =20 =20 Why mixture? Because air and fuel mixtures burn at different rates = depending on how rich or lean they are. So at a given RPM, MAP and = spark advance you can vary your effective timing by changing the = mixture. =20 =20 =C2=B7 Want to advance your timing? Change your mixture to a 50 = deg ROP mixture =E2=80=93 which is the fastest burning. =C2=B7 Want to retard your timing? Make your mixture richer or = leaner from 50 deg ROP. =20 And since optimal power is achieved at an effective timing of 16 deg = ATDC, advancing the spark timing may or MAY NOT increase horsepower = depending on the mixture. But advancing the timing will likely increase = the magnitude of peak intracylinder pressure leading to higher = intracylinder pressures, higher cylinder head temperatures and greater = stress =3D shorter enging life. =20 For those of you who are using electronic ignition (I am not): =C2=B7 Are you sure you are getting more horsepower? How do you = know? =C2=B7 If you are getting more horsepower, are you getting it = during all modes of engine operation? Rich of peak, lean of peak, high = MAP, low MAP, etc =C2=B7 What is happening to your TBO? =20 D. Brunner =20 The biggest advantage of any of the electronic systems (in my opinon) is = that they provide a spark advance that is a function of at least = manifold pressure, giving an advantage any time the manifold pressure is = much lower than maybe 25 inches. But there is very little combustion = taking place in the exhaust system regardless. The reason the exhaust = temperature rises is that more of the combustion occurs after TDC and = that means less of the energy is being converted to work. The down side = of advancing the spark is that since more combustion occurs at the = highest cylinder pressure, more heat is transferred to the cylinder head = and piston. =20 =20 ------=_NextPart_000_001C_01CB8577.01907D40 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

Scott,

 

I will concede your point about the hotter, longer and more = consistent spark, although in most flight regimes (no extreme of F/A = mixture) it probably doesn=E2=80=99t make much = difference.

 

With respect to your comment:

 

=E2= =80=9Cyour argument of moving timing by messing with the mixture is, uh, = not good operational practice=E2=80=9D

<= o:p> 

I think you misunderstood my point.=C2=A0 I certainly do not advocate = =E2=80=9Cmessing with the mixture=E2=80=9D =E2=80=93 especially at power = levels above 70%.=C2=A0

 

My point was that electronic ignition systems measure only 2 of the 3 = factors that influence timing.=C2=A0 Mixture can have a significant = effect on when Peak Intracylinder Pressure (=3D effective timing) = occurs.=C2=A0 Hence the effective timing at a best power mixture (50 to = 100 deg ROP) would be significantly advanced compared to the effective = timing at best economy mixture (approx 50 LOP).=C2=A0 This is not = accounted for by electronic ignition systems and could lead to excessive = spark advance.

 

D. Brunner<= o:p>

 

 

From:= = Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Sky2high@aol.com
Sent: Tuesday, November 16, 2010 9:25 = AM
To: lml@lancaironline.net
Subject: [LML] Re: = Electronic Ignition

 

D= oug,

&= nbsp;

I= have a problem with your argument.  It seems to be upside = down.  In reference I refer you to my 11/2/2010 email entitled = "NA Injected Engine Performance LOP".  In any event, for = any given proper fuel/air ratio (mixture), there is a = narrow timing range that produces efficient cylinder pressures = at the correct crank angle range.  The Lycoming engine manual (for = my 320) displays the acceptable range for the EGT for best power = as 100F to 180F ROP, and best economy as 0F to 80F LOP.  = Running 50F ROP is very bad for cylinder pressures as stated by GAMI - = thus your argument of moving timing by messing with the mixture is, uh, = not good operational practice.

&= nbsp;

S= econdly, you imply that the only function of an electronic ignition is = to advance the timing.  Au contraire mon ami!  An electronic = ignition provides for a hotter, longer, more consistent spark over a = greater plug gap that better insures the reliable and timely = ignition of the combustible mixture even though the F/A may be at some = extreme.  This results in greater efficiency/HP depending on the = way one looks at it.  See the pamphlet on the benefits of the LASAR = electronic ignition that shows speed increases for the same fuel burn or = reduced fuel burn at the same speed of a magneto driven = engine.

&= nbsp;

T= he fixed timing of a magneto (i.e. 25 DBTDC) is a compromise.  = Generally speaking, EIs advance the base spark = timing minimally until the power, as measured by RPM and = MAP, is reduced below 75%.  Bad events, such as pre-ignition, = detonation and incorrectly timed cyl pressure, are less likely in this = regime (that is why the GAMI lean test is done at less than 75% = power).  Furthermore, EGTs (representing F/A ratios) are still = maintained in the engine manufacturer's recommended ranges and the = timing is a better match for the combustion event = pressures.

&= nbsp;

N= ote that during my best power cruises at middle altitudes (2500 = RPM, MAP > 22", EGT > 120F ROP), the EI timing is about = 25 DBTDC plus or minus a = degree. 

&= nbsp;

Y= es, more HP.  Better speed for the same fuel burn holding other = conditions equal.

Y= es, in all the modes you mentioned.

&= nbsp;

I= haven't reached TBO yet, I go too fast to accumulate that much = time.

&= nbsp;

S= cott Krueger

I= O 320 Dual Lightspeed Plasma III EI

&= nbsp;

I= n a message dated 11/15/2010 8:21:27 P.M. Central Standard Time, = douglasbrunner@earthlink.net = writes:

At the risk of starting a =E2=80=9Ctheological=E2=80=9D controversy, = I would like to raise some reservations about electronic ignition = systems (other than reliability and loss of electrical = power)

 

Peak intracylinder pressure (the point in the combustion cycle at = which pressure in the cylinder is highest =3D effective timing) is = related to 3 things; spark timing, rpm and MIXTURE.  =

 

Why mixture? Because air and fuel mixtures burn at different rates = depending on how rich or lean they are.  So at a given RPM, MAP and = spark advance you can vary your effective timing by changing the = mixture. 

 

=C2=B7=      &nb= sp;   Want to advance your timing? Change your mixture to a 50 deg ROP = mixture =E2=80=93 which is the fastest burning.

=C2=B7=      &nb= sp;   Want to retard your timing?  Make your mixture richer or leaner = from 50 deg ROP.

 

And since optimal power is achieved at an effective timing of 16 deg = ATDC, advancing the spark timing may or MAY NOT increase = horsepower depending on the mixture.  But advancing the timing will = likely increase the magnitude of peak intracylinder pressure leading to = higher intracylinder pressures, higher cylinder head temperatures and = greater stress =3D shorter enging life.

 

For those of you who are using electronic ignition (I am = not):

=C2=B7=      &nb= sp;   Are you sure you are getting more horsepower?  How do you = know?

=C2=B7=      &nb= sp;   If you are getting more horsepower, are you getting it during all = modes of engine operation?  Rich of peak, lean of peak, high MAP, = low MAP, etc

=C2=B7=      &nb= sp;   What is happening to your TBO?

 

D. Brunner

 

The = biggest advantage of any of the electronic systems (in my opinon) is = that they provide a spark advance that is a function of at least = manifold pressure, giving an advantage any time the manifold pressure is = much lower than maybe 25 inches.  But there is very little = combustion taking place in the exhaust system regardless.  The = reason the exhaust temperature rises is that more of the combustion = occurs after TDC and that means less of the energy is being converted to = work.  The down side of advancing the spark is that since more = combustion occurs at the highest cylinder pressure, more heat is = transferred to the cylinder head and piston.  =

 

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