X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 16 Nov 2010 09:24:53 -0500 Message-ID: X-Original-Return-Path: Received: from imr-ma03.mx.aol.com ([64.12.206.41] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4580601 for lml@lancaironline.net; Tue, 16 Nov 2010 01:32:14 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.41; envelope-from=Sky2high@aol.com Received: from imo-ma03.mx.aol.com (imo-ma03.mx.aol.com [64.12.78.138]) by imr-ma03.mx.aol.com (8.14.1/8.14.1) with ESMTP id oAG6VZMe018481 for ; Tue, 16 Nov 2010 01:31:35 -0500 Received: from Sky2high@aol.com by imo-ma03.mx.aol.com (mail_out_v42.9.) id q.eaf.c052b25 (37555) for ; Tue, 16 Nov 2010 01:31:33 -0500 (EST) Received: from magic-m20.mail.aol.com (magic-m20.mail.aol.com [172.20.22.193]) by cia-mb03.mx.aol.com (v129.5) with ESMTP id MAILCIAMB034-92b34ce225452a7; Tue, 16 Nov 2010 01:31:33 -0500 From: Sky2high@aol.com X-Original-Message-ID: <2fde4.1cdec27f.3a137f45@aol.com> X-Original-Date: Tue, 16 Nov 2010 01:31:33 EST Subject: Re: [LML] Electronic Ignition X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_2fde4.1cdec27f.3a137f45_boundary" X-Mailer: AOL 9.5 sub 5400 X-AOL-IP: 24.15.17.119 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com --part1_2fde4.1cdec27f.3a137f45_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Doug, =20 I have a problem with your argument. It seems to be upside down. In=20 reference I refer you to my 11/2/2010 email entitled "NA Injected Engine= =20 Performance LOP". In any event, for any given proper fuel/air ratio (mix= ture),=20 there is a narrow timing range that produces efficient cylinder pressures= at=20 the correct crank angle range. The Lycoming engine manual (for my 320)= =20 displays the acceptable range for the EGT for best power as 100F to 180F= ROP,=20 and best economy as 0F to 80F LOP. Running 50F ROP is very bad for=20 cylinder pressures as stated by GAMI - thus your argument of moving timin= g by=20 messing with the mixture is, uh, not good operational practice. =20 Secondly, you imply that the only function of an electronic ignition is to= =20 advance the timing. Au contraire mon ami! An electronic ignition =20 provides for a hotter, longer, more consistent spark over a greater plug= gap that=20 better insures the reliable and timely ignition of the combustible mixtur= e=20 even though the F/A may be at some extreme. This results in greater=20 efficiency/HP depending on the way one looks at it. See the pamphlet on= the=20 benefits of the LASAR electronic ignition that shows speed increases for= the=20 same fuel burn or reduced fuel burn at the same speed of a magneto driven= =20 engine. =20 The fixed timing of a magneto (i.e. 25 DBTDC) is a compromise. Generally= =20 speaking, EIs advance the base spark timing minimally until the power, as= =20 measured by RPM and MAP, is reduced below 75%. Bad events, such as=20 pre-ignition, detonation and incorrectly timed cyl pressure, are less lik= ely in=20 this regime (that is why the GAMI lean test is done at less than 75% powe= r). =20 Furthermore, EGTs (representing F/A ratios) are still maintained in the= =20 engine manufacturer's recommended ranges and the timing is a better match= for=20 the combustion event pressures. =20 Note that during my best power cruises at middle altitudes (2500 RPM, MAP= =20 > 22", EGT > 120F ROP), the EI timing is about 25 DBTDC plus or minus a= =20 degree.=20 =20 Yes, more HP. Better speed for the same fuel burn holding other =20 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 =20 In a message dated 11/15/2010 8:21:27 P.M. Central Standard Time, =20 douglasbrunner@earthlink.net writes: =20 At the risk of starting a =E2=80=9Ctheological=E2=80=9D controversy, I wo= uld like to=20 raise some reservations about electronic ignition systems (other than=20 reliability and loss of electrical power)=20 Peak intracylinder pressure (the point in the combustion cycle at which= =20 pressure in the cylinder is highest =3D effective timing) is related to= 3=20 things; spark timing, rpm and MIXTURE. =20 Why mixture? Because air and fuel mixtures burn at different rates=20 depending on how rich or lean they are. So at a given RPM, MAP and spark= advance=20 you can vary your effective timing by changing the mixture. =20 =C2=B7 Want to advance your timing? Change your mixture to a 50= deg=20 ROP mixture =E2=80=93 which is the fastest burning.=20 =C2=B7 Want to retard your timing? Make your mixture richer or= leaner=20 from 50 deg ROP.=20 And since optimal power is achieved at an effective timing of 16 deg ATDC= ,=20 advancing the spark timing may or MAY NOT increase horsepower depending= =20 on the mixture. But advancing the timing will likely increase the magnit= ude=20 of peak intracylinder pressure leading to higher intracylinder pressures,= =20 higher cylinder head temperatures and greater stress =3D shorter enging= life.=20 For those of you who are using electronic ignition (I am not):=20 =C2=B7 Are you sure you are getting more horsepower? How do you= =20 know?=20 =C2=B7 If you are getting more horsepower, are you getting it du= ring=20 all modes of engine operation? Rich of peak, lean of peak, high MAP, low= =20 MAP, etc=20 =C2=B7 What is happening to your TBO?=20 D. Brunner=20 =20 The biggest advantage of any of the electronic systems (in my opinon) is= =20 that they provide a spark advance that is a function of at least manifold= =20 pressure, giving an advantage any time the manifold pressure is much lowe= r=20 than maybe 25 inches. But there is very little combustion taking place= in=20 the exhaust system regardless. The reason the exhaust temperature rises= is=20 that more of the combustion occurs after TDC and that means less of the= =20 energy is being converted to work. The down side of advancing the spark= is=20 that since more combustion occurs at the highest cylinder pressure, more= heat=20 is transferred to the cylinder head and piston. =20 --part1_2fde4.1cdec27f.3a137f45_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en <= FONT id=3Drole_document color=3D#000000 size=3D2 face=3DArial>
Doug,
 
I have a problem with your argument.  It seems to be upside=20 down.  In reference I refer you to my 11/2/2010 email entitled "NA In= jected=20 Engine Performance LOP".  In any event, for any given proper fue= l/air=20 ratio (mixture), there is a narrow timing range that produces efficie= nt=20 cylinder pressures at the correct crank angle range.  The Lycomi= ng=20 engine manual (for my 320) displays the acceptable range for the EG= T for=20 best power as 100F to 180F ROP, and best economy as 0F to 80F LOP.&nb= sp;=20 Running 50F ROP is very bad for cylinder pressures as stated by GAMI - thu= s your=20 argument of moving timing by messing with the mixture is, uh, not good=20 operational practice.
 
Secondly, you imply that the only function of an electronic ignition= is to=20 advance the timing.  Au contraire mon ami!  An electronic igniti= on=20 provides for a hotter, longer, more consistent spark over a greater plug= =20 gap that better insures the reliable and timely ignition of the= =20 combustible mixture even though the F/A may be at some extreme.  This= =20 results in greater efficiency/HP depending on the way one looks at it.&nbs= p; See=20 the pamphlet on the benefits of the LASAR electronic ignition that shows= speed=20 increases for the same fuel burn or reduced fuel burn at the same speed of= a=20 magneto driven engine.
 
The fixed timing of a magneto (i.e. 25 DBTDC) is a compromise.&n= bsp;=20 Generally speaking, EIs advance the base spark timing minimally= until=20 the power, as measured by RPM and MAP, is reduced below 75%.&nbs= p; Bad=20 events, such as pre-ignition, detonation and incorrectly timed cyl pressur= e, are=20 less likely in this regime (that is why the GAMI lean test is done at less= than=20 75% power).  Furthermore, EGTs (representing F/A ratios) are sti= ll=20 maintained in the engine manufacturer's recommended ranges and the ti= ming=20 is a better match for the combustion event pressures.
 
Note that during my best power cruises at middle altitudes (2500= RPM,=20 MAP > 22", EGT > 120F ROP), the EI timing is about 25 DBTDC plu= s or=20 minus a degree. 
 
Yes, more HP.  Better speed for the same fuel burn holding other= =20 conditions equal.
Yes, in all the modes you mentioned.
 
I haven't reached TBO yet, I go too fast to accumulate that much=20 time.
 
Scott Krueger
IO 320 Dual Lightspeed Plasma III EI
 
In a message dated 11/15/2010 8:21:27 P.M. Central Standard Time,=20 douglasbrunner@earthlink.net writes:

At=20 the risk of starting a =E2=80=9Ctheological=E2=80=9D controversy, I woul= d like to raise some=20 reservations about electronic ignition systems (other than reliability= and=20 loss of electrical power)

 

Peak=20 intracylinder pressure (the point in the combustion cycle at which press= ure in=20 the cylinder is highest =3D effective timing) is related to 3 things; sp= ark=20 timing, rpm and MIXTURE. 

 

Why=20 mixture? Because air and fuel mixtures burn at different rates depending= on=20 how rich or lean they are.  So at a given RPM, MAP and spark advanc= e you=20 can vary your effective timing by changing the mixture. =20

 

=C2=B7      &nb= sp; =20 Want=20 to advance your timing? Change your mixture to a 50 deg ROP mixture =E2= =80=93 which is=20 the fastest burning.

=C2=B7      &nb= sp; =20 Want=20 to retard your timing?  Make your mixture richer or leaner from 50= deg=20 ROP.

 

And=20 since optimal power is achieved at an effective timing of 16 deg ATDC,= =20 advancing the spark timing may or MAY NOT increase horsepo= wer=20 depending on the mixture.  But advancing the timing will likely inc= rease=20 the magnitude of peak intracylinder pressure leading to higher intracyli= nder=20 pressures, higher cylinder head temperatures and greater stress =3D shor= ter=20 enging life.

 

For=20 those of you who are using electronic ignition (I am=20 not):

=C2=B7      &nb= sp; =20 Are=20 you sure you are getting more horsepower?  How do you=20 know?

=C2=B7      &nb= sp; =20 If=20 you are getting more horsepower, are you getting it during all modes of= engine=20 operation?  Rich of peak, lean of peak, high MAP, low MAP,=20 etc

=C2=B7      &nb= sp; =20 What=20 is happening to your TBO?

 

D.=20 Brunner

 

The=20 biggest advantage of any of the electronic systems (in my opinon) is tha= t they=20 provide a spark advance that is a function of at least manifold pressure= ,=20 giving an advantage any time the manifold pressure is much lower than ma= ybe 25=20 inches.  But there is very little combustion taking place in the ex= haust=20 system regardless.  The reason the exhaust temperature rises is tha= t more=20 of the combustion occurs after TDC and that means less of the energy is= being=20 converted to work.  The down side of advancing the spark is that si= nce=20 more combustion occurs at the highest cylinder pressure, more heat is=20 transferred to the cylinder head and piston. =20

 

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