X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 19 Nov 2010 08:02:45 -0500 Message-ID: X-Original-Return-Path: Received: from imr-da02.mx.aol.com ([205.188.105.144] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4584353 for lml@lancaironline.net; Thu, 18 Nov 2010 20:00:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.144; envelope-from=Sky2high@aol.com Received: from imo-ma04.mx.aol.com (imo-ma04.mx.aol.com [64.12.78.139]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id oAJ0xPSC005164 for ; Thu, 18 Nov 2010 19:59:25 -0500 Received: from Sky2high@aol.com by imo-ma04.mx.aol.com (mail_out_v42.9.) id q.c2e.768105d1 (37032) for ; Thu, 18 Nov 2010 19:59:23 -0500 (EST) Received: from magic-d24.mail.aol.com (magic-d24.mail.aol.com [172.19.146.158]) by cia-db02.mx.aol.com (v129.7) with ESMTP id MAILCIADB022-90a84ce5cbebb4; Thu, 18 Nov 2010 19:59:23 -0500 From: Sky2high@aol.com X-Original-Message-ID: <1780f1.2579473a.3a1725eb@aol.com> X-Original-Date: Thu, 18 Nov 2010 19:59:23 EST Subject: Re: [LML] Re: Electronic Ignition X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_1780f1.2579473a.3a1725eb_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_1780f1.2579473a.3a1725eb_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Balderdash =20 =20 In a message dated 11/18/2010 6:56:18 P.M. Central Standard Time, =20 casey.gary@yahoo.com writes: =20 Scott, I have a problem with your problem with Doug's argument :-). Well, not= =20 much of a problem, but it does make for an interesting discussion. True,= for=20 any condition there is a range of timing that produces the most effective= =20 pressure profile - I wouldn't call it "efficient cylinder pressures". Th= at=20 profile has been stated by the GAMI guys as the timing that produces a=20 peak cylinder pressure at 16 ATC. But it's not like you're falling off= a =20 cliff on either side of this timing. And this peak pressure point does = move=20 with mixture changes - it's unavoidable. So one of the things you do wit= h=20 mixture is to try to put the peak cylinder pressure at the right angle.= =20 Indirectly, because there is no instrumentation to go by. Yes, there are other characteristics of "electronic" ignition that have = an=20 effect. Usually, a battery-power system that is electronically switched= =20 (Is that "electronic"? I suppose) provides more spark energy than with= a=20 magneto. And all magnetos (and some electronic systems) use shield spark= =20 plug wires and they "suck" some of the energy out of the spark. What's th= e=20 energy good for? To get more a combination of time and current in the sp= ark=20 that exceeds what would otherwise be available. There the approaches of= =20 different suppliers diverge. The Lightspeed system uses a capacitor-disc= harge=20 (CD) method that charges a capacitor to something over 100 volts and then= =20 discharges this into a coil. This produces a very high current, low durat= ion=20 spark. The duration is perhaps 1 or 2 microseconds(very, very short). = =20 The other suppliers typically use an inductive system just like in a magn= eto.=20 This produces a much lower current spark that lasts a "long" time maybe= 2=20 milliseconds. Each method works, but they have different limitations. = A=20 short duration spark has one chance to light the fire and if it misses =20 that, there is no second chance. A long duration spark might have less = of a=20 chance to light the fire in the first microsecond (less current means les= s=20 "intensity"), but it keeps trying. So Klaus built the "III" that =20 double-fires the spark. Problem is that the second spark can't come imme= diately after=20 the first one. I don't know the delay, but is suspect it might be 1=20 millisecond, maybe half that. At 2500 rpm the the crank turns 15 degrees= per=20 millisecond, so the second spark would be 15 degrees "late". Better late= =20 than never, I suppose. The biggest advantage of the double strike comes= in=20 starting and idling, when finding a combustible mixture near the plug at= any=20 given instant is not likely. When attempting to run lean mixtures,=20 automotive OEM's tried everything and finally gave up on CD technology.= The=20 inductive system lights a lean mixture better. And either technology can= fire a=20 larger plug gap, but the CD system can take advantage of it better. Another advantage of higher-energy sparks is that they reduce the "initia= l=20 combustion time". They can light more fuel molecules and that speeds up= =20 the initial portion of the fire. Imagine a bonfire where you light more= =20 kindling. The fire reaches its peak faster, but once the end result is= the=20 same. Now imagine the pressure in the cylinder immediately after ignitio= n -=20 there is almost no change initially, but once a substantial portion is=20 burning the pressure goes up rapidly and then there is no difference. So= , what=20 I'm getting at is that a higher powered spark results in combustion that= =20 behaves exactly like that lit with a low-power spark, but with a little= more=20 advance (maybe 2 degrees or so). That change shouldn't be construed as= an=20 advantage - you can get the same result by advancing the magneto timing. Oh, oh, we might have drifted into the "theological" discussion Doug was= =20 trying to avoid...:-) Gary From Scott: =20 =20 Doug,=20 =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= =20 at 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= =20 ROP, 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 =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 =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 =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 =20 Yes, more HP. Better speed for the same fuel burn holding other=20 conditions equal. =20 Yes, in all the modes you mentioned. =20 =20 I haven't reached TBO yet, I go too fast to accumulate that much time. =20 =20 Scott Krueger =20 IO 320 Dual Lightspeed Plasma III EI =20 =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 --part1_1780f1.2579473a.3a1725eb_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>
Balderdash
 
In a message dated 11/18/2010 6:56:18 P.M. Central Standard Time,=20 casey.gary@yahoo.com writes:
Scott,
I have a=20 problem with your problem with Doug's argument :-).  Well, not much= of a=20 problem, but it does make for an interesting discussion.  True, for= any=20 condition there is a range of timing that produces the most effective pr= essure=20 profile - I wouldn't call it "efficient cylinder pressures".  That= =20 profile has been stated by the GAMI guys as the timing that produces a= peak=20 cylinder pressure at 16 ATC.  But it's not like you're falling off= a=20 cliff on either side of this timing.  And this peak pressure point= does=20 move with mixture changes - it's unavoidable.  So one of the things= you=20 do with mixture is to try to put the peak cylinder pressure at the right= =20 angle.  Indirectly, because there is no instrumentation to go=20 by.

Yes, there are other characteristics of "electronic" ignition that= have=20 an effect.  Usually, a battery-power system that is electronically= =20 switched (Is that "electronic"?  I suppose) provides more spark ene= rgy=20 than with a magneto.  And all magnetos (and some electronic systems= ) use=20 shield spark plug wires and they "suck" some of the energy out of the sp= ark.=20  What's the energy good for?  To get more a combination of tim= e and=20 current in the spark that exceeds what would otherwise be available.=20  There the approaches of different suppliers diverge.  The=20 Lightspeed system uses a capacitor-discharge (CD) method that charges a= =20 capacitor to something over 100 volts and then discharges this into a co= il.=20  This produces a very high current, low duration spark.  The= =20 duration is perhaps 1 or 2 microseconds(very, very short).  The oth= er=20 suppliers typically use an inductive system just like in a magneto. &nbs= p;This=20 produces a much lower current spark that lasts a "long" time maybe 2=20 milliseconds.  Each method works, but they have different limitatio= ns.=20  A short duration spark has one chance to light the fire and if it= misses=20 that, there is no second chance.  A long duration spark might have= less=20 of a chance to light the fire in the first microsecond (less current mea= ns=20 less "intensity"), but it keeps trying.  So Klaus built the "III"= that=20 double-fires the spark.  Problem is that the second spark can't com= e=20 immediately after the first one.  I don't know the delay, but is su= spect=20 it might be 1 millisecond, maybe half that.  At 2500 rpm the the cr= ank=20 turns 15 degrees per millisecond, so the second spark would be 15 degree= s=20 "late".  Better late than never, I suppose.  The biggest advan= tage=20 of the double strike comes in starting and idling, when finding a combus= tible=20 mixture near the plug at any given instant is not likely.  When=20 attempting to run lean mixtures, automotive OEM's tried everything and= finally=20 gave up on CD technology.  The inductive system lights a lean mixtu= re=20 better.  And either technology can fire a larger plug gap, but the= CD=20 system can take advantage of it better.

Another advantage of higher-energy sparks is that they reduce the= =20 "initial combustion time".  They can light more fuel molecules and= that=20 speeds up the initial portion of the fire.  Imagine a bonfire where= you=20 light more kindling.  The fire reaches its peak faster, but once th= e end=20 result is the same.  Now imagine the pressure in the cylinder immed= iately=20 after ignition - there is almost no change initially, but once a substan= tial=20 portion is burning the pressure goes up rapidly and then there is no=20 difference.  So, what I'm getting at is that a higher powered spark= =20 results in combustion that behaves exactly like that lit with a low-powe= r=20 spark, but with a little more advance (maybe 2 degrees or so).  Tha= t=20 change shouldn't be construed as an advantage - you can get the same res= ult by=20 advancing the magneto timing.

Oh, oh, we might have drifted into the "theological" discussion Dou= g was=20 trying to avoid...:-)
Gary

From Scott:

Doug, 

I have a=20 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=20 (mixture), there is a narrow timing range that produces efficient= =20 cylinder pressures at the correct crank angle range.  The Lyco= ming=20 engine manual (for my 320) displays the acceptable rang= e for=20 the EGT for best power as 100F to 180F ROP, and best economy as 0F= to 80F=20 LOP.  Running 50F ROP is very bad for cylinder pressures as stated= by=20 GAMI - thus your argument of moving timing by messing with the mixture= is, uh,=20 not good operational practice.

 

Secondly, you=20 imply that the only function of an electronic ignition is to advance the= =20 timing.  Au contraire mon ami!  An electronic ignition provide= s for=20 a hotter, longer, more consistent spark over a greater plug gap tha= t=20 better insures the reliable and timely ignition of the combustible= =20 mixture even though the F/A may be at some extreme.  This results= in=20 greater efficiency/HP depending on the way one looks at it.  See th= e=20 pamphlet on the benefits of the LASAR electronic ignition that shows spe= ed=20 increases for the same fuel burn or reduced fuel burn at the same speed= of a=20 magneto driven engine.

 

The fixed=20 timing of a magneto (i.e. 25 DBTDC) is a compromise.  Generall= y=20 speaking, EIs advance the base spark timing minimally until th= e=20 power, as measured by RPM and MAP, is reduced below 75%. = Bad=20 events, such as pre-ignition, detonation and incorrectly timed cyl press= ure,=20 are less likely in this regime (that is why the GAMI lean test is done= at less=20 than 75% power).  Furthermore, EGTs (representing F/A ratios) = are=20 still maintained in the engine manufacturer's recommended ranges an= d the=20 timing is a better match for the combustion event pressures.

<= /DIV>

 

Note that=20 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 mi= nus a=20 degree. 

 

Yes, more=20 HP.  Better speed for the same fuel burn holding other conditions= =20 equal.

Yes, in all the=20 modes you mentioned.

 

I haven't=20 reached TBO yet, I go too fast to accumulate that much time.

<= /DIV>

 

Scott=20 Krueger

IO 320 Dual=20 Lightspeed Plasma III EI

 

In a message=20 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 wo= uld 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 pre= ssure=20 in the cylinder is highest =3D effective timing) is related to 3 thing= s; spark=20 timing, rpm=20 and MIXTURE. 


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