X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 21 Nov 2010 22:17:43 -0500 Message-ID: X-Original-Return-Path: Received: from web57514.mail.re1.yahoo.com ([66.196.100.81] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with SMTP id 4586221 for lml@lancaironline.net; Sat, 20 Nov 2010 09:04:54 -0500 Received-SPF: none receiver=logan.com; client-ip=66.196.100.81; envelope-from=casey.gary@yahoo.com Received: (qmail 21768 invoked by uid 60001); 20 Nov 2010 14:04:18 -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=vDIV96xZtB5BGyquwQ7nW7YmfB3SGnhQEwLwOwVK15vO3b7fv1yQOH35c74oqClrbceZdQ3gF7kqM+Kmgm5Ks4pYH+BQIb1nBHiD4jGtjc0DCmI6ZyqjkRads34SAlsfOwEYvbaK5CiU3OTPnlFai3gHAi7V60kzANYhNpjemQ0=; X-Original-Message-ID: <178760.21759.qm@web57514.mail.re1.yahoo.com> X-YMail-OSG: ldW7kN8VM1kG2pv7UDPVx2Z85V4Wfv7FLnY6hcWZHURYpez 5BOM.qDFLcOtBt3QGtAVN.u4gP0E27ulsHWbiuhBef_1dkbYJ_9CMPB4iaw1 2PITxtHebCHqHsKDgzuDE1JUlRzpDpSvDvhde5IGis_yyY5iNwjNti9MvE3. lggBoeYiHJd_vcaKBXQ6luRbkG8L4yvDzfLaWcEfuQc_Tb3rY362uJMKf27U PYokHZ43dvXKza1xELrWqcvoPM2DDY8urpSea4G_bcZaNmWOWPb97cdd8CVz n_KrHOO51WpBnRA-- Received: from [97.122.152.1] by web57514.mail.re1.yahoo.com via HTTP; Sat, 20 Nov 2010 06:04:17 PST X-Mailer: YahooMailRC/504.5 YahooMailWebService/0.8.107.285259 References: X-Original-Date: Sat, 20 Nov 2010 06:04:17 -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="0-1081507589-1290261857=:21759" --0-1081507589-1290261857=:21759 Content-Type: text/plain; charset=us-ascii Okay, now you've got me confused (not that it takes a lot for that to happen :-), which part of my discussion is incorrect? Gary From Scott: Balderdash In a message dated 11/18/2010 6:56:18 P.M. Central Standard Time, casey.gary@yahoo.com writes: Scott, >I have a problem with your problem with Doug's argument :-). Well, not much of >a problem, but it does make for an interesting discussion. True, for any >condition there is a range of timing that produces the most effective pressure >profile - I wouldn't call it "efficient cylinder pressures". That profile has >been stated by the GAMI guys as the timing that produces a peak 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 does move with mixture changes - >it's unavoidable. So one of the things you do with mixture is to try to put the >peak cylinder pressure at the right angle. Indirectly, because there is no >instrumentation to go by. > > >Yes, there are other characteristics of "electronic" ignition that have an >effect. Usually, a battery-power system that is electronically switched (Is >that "electronic"? I suppose) provides more spark energy than with a magneto. > And all magnetos (and some electronic systems) use shield spark plug wires and >they "suck" some of the energy out of the spark. What's the energy good for? > To get more a combination of time and current in the spark that exceeds what >would otherwise be available. There the approaches of different suppliers >diverge. The Lightspeed system uses a capacitor-discharge (CD) method that >charges a capacitor to something over 100 volts and then discharges this into a >coil. This produces a very high current, low duration spark. The duration is >perhaps 1 or 2 microseconds(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 method works, >but they have different limitations. A short duration spark has one chance to >light the fire and if it misses that, there is no second chance. A long >duration spark might have less of a chance to light the fire in the first >microsecond (less current means less "intensity"), but it keeps trying. So >Klaus built the "III" that double-fires the spark. 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 millisecond, maybe half that. At 2500 rpm the the >crank turns 15 degrees per millisecond, so the second spark would be 15 degrees >"late". Better late than never, I suppose. The biggest advantage of the double >strike comes in starting and idling, when finding a combustible mixture near the >plug at any given instant is not likely. When attempting to run lean mixtures, >automotive OEM's tried everything and finally gave up on CD technology. The >inductive system lights a lean mixture better. And either technology can fire a >larger plug gap, but the CD system can take advantage of it better. > > >Another advantage of higher-energy sparks is that they reduce the "initial >combustion time". They can light more fuel molecules and that speeds up the >initial portion of the fire. Imagine a bonfire where you light more kindling. > The fire reaches its peak faster, but once the end result is the same. Now >imagine the pressure in the cylinder immediately after ignition - there is >almost no change initially, but once a substantial portion is burning the >pressure goes up rapidly and then there is no difference. 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, but with a little more advance (maybe 2 >degrees or so). That change shouldn't be construed as an advantage - you can >get the same result by advancing the magneto timing. --0-1081507589-1290261857=:21759 Content-Type: text/html; charset=us-ascii
Okay, now you've got me confused (not that it takes a lot for that to happen :-), which part of my discussion is incorrect?
Gary

From Scott:
Balderdash
 
In a message dated 11/18/2010 6:56:18 P.M. Central Standard Time, casey.gary@yahoo.com writes:
Scott,
I have a problem with your problem with Doug's argument :-).  Well, not much of a problem, but it does make for an interesting discussion.  True, for any condition there is a range of timing that produces the most effective pressure profile - I wouldn't call it "efficient cylinder pressures".  That profile has been stated by the GAMI guys as the timing that produces a peak 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 does move with mixture changes - it's unavoidable.  So one of the things you do with mixture is to try to put the peak cylinder pressure at the right angle.  Indirectly, because there is no instrumentation to go by.

Yes, there are other characteristics of "electronic" ignition that have an effect.  Usually, a battery-power system that is electronically switched (Is that "electronic"?  I suppose) provides more spark energy than with a magneto.  And all magnetos (and some electronic systems) use shield spark plug wires and they "suck" some of the energy out of the spark.  What's the energy good for?  To get more a combination of time and current in the spark that exceeds what would otherwise be available.  There the approaches of different suppliers diverge.  The Lightspeed system uses a capacitor-discharge (CD) method that charges a capacitor to something over 100 volts and then discharges this into a coil.  This produces a very high current, low duration spark.  The duration is perhaps 1 or 2 microseconds(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 method works, but they have different limitations.  A short duration spark has one chance to light the fire and if it misses that, there is no second chance.  A long duration spark might have less of a chance to light the fire in the first microsecond (less current means less "intensity"), but it keeps trying.  So Klaus built the "III" that double-fires the spark.  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 millisecond, maybe half that.  At 2500 rpm the the crank turns 15 degrees per millisecond, so the second spark would be 15 degrees "late".  Better late than never, I suppose.  The biggest advantage of the double strike comes in starting and idling, when finding a combustible mixture near the plug at any given instant is not likely.  When attempting to run lean mixtures, automotive OEM's tried everything and finally gave up on CD technology.  The inductive system lights a lean mixture better.  And either technology can fire a larger plug gap, but the CD system can take advantage of it better.

Another advantage of higher-energy sparks is that they reduce the "initial combustion time".  They can light more fuel molecules and that speeds up the initial portion of the fire.  Imagine a bonfire where you light more kindling.  The fire reaches its peak faster, but once the end result is the same.  Now imagine the pressure in the cylinder immediately after ignition - there is almost no change initially, but once a substantial portion is burning the pressure goes up rapidly and then there is no difference.  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, but with a little more advance (maybe 2 degrees or so).  That change shouldn't be construed as an advantage - you can get the same result by advancing the magneto timing.

--0-1081507589-1290261857=:21759--