X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 18 Nov 2010 19:52:27 -0500 Message-ID: X-Original-Return-Path: Received: from web57506.mail.re1.yahoo.com ([66.196.100.73] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with SMTP id 4582180 for lml@lancaironline.net; Wed, 17 Nov 2010 08:10:56 -0500 Received-SPF: none receiver=logan.com; client-ip=66.196.100.73; envelope-from=casey.gary@yahoo.com Received: (qmail 62803 invoked by uid 60001); 17 Nov 2010 13:10:20 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=DnIhH1//ycl4wSmqMM5bxkhre1KT/cLKtkdJGNIKemE2Gjsmk6mON9B6TZamjCnD92comFanLBPBmwyYPpErd+cLInIwkPjJ9X0/377QB48dt/79yq/eshTt36mmMm9dvrXavY2+Fh8IfuR4iGFZF9Wz7eO3lTAQvCYsODsR46k=; X-Original-Message-ID: <661257.60824.qm@web57506.mail.re1.yahoo.com> X-YMail-OSG: 6.3zBjQVM1lbewldhI7qyjv2R1blqhl0wtgMQlCQ5.q3pH8 vSi.KEu1nuDVRqJ1AewLYM_r8n5bsoQBAvehwa.14CvLOAnWP49pyJ2W6R_P 9.A04RpveTMH3.tPIj0TCwSsLJntVIa4UYf1m6fN1RtXfeWUNxE0COZ1mSbe 64ypNvQghQcreCPEWn6UHeDgev8sw9k7f2aNi1I8yzbn_MUOGTD_n8.Pza9q WZho7IOLAEugVzLgmN2IuO.3LTWM.Ygf9Egakzuf0oWaO7KFlORD7ry.g14R CgriIoCBb1Oe3EUHQdaANgnFu1rSQB.kWijaRXfx6Dn_SA_8- Received: from [97.122.152.1] by web57506.mail.re1.yahoo.com via HTTP; Wed, 17 Nov 2010 05:10:20 PST X-Mailer: YahooMailRC/504.5 YahooMailWebService/0.8.107.285259 References: X-Original-Date: Wed, 17 Nov 2010 05:10:20 -0800 (PST) From: Gary Casey Subject: Re: Electronic Ignition X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-695800039-1289999420=:60824" --0-695800039-1289999420=:60824 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Scott,=0AI have a problem with your problem with Doug's argument :-). Well= , not much of =0Aa problem, but it does make for an interesting discussion.= True, for any =0Acondition there is a range of timing that produces the m= ost effective pressure =0Aprofile - I wouldn't call it "efficient cylinder = pressures". That profile has =0Abeen stated by the GAMI guys as the timing= that produces a peak cylinder =0Apressure at 16 ATC. But it's not like yo= u're falling off a cliff on either side =0Aof this timing. And this peak p= ressure point does move with mixture changes - =0Ait's unavoidable. So one= of the things you do with mixture is to try to put the =0Apeak cylinder pr= essure at the right angle. Indirectly, because there is no =0Ainstrumentat= ion to go by.=0A=0AYes, there are other characteristics of "electronic" ign= ition that have an =0Aeffect. Usually, a battery-power system that is elec= tronically switched (Is =0Athat "electronic"? I suppose) provides more spa= rk energy than with a magneto. =0A And all magnetos (and some electronic sy= stems) use shield spark plug wires and =0Athey "suck" some of the energy ou= t of the spark. What's the energy good for? =0A To get more a combination = of time and current in the spark that exceeds what =0Awould otherwise be av= ailable. There the approaches of different suppliers =0Adiverge. The Ligh= tspeed system uses a capacitor-discharge (CD) method that =0Acharges a capa= citor to something over 100 volts and then discharges this into a =0Acoil. = This produces a very high current, low duration spark. The duration is = =0Aperhaps 1 or 2 microseconds(very, very short). The other suppliers typi= cally =0Ause an inductive system just like in a magneto. This produces a m= uch lower =0Acurrent spark that lasts a "long" time maybe 2 milliseconds. = Each method works, =0Abut they have different limitations. A short duratio= n spark has one chance to =0Alight the fire and if it misses that, there is= no second chance. A long =0Aduration spark might have less of a chance to= light the fire in the first =0Amicrosecond (less current means less "inten= sity"), but it keeps trying. So =0AKlaus built the "III" that double-fires= the spark. Problem is that the second =0Aspark can't come immediately aft= er the first one. I don't know the delay, but =0Ais suspect it might be 1 = millisecond, maybe half that. At 2500 rpm the the =0Acrank turns 15 degree= s per millisecond, so the second spark would be 15 degrees =0A"late". Bett= er late than never, I suppose. The biggest advantage of the double =0Astri= ke comes in starting and idling, when finding a combustible mixture near th= e =0Aplug at any given instant is not likely. When attempting to run lean = mixtures, =0Aautomotive OEM's tried everything and finally gave up on CD te= chnology. The =0Ainductive system lights a lean mixture better. And eithe= r technology can fire a =0Alarger plug gap, but the CD system can take adva= ntage of it better.=0A=0AAnother advantage of higher-energy sparks is that = they reduce the "initial =0Acombustion time". They can light more fuel mol= ecules and that speeds up the =0Ainitial portion of the fire. Imagine a bo= nfire where you light more kindling. =0A The fire reaches its peak faster, = but once the end result is the same. Now =0Aimagine the pressure in the cy= linder immediately after ignition - there is =0Aalmost no change initially,= but once a substantial portion is burning the =0Apressure goes up rapidly = and then there is no difference. So, what I'm getting =0Aat is that a high= er powered spark results in combustion that behaves exactly =0Alike that li= t with a low-power spark, but with a little more advance (maybe 2 =0Adegree= s or so). That change shouldn't be construed as an advantage - you can =0A= get the same result by advancing the magneto timing.=0A=0AOh, oh, we might = have drifted into the "theological" discussion Doug was trying =0Ato avoid.= ..:-)=0AGary=0A=0AFrom Scott:=0ADoug, =0AI have a problem with your argumen= t. It seems to be upside down. In reference =0AI refer you to my 11/2/201= 0 email entitled "NA Injected Engine Performance =0ALOP". In any event, fo= r any given proper fuel/air ratio (mixture), there is a =0Anarrow timing ra= nge that produces efficient cylinder pressures at the correct =0Acrank angl= e range. The Lycoming engine manual (for my 320) displays =0Athe acceptabl= e range for the EGT for best power as 100F to 180F ROP, and best =0Aeconomy= as 0F to 80F LOP. Running 50F ROP is very bad for cylinder pressures as = =0Astated by GAMI - thus your argument of moving timing by messing with the= mixture =0Ais, uh, not good operational practice.=0A =0ASecondly, you impl= y that the only function of an electronic ignition is to =0Aadvance the tim= ing. Au contraire mon ami! An electronic ignition provides for =0Aa hotte= r, longer, more consistent spark over a greater plug gap that better =0Ains= ures the reliable and timely ignition of the combustible mixture even thoug= h =0Athe F/A may be at some extreme. This results in greater efficiency/HP= depending =0Aon the way one looks at it. See the pamphlet on the benefits= of the LASAR =0Aelectronic ignition that shows speed increases for the sam= e fuel burn or reduced =0Afuel burn at the same speed of a magneto driven e= ngine.=0A =0AThe fixed timing of a magneto (i.e. 25 DBTDC) is a compromise.= Generally =0Aspeaking, EIs advance the base spark timing minimally until = the power, as =0Ameasured by RPM and MAP, is reduced below 75%. Bad events= , such as =0Apre-ignition, detonation and incorrectly timed cyl pressure, a= re less likely in =0Athis regime (that is why the GAMI lean test is done at= less than 75% power). =0AFurthermore, EGTs (representing F/A ratios) are = still maintained in the engine =0Amanufacturer's recommended ranges and the= timing is a better match for the =0Acombustion event pressures.=0A =0ANote= that during my best power cruises at middle altitudes (2500 RPM, MAP > =0A= 22", EGT > 120F ROP), the EI timing is about 25 DBTDC plus or minus a degre= e. =0A =0AYes, more HP. Better speed for the same fuel burn holding other = conditions =0Aequal.=0AYes, in all the modes you mentioned.=0A =0AI haven't= reached TBO yet, I go too fast to accumulate that much time.=0A =0AScott K= rueger=0AIO 320 Dual Lightspeed Plasma III EI=0A =0AIn a message dated 11/1= 5/2010 8:21:27 P.M. Central Standard Time, =0Adouglasbrunner@earthlink.net = writes:=0AAt the risk of starting a =E2=80=9Ctheological=E2=80=9D controver= sy, I would like to raise some =0Areservations about electronic ignition sy= stems (other than reliability and loss =0Aof electrical power)=0A> =0A>Peak= intracylinder pressure (the point in the combustion cycle at which pressur= e =0A>in the cylinder is highest =3D effective timing) is related to 3 thin= gs; spark =0A>timing, rpm and MIXTURE. =0A=0A=0A --0-695800039-1289999420=:60824 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
I have a problem with your problem with Doug's argument :-).=  Well, not much of a problem, but it does make for an interesting dis= cussion.  True, for any condition there is a range of timing that produces the most effective pres= sure profile - I wouldn't call it "efficient cylinder pressures".  Tha= t profile has been stated by the GAMI guys as the timing that produces a pe= ak cylinder pressure at 16 ATC.  But it's not like you're falling off = a cliff on either side of this timing.  And this peak pressure point d= oes move with mixture changes - it's unavoidable.  So one of the thing= s you do with mixture is to try to put the peak cylinder pressure at the ri= ght angle.  Indirectly, because there is no instrumentation to go by.<= /span>

Yes, there are oth= er characteristics of "electronic" ignition that have an effect.  Usua= lly, a battery-power system that is electronically switched (Is that "elect= ronic"?  I suppose) provides more spark energy than with a magneto. &n= bsp;And all magnetos (and some electronic systems) use shield spark plug wi= res and they "suck" some of the energy out of the spark.  What's the e= nergy good for?  To get more a combination of time and current in the = spark that exceeds what would otherwise be available.  There the appro= aches of different suppliers diverge.  The Lightspeed system uses a ca= pacitor-discharge (CD) method that charges a capacitor to something over 10= 0 volts and then discharges this into a coil.  This produces a very hi= gh current, low duration spark.  The duration is perhaps 1 or 2 micros= econds(very, very short).  The other suppliers typically use an inductive system just like in a magneto.  This produces a much lower = current spark that lasts a "long" time maybe 2 milliseconds.  Each met= hod works, but they have different limitations.  A short duration spar= k has one chance to light the fire and if it misses that, there is no secon= d chance.  A long duration spark might have less of a chance to light = the fire in the first microsecond (less current means less "intensity"), bu= t it keeps trying.  So Klaus built the "III" that double-fires the spa= rk.  Problem is that the second spark can't come immediately after the= first one.  I don't know the delay, but is suspect it might be 1 mill= isecond, maybe half that.  At 2500 rpm the the crank turns 15 degrees = per millisecond, so the second spark would be 15 degrees "late".  Bett= er late than never, I suppose.  The biggest advantage of the double st= rike comes in starting and idling, when finding a combustible mixture near the plug at any given instant is not likely.  When attem= pting to run lean mixtures, automotive OEM's tried everything and finally g= ave up on CD technology.  The inductive system lights a lean mixture b= etter.  And either technology can fire a larger plug gap, but the CD s= ystem can take advantage of it better.

Another adv= antage of higher-energy sparks is that they reduce the "initial combustion = time".  They can light more fuel molecules and that speeds up the init= ial portion of the fire.  Imagine a bonfire where you light more kindl= ing.  The fire reaches its peak faster, but once the end result is the= same.  Now imagine the pressure in the cylinder immediately after ign= ition - there is almost no change initially, but once a substantial portion= is burning the pressure goes up rapidly and then there is no difference. &= nbsp;So, what I'm getting at is that a higher powered spark results in combustion that behaves exactly like that lit with a low-power spark, b= ut with a little more advance (maybe 2 degrees or so).  That change sh= ouldn't be construed as an advantage - you can get the same result by advan= cing the magneto timing.

Oh, oh, we might have dri= fted into the "theological" discussion Doug was trying to avoid...:-)
=
Gary

From Scott:

Doug, 

I have a p= roblem with your argument.  It seems to be upside down.  In refer= ence I refer you to my 11/2/2010 email entitled "NA Injected Engine Perform= ance LOP".  In any event, for any given proper fuel/air ratio (mi= xture), there is a narrow timing range that produces efficient cylinde= r pressures at the correct crank angle range.  The Lycoming engin= e manual (for my 320) displays the acceptable range for the EGT fo= r best power as 100F to 180F ROP, and best economy as 0F to 80F LOP.&n= bsp; 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, no= t good operational practice.

 

=

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

=

=  

The fixed timing of a magneto (i.e. = 25 DBTDC) is a compromise.  Generally speaking, EIs advance the b= ase spark timing minimally until the power, as measured by R= PM and MAP, is reduced below 75%.  Bad events, such as pre-igniti= on, 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).&nbs= p; Furthermore, EGTs (representing F/A ratios) are still maintained in= the engine manufacturer's recommended ranges and the timing is a bett= er match for the combustion event pressures.

 

Note that during my best = power cruises at middle altitudes (2500 RPM, MAP > 22", EGT > 12= 0F ROP), the EI timing is about 25 DBTDC plus or minus a degree. 

 

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

=

Yes, in all the modes you mentioned.

 

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

 <= /span>

Scott Krueger

<= p class=3D"MsoNormal" style=3D"margin-right: 0in; margin-left: 0in; font-si= ze: 12pt; font-family: serif; margin-top: 0in; margin-bottom: 0.0001pt; "><= span style=3D"font-size: 10pt; font-family: sans-serif; color: black; ">IO = 320 Dual Lightspeed Plasma III EI

 

In a message dated 11/15/2010 8:21:27 P.M. Centra= l 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 th= an 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. 

<= /div>
=0A=0A=0A

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